退火温度对FeNiCr中熵合金组织及力学性能的影响

Effect of Annealing Temperature on the Structure and Mechanical Properties of FeNiCr Medium Entropy Alloy

摘要: 采用磁悬浮感应熔炼法制备了FeNiCr中熵合金锭，经过80%压下量的室温冷轧变形后，分别在700℃、800℃、1000℃和1100℃下进行保温退火处理1 h，研究退火温度对FeNiCr中熵合金显微组织和力学性能的影响及其规律。结果表明：经不同温度退火处理后FeNiCr中熵合金始终保持着简单的单相FCC结构；轧制态FeNiCr中熵合金微观应变和位错密度均较高，随着退火温度升高中熵合金的位错密度和微观应变均逐步变小，到1100℃时微观应变几乎消失；在700℃低温退火后形成了一些细小等轴晶以及退火孪晶，再结晶不完全，到1000℃退火后发生了完全再结晶，退火温度继续增加就会出现晶粒粗大；从700℃升高至800℃时，平均晶粒尺寸增幅比较高并达到接近4倍，1100℃退火时晶粒尺寸最大且达到了21.3 μm。从其工程应力–应变曲线可知，在700℃退火时中熵合金屈服强度和抗拉强度分别高达886 MPa和982.9 MPa，断后伸长率仅为14.1%；但是随着退火温度不断升高，分别减少到1100℃的387 MPa和583 MPa，断后伸长率却提高到36.1%，其断口韧窝数量和大小均同步增大；退火温度从700℃升至1100℃时，合金显微硬度值则分别从428.1 HV0.2降低278.5 HV0.2，出现了大幅减少。

Abstract: FeNiCr medium entropy alloy ingots were prepared by magnetic levitation induction melting method. After being cold rolled and deformed at room temperature with an 80% reduction, they were subjected to insulation annealing treatment at 700˚C, 800˚C, 1000˚C, and 1100˚C for 1 hour. The effect of annealing temperature on the microstructure and mechanical properties of FeNiCr medium entropy alloy and its regularity were studied. The results show that the FeNiCr medium entropy alloy maintains a simple singlephase FCC structure after annealing at different temperatures; the micro strain and dislocation density of the rolled FeNiCr medium entropy alloy are both relatively high. As the annealing temperature increases, the dislocation density and micro strain of the high and high entropy alloy gradually decrease, and the micro strain almost disappears at 1100˚C; after low-temperature annealing at 700˚C, some fine equiaxed grains and annealing twins were formed, and the recrystallization was incomplete, after annealing at 1000˚C, complete recrystallization occurred, and further increase in annealing temperature would result in coarse grains; when the temperature rises from 700˚C to 800˚C, the average grain size increases significantly and reaches nearly four times. When annealed at 1100˚C, the grain size reaches its maximum and reaches 21.3 μm. From its engineering stress-strain curve, it can be seen that the yield strength and tensile strength of the medium entropy alloy are as high as 886 MPa and 982.9 MPa, the elongation after fracture is only 14.1%; however, as the annealing temperature continues to increase, it decreases to 387 MPa and 583 MPa at 1100˚C, respectively. However, the elongation after fracture increases to 36.1%, and the number and size of fracture toughness dimples increase simultaneously; when the annealing temperature increased from 700˚C to 1100˚C, the microhardness values of the alloy decreased significantly from 428.1 HV0.2 to 278.5 HV0.2, indicating a significant decrease.