原位自生碳化物增强CoCrFeNi高熵合金的显微组织与力学性能

Microstructure and Mechanical Properties of In-situ Carbides Reinforced CoCrFeNi High-entropy Alloys

为了提高面心立方(FCC)相高熵合金的强度,将Ti和C元素添加到FCC单相CoCrFeNi高熵合金中以实现强化效应。利用真空电弧熔炼法制备(CoCrFeNi)_(100-x)(TiC)_(x)(x=0、2、4、6、8(原子分数,%))高熵合金,研究了不同含量的Ti和C元素对CoCrFeNi合金显微组织和力学性能的影响。结果表明,添加Ti和C元素后,合金的微观结构由单一的FCC相转变为FCC基体相和原位自生富Ti碳化物,富Ti碳化物的形成并未改变基体相类型。富Ti碳化物沿着枝晶间凝固,呈片层状并相互连接形成网状组织。随着Ti和C含量的增加,FCC基体相含量逐渐降低,富Ti碳化物体积分数逐渐增大至12%。拉伸测试结果表明,随着富Ti碳化物含量的增加,合金的屈服强度和抗拉强度不断提高,延伸率呈下降趋势,当x=8时,抗拉强度从409 MPa(x=0)提升到618 MPa,同时合金能维持可应用的塑性,延伸率可达15.7%。硬度测试结果表明,随着富Ti碳化物含量的增加,合金的硬度呈上升趋势,当x=8时,硬度值为253HV_(0.2)。原位自生富Ti碳化物产生的第二相强化、固溶强化和枝晶间片层状、网状组织的协同效应使合金强度得到提升,同时合金还保持了较好的塑性。

In order to strengthen FCC-type high-entropy alloy(HEA),Ti and C were added to FCC single-phase CoCrFeNi HEA to realize the strengthening effect.(CoCrFeNi)_(100-x)(TiC)_(x)(x=0,2,4,6,8(atomic fraction,%))was prepared by vacuum arc melting.Effects of different contents of Ti and C on the microstructure and mechanical properties of CoCrFeNi HEA were studied.The results show that after adding Ti and C,the microstructure of(CoCrFeNi)_(100-x)(TiC)_(x) changes from single FCC phase to FCC matrix phase and in-situ Ti-rich carbides.The formation of Ti-rich carbides does not change the type of matrix phase.Ti-rich carbides solidify along the interdendrite,which is lamellar and connected with each other to form a network structure.With the increase of Ti and C content,the content of FCC matrix phase gradually decreases,and the vo-lume fraction of Ti-rich carbides gradually increases to 12%.The tensile test results show that with the increase of Ti-rich carbides content,the yield strength and tensile strength of the alloy increase continuously,while the elongation decreases;with x=8,the tensile strength can be increased from 409 MPa(x=0)to 618 MPa,with the applicable plasticity maintained,and the elongation can still reach 15.7%.The hardness test results show that the hardness of the alloy increases with the increase of Ti rich carbides content;with x=8,the hardness value is 253HV_(02).The second phase strengthening of in-situ Ti-rich carbides,solid solution strengthening and the synergistic effect of dendritic lamellar and network structure improve the strength of the alloy and ensures its good plasticity.