US3627518A - Modification of si and mg2si second phase in al alloys - Google Patents
Modification of si and mg2si second phase in al alloys Download PDFInfo
- Publication number
- US3627518A US3627518A US861459A US3627518DA US3627518A US 3627518 A US3627518 A US 3627518A US 861459 A US861459 A US 861459A US 3627518D A US3627518D A US 3627518DA US 3627518 A US3627518 A US 3627518A
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- alloys
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- 229910000838 Al alloy Inorganic materials 0.000 title abstract description 15
- 230000004048 modification Effects 0.000 title description 9
- 238000012986 modification Methods 0.000 title description 9
- 238000000034 method Methods 0.000 abstract description 7
- 229910045601 alloy Inorganic materials 0.000 description 13
- 239000000956 alloy Substances 0.000 description 13
- 239000000654 additive Substances 0.000 description 11
- 239000000155 melt Substances 0.000 description 10
- 239000002245 particle Substances 0.000 description 10
- 238000007792 addition Methods 0.000 description 9
- 238000005266 casting Methods 0.000 description 8
- 229910021364 Al-Si alloy Inorganic materials 0.000 description 6
- 239000011777 magnesium Substances 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910018125 Al-Si Inorganic materials 0.000 description 2
- 229910018520 Al—Si Inorganic materials 0.000 description 2
- 229910000676 Si alloy Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 230000005496 eutectics Effects 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 239000011856 silicon-based particle Substances 0.000 description 2
- 229910021365 Al-Mg-Si alloy Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- NRUQNUIWEUZVLI-UHFFFAOYSA-O diethanolammonium nitrate Chemical compound [O-][N+]([O-])=O.OCC[NH2+]CCO NRUQNUIWEUZVLI-UHFFFAOYSA-O 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910021338 magnesium silicide Inorganic materials 0.000 description 1
- YTHCQFKNFVSQBC-UHFFFAOYSA-N magnesium silicide Chemical compound [Mg]=[Si]=[Mg] YTHCQFKNFVSQBC-UHFFFAOYSA-N 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000003947 neutron activation analysis Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000010120 permanent mold casting Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000007528 sand casting Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- 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
- C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
- C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
-
- 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
Definitions
- Al alloys containing Si and/or Mg Si which are sand or permanent mold cast, have a microstructure of an Al matrix with needle or plate-like, interconnected second phase particles of Si or Mg Si.
- This dendritic type second phase structure is detrimental to castability and alloy performance.
- Such change can in the case of Al-Si alloys be accomplished by the addition of another element to a melt of the alloy.
- hypoeutectic Al-Si alloys (those alloys with higher Al than the Al-Si eutectic composition) are refined by the addition of small amounts of Na.
- P is commonly used with hypereutectic Al-Si alloys (those alloys with higher Si than the Al-Si eutectic composition).
- an object of the present invention is to provide a method of changing the morphology of Si and Mg Si second phase particles in Al alloys.
- the method of the present invention comprises adding Li and As to an Al alloy melt containing Si and optionally Mg and solidifying the resultant melt, e.g. sand or permanent mold casting.
- the Li-As addition affects the nucleation and growth of the Si and/or Mg Si second phase particles on solidification to produce near-spherical, non-connecting second phase particles. Such change in morphology produces increased fluidity of the alloy during casting and improved mechanical properties of the alloy casting.
- the amount of Li and As added is within the range of from about 0.01 to 2 weight percent each, based on the total weight of alloy melt plus additives. Preferably each should be added in an amount from about 0.1 wt. percent to 1.0 wt. percent.
- the Al alloys upon which the Li-As addition is effective include any Al alloy containing substantial proportions of Si and/or Mg Si, for example, Al alloys containing from about 2 to 40 wt. percent Si and/ or Mg Si. Other elements, such as Zn, which do not affect the structure of the second phase can also be present in the alloys.
- the microstructure of each of the castings was observed.
- the second phase particles of Mg Si and/ or Si in the castings without additives were needle or plate-like in structure and often interconnected.
- the second phase particles in the castings containing Li and As were chunky, nearspherical, non-connected in structure.
- the addition of Li and As had changed the morphology of second phase particles in a hypoeutectic and hypereutectic Al-Si alloy and Al-MggSi alloy. That this transformation is beneficial is shown in the next example.
- Example 5 An Al-33% Si melt was prepared and cast in a manner similar to those of Examples 14. To a portion of the melt was added 0.25 Li and 1.0% As prior to casting. The tensile strength of each casting was measured.
- the alloy had a tensile strength (TS) of 3 ksi without additives but with the Li and As the TS increased to 15 ksi. This increase is attributed to the change in morphology of the Si second phase particles caused by the addition of Li plus As.
