CN107881443A - A kind of high-entropy alloy squeezes pier composite modification technology - Google Patents

Abstract

The invention relates to a method for preparing a high-performance high-entropy alloy material with uniform structure by a plastic modification technology specially aimed at thermal processing and grain refinement of the high-entropy alloy material. The main purpose of the present invention is to provide a composite plastic modification method for extruded piers aimed at the service requirements of high-entropy alloys. According to the thermal processing characteristics of high-entropy alloys, the method of pier first and then extrusion, extrusion and then pier, and repeated pier extrusion can effectively control the stress state inside the high-entropy alloy material during the deformation process, increase the three-dimensional compressive stress, and effectively suppress lattice distortion. The initiation and propagation of induced micro-cracks refine the grains, improve the comprehensive mechanical properties, and realize the effective modification of high-entropy alloys. The extrusion composite process is easy to implement and low in cost. It can obtain high-entropy alloy ingot materials with uniform and excellent structure properties, and effectively improve its service ability. This method can not only promote the large-scale use of high-entropy alloys, but also effectively improve and Controlling the mechanical properties of high-entropy alloys.

Description

A composite modification technology of high-entropy alloy extruded pier

technical field

The invention relates to a plastic modification method specially aimed at thermal processing and grain refinement of high-entropy alloy materials.

Background technique

High-entropy alloys are emerging materials that have attracted widespread attention in recent years. They have good mechanical, physical and chemical properties such as high hardness, high strength, high wear resistance and high corrosion resistance, and have broad application prospects in modern engineering. However, due to the serious lattice distortion of high-entropy alloys, the as-cast structure is a typical dendrite structure, and the plasticity is low under high-temperature deformation conditions. At the same time, due to the existence of casting defects, it is easy to crack after high-temperature forging. It cannot be fully utilized in the application, which greatly limits the large-scale engineering application of high-entropy alloys. In order to eliminate casting defects, high-entropy alloys are usually modified by forging.

High-temperature forging is an important material processing technology. It can close microcracks, break up dendrites, and effectively improve the structure and properties of materials. It is an important modification method for metal materials. However, due to the serious lattice distortion of high-entropy alloys, cracks are easy to form during forging, which greatly hinders the application of plastic processing forging modification technology.

Upsetting is a forming process that reduces the height of the forging blank and increases the cross-sectional area in forging. When upsetting, due to the contact friction between the upper and lower end faces of the material and the cutting board of the forging equipment, the material will flow unevenly, which will lead to uneven temperature, stress, deformation degree, and tissue transformation in different regions of the material. For entropy alloy upsetting, due to the combined effect of the above problems and the lattice distortion problem, it is often easy to generate longitudinal or 45° direction cracks on the side surface.

Extrusion is the process of applying external force to the metal billet placed in the die cavity (or extrusion cylinder) to force the metal to extrude from the die hole to obtain the desired end face shape, size and extrusion parts with certain mechanical properties. The plastic processing method, whose stress state is a typical three-dimensional compressive stress, can effectively close microcracks.

In view of this, the present invention proposes a simple and easy-to-implement plastic processing technology, that is, extruded pier composite modification technology. Extruded pier composite can improve the stress state inside the material, increase the three-dimensional compressive stress, and reduce the level of tensile stress to improve the forming performance of the material. The forging method has an important role and significance in improving the plastic processing performance of high-entropy alloys. By applying sufficient multi-extrusion compound processing to the high-entropy alloy ingot, the internal stress distribution of the ingot during the plastic processing process can be effectively controlled, and a gradient three-dimensional compressive stress specific to the characteristics of the deformation process can be formed to effectively suppress microcracks during the deformation process of the high-entropy alloy. The initiation and expansion of the microstructure, the refinement of the grains, the refinement and effective control of the microstructure of the high-entropy alloy, and the realization of high-efficiency plastic modification. This process can be realized on processing equipment such as traditional extrusion cylinders and forging hammers, which is simple and easy. Easy to promote and apply.

