WO2022259136A1 - Aluminium-silicon casting alloy, and castings made from said alloy - Google Patents

Aluminium-silicon casting alloy, and castings made from said alloy Download PDF

Info

Publication number
WO2022259136A1
WO2022259136A1 PCT/IB2022/055280 IB2022055280W WO2022259136A1 WO 2022259136 A1 WO2022259136 A1 WO 2022259136A1 IB 2022055280 W IB2022055280 W IB 2022055280W WO 2022259136 A1 WO2022259136 A1 WO 2022259136A1
Authority
WO
WIPO (PCT)
Prior art keywords
comprised
aluminium
alloy
mpa
casting
Prior art date
Application number
PCT/IB2022/055280
Other languages
French (fr)
Inventor
Feras Allan
Peio Todorov Stoyanov
Abdulla Mohammad Jassim Bin Kalban
Original Assignee
Dubai Aluminium Pjsc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dubai Aluminium Pjsc filed Critical Dubai Aluminium Pjsc
Priority to EP22819725.7A priority Critical patent/EP4352273A1/en
Publication of WO2022259136A1 publication Critical patent/WO2022259136A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/026—Alloys based on aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
    • B22D21/04—Casting aluminium or magnesium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C22C21/04—Modified aluminium-silicon alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent

Definitions

  • the invention relates to the field of metallurgy of aluminium alloys, and more precisely to aluminium - silicon casting alloys.
  • the invention also relates to castings, that is to say to cast and solidified pieces, made from said alloy.
  • the invention also relates to heat- treatments applicable to aluminium-silicon alloy castings.
  • the invention also relates to certain cast pieces produced by casting said alloy into a given shape and heat-treating the solidified piece. These cast pieces, also called castings, need to comply with certain requirements, such as high mechanical strength, high elongation and high corrosion resistance.
  • the invention relates in particular to aluminium - silicon casting alloys with a rather low silicon content, not exceeding about 5 weight percent, and containing a small amount of magnesium.
  • Casting alloys of the AISi5Mg type are known for a long time. They are age-hardenable.
  • Aluminium und Aluminiumlegierungen » published in 1965 (Springer Verlag) by D. Altenpohl (see p. 811 )
  • a solution heat treatment between 525 °C and 530 °C (5h) and an artificial ageing to a T6-like temper after water quench between 155 °C and 160 °C for 10 h is disclosed for this alloy.
  • EP 3 370 900 (Mubea Performance Wheels) describes compositions with silicon from 3.5% to 5.0 %, magnesium 0.2 % to 0.7 %, and titanium 0.07 % to 0.12 %, and in particular an alloy for low pressure die casting containing Si 4.0 %, Mg 0.4 %, Ti 0.008 %, B 0.006 %, Cu 400 ppm, Zn 400 ppm, Sr 100 ppm, Sn 200 ppm, Ni 400 ppm, Mn 400 ppm, TiB 2 20 ppm; no heat treatment is described for this alloy.
  • US 2019/011 8251 discloses an alloy for low pressure die casting and gravity casting containing silicon from 4 % to 7 %, manganese less than 0.5 %, chromium between 0.15 % and 0.5 %, and magnesium not exceeding 0.8 %.
  • US 10,612,116 discloses a composition range with silicon 4 % to 6 %, chromium 0.2 % to 0.4 %, magnesium 0.1 % to 0.5 %; the use of this alloy is recommended for wheels.
  • CN 106319 299 (Citic Dicastal) described two alloys with the following compositions : Si 4.0 %, Mg 0.4 %, Cr 0.10 %, B 0.01 % with an elongation of 12 % and a yield strength of 280 MPa in T6 temper, and Si 0.4 %, Mg 0.6 %, Cr 0.15 %, B 0.001 % with an elongation of 11 % and a yield strength of 290 MPa in T6 temper.
  • JP 2015/045 033 discloses a die casting alloy with 4.5 % to 7.5 % silicon, 0.25 % to 0.75 % magnesium, and zinc up to 0.3 %.
  • EP 2 700 727 (KSM Castings) describes an alloy composition with 3.0 % to 3.8 % of silicon, 0.3 % to 0.6 % magnesium, 0.25 % to 0.35 % of chromium; this alloy can be heat treated to a T6 temper.
  • EP 2 954 081 discloses a casting alloy with silicon from 3.0 % to 3.8 %, magnesium from 0.3 % to 0.6 %, chromium 0.05 % to 0.25 %, and strontium between 0.010 % and 0.030 %.
  • These alloys can be used in particular in T6-like tempers, i.e. after solution heat treatment and age hardening to peak stength, where they usually exhibit mechanical properties which represent a certain compromise between mechanical strength and elongation at rupture, knowing that these two properties are usually following a conflicting path when optimizing the composition of the alloy or the heat treatment conditions of the cast piece : it is usually not difficult to increase one of the two properties while decreasing at the same time the other one.
  • These alloys can in particular be used for making wheels, in particular for cars and trucks. Their resistance to atmospheric corrosion is usually good. For this specific use, there is however an additional requirement, namely corrosion resistance in contact with water and seawater. There is now a need for aluminium-based casting alloys that have higher mechanical strength and, at the same time, higher elongation, and that also have an excellent corrosion resistance. This is the problem addressed by the present invention.
