CN107142410B - CrMoNbTiZr high entropy alloy materials and preparation method thereof - Google Patents

Abstract

The invention relates to a high-entropy alloy material and its preparation technology. The composition of the high-entropy alloy material is CrMoNbTiZr, wherein the molar ratio of Cr:Mo:Nb:Ti:Zr is: 1:1:1:1:1. The preparation process is as follows: (1) Powder preparation: Prepare metal powders according to equimolar ratio; (2) Powder mixing: Mix the prepared powder evenly on a V-type powder mixer; (3) Press into blocks: Mix the The powder is cold-pressed under a press; (4) Smelting alloy: a vacuum non-consumable arc melting furnace is used to melt the pressed block sample. The main composition phase of the CrMoNbTiZr high-entropy alloy prepared by the invention is a BCC solid solution phase and a small amount of Laves phase, and has the advantages of high hardness, strong corrosion resistance, and the like. The alloy has good application prospects in the fields of wear resistance and corrosion resistance.

Description

CrMoNbTiZr high entropy alloy material and preparation method thereof

technical field

The invention relates to a high-entropy alloy and a preparation method thereof, in particular to a wear-resistant and corrosion-resistant CrMoNbTiZr high-entropy alloy and a preparation method thereof, belonging to the technical field of alloy materials and preparation thereof.

Background technique

The traditional understanding of alloy performance is that alloy performance can be improved and improved by adding trace alloy elements, such as increasing strength, hardness, compressive strength, corrosion resistance, thermal stability, etc., but this method is not without disadvantages , if added too much, it will lead to a large number of brittle intermetallic compounds or even brittle complex phases, which will reduce the mechanical properties of the alloy. In addition, too many compounds will have an adverse effect on the study of the alloy structure. Therefore, for a long time, in the process of developing new alloys and improving alloys, scholars have always used an alloy element as the main component (generally more than 50%), and used the method of adding a small amount of alloy elements and improving the process to obtain excellent microstructure. and performance alloys. However, with the rapid development of today's industrial engineering technology, the lack of performance of a single material has become a problem that restricts its further development in the engineering field. Therefore, researchers are more and more inclined to use high-tech to develop and prepare new materials with high performance. Research and development of new materials with excellent strength, toughness, hardness and other properties have become the main direction of the development of the material field. As a new type of high-strength alloy that has emerged and developed rapidly in recent years, high-entropy alloys have attracted great attention from experts in the field of materials. Ye Junwei of Tsinghua University in Taiwan, China, took the lead in jumping out of the development framework of traditional alloys, and first proposed the design idea of multi-component high-entropy alloys in 2004. Multi-principal high-entropy alloys generally have 5 or more main elements. The main elements are arranged in an equimolar ratio or an approximately equimolar ratio. The mixing entropy of the alloy is extremely high. During the solidification process, the precipitation of brittle phases in traditional multi-component alloys is suppressed, such as intermetallic compounds; after solidification, a single solid solution with BCC or FCC structure is generally formed, which greatly reduces the brittleness of multi-component alloys. Multi-principal element high-entropy alloys break the traditional alloy design mode based on one alloy element, and can obtain structural characteristics such as simplified microstructure, nano-precipitates, amorphous structure, and nano-grains through the optimization design of alloy components. Combining alloys with excellent properties such as high strength, high hardness, wear resistance, corrosion resistance, high temperature creep resistance, high temperature oxidation resistance, and temper softening resistance, are widely used in high-pressure resistant, corrosion-resistant chemical containers and high-strength corrosion-resistant engineering pieces.

Contents of the invention

The purpose of the present invention is to develop a wear-resistant and corrosion-resistant high-entropy alloy with excellent performance——CrMoNbTiZr high-entropy alloy, so that it can meet people's requirements for material wear resistance in modern industry, so that the high-entropy alloy can be obtained in the application field widely used.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: a high-entropy alloy material, the composition is CrMoNbTiZr, wherein, the molar ratio of Cr:Mo:Nb:Ti:Zr is: 1:1:1:1: 1.

The technical solution adopted by the present invention to solve the above-mentioned technical problems also includes: a preparation method of a high-entropy alloy material whose composition is CrMoNbTiZr, which is characterized in that it is specifically completed according to the following steps:

1. Use metallurgical raw materials Cr, Mo, Nb, Ti and Zr metal powders with a purity of more than 99.5%, accurately weigh and mix them according to the equimolar ratio;

2. Use a press to press the mixed powder into blocks for the preparation of alloys from molten materials;

3. Use a vacuum non-consumable electrode arc furnace to smelt alloys. First, place the blocky samples in the peripheral smelting tank, and place the pure titanium particles in the middle smelting tank. After placing, close the furnace door and tighten it. Four closed knobs in the sample chamber;

