JPH10324938A - Zinc-copper-aluminum alloy and its die casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy increased in tensile strength and compressive strength. SOLUTION: It is found that the tensile strength and compressive strength of a zinc alloy can be increased by adding titanium to a zinc-base ally containing ε-phase as primary phase. This alloy is used for gravity casting, permanent mold casting, or die casting and can be cast into component parts or tools. In a preferred embodiment, 0.01-0.1 wt.% of titanium is added to a zinc-base alloy consisting of, by weight, 3-12% copper, 2-5% aluminum, trace components, and the balance zinc. This alloy shows an unexpected behavior so far unreported.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a zinc-based alloy.

[0002]

BACKGROUND OF THE INVENTION Zinc alloys have been used in various applications over the past several decades. Alloys such as Zamak 3 and Zamak 5 were developed in the 1920s to meet the requirements of the net shape die casting process.
Subsequently, two other alloys were developed, Zamak 2, which is also used in die casting, and Kirksite, which is used in gravity casting to produce prototype tools,
Widely used for that purpose. These alloys contain about 4 weight percent aluminum (Zamak 3) containing traces of copper, about 1 weight percent copper (Zamak 5),
And about 3 weight percent copper (Zamak 2 and Kirksite). Solidification of these alloys begins with the formation of primary η phase dendrites, which are in turn surrounded by (η + α) eutectics. The η phase has a hexagonal close-packed (HCP) crystal structure, while alpha (α) is a face-centered cube (FC
C).

The next significant development of zinc alloys is ZA-5,
A group of Zn-Al alloys called ZA-8, ZA-12 and ZA-27 was made about 25 years before the development. The numbers 5, 8, 12, and 27 represent the nominal weight percent of aluminum. Solidification of these alloys begins with the formation of primary α-phase dendrites, which are then surrounded by the (η + α) eutectic. In all of the above alloys, aluminum is considered to be the primary strengthening agent. The above-described alloys can be cast or manufactured in various casting methods with tight dimensional tolerances and relatively low cost. Typical casting methods are a gravity casting method and a die casting method. The molten zinc alloy is poured into a cavity having a constant volume without pressurizing (gravity casting method) or under a pressurized state (die casting method).

[0004] Commercially available zinc alloys for die casting (Zamak and Zn-Al (ZA) alloys) are used for decorative or non-structural applications due to their low strength and / or creep properties. To meet higher requirements,
Use a stronger material such as steel. Steel parts are usually machined, while zinc alloys can be die cast into certain shapes. Kirk Site (4
Other zinc alloys (weight percent Al, 3 weight percent Cu, residual zinc) are routinely used for prototype tools for stamping sheet metal. However, Kirksite tools are relatively soft and are generally not suitable for mass production.

A recently developed zinc-based alloy known as ACuZinc® (2-4 weight percent Al, 4-11 weight percent Cu, residual zinc) is disclosed in US Pat. As disclosed in 990,310, it can be used as a creep resistant zinc alloy. These alloys include (η + α + ε) ternary eutectic and ε dendrites surrounded by some η phase. The volume fraction and size of the ε-phase dendrites increase with the copper content. Such alloys have been found to be stronger and more durable than existing commercial alloys. Recently, the strength of such alloys has increased with increasing strain rate,
It has also been found that such strength is greater at higher temperatures.

[0006]

SUMMARY OF THE INVENTION The present invention further improves the above-mentioned ACuZinc (registered trademark) alloy.

According to the present invention, epsilon (ε) is used as a primary phase.
Including the discovery that the addition of titanium to a zinc-based alloy containing, increases the tensile and compressive strength of the alloy. The alloy can be used in gravity casting, permanent mold or die casting to cast parts or tools. In a preferred embodiment, about 0.01-0.1 weight percent titanium is replaced with about 3-12 weight percent copper, about 2
-5 weight percent aluminum, minor components, and
It is added to a zinc-based alloy containing a residual amount of zinc. The observed behavior was unexpected and not previously reported. The cause of such behavior is unknown.

[0008] The above additions have improved the toughness of the zinc-based alloy. Novel Al-Zn-Ti phase (Al ₅ Ti ₁₀ Zn ₃₎ is formed. This Al—Zn—Ti phase acts as a nucleus for forming a large number of fine ε phases (Zn ₄ Cu),
It had a large surface area as compared with a Zn-Cu-Al alloy containing no titanium. The size of the number of hard ε-phases and the surface area improved the toughness of the alloy.