  • the aluminium casting alloy comprises, expressed in weight percent : from 3.5 % to 4.5 % of silicon; from 0.35 % to 0.55 % of magnesium; from 0.05 % to 0.25 % of chromium; from 0.05 % to 0.30 % of nickel; from 0.005 % to 0.020 % of strontium; not more than 0.12 % of iron; not more than 0.15 % of titanium; not more than 0.05 %, and preferably not more than 0.03 %, of manganese; optionally comprising from 0.05 % to 0.20 % of copper; optionally comprising from 0.05 % to 0.30 % of silver; other impurities not more than 0.02 each and not more than 0.10 in total, the remainder being aluminium.
  • This alloy is the first object of the present invention.
  • a second object of the invention is an aluminium alloy casting made from this alloy, presenting the following set of properties : yield strength R p0 ,2 is comprised between about 255 MPa and about 300 MPa, tensile strength R m is comprised between about 340 MPa and about 370 MPa, and elongation at fracture is comprised between about 11.0 % and about 20.0 %.
  • a third object of the invention is a process for obtaining an aluminium casting according to the second object of the invention, comprising solidifying a liquid aluminium casting alloy according to the first object, carrying out a solution heat treatment of 4 h to 10 h at a temperature comprised between 535 °C and 555 °C, and preferably of 4 h to 8 h between 540 °C and 550 °C, followed by quenching and artifial aging treatment of 4 h to 10 h at a temperature between 150 °C and 170 °C, and preferably of 6 h to 8 h at a temperature between 160 °C and 170 °C.
  • the aluminium casting alloy comprises, expressed in weight percent : from 3.5 % to 4.5 % of silicon; from 0.35 % to 0.55 % of magnesium; from 0.05 % to 0.25 % of chromium; from 0.05 % to 0.30 % of nickel; from 0.005 % to 0.020 % of strontium; not more than 0.12 % of iron; not more than 0.15 % of titanium; not more than 0.05 %, and preferably not more than 0.03 %, of manganese; optionally comprising from 0.05 % to 0.20 % of copper; optionally comprising from 0.05 % to 0.30 % of silver; other impurities not more than 0.02 % each and not more than 0.10 % in total, the remainder being aluminium.
  • the silicon content is comprised between 3.7 % and 4.3 %, and still more preferably between 3.8 % and 4.3 %, and even more preferably between 3.85 % and 4.25 %;
  • the strontium content does not exceed 0.015 %;
  • the chromium content does not exceed 0.20 %, and still more preferably the chromium content is comprised between 0.06 % and 0.15 %;
  • the nickel content is comprised between 0.08 % and 0.22 %, and preferably between 0.10 % and 0.20 %;
  • the manganese content is comprised between 0.001% and 0.03 %; other impurities do not exceed 0.015 % each and 0.10 % in total (and preferably do not exceed 0.09 % in total).
  • Nickel is an essential feature of the alloy according to the invention.
  • the addition of nickel to the base alloy results in a fundamental change in the microstructure.
  • the inventors have found that a nickel concentration as low as 0.05 wt-% modifies the phase profile and the distribution of other elements.
  • excess magnesium is consumed by AI 3 Ni phases, and very few Mg 2 Si phases are formed, thereby enabling higher solution heat treatment temperatures. With Ni 0.15 % nearly all magnesium is dissolved in the matrix. To a significant extent, AI 3 Ni phases survive the heat treatments leading to T6 temper.
  • Chromium combines with nickel to AICrNi(Fe) phases which are stable and present in T6 temper.
  • this allow further comprises from 0.05 % to 0.20 % of copper, and preferably between 0.07 % and 0.15 %.
  • this alloy further comprises from 0.05 % to 0.30 % of silver, and preferably between 0.05 % and 0.20 %.
  • this alloy further comprises from 0.05 % to 0.20 % of copper and from 0.05 % to 0.30 % of silver; it preferably comprises between 0.07 % and 0.15 % of copper and between 0.05 % and 0.20 % of silver.
  • the alloy composition in all of its variants and embodiments, can comprise controlled amounts of certain minor elements; these controlled amount can result from the voluntary addition of said minor elements, or from the control of their impurity level.
  • the calcium content is less than 200 ppm ; this increases the corrosion resistance of the castings in certain tempers.
  • vanadium does not exceed 0.02 %, and/or gallium does not exceed 0.02 %.
  • the iron content is below 0.10 %; this low iron content leads to a higher elongation at rupture of the castings, which is desirable.
  • a minor addition of manganese may be desirable.
  • the preferentiel manganese range is between 0.001 % and 0.03 %, and preferably between 0.003 % and 0.03 %, and even more preferably between 0.005 % and 0.02 %.
  • the inventors have found that this presence of a minute amout of manganese promotes the formation of Mn-Fe intermetallic phases which act as strain hardeners; this increases strenghth of the castings, but does not lead to a decrease in elongation at rupture.
  • titanium is introduced into the alloy in the form of an AITi 3 master alloy or another master alloy that does not contain boron, but not as TiB 2 .
  • the casting alloy according to the invention can be used for making cast parts, also called castings, using various casting processes, depending on the purpose. These casting techniques are known as such; in general the liquid metal is admitted into a die (possibly under pressure), where is solidifies.
  • casting of remelting ingots can be carried out as open casting or direct chill casting.
