CN-118086751-B - Low dislocation density nano Cantor alloy and preparation method thereof

CN118086751BCN 118086751 BCN118086751 BCN 118086751BCN-118086751-B

Abstract

The invention belongs to the field of material preparation, and particularly relates to a low dislocation density nano Cantor alloy and a preparation method thereof. The method comprises the steps of (1) multidirectional forging, namely performing multidirectional forging treatment on an initial Cantor alloy, (2) homogenizing, namely annealing at a high temperature for a long time to obtain uniform large-size grain structures, (3) cryogenic rolling, namely cryogenic rolling the homogenized Cantor alloy, and intensively refining grains through low-temperature induced twinning and large-strain combination, and (4) high-temperature instantaneous annealing, namely obtaining the Cantor alloy with nano-scale grains with low dislocation density through high-temperature instantaneous annealing. The low dislocation density characteristic of the microstructure prepared by the invention is beneficial to theoretical research and structural design of new alloys in the future, the material utilization rate is high, and the characteristic structure, namely the microstructure, can be obviously thinned to the nanoscale in the whole volume, so that uniform nano grains are obtained.

Inventors

LI YUSHENG
FANG WEI
ZHANG DONGMEI
SUN GUOQI
LING XINNAN
CHEN SIWEI

Assignees

南京理工大学

Dates

Publication Date: 20260512
Application Date: 20231211

Claims (4)

1. The preparation method of the low dislocation density nano Cantor alloy is characterized by comprising the following steps of: the multi-directional forging is carried out on the initial Cantor alloy; homogenizing, namely annealing at a high temperature for a long time to obtain a uniform large-size grain structure; The step (3) of cryogenic rolling, which is to conduct cryogenic rolling on the homogenized Cantor alloy, and strongly refine grains through low-temperature induced twinning and large strain quantity combination; step (4), high-temperature instantaneous annealing, namely obtaining the Cantor alloy with nano-scale grains with low dislocation density through the high-temperature instantaneous annealing; the Cantor alloy comprises Co, cr, fe, mn and Ni in equimolar ratio; Placing the Cantor alloy in an annealing furnace, and preserving the temperature at 1200+/-10 ℃ for 20+/-2 min to obtain a uniform coarse crystal structure; the step (2) is specifically that the temperature is kept for 2+/-0.1 h at 1100+/-10 ℃; The total rolling reduction of the step (3) is 75% -95%; The step (3) of deep cold rolling is that the homogenized Cantor alloy is soaked in liquid nitrogen for 3 to 10 hours to reach uniform deep cooling temperature; the Cantor alloy reaching the cryogenic temperature is placed in a cold-hot two-roll mill for repeated cryogenic rolling, the rolling speed is 35HZ, each pass of rolling is reduced by 0.2mm, and after each pass of rolling, a sample is placed back into liquid nitrogen for soaking for 10-30min so as to ensure the cryogenic temperature; The step (4) is that the Cantor alloy after deep cold rolling is placed in an induction coil heating furnace for rapid annealing at 900-1000 ℃ for 25-45 seconds and then cooled in an air cooling mode.
2. The method according to claim 1, wherein the total reduction of the cryogenic rolling in step (3) is 90%.
3. The method of claim 2, wherein the high temperature transient anneal is at 975 ℃ for 30 seconds.
4. A low dislocation density nano Cantor alloy prepared by the method of any one of claims 1 to 3, wherein the average grain size in the low dislocation density nano-grain structure is refined to below 800 nm.