- Examples 6-17 A series of Al-7% Si alloy melts were prepared. Varying amounts of Li and As were added and the resultant melts cast after holding the melts at temperature (1350 F.) for varying periods of time. The amounts of Li and As retained were analyzed and the microstructures observed to determine the relative amount of second phase modification. These microstructures were compared against the unmodified microstructure of a sample of AI-7% Si containing no additives and microstructure of a sample modified with Na, a conventional additive. The latter microstructure was considered good in that almost all the Si second phase was in the near-spheroidal form. Those samples with As and Li additives with comparable microstructures were rated accordingly. Samples with lesser but still significant degrees of modification were rated some or little modification in comparison to the Na additive sample. The results are tabulated in Table I.
- An alloy having near-spherical, non-connecting Si or Mg Si second phase particles consisting essentially of from about 0.01 to 2 wt. percent Li, from about 0.01 to 2 wt. percent As, Si and optionally Mg Si in a total amount of from about 2 to Wt. percent, and balance aluminum.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Continuous Casting (AREA)
Abstract
A METHOD OF CHANGING THE MORPHOLOGY OF SI AND MG-SI SECOND PHASE IN AL ALLOYS BY ADDING LI AND AS TO THE AL ALLOY MELT.
Description
United States Patent 3,627,518 MODIFICATION OF Si and Mg Si SECOND PHASE IN Al ALLOYS Garth D. Lawrence and George S. Foerster, Midland,
Mich., assignors to the Dow Chemical Company, Midland, Mich. No Drawing. Filed Sept. 26, 1969, Ser. No. 861,459 Int. Cl. C22c 21/00, 21/04 US. Cl. 75l47 4 Claims ABSTRACT OF THE DISCLOSURE A method of changing the morphology of Si and Mg Si second phase in Al alloys by adding Li and As to the Al alloy melt.
BACKGROUND OF THE INVENTION Al alloys containing Si and/or Mg Si (magnesium silicide) which are sand or permanent mold cast, have a microstructure of an Al matrix with needle or plate-like, interconnected second phase particles of Si or Mg Si. This dendritic type second phase structure is detrimental to castability and alloy performance. Thus it is desirable to be able to change or refine the physical structure (morphology) of the Si and Mg- Si particles.
Such change can in the case of Al-Si alloys be accomplished by the addition of another element to a melt of the alloy. For example, hypoeutectic Al-Si alloys (those alloys with higher Al than the Al-Si eutectic composition) are refined by the addition of small amounts of Na. P is commonly used with hypereutectic Al-Si alloys (those alloys with higher Si than the Al-Si eutectic composition). These additives produce a microstructure having nearspherical, non-connected Si particles.
To the best of our knowledge there is no known additive for changing the morphology of Mg Si second phase in Al alloys.
Therefore, an object of the present invention is to provide a method of changing the morphology of Si and Mg Si second phase particles in Al alloys.
THE INVENTION The method of the present invention comprises adding Li and As to an Al alloy melt containing Si and optionally Mg and solidifying the resultant melt, e.g. sand or permanent mold casting. The Li-As addition affects the nucleation and growth of the Si and/or Mg Si second phase particles on solidification to produce near-spherical, non-connecting second phase particles. Such change in morphology produces increased fluidity of the alloy during casting and improved mechanical properties of the alloy casting.
The amount of Li and As added is within the range of from about 0.01 to 2 weight percent each, based on the total weight of alloy melt plus additives. Preferably each should be added in an amount from about 0.1 wt. percent to 1.0 wt. percent.
The Al alloys upon which the Li-As addition is effective include any Al alloy containing substantial proportions of Si and/or Mg Si, for example, Al alloys containing from about 2 to 40 wt. percent Si and/ or Mg Si. Other elements, such as Zn, which do not affect the structure of the second phase can also be present in the alloys.
3,627,518 Patented Dec. 14, 1971 "ice In the practice of the present invention an Al alloy melt containing Si and optionally Mg is prepared. The Li and As are added in elemental form, or by way of master alloys or other appropriate means, and admixed with the melt. The melt is then cast or otherwise solidified in conventional manner.
The following examples are representative of the present invention. The percentages stated herein are weight percent based on the total weight of the composition unless otherwise indicated.
Examples 14 The following four Al alloys melts were prepared:
(1) Al-6.I% Mg.-3.5% Si (hypoeutectic AI-Mg Si alloy) (2) Al-12% Mg-7% Si(hypereutectic Al-Mg Si alloy) (3) A1-33% Si (hypereutectic Al-Si alloy) (4) Al-8% Si (hypoeutectic Al-Si alloy) A portion of each melt was cast in cylindrical graphite molds-2 /2 inches inside diameter, 2 /2 inches deep. The castings were cooled at a rate of about 2 F./min. to produce a slow cooled microstructure.
Additions of 1% As and 0.25% Li were admixed with each of the remaining alloy portions. These portions were then similarly cast as described above.
The microstructure of each of the castings was observed. The second phase particles of Mg Si and/ or Si in the castings without additives were needle or plate-like in structure and often interconnected. The second phase particles in the castings containing Li and As were chunky, nearspherical, non-connected in structure. The addition of Li and As had changed the morphology of second phase particles in a hypoeutectic and hypereutectic Al-Si alloy and Al-MggSi alloy. That this transformation is beneficial is shown in the next example.
