电子束选区熔化TaNbTiZr难熔高熵合金的微观组织与力学性能

Microstructure and mechanical properties of TaNbTiZr refractory high-entropy alloy fabricated by EBM

难熔高熵合金(RHEAs)表现出优异的高温性能,在航空航天、核能等领域具有广泛应用前景。然而,由于难熔高熵合金(RHEAs)组成元素熔点高,因此常规加工制造方法制备难度大。本研究以等离子旋转电极雾化法(PREP)制备的高质量TaNbTiZr难熔高熵合金球形粉末为原料,通过电子束选区熔化(EBM)制备TaNbTiZr难熔高熵合金,利用正交实验研究了工艺参数对合金微观组织和力学性能的影响。结果表明:EBM样品的致密度随着线能量密度的增大呈先上升后下降的趋势,线能量密度为37.5 J/m的样品致密度最高,相对致密度达到98%。TaNbTiZr难熔高熵合金在XOY和XOZ面均呈细小的等轴晶结构,平均晶粒尺寸分别为6.32μm和6.93μm。晶粒内部由富含Nb、Ta的BCC1基体相和富Zr的BCC2网状边界组成。TaNbTiZr难熔高熵合金具有优异的力学性能,其屈服强度、抗拉强度、断裂伸长率分别为988 MPa、1173 MPa和3.99%。理论计算表明,该合金的高屈服强度主要源于高晶格畸变强化和高细晶强化效应。

Refractory high-entropy alloys(RHEAs)exhibit excellent high-temperature performance and have broad application prospects in aerospace,nuclear energy,and other fields.However,it is difficult to prepare RHEAs through conventional manufacturing methods because of the high melting points of the constituent elements.In this study,high-quality TaNbTiZr RHEA spherical powders prepared by plasma rotating electrode process(PREP)were used as raw materials to fabricate the TaNbTiZr RHEA by electron beam melting(EBM).The effects of process parameters on the microstructure and mechanical properties were investigated by orthogonal experiments.The results show that the density of the EBMed samples increase initially and then decrease with the increase of energy density,and the EBMed sample at an energy density of 37.5 J/m has the highest relative density of 98%.The TaNbTiZr RHEA consists of fine equiaxed grains on both the XOY and XOZ planes,with average grain sizes of 6.32μm and 6.93μm,respectively.There are(Nb,Ta)-rich BCC1 matrix phase and Zr-rich BCC2 network phase inside the grains.The TaNbTiZr RHEA exhibits excellent mechanical properties,with yield strength,tensile strength,and elongation of 988 MPa,1173 MPa,and 3.99%,respectively.Theoretical calculation shows that the high yield strength of the TaNbTiZr RHEA is mainly due to the effects of high lattice distortion strengthening and high grain boundary strengthening.