CN116219243B

CN116219243B - Ultrahigh-strength rare earth magnesium alloy and high-temperature single-phase region forging forming process thereof

Info

Publication number: CN116219243B
Application number: CN202211588393.3A
Authority: CN
Inventors: 潘虎成; 张栋栋; 曾志浩; 唐伟能; 莫宁; 秦高梧
Original assignee: Baosteel Metal Co Ltd; Northeastern University China
Current assignee: Baosteel Metal Co Ltd; Northeastern University China
Priority date: 2022-12-12
Filing date: 2022-12-12
Publication date: 2024-12-17
Anticipated expiration: 2042-12-12
Also published as: CN116219243A

Abstract

The invention discloses an ultrahigh-strength rare earth magnesium alloy and a high-temperature single-phase region forging forming process thereof, and relates to the technical field of nonferrous metal materials and processing thereof, wherein the ultrahigh-strength rare earth magnesium alloy comprises 12.8-13.4wt.% of Gd, less than or equal to 0.05% of Fe, less than or equal to 0.05% of Cu, less than or equal to 0.05% of Si, less than or equal to 0.005% of Ni and the balance Mg; the single-phase region high-temperature forging is performed in a range of 500-450 ℃, the forging ratio of 500 ℃ is about 1.18, the annealing treatment is performed for 40min at 450 ℃ after forging, the forging ratio of 450 ℃ is about 2.64, and the cold water quenching is performed after final forging.

Description

Ultrahigh-strength rare earth magnesium alloy and high-temperature single-phase region forging forming process thereof

Technical Field

The invention belongs to the technical field of nonferrous metal structural materials and processing thereof, and particularly relates to a magnesium alloy forging technology and a design, preparation and processing method of an ultrahigh-strength magnesium alloy.

Background

As the lightest metal structural material at present, the magnesium alloy has high specific strength and specific rigidity, good cutting processing performance, electromagnetic shielding performance and damping and shock absorbing performance, and abundant and easily recovered resources, so the magnesium alloy has wide application prospect in the fields of aerospace, automobiles, electronic consumer products, military industry and the like, but compared with the traditional alloys such as steel, aluminum, titanium and the like, the magnesium alloy has low absolute strength, thereby seriously impeding the wide application of the magnesium alloy, especially in the high technical fields of aerospace, military industry and the like.

At present, aiming at the technical problem of low strength of magnesium alloy, the main solution is to (1) optimize the alloy component design and (2) adopt plastic processing technology. Numerous studies have demonstrated that rare earth magnesium alloys are currently the most promising ultra-high strength magnesium alloy systems, such as WE43/54 and Mg-Gd-Y (-Zn) -Zr (GW) series magnesium alloys, and in addition, the currently prevailing plastic working techniques include extrusion, rolling and forging, which can be used to produce magnesium profiles, bars, plates and strips, etc.

The free surface of the magnesium blank is easy to crack under the action of impact load in the forging process of the magnesium alloy, so that the yield of the forged magnesium alloy is very low, the forging process is usually carried out at high temperature due to the poor plastic deformation capability of the magnesium alloy, so that a fine grain structure is difficult to obtain in the forging process, and on the other hand, the strength of the alloy can be obviously improved due to the composite addition of a large amount of rare earth elements such as Gd, Y, nd and the like, but the deformation resistance of the alloy is also increased, so that a narrower processing temperature window is caused, and the magnesium alloy is also a technical bottleneck for restricting the development of high-performance rare earth magnesium alloy forgings.

At present, no report exists on the preparation technology of large-size and high-performance rare earth magnesium alloy forgings with the yield strength more than or equal to 450 MPa.

Aiming at the urgent need of the high technical fields such as aerospace in China for ultrahigh-strength and large-size magnesium forgings, the method for designing the high-performance magnesium alloy by discarding the traditional multi-element rare earth composite reinforcement is firstly provided, and the aging-reinforced Mg-13Gd binary alloy is designed by using Gd element with high solid solubility, and the 'shape control and control' of the magnesium forgings is realized by combining a high-temperature single-phase region forging forming process, so that the large-specification and ultrahigh-strength magnesium forgings are prepared.

