CN109338132B

CN109338132B - Preparation method of rare earth wrought magnesium alloy blank

Info

Publication number: CN109338132B
Application number: CN201811112019.XA
Authority: CN
Inventors: 胡志; 殷正; 褚晨亮; 闫洪
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2018-09-25
Filing date: 2018-09-25
Publication date: 2021-01-05
Anticipated expiration: 2038-09-25
Also published as: CN109338132A

Abstract

A method for preparing a rare earth wrought magnesium alloy blank comprises the steps of putting Mg-Al-Zn alloy into a crucible for melting, adding small block-shaped Mg-20% Gd wrapped by aluminum foil paper, preserving heat for 10min, cooling to 700 ℃, cooling at 15-20 ℃/s, and solidifying, wherein the weight percentage of each component of the alloy is as follows: 2.0-5.0% of aluminum, 0.8-1.2% of zinc, 2.0-2.5% of gadolinium, 0.3-0.5% of manganese and the balance of magnesium; and (3) putting the alloy ingot into a heat treatment furnace, carrying out isothermal heat treatment at 595-615 ℃ for 20-40 min in a protective gas atmosphere, and taking out for water quenching. The invention can make the layer (Mg, Al)₃Transformation of Gd phase to granular Al₂The Gd phase obviously improves the plasticity and the ductility of the rare earth wrought magnesium alloy. Al (Al)₂The Gd particles can be used as heterogeneous cores of alpha-Mg crystal grains, so that the rare earth wrought magnesium alloy blank has fine and round structure and good plasticity, and completely meets the thixoforming requirement.

Description

Preparation method of rare earth wrought magnesium alloy blank

Technical Field

The present invention belongs to the field of alloy and non-ferrous metal treating technology.

Background

The magnesium-aluminum (Mg-Al) alloy is the most widely applied alloy in magnesium alloys, has obvious excellent comprehensive performance, and contains a small amount of Mn, thereby being beneficial to eliminating the adverse effect of harmful elements and improving the corrosion resistance. However, the alloy has low mechanical properties and poor heat resistance and plastic workability.

The emergence of a novel semi-solid forming process provides a new way for solving the obstacles faced by the traditional solidification and plastic forming, and is considered as the most promising material forming method in the 21 st century. How to obtain a good semi-solid non-dendritic structure is the basis and the key of the semi-solid forming technology. The pipe kernel national teaching of the university of northeast and the like provides a wave-shaped inclined plate vibration semi-solid forming technology; the professor Yangxiangjie of Nanchang university proposes a rotary inclined cylinder type packaging technology; a coiled pipe channel winding casting method is developed by professor of Mao Weimin, Beijing university of science and technology; the Beijing general institute of nonferrous metals developed a damping cooling tube method. The semi-solid isothermal heat treatment is a new method developed in recent years, the non-dendritic ingot material for semi-solid forming prepared by the method can be directly changed from the as-cast ingot material into the non-dendritic ingot material in the secondary heating process, the special procedure required for manufacturing semi-solid slurry is omitted, and the method is widely used for preparing the semi-solid blank material for casting the magnesium alloy, but the method is still in the exploration stage for the preparation research of the deformed magnesium alloy blank material.

The rare earth element has unique extra-nuclear electron arrangement, so that the rare earth element can generate special effect in the magnesium alloy, wherein the rare earth element Gd has obvious modification capability on the Mg-Al alloy, and the rare earth element Gd can refine the AZ31 cast structure by Gu Song Wei and the like of the university of the continuousness engineering. Meanwhile, the documents [ B, Pourbahari, M, Emamy, H, Mirzadeh, "Synergistic effect of Al and Gd on enhancement of mechanical properties of magnesium alloys", growth in Natural Science: Materials International, 27 (2017) 228-]It is proposed that after Gd element is added, Al is formed₂The Gd phase forms another layer (Mg, Al)₃The Gd phase, which is a lamellar phase, not only influences the plastic forming capability of the deformed magnesium alloy, but also causes the generation of high stress concentration points, and provides a proper position for the nucleation and the propagation of microcracks. Thus, (Mg, Al)₃The formation of Gd phase results in a decrease in the properties of wrought magnesium alloys.