As a result of the increase in compressive strength and toughness due to the addition of titanium, the zinc alloys described above can be used reliably in automotive or non-automotive parts or tools where such behavior is beneficial. it can. The alloys of the present invention are used in shaped casting dies to form sheet metal, various forming and impact tools, components subjected to compressive forces, and other components that must withstand high forces. be able to. The alloy component of the present invention can be manufactured into a shape or a near-net shape by a die casting method or a gravity casting method.

The above and other objects, features and advantages of the present invention are described in the following description of the embodiments of the invention, descriptions of the brief description of drawings, descriptions of the claims in the introduction, and
It will be clear from the drawings.

[0011]

DETAILED DESCRIPTION OF THE INVENTION A zinc alloy suitable for practicing the present invention comprises titanium in an amount between 0.01 and 0.1 weight percent, and about 3 and 12 weight percent titanium. Copper in an amount between about 2 and 5 weight percent aluminum, magnesium in an amount between 0 and 0.05 weight percent, iron and other typical impurities And a residual amount of material that is substantially zinc. The preferred copper content for hot chamber die casting is a value between about 5 and 7 weight percent. 4
Alloys containing less than about weight percent copper cannot form a significant ε-phase, while if more than about 8 weight percent copper, the melting point will be high and the typical hot chamber die casting process will be difficult. Can not be implemented. In contrast, the preferred copper content range for cold chamber alloys is between about 9 and 11 weight percent. If the copper content is higher than about 12 weight percent, another phase is formed that inhibits the desired (ε-η) eutectic microstructure.

The preferred range of aluminum content of the alloy in practicing the present invention is between about 2 and 5 weight percent. The aluminum content is desirably at least about 2 weight percent to obtain sufficient flowability convenient for handling at typical die casting temperatures. Alloys containing more than about 4 weight percent aluminum will form an undesirable alpha phase.

It is desirable that a small amount of magnesium be present to improve dimensional accuracy and reduce stress corrosion cracking. A preferred range of magnesium content is
It is between about 0.025 weight percent and 0.05 weight percent.

Hereinafter, examples of the alloy of the present invention and the results thereof will be described. The main metal selected for this example was an industrial purity zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium. The alloy was melted in a coreless induction furnace and cast into a tension sand mold for tension. An appropriate amount of Al, 5 weight percent titanium and 1 weight percent boron are added to the molten metal as a master alloy at 650 ° C (ie, about 100 ° C above the temperature of the liquid) for 30 minutes. It was held and cast into molds for tensile and compression specimens.

Tensile test piece (gauge length 50.8 mm,
Diameter 12.9 mm) and compression test piece (gauge length 5
0 mm, diameter 18 mm) was applied to an Instron Universal equipped with a box furnace.
sal) Tested on a testing machine. The tensile test was performed on the as-cast test pieces at room temperature. Compression tests were performed on both as-cast specimens and specimens that had been aged in a constant temperature oil bath at 100 ° C. or 200 ° C. for 10 days. These compression tests were performed at room temperature, 93 ° C (20 ° C).
0 ° F), 150 ° C (300 ° F) and 177 ° C
(350 ° F.). The temperature of the specimen was continuously monitored by a thermocouple attached to the surface of the specimen. Specimens were compressed at a crosshead speed of 2.5 mm / min. During the test, the load-elongation data was recorded automatically. From these data, the proportional limit (ie, the stress at which measurable plastic flow occurs) and the yield stress values of 0.5 percent and 1 percent were determined.

When titanium was added to a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium, an improvement in tensile properties was observed. The maximum tensile strength (UTS) without adding titanium was 301 MPa. The range of UTS when 0.01% to 0.1% of titanium is added is 342 MPa and 353 MPa.
MPa, and the rate of increase was 13-17 percent (FIG. 1). The yield strength changed only slightly. Most of the increase occurs at 0.01 percent titanium. Contrary to conventional recognition, UT
The toughness increased with increasing S. The plastic strain ranges from 0.22% when titanium is not added to about 0.5% when titanium is added at 0.01 to 0.1%.
The percentage (FIG. 2).

The proportional limit is a measure of the onset of deformation and gives a measure of the strength of the material. The proportional limit during compression as a function of titanium concentration is plotted in FIGS. At room temperature, for both types (as-cast and aged) specimens, the proportional limit was increased by almost 20 MPa at up to 0.015 percent titanium loading. This tendency was reversed with increasing titanium additions, tending to reduce the proportional limit. This reduction was more pronounced in as-cast materials than in materials aged at higher temperatures. FIG. 4 shows the tendency of the test pieces aged at 100 ° C. for 10 days, and FIG.
4 shows the tendency of a specimen aged at 00 ° C. for 10 days.