Disclosure of Invention

Aiming at the defects existing in the prior art, the invention aims to provide the aging-enhanced Mg-13Gd binary alloy designed by using the Gd element with high solid solubility, and realizes the shape control property of the high-strength magnesium forging by combining a high-temperature single-phase region forging forming process, thereby having important significance for further promoting the application of the large-size high-strength magnesium forging in the high technical fields such as aerospace and the like in China.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows.

The ultrahigh-strength rare earth magnesium alloy comprises, by mass, 12.8-13.4% of Gd, less than or equal to 0.05% of Fe, less than or equal to 0.05% of Cu, less than or equal to 0.05% of Si, less than or equal to 0.005% of Ni and the balance of Mg.

A forging forming process of a high-temperature single-phase region of an ultrahigh-strength rare earth magnesium alloy comprises the following steps:

(a) And preparing a large-size high-quality cast ingot by a semi-continuous casting technology, wherein the casting temperature is 720-740 ℃, the casting speed is 40-50 mm/min, and the cooling water pressure is 0.02-0.03 MPa.

(B) And carrying out solution treatment at a high temperature for a long time, namely, carrying out solution treatment at a solution temperature of 520-530 ℃ for 20-30 hours, and slowly immersing the solution in hot water at 80-100 ℃ for quenching after the solution treatment is completed.

(C) The forging method comprises the steps of upsetting a forging stock with small deformation by adopting a drop hammer forging machine, upsetting reduction is about 5-8%, then performing drawing forging along the radial direction, and taking two mutually perpendicular radial directions of the cylindrical forging stock as equivalent forging directions, wherein the axial direction of the forging stock is the drawing direction. The upper cutting board and the lower cutting board are preheated to 250-300 ℃, the impact frequency of a forging hammer is about 60-100 times/min, the average strain rate is about 13-15 s < -1 >, the inter-pass annealing time before forging is about 30-40 min, the forging ratio of the 1 st or 2 nd pass of 500 ℃ forging is kept between 1.17-2.64, the inter-pass annealing temperature is 500 ℃, the annealing temperature after 500 ℃ final forging is 450 ℃, then the forging is carried out for 1 pass at 450 ℃, the forging ratio is about 2.25-2.65, and the cold water quenching is carried out after 450 ℃ final forging.

(D) Isothermal aging treatment, namely, carrying out isothermal aging treatment at 200 ℃ for 40-45 hours.

Further improvements, the inter-pass annealing temperature in step (c) corresponds to the forging temperature of the next pass.

Further optimization and improvement of the above technical scheme, in the step (C), forging is firstly performed at 500 ℃ for 1 st pass, the forging ratio is about 1.18, annealing is performed at 450 ℃ for 40min after forging, then forging is performed at 450 ℃ for 2 nd pass, the forging ratio is about 2.64, and cold water quenching is performed after forging.

Further optimization and improvement of the technical scheme,

In the step (C), the forging stock is kept at 500 ℃ for 40min, then is forged at 500 ℃ for 2 times, the forging ratio of the first time is 1.18, the forging ratio of the second time is 2.64, the annealing temperature between the times is 450 ℃, the annealing time between the times is 40min, and the cold water quenching is carried out after the final forging at 450 DEG C

Isothermal aging treatment is carried out at 200 ℃, and the heat preservation time is 40 hours;

The yield strength of the forge piece in the drawing direction is more than or equal to 458MPa, the tensile strength is more than or equal to 493MPa, and the elongation is more than or equal to 3.5%.

Compared with the prior art, the invention has the following further advantages:

the ultrahigh-strength rare earth magnesium alloy takes the heavy rare earth Gd with high solid solubility as the sole alloying element, can form quasi-single-phase solid solution structure after high-temperature solid solution, is beneficial to high-temperature forging forming, and simultaneously, because Gd can reduce the stacking fault energy of the magnesium alloy, promote non-basal plane slip and improve the plasticity of the magnesium alloy. The adopted high-temperature single-phase region forging forming process effectively inhibits the dynamic precipitation of coarse Mg ₅ Gd phases in the forging process, and meanwhile, the high-temperature forging ensures that Gd solutes are uniformly diffused, so that solute segregation is avoided, and the formation of basal plane textures is promoted. Thus, the structure of the wrought alloy is a near single-phase solid solution structure, similar to an as-cast solid solution alloy. But unlike as-cast solid solution alloys, the structure of wrought alloys also has a strong basal texture. Therefore, supersaturated Gd solute in the forged tissue provides good tissue conditions for subsequent maximization of precipitation. After aging treatment, high-density cylindrical precipitated phases are dispersed and distributed in a magnesium matrix, dislocation slip and mechanical twinning can be effectively prevented, and ultrahigh strength is contributed.