Disclosure of Invention

The invention aims to provide a method for preparing a rare earth wrought magnesium alloy blank, which is layered (Mg, Al)₃Transformation of Gd phase to granular Al₂The plasticity and the ductility of the rare earth wrought magnesium alloy are obviously improved by the Gd phase.

The invention is realized by the following technical scheme.

The invention relates to a preparation method of a rare earth wrought magnesium alloy blank, which is characterized by comprising the following steps of putting Mg-Al-Zn alloy into a crucible with a furnace temperature of 740-760 ℃ for heating until the Mg-Al-Zn alloy is molten, adding a small blocky Mg-20% Gd intermediate alloy wrapped by aluminum foil paper, keeping the temperature for 10 minutes, cooling an alloy melt to 700 ℃, cooling at a cooling speed of 15-20 ℃/s, and solidifying to obtain an alloy ingot, wherein the alloy comprises the following components in percentage by weight: 2.0-5.0% of aluminum, 0.8-1.2% of zinc, 2.0-2.5% of gadolinium, 0.3-0.5% of manganese and the balance of magnesium; and putting the obtained alloy ingot into a heat treatment furnace, carrying out isothermal heat treatment in a protective gas atmosphere, wherein the isothermal heat treatment temperature is 595-615 ℃, the heat preservation time is 20-40 minutes, taking out, and carrying out water quenching to obtain a fine spherical semi-solid rare earth magnesium alloy blank.

The invention has the technical effects that: the method for preparing the wrought magnesium alloy blank can ensure that the wrought magnesium alloy blank is layered (Mg, Al)₃Transformation of Gd phase to granular Al₂The plasticity and the ductility of the rare earth wrought magnesium alloy are obviously improved by the Gd phase. At the same time, Al₂The Gd particles can be used as heterogeneous cores of alpha-Mg crystal grains, so that the finally obtained rare earth wrought magnesium alloy blank has fine and round tissue and good plasticity, and completely meets the requirement of thixoforming.

Drawings

FIG. 1 is an optical microstructure of an alloy ingot prepared under the conditions of example 2.

FIG. 2 is an SEM microstructure of an alloy ingot prepared under the conditions of example 2.

FIG. 3 is an optical microstructure of a wrought magnesium alloy billet prepared under the conditions of example 2

FIG. 4 is an SEM microstructure of a wrought magnesium alloy blank prepared under the conditions of example 2.

Detailed Description

The invention will be further illustrated by the following examples.

Example 1: in the embodiment, Mg-Al-Zn alloy (the mass percent of Al is 2%, the mass percent of Zn is 0.8%, and the balance is Mg) is heated to 740 ℃, after the alloy is completely melted, a small block-shaped Mg-20% Gd intermediate alloy wrapped by aluminum foil paper is added, wherein the mass fraction of rare earth element Gd accounts for 2.0% of the melt, the alloy melt is cooled to 700 ℃ after heat preservation is carried out for 10 minutes, then the alloy melt is cooled at a cooling speed of 15 ℃, and an alloy ingot is obtained after solidification; and carrying out isothermal heat treatment on the obtained alloy ingot, wherein the isothermal heat treatment temperature is 595 ℃, the heat preservation time is 40 minutes, taking out and carrying out water quenching to obtain the rare earth magnesium alloy semi-solid blank.

Example 2: in the embodiment, Mg-Al-Zn alloy (the mass percent of Al is 3%, the mass percent of Zn is 1%, and the balance is Mg) is heated to 750 ℃, after the alloy is completely melted, a small blocky Mg-20% Gd intermediate alloy wrapped by aluminum foil paper is added, wherein the mass fraction of rare earth element Gd in the molten liquid is 2.0%, the alloy melt is cooled to 700 ℃ after heat preservation is carried out for 10 minutes, then the alloy melt is cooled at a cooling speed of 20 ℃, and an alloy ingot is obtained after solidification; and carrying out isothermal heat treatment on the obtained alloy ingot, wherein the isothermal heat treatment temperature is 605 ℃, the heat preservation time is 30 minutes, and taking out for water quenching to obtain the rare earth magnesium alloy semi-solid blank.