In hot compaction at 93 ° C., 150 ° C. and 177 ° C., the effect of titanium was different from that at room temperature. When 0.015 weight percent of titanium was added, the proportional limit of the zinc alloy could be 20-, depending on the history of the specimen (temperature and time of aging treatment).
It decreased by 25 MPa. Increasing the titanium concentration for both types of test specimens resulted in 0.015
The above tendency of the decrease in strength when weight percent was added was reversed, and the strength was almost the same as the strength without the addition of titanium.

The as-cast microstructure of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium (FIG. 6) shows a large ε (Zn ₄ Cu) primary Phase (white dendrite) and a small amount of η as a product of the binary peritectic reaction
Phase and (η + α + ε) ternary eutectics, which precipitate in the final solidification stage at 378 ° C.
By adding titanium, remarkable grain refinement was observed in the microstructure. When titanium was added, as shown in FIG. 6, the primary crystal of the ε phase (white), which is a hard phase of the alloy, became finer and became “non-dendritic, that is, non-dendritic”. FIG. 7 shows a state in which the ε phase appears at the center of the intermetallic compound. The intermetallic compound was confirmed by energy dispersive X-ray analysis,
It is based on ₅ Ti ₁₀ Zn ₃ and probably formed from Al ₃ Ti which has acted as a nucleus for heterogeneous crystallization.

The above results are believed to be the first reports on a new phase. The presence of a small grain size is not the only cause for improving properties. The evidence also points to peritectic reactions as another cause for improving and increasing strength. The first nucleated ε phase reacts with the liquid and is covered with a solid η phase (gray).
The large volume fraction of the η phase is observed in the atomized alloy because the surface area of the larger volume fraction of the ε phase is available to cause peritectic transformation. Although there is grounds for grain refinement of the ε phase, the details of the actual mechanism for increasing the strength are not clear.

The effect of titanium addition on the mechanical properties at room temperature of an as-cast alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium is 0.015 weight percent. Reaches its maximum value in the amount of added titanium,
The TS was 350 MPa and the proportional limit on compression was 255 MPa. Aged alloys containing titanium appear to behave similarly. This behavior is due to the fact that all zinc alloys (ACuZinc® 5 and ACuZi, including the ε phase as the primary phase and produced by gravity casting, permanent mold or die casting)
nc®10) was expected to have a similar effect. Combining this recognition with the knowledge that materials containing up to 0.1 weight percent titanium have a higher dimensional stability during aging at different temperatures than alloys with no added titanium, alloys containing titanium are: It can be said that it is preferable to use in a fixed casting mold used at room temperature.

The die cast of the present invention was formed from a zinc-based copper / aluminum / titanium alloy using a conventional cold chamber die casting machine, shown schematically in FIG. The machine 10 includes a movable platen 11 and a fixed platen 1
3 can be provided. Mold halves 12,14 are mounted on platens 11,13, respectively, and are cooled by water circulated through passages (not shown). In the illustrated closed position, the mold halves 12, 14 cooperate to define a volume of mold cavity 16. The mold cavity 16 has the appropriate dimensions and shape to produce the desired form of the casting. At the appropriate time during the casting cycle, the platen 11 moves relative to the platen 13 so that the mold halves 1
2, 14 are separated so that the product casting can be discharged. Machine 10 further includes a shot device 20 that includes a generally cylindrical shot sleeve 22 that communicates with cavity 16. The sleeve 22 has, for example, an inlet 24 that allows the injection of a charge 26 of molten metal from a suitable ladle 28. A hydraulically driven shot plunger 30 is slidably received within sleeve 22 and advances toward the mold section to remove metal from sleeve 22.
From inside into the cavity 16.

The zinc die casting of the present invention was also manufactured using a hot chamber die casting machine 50 shown schematically in FIG. The machine 50 includes water-cooled mold halves 52, 54 attached to a stationary platen 53 and a movable platen 55, respectively. The movable platen 55 moves the mold half between a closed position and an open position shown in FIG. In the closed position, the mold halves cooperate to form a casting cavity 56, and in the open position, the mold halves are separated along a plane indicated by a dashed line 58, The product, a casting, can be discharged. In accordance with conventional hot chamber die casting, the die casting machine 50 includes a shot apparatus 60 having a gooseneck sleeve 62 partially immersed in a molten metal bath 64 held in a crucible 63.
It has. The shot device 60 further includes a hydraulically operated plunger 68 slidably housed in the gooseneck 62. When the plunger 68 is in the retracted position shown in FIG. 9, a charge of molten metal from the bath 64 passes through the inlet port 66 and the gooseneck 62.
Fill. To perform the casting operation, the plunger 68 is driven downward to force the molten metal through the sleeve 62 and into the mold cavity 56.