4. Vacuum the sample chamber. When the vacuum degree reaches 5×10 ^-3 Pa, fill in argon gas with a purity of 99.99% until the pressure in the furnace reaches half an atmosphere, and repeat this step 2 or 3 times; The purpose is to wash the gas, repeatedly filling and discharging argon to minimize the air in the melting furnace;

5. After vacuuming, fill and release argon until the pressure in the furnace reaches half an atmospheric pressure, then you can start melting; before melting the sample, first melt the pure titanium particles in the melting pool, and try to remove the remaining oxygen in the furnace. depleted;

6. In order to mix the raw materials evenly during the smelting process, after each smelting alloy is melted, the arc is kept for 90-120s, and the alloy block is turned over after it cools down, and this is repeated more than 4 times;

7. After the smelting is completed, according to the size and shape of the required product, the alloy liquid after repeated smelting can be cast in the mold, and then cooled to obtain it.

Principle of the present invention and beneficial effect are:

1. The present invention provides a kind of CrMoNbTiZr high-entropy alloy, described high-entropy alloy is made up of the solid solution phase of simple structure and a small amount of laves phase, alloy structure is uniform, has higher hardness and excellent corrosion resistance, the alloy's The microhardness is as high as 689HV. with broadly application foreground;

2. The present invention provides a method for preparing a CrMoNbTiZr high-entropy alloy, which is prepared by high-vacuum alloy arc melting, and the preparation method is simple and reliable.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the CrMoNbTiZr high entropy alloy prepared in the embodiment.

Fig. 2 is the scanning electron microstructure of the CrMoNbTiZr high-entropy alloy prepared in the embodiment.

Detailed ways

The preparation method and process performance of the present invention are illustrated by specific specific examples below, and those skilled in the art can fully understand the advantages and functions of the present invention from the contents disclosed in this specification.

1. CrMoNbTiZr high entropy alloy composition design.

This embodiment is a CrMoNbTiZr high-entropy alloy composed of five elements: Cr, Mo, Nb, Ti and Zr, wherein the molar ratio of Cr:Mo:Nb:Ti:Zr is: 1:1:1:1 :1.

2. Preparation of CrMoNbTiZr high entropy alloy.

The preparation of high-entropy alloys is the most critical step, and the preparation process is as follows:

1) Raw material preparation: the alloy smelting raw materials used in the present invention are high-purity (purity above 99.5%) Cr, Mo, Nb, Ti and Zr elements, and all raw materials used are powder materials;

2) Weighing and mixing powder: Carry out accurate weighing and mixing ratio according to the molar ratio, and mix the weighed powder materials together, and use a V-type powder mixing machine to mix at a constant speed for 10 hours;

3) Pressing into blocks: cold press the mixed powder on a cold press with a pressure of 200MPa, and the holding time is about 90-120s;

4) Melting high-entropy alloys: ①Use a vacuum non-consumable electrode electric arc furnace to melt the alloy. First, place the blocky samples in the four peripheral melting tanks, and place the pure titanium particles in the middle melting tank. After completion, close the furnace door and tighten the four closed knobs of the sample chamber; ② Vacuumize the sample chamber. When the vacuum reaches 5×10 ^-3 Pa, fill in argon with a purity of 99.99% until the pressure in the furnace reaches half an atmosphere. And repeat this step 2 to 3 times; the purpose of repeated vacuuming is to wash the gas, repeatedly filling and discharging argon to minimize the air in the melting furnace; ③After vacuuming, fill and discharge argon until the pressure in the furnace reaches half Atmospheric pressure, the smelting can start at this time; before smelting the sample, smelt the pure titanium particles in the smelting pool to try to consume the residual oxygen in the furnace; After each smelting alloy is melted, the arc is kept for 90~120s, and the alloy block is turned over after cooling, and this is repeated more than 4 times; The sample was taken out of the furnace, and finally an ellipsoidal CrMoNbTiZr high-entropy alloy ingot was obtained.

3. Microstructure and properties of CrMoNbTiZr high-entropy alloys.

1) X-ray diffraction (XRD) test and phase composition analysis

Cut the obtained ingot into a square sample with a size of 5mm×5mm×4mm by wire cutting, and then carefully grind the sample with 800#, 1200#, 1500# and 2000# metallographic sandpaper in turn, and then polish it with a polishing machine . X-ray diffraction phase analysis was performed on a Rigaku D/Max 2500 X-ray diffractometer. Technical specifications of the equipment: use Cu as the radiation source, graphite monochromator, operating voltage 40kV, current 250mA, self-rotating target. The scan rate is 8°/min, and the diffraction angle range is selected to be 2θ=5-90°. MDI-Jade 6.0 software was used to analyze the experimental data and determine the phase. The XRD test results of the CrMoNbTiZr high-entropy alloy shown in Figure 1 show that the main constituent phase of the CrMoNbTiZr high-entropy alloy is a solid solution phase with a body-centered cubic structure and a small amount of Laves phase. The Laves phases are mainly CrTi ₂ , Mo ₃ Nb intermetallic compounds.

