Low-cost high-heat-conduction die-casting magnesium alloy and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-10870905-B2
Application number	US-201615780161-A
Country	US
Kind code	B2
Filing date	Dec 6, 2016
Priority date	Dec 14, 2015
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

A die-casting magnesium alloy. The die-casting magnesium alloy comprises, by mass percent, 1% to 5% of La, 0.5% to 3% of Zn, 0.1% to 2% of Ca, 0.1% to 1% of Mn and the balance Mg and other inevitable impurities. The die-casting magnesium alloy manufacturing method comprises smelting, refinement and die-casting. The die-casting magnesium alloy has good mechanical performance, die-casting performance and heat conduction performance.

First claim

The invention claimed is:

1. A heat-conduction die-casting magnesium alloy consisting of by mass,
La: 1 to 5%;
Zn: 2.5 to 3%;
Ca: 0.1 to 2%;
Mn: 0.1 to 1%; and
the balance is Mg and other inevitable impurities;
wherein the magnesium alloy has a microstructure comprising α-magnesium matrix and precipitation phases, and wherein the α-magnesium matrix comprises fine grains and a small amount of relatively larger grains, and the relatively larger grains have a volume ratio of 20% or less; and
wherein the fine grains have a size of 3-15 μm and the relatively larger grains have a size of 40-100 μm.

2. The heat-conduction die-casting magnesium alloy of claim 1 , wherein the precipitation phases comprises a Mg—Zn—La—Ca quaternary phase that is continuously distributed around grain boundaries and a Mg—Zn phase precipitated inside the grains.

3. The heat-conduction die-casting magnesium alloy of claim 2 , wherein the Mg—Zn phase has a width of 1-20 nm and a length of 10-1000 nm.

4. The heat-conduction die-casting magnesium alloy of claim 1 , wherein the magnesium alloy has a thermal conductivity of 110 W/m·K or more, a tensile strength of 200-270 MPa, a yield strength of 150-190 MPa, and an elongation of 2-10%.

5. A manufacturing method for a heat-conduction die-casting magnesium alloy, comprising the following steps:
(1) melting pure Mg ingots and pure Zn ingots in a smelting furnace;
(2) adding Mg—Ca and Mg—Mn master alloys to the smelting furnace and melting them completely;
(3) adding Mg—La master alloy to the smelting furnace and melting it completely, and adding flux at the same time to cover the surface of a resulting melt;
(4) refining the melt;
(5) cooling the refined melt to 630-750° C.; and
(6) die-casting the melt to obtain a heat-conduction die-casting magnesium alloy consisting of by mass:
La: 1 to 5%;
Zn: 2.5 to 3%;
Ca: 0.1 to 2%;
Mn: 0.1 to 1%; and
the balance is Mg and other inevitable impurities;
wherein the magnesium alloy has a microstructure comprising α-magnesium matrix and precipitation phases, and wherein the α-magnesium matrix comprises fine grains and a small amount of relatively larger grains, and the relatively larger grains have a volume ratio of 20% or less; and
wherein the fine grains have a size of 3-15 μm and the relatively larger grains have a size of 40-100 μm.

6. The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5 , wherein in the step (1), temperature in the smelting furnace is controlled to 700-760° C., and the melting is performed under the protection of SF 6 gas.

7. The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5 , wherein in the step (2), temperature in the smelting furnace is controlled to 700-760° C., and the melting is performed under the protection of SF 6 gas.

8. The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5 , wherein in the step (3), temperature in the smelting furnace is controlled to 700-760° C., and the smelting is performed under the protection of SF 6 gas.

9. The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5 , wherein in the step (4), temperature in the smelting furnace is controlled to 730-780° C., and Ar gas is introduced into the melt or the melt is manually stirred, while flux is simultaneously added for refining for 5-15 minutes to obtain a refined melt; and then the refined melt is kept standing at 730-760° C. for 80-120 minutes.

10. The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5 , wherein in the step (6), the die-casting is controlled such that an injection speed is 2-50 m/s, a die temperature is 220-400° C., and a casting pressure is 10-90 MPa.

Assignees

• Baoshan Iron & Steel

Inventors

• Xu Shiwei
• Dai Jichun
• Tang Weineng
• Zhuo Changlong
• Jiang Haomin
• Zhang Pijun

Classifications

• C22C23/06 Primary

  with a rare earth metal as the next major constituent · CPC title

• C22C23/04

  with zinc or cadmium as the next major constituent · CPC title

• B22D27/003

  by using inert gases · CPC title

• C22C23/00 Primary

  Alloys based on magnesium · CPC title

• B22D17/00

  Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure · CPC title