  • Casting of parts, such as wheels, suspension parts - subframes, cross members, knuckles can be carried out in particular by low pressure die casting, by gravity die casting or counter pressure die casting.
  • Cast parts according to the invention can be heat treated in various ways.
  • An advantageous heat treatment comprises a specific combination of solution heat treatment and artificial ageing. In this way, a T6 like temper can be obtained.
  • This temper is a particularly interesting one for making parts that need to exhibit both high mechanical strength and high elongation; such parts are in particular wheels for cars and trucks.
  • An advantageous process for obtaining such a heat treated aluminium casting comprises a first step of solution heat treatment of about 4 h to about 10 h at a temperature comprised between about 535 °C and about 555 °C, and preferably of 4 h to 8 h between 540 °C and 550 °C. This solution heat treatment can be terminated by quenching.
  • the casting is submitted to artificial ageing of about 4 h to about 10 h at a temperature between about 150 °C and about 170 °C, and preferably of 6 h to 9 h at a temperature between 160 °C and 170 °C.
  • the duration of the ageing treatment is a particularly critical parameter that determines the mechanical properties of the cast part. For this reason, the most preferred ageing conditions are betwen 6 h and 8 h at a temperature between 160 °C and 170 °C.
  • yield strength R p0 ,2 is comprised between about 255 MPa and about 310 MPa
  • tensile strength R m is comprised between about 340 MPa and about 370 MPa
  • elongation at fracture is comprised between about 11 .0 % and about 20.0 %.
  • yield strength R p0 ,2 is comprised between about 255 MPa and about 285 MPa
  • tensile strength is R m comprised between about 340 MPa and about 370 MPa
  • elongation at fracture is comprised between about 14.0 % and about 20.0 %.
  • yield strength R p0 ,2 is comprised between 265 MPa and 280 MPa
  • tensile strength is R m comprised between 350 MPa and 365 MPa
  • elongation at fracture is comprised between 15.0 % and 18.0 %.
  • the solution heat treatment is carried out at a temperature comprised between 541 °C and 549 °C for a duration comprised between 5 h and 7 h
  • the artificial ageing is carried out a temperature comprised between 157 °C and 163 °C for a duration between 6 h and 9 h.
  • the artifical ageing treatment can also be carried out in two or more steps at different temperatures; this will however render the industrial production more complex.
  • a base alloy composition was prepared with the following target composition:
  • the following amounts of elements were added: Cr 0.10 % and Ni 0.15 %.
  • the alloy was cast in a mould. After solidification the following heat treatment was applied: solution heat treatment of 6 hours at 545 °C followed by artifical ageing at varying conditions, as explained in Table 1 which summarizes the results.
  • Example 9 is the same chemical composition as examples 1 to 6.
  • Example 10 is the same chemical composition as examples 7 and 8.
  • Examples 9 and 10 have been submitted to the same solution heat treatment as in Examples 1 to 8, namely 6 h at 545 °C.
  • Examples 9 and 10 have then been submitted to a two-step ageing treatment, as follows: a first step of 1 h at 110 °C, and a second step of 2 h at 170°C.
  • Mg 2 Si Mg 2 Si
  • tt-AIFeSi applying usually as needles or branched
  • AI 3 Ni applying usually blocky, sometimes elongated
  • AICrNi(Fe) applying usually blocky.
  • Higher Mg values (up to 20 at-%) are found in tt-AIFeSi, but also Ni concentrations up to 2.5 at-%.
  • Chromium resides in tt-AIFeSi and AI 3 Ni phases (about 0.1 - 0.2 at-%) but shows a major function in AICrNi(Fe) phases.
  • AI3Ni phases had a blocky, sometimes acicular morphology, and a typical size between 1 pm to 5 pm (blocky); needles were rare and could be up to 10 pm. They were often found close to tt-AIFeSi phases, and between tt-AIFeSi and AICrNi(Fe) phases.
  • the chemical composition of AI 3 Ni phases was as follows: Al 70 - 75 at-%; Ni 7.5 - 17.5 at-%; Si 2 - 19 at-%;
  • AICrNi(Fe) phases had a blocky morphology, and a typical size between 1 pm to 5 pm (sometimes up to 7.5 pm). They were often found close to tt-AIFeSi and AI 3 Ni phases.
  • the chemical composition of AICrNi(Fe) phases was as follows:
  • Al about 70 at-%; Ni 4 - 6 at-%; Si 10 - 15 at-%; Mg 0.5 - 1 .5 at-%; Fe 2 at-%; Cr 5 - 7.5 at-%.
  • tt-AIFeSi applying usually as fragments
  • AI 2 oNi 2 Fe applying usually as fragments, blocky or acicular
  • AI 3 Ni applying usually blocky, rounded
  • AICrNi(Fe) applying usually blocky
  • AI 3 Ni phases had a small rounded or blocky morphology, and a typical size between 1 pm to 3 pm. Very few of these phases were found; upon heat treatment theses phases tend to fragment or to dissolve.
  • the chemical composition of AI 3 Ni phases was as follows:
  • AICrNi(Fe) phases had a blocky morphology, and a typical size between 1 pm to 5 pm (sometimes up to 7.5 pm). They were often found close to tt-AIFeSi and AI3Ni phases. Upon heat treatment AICrNi(Fe) phases showed hardly any change.
  • the chemical composition of AICrNi(Fe) phases was as follows:
  • AI 2 oNi 2 Fe phases had a fragmented or acicular morphology, mostly comprised between 1 pm to 10 pm.
  • the chemical composition of these phases was as follows:

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Forging (AREA)

Abstract

Aluminium casting alloy, comprising, expressed in weight percent, from 3.5 % to 4.5 % of silicon; from 0.35 % to 0.55 % of magnesium; from 0.05 % to 0.25 % of chromium; from 0.05 % to 0.30 % of nickel; from 0.005 % to 0.020 % of strontium; not more than 0.12 % of iron; not more than 0.15 % of titanium; not more than 0.05 % of manganese; other impurities not more than 0.02 % each and not more than 0.10 % in total, the remainder being aluminium.

Description

ALUMINIUM-SILICON CASTING ALLOY, AND CASTINGS MADE FROM SAID
ALLOY
Technical field of the invention
The invention relates to the field of metallurgy of aluminium alloys, and more precisely to aluminium - silicon casting alloys. The invention also relates to castings, that is to say to cast and solidified pieces, made from said alloy. The invention also relates to heat- treatments applicable to aluminium-silicon alloy castings. The invention also relates to certain cast pieces produced by casting said alloy into a given shape and heat-treating the solidified piece. These cast pieces, also called castings, need to comply with certain requirements, such as high mechanical strength, high elongation and high corrosion resistance.
The invention relates in particular to aluminium - silicon casting alloys with a rather low silicon content, not exceeding about 5 weight percent, and containing a small amount of magnesium.
Prior art
Casting alloys of the AISi5Mg type (according to DIN 1725-2) are known for a long time. They are age-hardenable. In the early handbook « Aluminium und Aluminiumlegierungen » published in 1965 (Springer Verlag) by D. Altenpohl (see p. 811 ), a solution heat treatment between 525 °C and 530 °C (5h) and an artificial ageing to a T6-like temper after water quench between 155 °C and 160 °C for 10 h is disclosed for this alloy.
Since then, many studies documented in the patent litterature have explored the properties of Al-Si alloys with low magnesium content in a wide range of composition. As an example, US 2011/011 6966 and JP 2011/162 883 (Toyota) disclose an aluminium alloy composition with 3.5 % to 7.5 % of silicon, 0.45 % to 0.8 % magnesium, and 0.05 % to 0.035 % chromium; these documents teach that a silicon content above 4.5 % is preferred. EP 3 175 009 (KSM Castings) discloses an alloy composition with Si 3.8 % to 5.8 %, magnesium 0.1 % to 0.6 %, and chromium 0.05 % to 1 .3 %.
EP 3 370 900 (Mubea Performance Wheels) describes compositions with silicon from 3.5% to 5.0 %, magnesium 0.2 % to 0.7 %, and titanium 0.07 % to 0.12 %, and in particular an alloy for low pressure die casting containing Si 4.0 %, Mg 0.4 %, Ti 0.008 %, B 0.006 %, Cu 400 ppm, Zn 400 ppm, Sr 100 ppm, Sn 200 ppm, Ni 400 ppm, Mn 400 ppm, TiB2 20 ppm; no heat treatment is described for this alloy.
US 2019/011 8251 (GM Global Technology) discloses an alloy for low pressure die casting and gravity casting containing silicon from 4 % to 7 %, manganese less than 0.5 %, chromium between 0.15 % and 0.5 %, and magnesium not exceeding 0.8 %. US 10,612,116 (GM Global Technology) discloses a composition range with silicon 4 % to 6 %, chromium 0.2 % to 0.4 %, magnesium 0.1 % to 0.5 %; the use of this alloy is recommended for wheels.
CN 106319 299 (Citic Dicastal) described two alloys with the following compositions : Si 4.0 %, Mg 0.4 %, Cr 0.10 %, B 0.01 % with an elongation of 12 % and a yield strength of 280 MPa in T6 temper, and Si 0.4 %, Mg 0.6 %, Cr 0.15 %, B 0.001 % with an elongation of 11 % and a yield strength of 290 MPa in T6 temper.
On the high silicon edge, JP 2015/045 033 (Nissin Kogyo) discloses a die casting alloy with 4.5 % to 7.5 % silicon, 0.25 % to 0.75 % magnesium, and zinc up to 0.3 %.
On the low silicon edge, EP 2 700 727 (KSM Castings) describes an alloy composition with 3.0 % to 3.8 % of silicon, 0.3 % to 0.6 % magnesium, 0.25 % to 0.35 % of chromium; this alloy can be heat treated to a T6 temper. EP 2 954 081 (KSM Castings) discloses a casting alloy with silicon from 3.0 % to 3.8 %, magnesium from 0.3 % to 0.6 %, chromium 0.05 % to 0.25 %, and strontium between 0.010 % and 0.030 %.
These alloys can be used in particular in T6-like tempers, i.e. after solution heat treatment and age hardening to peak stength, where they usually exhibit mechanical properties which represent a certain compromise between mechanical strength and elongation at rupture, knowing that these two properties are usually following a conflicting path when optimizing the composition of the alloy or the heat treatment conditions of the cast piece : it is usually not difficult to increase one of the two properties while decreasing at the same time the other one. These alloys can in particular be used for making wheels, in particular for cars and trucks. Their resistance to atmospheric corrosion is usually good. For this specific use, there is however an additional requirement, namely corrosion resistance in contact with water and seawater. There is now a need for aluminium-based casting alloys that have higher mechanical strength and, at the same time, higher elongation, and that also have an excellent corrosion resistance. This is the problem addressed by the present invention.
Objects of the invention
According to the invention, the aluminium casting alloy comprises, expressed in weight percent : from 3.5 % to 4.5 % of silicon; from 0.35 % to 0.55 % of magnesium; from 0.05 % to 0.25 % of chromium; from 0.05 % to 0.30 % of nickel; from 0.005 % to 0.020 % of strontium; not more than 0.12 % of iron; not more than 0.15 % of titanium; not more than 0.05 %, and preferably not more than 0.03 %, of manganese; optionally comprising from 0.05 % to 0.20 % of copper; optionally comprising from 0.05 % to 0.30 % of silver; other impurities not more than 0.02 each and not more than 0.10 in total, the remainder being aluminium.
This alloy is the first object of the present invention.
A second object of the invention is an aluminium alloy casting made from this alloy, presenting the following set of properties : yield strength Rp0,2 is comprised between about 255 MPa and about 300 MPa, tensile strength Rm is comprised between about 340 MPa and about 370 MPa, and elongation at fracture is comprised between about 11.0 % and about 20.0 %.
A third object of the invention is a process for obtaining an aluminium casting according to the second objet of the invention, comprising solidifying a liquid aluminium casting alloy according to the first object, carrying out a solution heat treatment of 4 h to 10 h at a temperature comprised between 535 °C and 555 °C, and preferably of 4 h to 8 h between 540 °C and 550 °C, followed by quenching and artifial aging treatment of 4 h to 10 h at a temperature between 150 °C and 170 °C, and preferably of 6 h to 8 h at a temperature between 160 °C and 170 °C.