Example 3: in the embodiment, Mg-Al-Zn alloy (Al is 4% by mass, Zn is 1.2% by mass, and the balance is Mg) is heated to 760 ℃, after the alloy is completely melted, a small block-shaped Mg-20% Gd intermediate alloy wrapped by aluminum foil paper is added, wherein the rare earth element Gd accounts for 2.5% by mass of the molten liquid, the alloy melt is cooled to 700 ℃ after heat preservation is carried out for 10 minutes, then the alloy melt is cooled at a cooling speed of 15 ℃, and an alloy ingot is obtained after solidification; and carrying out isothermal heat treatment on the obtained alloy ingot, wherein the isothermal heat treatment temperature is 605 ℃, the heat preservation time is 30 minutes, and taking out for water quenching to obtain the rare earth magnesium alloy semi-solid blank.

Example 4: in the embodiment, Mg-Al-Zn alloy (5 mass percent of Al, 1 mass percent of Zn and the balance of Mg) is heated to 750 ℃, after the alloy is completely melted, a small blocky Mg-20% Gd intermediate alloy wrapped by aluminum foil paper is added, wherein the mass fraction of rare earth element Gd in the molten liquid is 2.5%, the alloy melt is cooled to 700 ℃ after heat preservation is carried out for 10 minutes, then the alloy melt is cooled at a cooling speed of 20 ℃, and an alloy ingot is obtained after solidification; and carrying out isothermal heat treatment on the obtained alloy ingot, wherein the isothermal heat treatment temperature is 615 ℃, the heat preservation time is 20 minutes, and taking out for water quenching to obtain the rare earth magnesium alloy semi-solid blank.

The alloy ingot prepared in example 2 and the wrought magnesium alloy ingot subjected to isothermal heat treatment were sampled, and the microstructure of the alloy was observed under an optical microscope after being polished, polished and corroded, as shown in fig. 1 and 3.The alloy ingot prepared in example 2 and the wrought magnesium alloy blank subjected to isothermal heat treatment were sampled and observed under a scanning electron microscope for rare earth phase distribution in the alloy, as shown in fig. 2 and fig. 4. As can be seen from the figure, the isothermal heat treatment process can make the (Mg, Al) layered₃Gd is converted into granular Al₂Gd. Meanwhile, part of Al₂Gd particles are used as heterogeneous cores of alpha-Mg grains, and the rest Al₂The Gd particles are uniformly distributed, so that the finally obtained rare earth wrought magnesium alloy blank has fine and round tissue and good plasticity, and completely meets the requirement of thixoforming.

Claims

1. A preparation method of a rare earth wrought magnesium alloy blank is characterized by placing Mg-Al-Zn alloy into a crucible with a furnace temperature of 740-760 ℃ to be heated to be molten, adding a small blocky Mg-20% Gd intermediate alloy wrapped by aluminum foil paper, keeping the temperature for 10 minutes, cooling an alloy melt to 700 ℃, then cooling at a cooling speed of 15-20 ℃/s, and obtaining an alloy ingot after solidification, wherein the alloy comprises the following components in percentage by weight: 2.0-5.0% of aluminum, 0.8-1.2% of zinc, 2.0-2.5% of gadolinium, 0.3-0.5% of manganese and the balance of magnesium; and putting the obtained alloy ingot into a heat treatment furnace, carrying out isothermal heat treatment in a protective gas atmosphere, wherein the isothermal heat treatment temperature is 595-615 ℃, the heat preservation time is 20-40 minutes, taking out, and carrying out water quenching to obtain a fine spherical semi-solid rare earth magnesium alloy blank.