Description

Low dislocation density nano Cantor alloy and preparation method thereof Technical Field The invention belongs to the field of material preparation, and particularly relates to a low dislocation density nano Cantor alloy and a preparation method thereof. Background High-entropy alloys (High entropy alloys, HEAs) have received extensive attention from scientists for their excellent properties, whereas Cantor (CoCrFeNiMn) alloys are most notable for their excellent ductility and low temperature properties in large high-entropy alloy systems. According to the hall-petition relationship, the strength of conventional metals increases with decreasing grain size. Therefore, an alloy having UFG structure has higher mechanical strength than coarse-grain alloy (CG). For example, journal MATERIALS SCIENCE & ENGINEERING A, volume 705, 9.29.2017, pages 411-419, shahmir, et al, refined the grain size of Cantor alloy by equal channel angular Extrusion (ECAP), and achieved ultimate tensile strength of ≡990 MPa. Numerous studies have shown that the strength of high-entropy alloys has a direct relationship with the platelet thickness and grain size. When the sheet thickness is above submicron, the relationship between the strength and thickness of the material satisfies the general Hall-Petch relationship in the broad sense that the yield strength is proportional to the inverse of the square root of the thickness. However, when the thickness of the lamellar layer is reduced to the nanometer level, the constitutive relationship between the strength and thickness of the material has not been fully studied. At present, a plurality of methods for preparing ultrafine-grain high-entropy alloy exist on the market, for example, chinese patent CN201410545199.6 discloses a method for preparing high-strength and high-toughness ultrafine-grain high-entropy alloy by adopting a powder metallurgy method, but the powder metallurgy method is known to have higher cost and can only prepare small samples, and can not meet the preparation of larger samples in industrial production. In the field of high-entropy alloy, the prior Strong Plastic Deformation (SPD) technology, high-pressure torsion (HPT), equal channel Extrusion (ECAP) and other methods are adopted by the existing researchers to refine grains, so that ultra-fine grain or nanocrystalline high-strength high-entropy alloy is obtained, but the prior SPD method has strict requirements on the preparation process, and can only prepare small-size samples similar to powder metallurgy, so that large-scale industrial production and application are difficult to realize. Disclosure of Invention The invention aims to provide a low dislocation density nano Cantor alloy and a preparation method thereof. The technical scheme for realizing the aim of the invention is that the preparation method of the low dislocation density nano Cantor alloy comprises the following steps: the multi-directional forging is carried out on the initial Cantor alloy; homogenizing, namely annealing at a high temperature for a long time to obtain a uniform large-size grain structure; The step (3) of cryogenic rolling, which is to conduct cryogenic rolling on the homogenized Cantor alloy, and strongly refine grains through low-temperature induced twinning and large strain quantity combination; and (4) carrying out high-temperature instantaneous annealing, namely obtaining the Cantor alloy with nano-scale grains with low dislocation density through the high-temperature instantaneous annealing. Further, the composition of the Cantor alloy is Co, cr, fe, mn and Ni in equimolar ratio. Further, the step (1) comprises the steps of placing the Cantor alloy in an annealing furnace, preserving heat for 20+/-2 min at 1200+/-10 ℃ to obtain a uniform coarse crystal structure, and then continuously drawing out for three times under an air forging hammer to remove defects in the premelted alloy. Further, the step (2) is specifically to keep the temperature at 1100+/-10 ℃ for 2+/-0.1 h. Further, the total reduction of the cryogenic rolling in the step (3) is 75% -95%. Further, the total reduction of the cryogenic rolling in the step (3) is 90%. Further, the step (3) of deep cold rolling is specifically to soak the homogenized Cantor alloy in liquid nitrogen for 3-10 hours to reach uniform deep cooling temperature; And (3) placing the Cantor alloy reaching the cryogenic temperature in a cold and hot two-roll mill for repeated cryogenic rolling, wherein the rolling speed is 35HZ, the rolling reduction is 0.2mm in each pass, and the sample is placed back into liquid nitrogen after each pass of rolling to be soaked for 10-30min so as to ensure the cryogenic temperature. Further, the step (4) is specifically that the Cantor alloy subjected to deep cold rolling is placed in an induction coil heating furnace for rapid annealing at 900-1000 ℃ for 25-45 seconds and then cooled in an air cooling mode. Further, the high temperature transient annealing