Description
Unless otherwise specified, all percentage values or ppm (parts per million) values relating to a chemical composition are given in weight percent or weight ppm, respectively. All temper designations are according to EN 1706 « Aluminium and aluminium alloys. Casting. Chemical composition and mechanical properties ». In particular, this standard defines T6 temper as « solution heat treated and fully artificially aged ». All mechanical properties refer to the definitions, test pieces and measurement conditions of ISO 6892-1 « Metallic materials - Tensile Testing - Part 1: Method of test at room temperature ».
According to the invention, the aluminium casting alloy comprises, expressed in weight percent : from 3.5 % to 4.5 % of silicon; from 0.35 % to 0.55 % of magnesium; from 0.05 % to 0.25 % of chromium; from 0.05 % to 0.30 % of nickel; from 0.005 % to 0.020 % of strontium; not more than 0.12 % of iron; not more than 0.15 % of titanium; not more than 0.05 %, and preferably not more than 0.03 %, of manganese; optionally comprising from 0.05 % to 0.20 % of copper; optionally comprising from 0.05 % to 0.30 % of silver; other impurities not more than 0.02 % each and not more than 0.10 % in total, the remainder being aluminium.
In preferred embodiments, which can be combined with each other, and with all the other variants end embodiments presented below: the silicon content is comprised between 3.7 % and 4.3 %, and still more preferably between 3.8 % and 4.3 %, and even more preferably between 3.85 % and 4.25 %; the strontium content does not exceed 0.015 %; the chromium content does not exceed 0.20 %, and still more preferably the chromium content is comprised between 0.06 % and 0.15 %; the nickel content is comprised between 0.08 % and 0.22 %, and preferably between 0.10 % and 0.20 %; the manganese content is comprised between 0.001% and 0.03 %; other impurities do not exceed 0.015 % each and 0.10 % in total (and preferably do not exceed 0.09 % in total).
Concerning magnesium, the inventors have tested an alloy with 0.60 % of magnesium, and did not achieve a satisfactory improvement of mechanical properties.
Nickel is an essential feature of the alloy according to the invention. The addition of nickel to the base alloy results in a fundamental change in the microstructure. The inventors have found that a nickel concentration as low as 0.05 wt-% modifies the phase profile and the distribution of other elements. In particular, in the as-cast alloy, excess magnesium is consumed by AI3Ni phases, and very few Mg2Si phases are formed, thereby enabling higher solution heat treatment temperatures. With Ni 0.15 % nearly all magnesium is dissolved in the matrix. To a significant extent, AI3Ni phases survive the heat treatments leading to T6 temper.
Concerning chromium, the optimum value is 0.10 %. Chromium combines with nickel to AICrNi(Fe) phases which are stable and present in T6 temper.
In a first variant, this allow further comprises from 0.05 % to 0.20 % of copper, and preferably between 0.07 % and 0.15 %.
In a second variant, this alloy further comprises from 0.05 % to 0.30 % of silver, and preferably between 0.05 % and 0.20 %.
In a third variant, this alloy further comprises from 0.05 % to 0.20 % of copper and from 0.05 % to 0.30 % of silver; it preferably comprises between 0.07 % and 0.15 % of copper and between 0.05 % and 0.20 % of silver.
These additions may lead to improved mechanical properties in T6 temper. They also tend to modify the flowability of the liquid metal, which may be an important parameter for casting certain types of parts involving molds of complex shape. More precisely, the addition of 0.1 % of silver has been found to lead to an increase of flow length, but flow length decreases above 0.3 % of silver. The alloy composition, in all of its variants and embodiments, can comprise controlled amounts of certain minor elements; these controlled amount can result from the voluntary addition of said minor elements, or from the control of their impurity level.
In such an advantageous embodiment, the calcium content is less than 200 ppm ; this increases the corrosion resistance of the castings in certain tempers.
In another andvantageous embodiment vanadium does not exceed 0.02 %, and/or gallium does not exceed 0.02 %.
In another preferred embodiment, which can be combined with each of the two foregoing advantageous embodiments, and preferably with both, the iron content is below 0.10 %; this low iron content leads to a higher elongation at rupture of the castings, which is desirable.
In another advantageous embodiment, a minor addition of manganese, the concentration of which must not exceed the specified maximum value, may be desirable. For this reason the preferentiel manganese range is between 0.001 % and 0.03 %, and preferably between 0.003 % and 0.03 %, and even more preferably between 0.005 % and 0.02 %. The inventors have found that this presence of a minute amout of manganese promotes the formation of Mn-Fe intermetallic phases which act as strain hardeners; this increases strenghth of the castings, but does not lead to a decrease in elongation at rupture.
In another advantageous embodiment, titanium is introduced into the alloy in the form of an AITi3 master alloy or another master alloy that does not contain boron, but not as TiB2.
The casting alloy according to the invention can be used for making cast parts, also called castings, using various casting processes, depending on the purpose. These casting techniques are known as such; in general the liquid metal is admitted into a die (possibly under pressure), where is solidifies. Advantageously, casting of remelting ingots can be carried out as open casting or direct chill casting. Casting of parts, such as wheels, suspension parts - subframes, cross members, knuckles can be carried out in particular by low pressure die casting, by gravity die casting or counter pressure die casting. Cast parts according to the invention can be heat treated in various ways. An advantageous heat treatment comprises a specific combination of solution heat treatment and artificial ageing. In this way, a T6 like temper can be obtained. This temper is a particularly interesting one for making parts that need to exhibit both high mechanical strength and high elongation; such parts are in particular wheels for cars and trucks.