The test result shows that the mechanical property of the ultrahigh-strength Mg-13Gd wrought alloy prepared by the high-temperature single-phase region forging forming process is that the yield strength is 426-458 MPa, the tensile strength is 431-493 MPa, and the elongation is 0.93-3.5%.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention.

FIG. 1 is a metallurgical structure of an ultra-high strength wrought magnesium gadolinium alloy prepared in example 2 of the present invention.

FIG. 2 is a stress-strain curve of an ultra-high strength wrought magnesium gadolinium alloy prepared in example 2 of the present invention.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making creative efforts based on the embodiments of the present invention are included in the protection scope of the present invention.

Example 1

The ultrahigh-strength rare earth magnesium alloy comprises 12.8% by mass of Gd, less than or equal to 0.05% by mass of Fe, less than or equal to 0.05% by mass of Cu, less than or equal to 0.05% by mass of Si, less than or equal to 0.005% by mass of Ni and the balance of Mg.

The forging forming process of the high-temperature single-phase region of the ultrahigh-strength rare earth magnesium alloy comprises the following steps of:

(1) Preparing a Mg-12.8Gd (wt.%) casting blank by adopting a semi-continuous casting technology, wherein the casting temperature is 720-740 ℃, the casting speed is 40-50 mm/min, and the cooling water pressure is 0.02-0.03 MPa;

(2) Then carrying out quenching in hot water at the temperature of 80-100 ℃ after heat preservation for 24 hours at the temperature of 520 ℃;

(3) Processing into forging stock with height of 100mm and diameter of 80 mm;

The forging method comprises the steps of upsetting a forging stock with small deformation by adopting a drop hammer forging machine, wherein upsetting depression is about 5-8%, then performing drawing forging along the radial direction, taking two mutually perpendicular radial directions of a cylindrical forging stock as equivalent forging directions, and taking the axial direction of the forging stock as the drawing direction, preheating an upper cutting board and a lower cutting board to 250-300 ℃, wherein the impact frequency of the forging hammer is about 60-100 times per minute, the average strain rate is about 13-15 s ^-1, and the inter-pass annealing time is about 30-40 minutes;

The forging stock is preserved at 500 ℃ for 40min, then is forged for 2 times at 500 ℃, the forging ratio of the first time is 1.18, the forging ratio of the 2 nd time is 1.69, the total forging ratio is 2.01, the annealing temperature between the passes is 500 ℃, the annealing time between the passes is 40min, and cold water quenching is carried out after final forging at 450 ℃;

(4) Isothermal aging treatment is carried out at 200 ℃ for 45 hours.

The Mg-12.8Gd forging prepared in example 1 of the invention was subjected to room temperature mechanical property test according to the standard of GBT-228.1-2021 Metal Material-tensile test-part 1 room temperature test method, the tensile direction was parallel to the forging drawing direction, and the test results are shown in Table 1.

Example 2

The ultrahigh-strength rare earth magnesium alloy comprises the following components in percentage by mass of Gd13.2%, fe less than or equal to 0.05%, cu less than or equal to 0.05%, si less than or equal to 0.05%, ni less than or equal to 0.005% and the balance Mg.

(1) Preparing a Mg-13.2Gd (wt%) casting blank by adopting a semi-continuous casting technology, wherein the casting temperature is 720-740 ℃, the casting speed is 40-50 mm/min, and the cooling water pressure is 0.02-0.03 MPa;

(2) Then carrying out quenching in hot water at the temperature of 80-100 ℃ after heat preservation for 28 hours at the temperature of 520 ℃;

(3) Processing into forging stock with height of 100mm and diameter of 80 mm;

the forging stock is preserved at 500 ℃ for 40min, then is forged for 2 times at 500 ℃, the forging ratio of the first pass is 1.18, the forging ratio of the 2 nd pass is 2.64, the annealing temperature between passes is 450 ℃, the annealing time between passes is 40min, and cold water quenching is carried out after final forging at 450 ℃, and (4) isothermal aging treatment is carried out at 200 ℃, and the heat preservation time is 40 hours.