Contents of the invention

The purpose of the present invention is to provide a compound plastic modification method for extruded piers aimed at the service requirements of high-entropy alloys. According to the thermal processing characteristics of high-entropy alloys, the method of pier first and then extrusion, extrusion and then pier, and repeated pier extrusion can effectively control the stress state inside the high-entropy alloy material during the deformation process, increase the three-dimensional compressive stress, and effectively suppress lattice distortion. The initiation and propagation of induced micro-cracks refine the grains, improve the comprehensive mechanical properties, and realize the effective modification of high-entropy alloys.

The extrusion composite process is easy to implement and low in cost. It can obtain high-entropy alloy ingot materials with uniform and excellent structure properties, and effectively improve its service ability. This method can not only promote the large-scale use of high-entropy alloys, but also effectively improve and Controlling the mechanical properties of high-entropy alloys.

In order to solve the above-mentioned technical problems, the compound modified method of extruded pier of the present invention adopts the following technical solutions to realize:

The first step: the production of the original blank of the high-entropy alloy. According to the size of the ingot, the high-entropy alloy bar is cut, and then according to the composition of the high-entropy alloy, it is heated to an initial temperature of 900°C-1200°C, and the heat preservation treatment is carried out according to the thickness of the bar 0.8-1min/mm. 12-100h, to promote the uniformity of its internal organization.

The second step: Analysis of high-entropy alloy bar pier roughing process and upsetting process. Combined with the composition and deformation characteristics of the selected high-entropy alloy, through software calculation and simulation, the stress characteristics and laws of different parts of the ingot during the thick deformation of the pier, especially the distribution of three-dimensional compressive stress and damage distribution, are obtained. On this basis, combined with the material stress and damage characteristics, the deformation of the high-entropy alloy under different pier thickness conditions and the change of three-dimensional compressive stress and damage distribution are analyzed to obtain the most suitable pier thickness height-to-diameter ratio, and then optimize the pier thickness scheme. Avoid pier thickening to produce drum-shaped cracks. On this basis, relying on the optimized upsetting scheme, the high-entropy alloy ingot that has been homogenized in the first step is upset. The upper and lower cutting boards are flat cutting boards. The cutting boards are preheated to 500 degrees and the strain rate is 0.01s ^-1 - 0.1s ^-1 , 0.05s ^-1 is preferred.

The third step: high-entropy alloy extrusion process analysis and extrusion processing. After the pier is thickened, high-temperature extrusion is performed on the deformed high-entropy alloy billet. Through software calculation and simulation, the material flow characteristics of the high-entropy alloy in the extrusion process are analyzed, and the optimized extrusion process scheme is obtained. On this basis, combined with the analysis results, high-entropy alloy extrusion processing was carried out to reduce the diameter of the billet and increase the length of the material. The extrusion temperature is 900-1100 degrees, and the extrusion ratio is less than 2.

The fourth step: thick loop pier. Put the extruded high-entropy alloy bar into the heating furnace to raise the temperature and keep it warm. When the deformation temperature is reached, the high-entropy alloy is taken out for another high-temperature pier rough machining modification. The deformation temperature is 900°C-1200°C, preferably 1100°C, and the strain rate is 0.01s ^-1 -0.1s ^-1 , preferably 0.05s ^-1 .

Step 5: Loop Extrusion. Re-extrude the high-entropy alloy billet after re-upsetting, the extrusion temperature is 900-1100 degrees, and the extrusion ratio is less than 2.

Continue to repeat the process of the fourth and fifth steps, upsetting and extruding compound cycle, until a high-entropy alloy ingot with fine grain structure and uniform structure and excellent service ability is obtained, and the structure and performance of the processed high-entropy alloy meet the service requirements.

Compared with the prior art, the beneficial effects of the present invention are as follows:

High-entropy alloys are composed of multi-element components, and their as-cast structures are mostly coarse dendrites, which will seriously affect the comprehensive properties of high-entropy alloys. Plastic processing can break dendrites and refine grains, but due to the existence of large atomic radius components in high-entropy alloys, there are serious lattice distortions, which can easily lead to cracks during plastic deformation, and the formation of cracks will be serious. affect the application of the material. The compressive stress can be effectively increased by the composite processing of piers, the stress state inside the high-entropy alloy material can be controlled during the deformation process, the three-dimensional compressive stress can be increased, and the coarse dendrites can be broken while inhibiting the initiation and expansion of micro-cracks induced by lattice distortion. Crystallization, improve comprehensive mechanical properties, improve the microstructure and mechanical properties of materials, and realize processing modification.