An advantageous process for obtaining such a heat treated aluminium casting comprises a first step of solution heat treatment of about 4 h to about 10 h at a temperature comprised between about 535 °C and about 555 °C, and preferably of 4 h to 8 h between 540 °C and 550 °C. This solution heat treatment can be terminated by quenching.
In a second step, the casting is submitted to artificial ageing of about 4 h to about 10 h at a temperature between about 150 °C and about 170 °C, and preferably of 6 h to 9 h at a temperature between 160 °C and 170 °C.
The inventors have found that for the alloy composition according to the invention, the duration of the ageing treatment is a particularly critical parameter that determines the mechanical properties of the cast part. For this reason, the most preferred ageing conditions are betwen 6 h and 8 h at a temperature between 160 °C and 170 °C.
In this way, aluminium alloy castings in T6-like tempers with the following set of properties can be obtained: yield strength Rp0,2 is comprised between about 255 MPa and about 310 MPa, tensile strength Rm is comprised between about 340 MPa and about 370 MPa, and elongation at fracture is comprised between about 11 .0 % and about 20.0 %.
In an advantageous embodiment, yield strength Rp0,2 is comprised between about 255 MPa and about 285 MPa, tensile strength is Rm comprised between about 340 MPa and about 370 MPa, and elongation at fracture is comprised between about 14.0 % and about 20.0 %.
In another advantageous embodiment, yield strength Rp0,2 is comprised between 265 MPa and 280 MPa, tensile strength is Rm comprised between 350 MPa and 365 MPa, and elongation at fracture is comprised between 15.0 % and 18.0 %. In still more advantageous embodiment, which is particularly useful for wheels of cars and trucks, the solution heat treatment is carried out at a temperature comprised between 541 °C and 549 °C for a duration comprised between 5 h and 7 h, and/or the artificial ageing is carried out a temperature comprised between 157 °C and 163 °C for a duration between 6 h and 9 h.
The artifical ageing treatment can also be carried out in two or more steps at different temperatures; this will however render the industrial production more complex.
Examples
Examples 1 to 6:
A base alloy composition was prepared with the following target composition:
Si 4.0 %, Mg 0.50 %, Fe < 0.12 %, Ti 0.12 %, Sr 0.0080 %. The following amounts of elements were added: Cr 0.10 % and Ni 0.15 %.
The alloy was cast in a mould. After solidification the following heat treatment was applied: solution heat treatment of 6 hours at 545 °C followed by artifical ageing at varying conditions, as explained in Table 1 which summarizes the results.
[Table 1]
Figure imgf000009_0001
Examples 7 and 8:
The same base alloy as for examples 1 to 6 was used, but with the addition of the following amounts of elements: Cr 0.10 % and Ni 0.15 % and Cu 0.10 %.
The alloy was cast in a mould. After solidification the following heat treatment was applied : solution heat treatment of 6 hours at 545 °C followed by artifical ageing at varying conditions, as explained in Table 2 which summarizes the results. [Table 2 ]
Figure imgf000010_0001
Examples 9 and 10: Example 9 is the same chemical composition as examples 1 to 6.
Example 10 is the same chemical composition as examples 7 and 8.
Examples 9 and 10 have been submitted to the same solution heat treatment as in Examples 1 to 8, namely 6 h at 545 °C.
Examples 9 and 10 have then been submitted to a two-step ageing treatment, as follows: a first step of 1 h at 110 °C, and a second step of 2 h at 170°C.
Examples are summarized in Table 3.
[Table 3]
Figure imgf000011_0001
Example 11 :
A microstructural analysis of the as-cast alloy composition used for examples 1 to 6 was carried out, using conventional techniques of electron microscopy as known to a person skilled in the art. Chemcial composition of intermetallic phases is given in atomic percent (at-%).
Among as-cast phases are: Mg2Si, tt-AIFeSi (appearing usually as needles or branched), AI3Ni (appearing usually blocky, sometimes elongated), AICrNi(Fe) (appearing usually blocky). Iron seems to be mainly bound as tt-AIFeSi but is also dissolved in AICrNi(Fe). Very few Mg2Si phases were found, indicating that excess Mg is consumed by AI3Ni and in small amounts by AICrNi(Fe). Higher Mg values (up to 20 at-%) are found in tt-AIFeSi, but also Ni concentrations up to 2.5 at-%.
Chromium resides in tt-AIFeSi and AI3Ni phases (about 0.1 - 0.2 at-%) but shows a major function in AICrNi(Fe) phases.
AI3Ni phases had a blocky, sometimes acicular morphology, and a typical size between 1 pm to 5 pm (blocky); needles were rare and could be up to 10 pm. They were often found close to tt-AIFeSi phases, and between tt-AIFeSi and AICrNi(Fe) phases. The chemical composition of AI3Ni phases was as follows: Al 70 - 75 at-%; Ni 7.5 - 17.5 at-%; Si 2 - 19 at-%;
Mg 0.5 - 3 at-%; Fe 0.1 - 0.5 at-%; Cr 0.1 - 0.5 at-%.
AICrNi(Fe) phases had a blocky morphology, and a typical size between 1 pm to 5 pm (sometimes up to 7.5 pm). They were often found close to tt-AIFeSi and AI3Ni phases. The chemical composition of AICrNi(Fe) phases was as follows:
Al about 70 at-%; Ni 4 - 6 at-%; Si 10 - 15 at-%; Mg 0.5 - 1 .5 at-%; Fe 2 at-%; Cr 5 - 7.5 at-%.
Example 12:
A microstructural analysis of the alloy composition used for examples 1 to 6 was carried out in T6 temper, using conventional techniques of electron microscopy as known to a person skilled in the art. Chemcial composition of intermetallic phases is given in atomic percent (at-%).
Among as-cast phases are: tt-AIFeSi (appearing usually as fragments), AI2oNi2Fe (appearing usually as fragments, blocky or acicular), AI3Ni (appearing usually blocky, rounded), AICrNi(Fe) (appearing usually blocky).
Very few tt-AIFeSi were found.
AI3Ni phases had a small rounded or blocky morphology, and a typical size between 1 pm to 3 pm. Very few of these phases were found; upon heat treatment theses phases tend to fragment or to dissolve. The chemical composition of AI3Ni phases was as follows:
Al 75 - 80 at-%; Ni 15 - 25 at-%; Si 1 - 5 at-%;
Mg 0.5 - 1 at-%; Fe 0.1 - 0.5 at-%; Cr not detected.
AICrNi(Fe) phases had a blocky morphology, and a typical size between 1 pm to 5 pm (sometimes up to 7.5 pm). They were often found close to tt-AIFeSi and AI3Ni phases. Upon heat treatment AICrNi(Fe) phases showed hardly any change. The chemical composition of AICrNi(Fe) phases was as follows:
Al 75 - 80 at-%; Ni 4 - 6 at-%; Si 10 - 15 at-%; Mg 0.5 - 1 at-%; Fe 2 - 3 at-%; Cr 5 - 7.5 at-%. AI2oNi2Fe phases had a fragmented or acicular morphology, mostly comprised between 1 pm to 10 pm. The chemical composition of these phases was as follows:
Al 75 - 85 at-%; Si 1 - 10 at-%; Mg 0.5 - 1 at-%; Fe 1 - 3.5 at-%.