[Brief description of the drawings]

1 shows the maximum tensile strength (UTS) at room temperature and 0.2% yield strength (0.2%) of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium. %
5 is a graph showing the effect of adding titanium to YS).

FIG. 2 is a graph showing the effect of titanium addition on the tensile elongation at room temperature of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium.

FIG. 3 is a graph showing the effect of titanium concentration on the proportional limit of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium for an as-cast case. .

FIG. 4 shows the effect of titanium concentration on the proportional limit of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium by aging at 100 ° C. for 10 days. 7 is a graph showing a case where the above is performed.

FIG. 5 shows the effect of titanium concentration on the proportional limit of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium at 200 ° C. for 10 days. 7 is a graph showing a case where the above is performed.

FIG. 6 shows the effect of titanium concentration on the microstructure of a zinc alloy containing 10.4 weight percent copper, 4.1 weight percent aluminum and 0.05 weight percent magnesium, with (a) the absence of titanium added. As-cast microstructure (large ε (Zn ₄ Cu) primary phase (white dendrite), small amount of η as product of binary peritectic reaction
Phase and (η + α + ε) ternary eutectic)
(B) As-cast microstructure when 0.015% by weight of titanium is added (showing remarkable grain refinement of ε (Zn ₄ Cu) primary phase which is a hard phase in the alloy)
3 is a photomicrograph showing a comparison of the two.

7 is a graph of the energy dispersive X-ray analysis of particles based on Al ₅ Ti _{1 0} Zn ₃ in the zinc alloy of the present invention containing 0.015% by weight of titanium, 0.015 with ε-phase FIG. 7 shows an enlarged view of the micrograph of FIG. 6 for a weight percent titanium alloy (identified as Al ₅ Ti ₁₀ Zn ₃ as shown).

FIG. 8 is a sectional view of a cold chamber die casting machine for casting a zinc / aluminum / copper / titanium alloy of the present invention.

FIG. 9 is a sectional view of a hot chamber die casting machine for casting a zinc / aluminum / copper / titanium alloy of the present invention.

[Explanation of symbols]

 10, 50 Die casting machine 11, 55 Fixed platen 13, 53 Movable platen 12, 14, 52, 54 Mold half 16, 56 Mold cavity

 ──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Moinudin Sadhar Rashid 48302, Michigan, USA, Bloomfield Hills, Palmetto Court 1776

Claims (13)

[Claims] 1. A method according to claim 1, wherein the composition comprises about 0.01 to about 0.1 weight percent titanium, about 3 to about 12 weight percent copper, about 2 to about 5 weight percent aluminum, and about 81 to about 95 weight percent. An alloy containing zinc. 2. The alloy according to claim 1, comprising an ε primary phase, an η phase, and a (η + α + ε) ternary eutectic. 3. The alloy of claim 1, wherein the alloy comprises 4 to 7 weight percent copper and is cast by hot chamber die casting. 4. The alloy of claim 1, wherein the alloy comprises 7 to 11 weight percent copper and is cast by cold chamber die casting. 5. The alloy according to claim 1, wherein the alloy has a thickness of about 0.5 μm.
An alloy comprising from 0.01 to 0.015 weight percent titanium. 6. The alloy according to claim 1, further comprising a minor component. 7. An alloy comprising particles of Al ₅ Ti ₁₀ Zn ₃ . 8. The composition of claim 1, wherein the composition comprises about 0.01 to about 0.1 weight percent titanium, about 3 to about 12 weight percent copper, about 2 to about 5 weight percent aluminum, and about 81 to about 95 weight percent. Die casting characterized by containing zinc. 9. The die casting according to claim 8, wherein
A die casting comprising an ε primary phase, an η phase, and a (η + α + ε) ternary eutectic. 10. A zinc / copper / aluminum based alloy comprising a titanium / copper / aluminum based alloy, wherein the zinc / copper / aluminum based alloy comprises titanium in an amount sufficient to enhance the tensile strength of the alloy. 11. The zinc / copper / aluminum based alloy of claim 10, wherein about 3 to 12 weight percent copper; about 2 to about 5 weight percent aluminum;
A zinc / copper / aluminum alloy comprising about 81-95 weight percent zinc. 12. A zinc / copper / aluminum based alloy comprising a titanium / copper / aluminum alloy comprising titanium in an amount sufficient to increase the surface area of the ε-phase as compared to an alloy containing no titanium. Aluminum alloy. 13. The zinc / copper / aluminum based alloy of claim 12, wherein about 3 to 12 weight percent copper, about 2 to about 5 weight percent aluminum,
A zinc / copper / aluminum alloy comprising about 81-95 weight percent zinc.