Description of drawings

Fig. 1 is the process flow of high entropy alloy ingot preparation, see the accompanying drawings.

Detailed ways

Taking AlCrFeNiCuMu as an example, this embodiment is a method for preparing an AlCrFeNiCuMu _0.5 high-entropy alloy ingot with a uniform structure and significantly improved mechanical properties through pier extrusion composite technology. Specifically, it is completed according to the following steps:

(1) Prepare a high-entropy alloy: AlCrFeNiCuMu _0.5 ingot: Select an ingot of a high-entropy alloy with a composition of AlCrFeNiCuMu _0.5 , and the molar ratios of the five elements are Al:Cr:Fe:Ni:Cu:Mu=1:1: 1:1:1:0.5.

(2) Homogenization heat treatment: perform homogenization heat treatment on the AlCrFeNiCuMu _0.5 high-entropy alloy ingot selected in step (1), the temperature of the homogenization heat treatment is 1000°C-1100°C, and then heat preservation according to the thickness of the ingot 0.8-1min/mm Treatment, the heat preservation time of homogenization heat treatment is 12h-100h, and the high-entropy alloy ingot with homogenized internal structure components is obtained.

(3) Simulation of pier coarse deformation process: Computer simulation of the deformation process is carried out through numerical simulation software to obtain the stress characteristics and laws of different parts of the ingot during the deformation process, especially the distribution of three-dimensional compressive stress and damage distribution. On this basis, combined with the material stress and damage characteristics, the deformation of the high-entropy alloy under different pier thickness conditions and the change of three-dimensional compressive stress and damage distribution are analyzed, and the pier thickness scheme and pier thickness ratio are optimized to avoid belly cracks due to pier thickness . Monitor the structure change and grain size change of high entropy alloy.

On this basis, relying on the optimized upsetting scheme, the AlCrFeNiCuMu _0.5 high-entropy alloy ingot that has been homogenized in the first step is subjected to upsetting processing. The upper and lower cutting boards are flat cutting boards ^{. 1} -0.1s ^-1 , preferably 0.05s ^-1 .

(4) Extrusion processing design and simulation: Through software calculation and simulation, the material flow characteristics of AlCrFeNiCuMu _0.5 high-entropy alloy during extrusion were analyzed, and an optimized extrusion process plan was obtained. On this basis, combined with the analysis results, the extrusion processing of AlCrFeNiCuMu _0.5 high-entropy alloy was carried out. The extrusion temperature is 900-1200 degrees, and the extrusion ratio is less than 2.

(5) Thickening and extrusion processing again: Put the AlCrFeNiCuMu _0.5 after extrusion processing into the heating furnace for heating, and repeat the process of step 3 and step 4, repeatedly pier extrusion to refine the AlCrFeNiCuMu _0.5 high-entropy alloy structure, and at the same time Through the combination of piercing process, the initiation and propagation of micro-cracks caused by the severe lattice distortion of high-entropy alloys are suppressed, combined with metallographic analysis and mechanical performance testing, the final grain size is finer and the structure is uniform, with excellent serviceability high-entropy alloy ingots.

The advantage of this implementation mode:

(1) In this embodiment, the high-entropy alloy component prepared by the extruding pier composite modification method can well suppress the serious crystallization of the high-entropy alloy due to repeated extrusion and pier thickening of the high-entropy alloy blank during the processing process. The initiation and propagation of micro-cracks caused by lattice distortion can obtain a high-entropy alloy ingot with finer grains, uniform structure, and excellent serviceability.

(2) This embodiment can prepare larger-sized high-entropy alloy components, and the processing process can be realized on processing equipment such as traditional hydraulic presses or forging hammers, which is simple and easy to popularize and apply.