The Mg-13.2Gd forging prepared in example 2 of the invention was subjected to room temperature mechanical property test according to the standard of GBT-228.1-2021 Metal Material-tensile test-part 1 room temperature test method, the tensile direction was parallel to the forging drawing direction, and the test results are shown in Table 1.

Example 3

The ultrahigh-strength rare earth magnesium alloy comprises the following components in percentage by mass of Gd13.4%, fe less than or equal to 0.05%, cu less than or equal to 0.05%, si less than or equal to 0.05%, ni less than or equal to 0.005% and the balance Mg.

(2) Then heat preservation is carried out for 25 hours at 525 ℃ and quenching is carried out in hot water at 80-100 ℃;

(3) Processing into forging stock with height of 100mm and diameter of 80 mm;

The forging method comprises the steps of upsetting a forging stock with small deformation by adopting a drop hammer forging machine, wherein upsetting depression is about 5-8%, then performing drawing forging along the radial direction, taking two mutually perpendicular radial directions of a cylindrical forging stock as equivalent forging directions, and taking the axial direction of the forging stock as the drawing direction, preheating an upper cutting board and a lower cutting board to 250-300 ℃, wherein the impact frequency of the forging hammer is about 80-120 times per minute, the average strain rate is about 13-15 s ^-1, and the inter-pass annealing time is about 30-40 minutes;

Forging at 500 deg.C for 1 st pass with forging ratio of about 1.18, annealing at 500 deg.C for 35min, then forging at 500 deg.C for 2 nd pass with forging ratio of about 1.17, annealing at 450 deg.C for 40min, then forging at 450 deg.C for 3 rd pass with forging ratio of about 1.42, and quenching with cold water after forging;

(4) Isothermal aging treatment is carried out at 200 ℃ for 45 hours.

The Mg-13.4Gd forging prepared in example 3 of the invention was subjected to room temperature mechanical property test according to the standard of GBT-228.1-2021 Metal Material-tensile test-part 1 room temperature test method, the tensile direction was parallel to the forging drawing direction, and the test results are shown in Table 1.

Table 1. Room temperature mechanical properties of forgings prepared in examples 1 to 3 in the draw-down direction:

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The high temperature single phase zone forging process of ultra-high strength rare earth magnesium alloy has the following steps:

(a) Take a target rare earth magnesium alloy ingot, whose mass percentage composition is Gd: 13.2~13.4%, Fe≤0.05%, Cu≤0.05%, Si≤0.05%, Ni≤0.005%, and the balance is Mg;

(b) Semi-continuous casting technology is used to prepare large-sized high-quality ingots: the casting temperature is 720~740ºC, the casting speed is 40~50mm/min, and the cooling water pressure is 0.02~0.03 MPa;

(c) High temperature and long time solution treatment: solution temperature 520~530ºC, time 20~30 hours, after solution treatment, slowly immerse in 80~100 ºC hot water for quenching;

(d) Use a drop hammer forging machine to roughen the forging billet with a small deformation amount, and the roughing reduction is 5~8%; then stretch forging is performed in the radial direction, with the two mutually perpendicular radial directions of the cylindrical forging billet as the equivalent forging direction, and the axial direction of the forging billet as the stretching direction; the upper and lower anvils are preheated to 250-300ºC, the forging hammer impact frequency is 60~100 times/minute, the average strain rate is 13~15 s-1, and the annealing time between passes before forging is 30~40 minutes; the forging ratio of the first or second pass of 500ºC forging is maintained between 1.17~2.64, the annealing temperature between passes is 500ºC, but the annealing temperature after 500ºC final forging is 450ºC; then forge one pass at 450ºC, the forging ratio is 2.25~2.65, and cold water quenching is performed after final forging at 450ºC;

(e) Isothermal aging treatment: Isothermal aging treatment is carried out at 200°C for 40 to 45 hours.

2. According to the high temperature single phase zone forging forming process of an ultra-high strength rare earth magnesium alloy as described in claim 1, the inter-pass annealing temperature in step (d) corresponds to the forging temperature of the next pass.

3. According to the high temperature single-phase zone forging forming process of an ultra-high strength rare earth magnesium alloy according to claim 1, first forging the first pass at 500ºC with a forging ratio of 1.18, and annealing at 450ºC for 40 minutes after forging; then forging the second pass at 450ºC with a forging ratio of 2.64, and cold quenching after forging.