Example 5 An Al-33% Si melt was prepared and cast in a manner similar to those of Examples 14. To a portion of the melt was added 0.25 Li and 1.0% As prior to casting. The tensile strength of each casting was measured.
The alloy had a tensile strength (TS) of 3 ksi without additives but with the Li and As the TS increased to 15 ksi. This increase is attributed to the change in morphology of the Si second phase particles caused by the addition of Li plus As.
Examples 6-17 A series of Al-7% Si alloy melts were prepared. Varying amounts of Li and As were added and the resultant melts cast after holding the melts at temperature (1350 F.) for varying periods of time. The amounts of Li and As retained were analyzed and the microstructures observed to determine the relative amount of second phase modification. These microstructures were compared against the unmodified microstructure of a sample of AI-7% Si containing no additives and microstructure of a sample modified with Na, a conventional additive. The latter microstructure was considered good in that almost all the Si second phase was in the near-spheroidal form. Those samples with As and Li additives with comparable microstructures were rated accordingly. Samples with lesser but still significant degrees of modification were rated some or little modification in comparison to the Na additive sample. The results are tabulated in Table I.
TABLE I Holding Percent Percent tim e, Example As 1 L1 2 As/Ll hrs. Modification 0. 033 0. 02 1. 7 0. 1 Little. 0. 036 0.05 0. 73 0. 5 Good. 0. 033 0. 09 0. 3B 1. 5 D0. 0. 037 0. 08 0. 47 2. 5 Do. 0.012 0. 02 0. 62 3 3. 1 D 0. 018 0. l2 0. 15 0. 6 Do. 0. 031 0. 08 0. 38 1. 0 Some. 0. 104 0. 02 5. 2 2. 0 Little. 0. 118 0. 02 5. 9 2. Do. 0. 082 0. 22 0. 38 3. 0 Good. 0. 030 0. 50 0. 06 3 3. 3 0.011 O. 60 0. 02 3. 6
1 Determined by neutron activation analysis.
2 Determined by speetrographic analysis.
3 C12 fluxing of melt {or 20 minutes.
4 Good but had formation of Li-Si second phase.
Although in each case of Li-As addition modification occurred, the additives were most effective when added within a As/Li ratio range of 1:1 to 1:10. Ratios greater than 1:1 produce lesser amounts of modification (Examples 6, 13, 14). Ratios less than 1:10 produce good modification but also form a Li-Si second phase, which could be detrimental in other regards (Examples 16 and 17). It is also significant that the beneficial effect of Li-As addition was maintained even after holding the melt at temperature for 2 to 3 hours and/or C1 fiuxing of the melt.
What is claimed is:
1. A method which comprises:
(a) adding Li and As to an Al alloy melt containing Si and optionally Mg, the Li and As each in an amount within the range of from about 0. 01 to 2 weight percent based on total weight of melt plus additives; and
(b) solidifying said melt to produce near-spherical, non-connecting Si or Mg Si second phase particles.
2. The method of claim 1 wherein Li and As are added each in an amount within the range of from about 0.1 to 1 weight percent.
3. The method of claim 1 wherein Li and As are added Within the As to Li weight ratios of 1:1 and 1: 10.
4. An alloy having near-spherical, non-connecting Si or Mg Si second phase particles consisting essentially of from about 0.01 to 2 wt. percent Li, from about 0.01 to 2 wt. percent As, Si and optionally Mg Si in a total amount of from about 2 to Wt. percent, and balance aluminum.
References Cited FOREIGN PATENTS 616,413 1/1949 Great Britain -147 RICHARD O. DEAN, Primary Examiner US. Cl. X.R.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86145969A | 1969-09-26 | 1969-09-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3627518A true US3627518A (en) | 1971-12-14 |
Family
ID=25335854
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US861459A Expired - Lifetime US3627518A (en) | 1969-09-26 | 1969-09-26 | Modification of si and mg2si second phase in al alloys |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3627518A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5178686A (en) * | 1988-12-20 | 1993-01-12 | Metallgesellschaft Aktiengesellschaft | Lightweight cast material |
| US20150321293A9 (en) * | 2012-05-07 | 2015-11-12 | Uacj Corporation | Aluminum alloy brazing sheet |
| CN110093524A (en) * | 2019-05-08 | 2019-08-06 | 上海交通大学 | A kind of silumin alterant and its application method |
-
1969
- 1969-09-26 US US861459A patent/US3627518A/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5178686A (en) * | 1988-12-20 | 1993-01-12 | Metallgesellschaft Aktiengesellschaft | Lightweight cast material |
| US20150321293A9 (en) * | 2012-05-07 | 2015-11-12 | Uacj Corporation | Aluminum alloy brazing sheet |
| US9914185B2 (en) * | 2012-05-07 | 2018-03-13 | Uacj Corporation | Aluminum alloy brazing sheet |
| CN110093524A (en) * | 2019-05-08 | 2019-08-06 | 上海交通大学 | A kind of silumin alterant and its application method |
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