热处理对铁基中熵合金微观结构及力学性能的影响

Effect of Heat Treatment on Microstructure and Properties of Iron-based Medium-entropy Alloys

以水冷铜坩埚磁悬浮熔炼-铜模负压吸铸法制备了Fe_(77.3-x)Mn_(x)Si_(9.1)Cr_(9.8)C_(3.8)(x=14,23)中熵合金,研究了不同时间高温热处理对其微观组织及压缩力学性能的影响。结果表明:Fe_(77.3-x)Mn_(x)Si_(9.1)Cr_(9.8)C_(3.8)中熵合金均为低层错能合金;Fe_(63.3)Mn_(14)Si_(9.1)Cr_(9.8)C_(3.8)在热处理前后均为单一的FCC结构;Fe_(54.3)Mn_(23)Si_(9.1)Cr_(9.8)C_(3.8)铸态合金为FCC+HCP双相组织,在1100℃淬火处理中HCP转变为FCC结构。Fe_(77.3-x)Mn_(x)Si_(9.1)Cr_(9.8)C_(3.8)中熵合金的综合力学性能在保温时间为20 min时达到最佳;Fe_(63.3)Mn_(14)Si_(9.1)Cr_(9.8)C_(3.8)热处理后断裂强度和塑性分别可达3250 MPa和24.5%,其断口形貌中河流花样密集,断口中心区域韧窝密集均匀。

Fe_(77.3-x)Mn_(x)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloys were prepared by water-cooled copper crucible magnetic levitation melting-copper mold ne-gative pressure suction casting method,and the effect of quenching at 1100℃for different time on microstructure and mechanical properties of the alloys was studied.The results show that the Fe_(77.3-x)Mn_(x)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloys are all low stacking fault energy alloys,the structure of the Fe 63.3 Mn_(14)Si_(9.1)Cr_(9.8)C_(3.8)alloy is a single FCC structure before and after heat treatment,the structure of the as-cast Fe_(54.3)Mn_(23)-Si_(9.1)Cr_(9.8)C_(3.8)alloy is FCC and HCP dual-phase structure,and the HCP structure is transformed into FCC structure during quenching at 1100℃.The comprehensive mechanical properties of the Fe_(77.3-x)Mn_(x)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloys are the best when the holding time is 20 min.The fracture strength and plasticity of the Fe_(63.3)Mn_(14)Si_(9.1)Cr_(9.8)C_(3.8)alloy after heat treatment are respectively 3250 MPa and 24.5%,and the river pattern is dense in the fracture morphology,and the dimples in the central region of the fracture surface are dense and uniform.