Claims (2)

1. it is a kind of specifically for the hot-working of high entropy alloy material and the plastics modification technology of crystal grain refinement, prepare even tissue The method of high-performance high entropy alloy material, is specifically completed according to the following steps：

(1) making of high-entropy alloy original blank:, then will be according to high-entropy alloy according to ingot blank measure high-entropy alloy bar Morphological element difference, be heated to 900 DEG C -1200 DEG C of initial temperature, be incubated according to bar thickness 0.8-1min/mm Processing, 12-100h is incubated, makes its interior tissue uniform；

(2) the upset processing of bar and analysis:With reference to the composition and deformation characteristicses of selected high-entropy alloy, by software calculate with Analog simulation, obtain the stress characteristics and rule of ingot blank different parts during mushrooming deformation, especially three-dimensional compression stress The regularity of distribution and damage profile, on this basis, bond material stress and damage characteristic, analysis high-entropy alloy is in different upset bars Deformation and three-dimensional compression stress under part change with damage profile, optimize upset scheme and upset ratio, avoid upset produce from rousing Tripe crackle, on this basis, the jumping-up scheme of optimization is relied on, jumping-up processing is carried out to the high-entropy alloy ingot blank homogenized, Upper and lower chopping block uses flat anvil plate, and chopping block is preheated to 500 degree, strain rate 0.01s^-1-0.1s^-1, preferred 0.05s^-1；

(3) extrusion process and analysis:After the completion of upset, high temperature extrusion is carried out to strained high-entropy alloy embryo material, passes through software Calculating and analog simulation, the material flow performance of high-entropy alloy in extrusion process is analyzed, obtain the extrusion technology program of optimization, On the basis of this, binding analysis result, carry out high-entropy alloy extrusion process, reduce blank diameter, increase length of material, extrusion temperature 900-1100 degree, extrusion ratio are less than 2；

(4) upset processing again:High-entropy alloy bar after the completion of extruding is being put into heating furnace heating, insulation, when reaching After deformation temperature, high-entropy alloy is taken out into progress, and high temperature is upset processing modified again, and deformation temperature is according to material different about 900 DEG C -1200 DEG C, preferably 1100 DEG C, strain rate 0.01s^-1-0.1s^-1, preferred 0.05s^-1；

(5) extrusion process again:Continue the flow of step (3) and step (4) repeatedly, jumping-up extrusion cladding, needed back after extruding Stove heat, being squeezed by pier repeatedly improves high-entropy alloy tissue, suppresses the fine fisssure caused by high-entropy alloy severe lattice distorts The germinating and extension of line, obtain the high-entropy alloy ingot blank that crystal grain is more tiny and even tissue, has excellent service ability.

It is 2. according to claim 1 a kind of specifically for the hot-working of high entropy alloy material and the plastics modification of crystal grain refinement The method that technology prepares the high-performance high entropy alloy material of even tissue, it is characterised in that：1. pier combination process is squeezed to be easily achieved, Cost is cheap, can obtain the uniform excellent high-entropy alloy ingot blank material of structure property, its service ability be effectively improved, using this Method can not only promote the high-volume of high-entropy alloy to use, but also can be effectively improved and control the mechanical property of high-entropy alloy Energy；2. due in process all the time to high-entropy alloy blank implement repeatedly extruding and it is upset, high entropy can be suppressed well The germinating and extension of the caused micro-crack of alloy severe lattice distortion, obtain that crystal grain is more tiny and even tissue, have excellent The high-entropy alloy ingot blank of good service ability；3. the three-dimensional compression stress formed in extrusion process used for forming can suppress have high lattice The germinating and extension of micro-crack in the high-entropy alloy deformation process of distortion, efficiently accomplish the tune that becomes more meticulous of high-entropy alloy microstructure Control；4. as cast condition high-entropy alloy large dendritic crystal can be crushed by being squeezed by pier repeatedly, improve structural homogenity, significantly improve high-entropy alloy Service ability under the extreme conditions such as service ability, especially shock resistance.