2) Microstructure analysis

Cut the obtained ingot into a square sample with a size of 5mm×5mm×4mm by wire cutting, and then carefully grind the sample with 800#, 1200#, 1500# and 2000# metallographic sandpaper in turn, and then polish it with a polishing machine . The morphology of the samples was observed with a scanning electron microscope. It can be seen from Figure 2 that the cellular structure of the CrMoNbTiZr high-entropy alloy is formed.

3) Microhardness measurement and analysis

Cut the obtained ingot into a square sample with a size of 5mm×5mm×4mm by wire cutting, and then carefully grind the sample with 800#, 1200#, 1500# and 2000# metallographic sandpaper in turn, and then polish it with a polishing machine . A HZr-1000 microhardness tester was used to test the hardness of the sample, the test force of the microhardness tester was 9.807N (1kgf), and the load was 15s. Select 7 different positions of the sample to measure its microhardness, remove the highest hardness value and the lowest hardness value, take the average value of the remaining hardness values as the microhardness value of the sample, and finally obtain the microhardness value of the alloy as 689HV.

4) Corrosion resistance of the alloy

Cut the obtained ingot into a square sample with a size of 5mm×5mm×4mm by wire cutting, and then carefully grind the sample with 800#, 1200#, 1500# and 2000# metallographic sandpaper in turn, and then polish it with a polishing machine . Put the ground and polished samples into alcohol and clean them with an ultrasonic cleaner for 30 minutes, dry and weigh them, and then immerse the samples in 5%, 15%, 30% _HNO3 solutions and 3.5% NaCl solutions respectively. After keeping for 6h, 12h, 24h, 48h, 96h, take it out, and analyze the surface state and weight change of the sample before and after corrosion.

It can be seen from Table 1 that the quality of the alloy changes little in different corrosive solutions, and the surface of the alloy hardly changes, indicating that the CrMoNbTiZr high-entropy alloy prepared by the present application has excellent corrosion resistance.

In the example of Table 1, the CrMoNbTiZr high-entropy alloy was soaked in 3.5% NaCl solution and 5%, 15%, 30% HNO3 solution after 96h mass change Corrosive solution 3.5%NaCl 5% _HNO3 15% _HNO3 30% _HNO3 Mass before corrosion/g 0.7359 0.6776 0.7663 0.7219 Mass after corrosion/g 0.7360 0.6786 0.7668 0.7210 Mass change/g 0.0001 0.0010 0.0005 -0.0009

Claims (2)

1. a kind of high entropy alloy material, it is characterised in that：The high-entropy alloy ingredient is CrMoNbTiZr, wherein Cr:Mo:Nb: Ti:The molar ratio of Zr is followed successively by：1:1:1:1:1；The preparation method of the CrMoNbTiZr high entropy alloy materials, it is characterised in that It is specifically realized by the following steps：

One, it using Cr, Mo, Nb, Ti and Zr metal powder, carries out accurate weigh according to equimolar ratio and matches, be mixed Uniformly；

Two, it using pressure-like machine by mixed powder briquet, prepares alloy for melt and uses；

Three, using vacuum non-consumable electrode electric arc furnace molten alloy, block-like sample is placed in the melting slot of periphery first, And be placed on pure titanium grain in most intermediate melting slot, placement closes fire door after finishing, and tightens four, sample room closing knob；

Four, sample room is vacuumized, when vacuum degree reaches 5 × 10^-3After Pa, be filled with purity be 99.99% argon gas until stove internal pressure Power reaches half of atmospheric pressure, and repeats this step 2~3 time；The purpose that repetition vacuumizes is gas washing, and charge and discharge argon gas makes repeatedly Air in smelting furnace minimizes as possible；

Five, charge and discharge argon gas reaches half of atmospheric pressure until furnace pressure after vacuum exhausts, and can proceed by melting at this time； It is as possible that remaining oxygen in stove is depleted first by the pure titanium grain melting one time in melting pond before melting sample；

Six, in order to make raw material be better mixed uniformly in fusion process, after each molten alloy fusing, the electric arc retention time is 90 ~120s is overturn after alloy block cooling, is so repeated 4 times above；

Seven, after melting is completed, according to the size shape of required product, the aluminium alloy after repetition melting can be cast in mold It is interior, it is then cooling to obtain.

2. high entropy alloy material according to claim 1, it is characterised in that Cr, Mo, Nb, Ti and Zr described in step 1 The purity of metal powder is 99.5% or more.