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Mg-Al series alloy composite grain refiner and method for making same

A compound crystal and refiner technology, applied in the field of metal materials, can solve the problems of affecting grain growth kinetics, slow Ca atom diffusion speed, low solid solubility, etc., achieve good interface and thermodynamic stability, and be easy to industrialize batches The effect of simple production and preparation process

Inactive Publication Date: 2008-03-05
WUHAN UNIV OF TECH
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  • Abstract
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  • Claims
  • Application Information

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Problems solved by technology

The refinement effect of Ca is mainly manifested in the supercooling of a small amount of Ca atoms in the magnesium alloy liquid in the diffusion layer at the front of the alloy solidified / liquid interface, which activates the potential nucleation particles in the supercooled area, resulting in more Polycrystalline nuclei to refine the grains; in addition, the diffusion rate of Ca atoms is slow, and the precipitation at the interface hinders the growth of grains, restricts its growth rate, and leads to further refinement of grains
Sr refines the grains of magnesium alloys due to the formation of an adsorption film containing Sr on the growth interface, which leads to a decrease in the grain growth rate, so that the melt has sufficient time to form crystal nuclei, thereby refining the grains, but some scholars believe that Sr refining magnesium alloy is due to the low solid solubility of Sr in magnesium (about 0.11%), Sr enrichment will appear in the liquid phase at the front of the growth interface during solidification, which affects the growth kinetics of grains, so that Grain Refinement

Method used

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  • Mg-Al series alloy composite grain refiner and method for making same

Examples

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example 1

[0039] Example 1: Al-32% Al 4 C 3 Preparation of -4% Sr Composite Grain Refiner

[0040] (1) Dry mix 80% aluminum powder and 20% carbon powder on a mixer for 6 hours, then cold press into a prefabricated block with a relative density of 50%, wrap it with aluminum foil, dry it and embed it In a corundum crucible;

[0041] (2) Isothermal treatment at 1200°C for 40 minutes in a box-type resistance furnace;

[0042] (3) Take out the prefabricated block and make Al-80%Al 4 C 3 master alloy;

[0043] (4) Al ingot of 20% by weight, 40% of Al-80% Al 4 C 3 Master alloy and 40% Al-10% Sr master alloy are remelted to produce Al-32% Al 4 C 3 -4% Sr composite grain refiner.

[0044] (5) After adding 1.4% of the composite grain refiner to AZ91 magnesium alloy, the grain size can be reduced from 96 μm to 68 μm.

example 2

[0045] Example 2: Al-24%Al 4 C 3 Preparation of -5% Sr Composite Grain Refiner

[0046] (1) Dry mix 85% aluminum powder and 15% carbon powder on a mixer for 12 hours, then cold press into a prefabricated block with a relative density of 46%, wrap it with aluminum foil, dry it and embed it In a corundum crucible;

[0047] (2) Isothermal treatment at 1000°C for 120min in a box-type resistance furnace;

[0048] (3) Take out the prefabricated block and make Al-60%Al 4 C 3 master alloy;

[0049] (4) Al ingot of 10% by weight, 40% Al-60% Al 4 C 3 Master alloy and 50% Al-10% Sr master alloy are remelted to produce Al-24% Al 4 C 3 -5% Sr composite grain refiner.

[0050] (5) After adding 1.0% of the composite grain refiner to AZ91 magnesium alloy, the grain size can be reduced from 96 μm to 70 μm.

example 3

[0051] Example 3: Al-35%Al 4 C 3 Preparation of -21%Ca Composite Grain Refiner

[0052] (1) Dry mix 82.5% aluminum powder and 17.5% carbon powder on a mixer for 10 hours, then cold press into a prefabricated block with a relative density of 47%, wrap it with aluminum foil, dry it and embed it In a corundum crucible;

[0053] (2) Isothermal treatment at 1150°C for 90 minutes in a box-type resistance furnace;

[0054] (3) Take out the prefabricated block and make Al-70%Al 4 C 3 master alloy;

[0055] (4) Al ingot of 20% by weight, 50% of Al-70% Al 4 C 3 Master alloy and 30%Al-70%Ca master alloy are remelted to produce Al-35%Al 4 C 3 -21% Ca complex grain refiner.

[0056] (5) After adding 0.5% of the composite grain refiner to AZ91 magnesium alloy, the grain size of the alloy can be reduced from 96 μm to 74 μm.

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Abstract

The present invention provides one kind of composite grain refiner for Mg-Al alloy and its preparation process. The composite grain refiner has the chemical composition including C 5-15 wt%, calcium 2.8-28 wt% or Ce 3-6 wt%, and Al for the rest. Its preparation process includes the following steps: mixing aluminum powder and carbon powder; pressing into block and stoving, setting inside corundum crucible and covering with refractory powder, isothermal treatment inside a box-type resistance furnace at 1000-1200 deg.c for 30-120 min to prepare intermediate Al-Al4C3 alloy, and remelting together with aluminum ingot and intermediate Al-70 %Ca or Al-10 %Sr alloy to prepare Al-Al4C3-Ca / Sr as composite grain refiner finally. The composite grain refiner can fine grains of Mg-Al alloy obviously.

Description

technical field [0001] The invention relates to metal materials, in particular to a Mg-Al alloy composite grain refiner and a preparation method thereof. The prepared composite grain refiner can effectively refine the grains of magnesium and aluminum alloys. Background technique [0002] Mg-Al alloys are the most widely used magnesium alloy series due to their excellent casting properties and certain mechanical properties. From the 1930s to the present, the microstructure and properties of the alloy system have been systematically studied. The as-cast structure of Mg-Al alloy consists of α-Mg solid solution and the second phase β-Mg 17 Al 12 phase composition. β-Mg 17 Al 12 The phase is a hard and brittle phase, which is distributed in the grain boundary or between dendrites of the primary α-Mg phase in an irregular network. When the working temperature exceeds 120 ° C, the softening and coarsening of the β phase on the grain boundary will make the mechanical properties...

Claims

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Application Information

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IPC IPC(8): C22C1/06C22C1/03
Inventor 刘生发康柳根刘林艳
Owner WUHAN UNIV OF TECH
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