Claims

Claims
1 . Aluminium casting alloy, comprising, expressed in weight percent, from 3.5 % to 4.5 % of silicon; from 0.35 % to 0.55 % of magnesium; from 0.05 % to 0.25 % of chromium; from 0.05 % to 0.30 % of nickel; from 0.005 % to 0.020 %, and preferably from 0.005 % to 0.015 % of strontium; not more than 0.12 %, and preferably less than 0.10 % of iron; not more than 0.15 % of titanium; not more than 0.05 %, and preferably not more than 0.03 %, of manganese; optionally comprising from 0.05 % to 0.20 % of copper; optionally comprising from 0.05 % to 0.30 % of silver; other impurities not more than 0.02 % each and not more than 0.10 % in total, the remainder being aluminium.
2. Aluminium casting alloy according to claim 1 , wherein the silicon content is comprised between 3.7 % and 4.3 %, preferably between 3.8 % and 4.3 %, and more preferably between 3.85 % and 4.25 %.
3. Aluminium casting alloy according to claim 1 or 2, wherein the chromium content does not exceed 0.20 %, and preferably is comprised between 0.06 % and 0.15 %.
4. Aluminium casting alloy according to any of claims 1 to 3, wherein the nickel content is comprised between 0.08 % and 0.22 %, and preferably between 0.10 % and 0.20 %.
5. Aluminium casting alloy according to any of claims 1 to 4, wherein the manganese content is comprised between 0.001 % and 0.03 %, and preferably between 0.003 % and 0.03 %, and even more preferably between 0.005 % and 0.02 %.
6. Aluminium casting alloy according to any of claims 1 to 5, comprising from 0.05 % to 0.20 % of copper, and preferably from 0.07 % to 0.15 % of copper.
7. Aluminium casting alloy according to any of claims 1 to 6, comprising from 0.05 % to 0.30 % of silver, and preferably from 0.05 % to 0.20 % of silver.
8. Aluminium casting alloy according to any of claims 1 to 7, wherein the calcium content is less than 200 ppm.
9. Aluminium casting alloy according to any of claims 1 to 8, wherein vanadium does not exceed 0.02 %, and/or gallium does not exceed 0.02 %.
10. Aluminium alloy casting made from a casting alloy according to any of claims 1 to 9.
11. Aluminium alloy casting according to claim 10, having in the T6 temper a yield strength Rp0,2 comprised between 255 MPa and 310 MPa, a tensile strength Rm comprised between 340 MPa and 370 MPa, and an elongation at fracture comprised between 11 % and 20 %.
12. Aluminium alloy casting according to claim 11 , having in the T6 temper a yield strength Rp0,2 comprised between 265 MPa and 280 MPa, a tensile strength Rm comprised between 350 MPa and 365 MPa, and an elongation at fracture comprised between 15.0 % and 18.0 %.
13. Process for obtaining an aluminium casting according to claim 11 or 12, comprising solidifying a liquid aluminium casting alloy according to any of claims 1 to 9 in a mould, carrying out a solution heat treatment of 4 h to 10 h at a temperature comprised between 535 °C and 555 °C, and preferably of 4 h to 8 h between 540 °C and 550 °C, followed by quenching and artifial aging treatment of 4 h to 10 h at a temperature between 150 °C and 170 °C, and preferably of 6 h to 8 h at a temperature between 160 °C and 170 °C.
14. Process according to claim 13, wherein the solution heat treatment is carried out at a temperature comprised between 541 °C and 549 °C for a duration comprised between 5 h and 7 h, and/or the artificial ageing is carried out a temperature comprised between 157 °C and 163 °C for a duration between 6 h and 9 h.
15. Process according to claim 13 or 14, wherein titanium is introduced into said liquid aluminium casting alloy using an AITi3 master alloy or another master alloy that does not contain boron.
PCT/IB2022/055280 2021-06-07 2022-06-07 Aluminium-silicon casting alloy, and castings made from said alloy WO2022259136A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP22819725.7A EP4352273A1 (en) 2021-06-07 2022-06-07 Aluminium-silicon casting alloy, and castings made from said alloy

