Sathiyamoorthi Praveen, Bae Jae Wung, Asghari-Rad Peyman, Park Jeong Min, Kim Jung Gi, Kim Hyoung Seop
Department of Material Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
Center for High Entropy Alloys, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
Entropy (Basel). 2018 Nov 6;20(11):849. doi: 10.3390/e20110849.
Annealing of severely plastic deformed materials is expected to produce a good combination of strength and ductility, which has been widely demonstrated in conventional materials. In the present study, high-pressure torsion processed CoCrNi medium entropy alloy consisting of a single face-centered cubic (FCC) phase with a grain size of 50 nm was subjected to different annealing conditions, and its effect on microstructure and mechanical behavior was investigated. The annealing of high-pressure torsion processed CoCrNi alloy exhibits partial recrystallization and near full recrystallization based on the annealing temperature and time. The samples annealed at 700 °C for 2 min exhibit very fine grain size, a high fraction of low angle grain boundaries, and high kernel average misorientation value, indicating partially recrystallized microstructure. The samples annealed for a longer duration (>2 min) exhibit relatively larger grain size, a low fraction of low angle grain boundaries, and low kernel average misorientation value, indicating nearly full recrystallized microstructure. The annealed samples with different microstructures significantly influence the uniform elongation, tensile strength, and work hardening rate. The sample annealed at 700 °C for 15 min exhibits a remarkable combination of tensile strength (1090 MPa) and strain to failure (~41%).
严重塑性变形材料的退火有望产生强度和延展性的良好结合，这在传统材料中已得到广泛证明。在本研究中，对经过高压扭转处理的CoCrNi中熵合金进行了不同的退火处理，该合金由单一的面心立方（FCC）相组成，晶粒尺寸约为50纳米，并研究了其对微观结构和力学行为的影响。基于退火温度和时间，高压扭转处理的CoCrNi合金的退火表现出部分再结晶和近完全再结晶。在700°C下退火2分钟的样品显示出非常细的晶粒尺寸、高比例的低角度晶界和高的内核平均取向差数值，表明为部分再结晶微观结构。退火时间更长（>2分钟）的样品显示出相对较大的晶粒尺寸、低比例的低角度晶界和低的内核平均取向差数值，表明为近完全再结晶微观结构。具有不同微观结构的退火样品对均匀伸长率、抗拉强度和加工硬化率有显著影响。在700°C下退火15分钟的样品表现出抗拉强度（约1090兆帕）和断裂应变（约41%）的显著结合。