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP21178006.9 2021-06-07
EP21178006.9A EP4101941A1 (en) 2021-06-07 2021-06-07 Aluminium-silicon casting alloy, and castings made from said alloy

Publications (1)

Publication Number Publication Date
WO2022259136A1 true WO2022259136A1 (en) 2022-12-15

Family

ID=76305801

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2022/055280 WO2022259136A1 (en) 2021-06-07 2022-06-07 Aluminium-silicon casting alloy, and castings made from said alloy

Country Status (2)

Country Link
EP (2) EP4101941A1 (en)
WO (1) WO2022259136A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008055928A1 (en) * 2007-11-08 2009-08-27 Ksm Castings Gmbh Al-cast alloys
CN108085521A (en) * 2017-11-20 2018-05-29 湖州亨达铝业有限公司 A kind of preparation method of the Automobile Plate aluminium alloy of high ductibility

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010018875A (en) 2008-07-14 2010-01-28 Toyota Central R&D Labs Inc High strength aluminum alloy, method for producing high strength aluminum alloy casting, and method for producing high strength aluminum alloy member
JP5575028B2 (en) 2011-03-24 2014-08-20 株式会社豊田中央研究所 High strength aluminum alloy, high strength aluminum alloy casting manufacturing method and high strength aluminum alloy member manufacturing method
DE102013108127A1 (en) 2012-08-23 2014-02-27 Ksm Castings Group Gmbh Al-cast alloy
BR112015016608A2 (en) 2013-02-06 2017-07-11 Ksm Castings Group Gmbh al cast alloy
JP2015045033A (en) 2013-08-27 2015-03-12 日信工業株式会社 Aluminum alloy casting
EP3162460A1 (en) * 2015-11-02 2017-05-03 Mubea Performance Wheels GmbH Light metal casting part and method of its production
DE112017001083A5 (en) * 2016-03-01 2018-11-22 Ksm Castings Group Gmbh Al-cast alloy
US20190118251A1 (en) 2016-04-20 2019-04-25 GM Global Technology Operations LLC High strength aluminum alloys for low pressure die casting and gravity casting
CN106319299A (en) 2016-08-31 2017-01-11 中信戴卡股份有限公司 Novel aluminum alloy and preparing method thereof
US10612116B2 (en) 2016-11-08 2020-04-07 GM Global Technology Operations LLC Increasing strength of an aluminum alloy

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008055928A1 (en) * 2007-11-08 2009-08-27 Ksm Castings Gmbh Al-cast alloys
CN108085521A (en) * 2017-11-20 2018-05-29 湖州亨达铝业有限公司 A kind of preparation method of the Automobile Plate aluminium alloy of high ductibility

Also Published As

Publication number Publication date
EP4101941A1 (en) 2022-12-14
EP4352273A1 (en) 2024-04-17

Similar Documents

Publication Publication Date Title
AU2005269483B2 (en) An Al-Si-Mg-Zn-Cu alloy for aerospace and automotive castings
CA2510545C (en) Aluminium diecasting alloy
CN111032897A (en) Method of forming cast aluminum alloy
US4758286A (en) Heat treated and aged Al-base alloys containing lithium, magnesium and copper and process
US20100288401A1 (en) Aluminum casting alloy
US5855697A (en) Magnesium alloy having superior elevated-temperature properties and die castability
CN111187950B (en) 6-series aluminum alloy, preparation method thereof and mobile terminal
EP2369025B1 (en) Magnesium alloy and magnesium alloy casting
WO2006014948A2 (en) An al-si-mg-zn-cu alloy for aerospace and automotive castings
JP5703881B2 (en) High strength magnesium alloy and method for producing the same
KR20170138916A (en) Aluminum alloy for die casting, and die-cast aluminum alloy using same
EP1882754B1 (en) Aluminium alloy
WO2005106057A2 (en) Heat treatable al-zn-mg alloy for aerospace and automotive castings
JP2009506215A (en) Cast aluminum alloy
JP5525444B2 (en) Magnesium-based alloy and method for producing the same
JP4526768B2 (en) Magnesium alloy
JP2006028548A (en) Magnesium alloy to be plastic-worked and magnesium alloy member
WO2022259136A1 (en) Aluminium-silicon casting alloy, and castings made from said alloy
CA3135702C (en) Aluminium casting alloy
JPH0713275B2 (en) High-strength stress corrosion cracking resistant aluminum-based powder metallurgy alloy
CN115491558A (en) Die-casting magnesium alloy and preparation method and application thereof
CN110951983A (en) Method for refining 2618 aluminum alloy as-cast grain structure
JPH06172948A (en) Production of heat resistant magnesium alloy
JPH0819504B2 (en) Zinc alloy for casting, dimensional change-free, cast parts and heat treatment method for cast parts
CN115537620B (en) Die-casting magnesium alloy and preparation method and application thereof

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22819725

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: MX/A/2023/014538

Country of ref document: MX

Ref document number: P6003163/2023

Country of ref document: AE

WWE Wipo information: entry into national phase

Ref document number: 2022819725

Country of ref document: EP

NENP Non-entry into the national phase

Ref country code: DE

ENP Entry into the national phase

Ref document number: 2022819725

Country of ref document: EP

Effective date: 20240108