镍基合金TLP扩散焊接头中二元共晶沉淀相Ni-M(B、Si、Zr和Hf)的性能

采用基于密度泛函理论的第一性原理平面波赝势计算方法,计算了Ni-M(B、Si、Zr和Hf)二元共晶沉淀相(Ni2B、Ni3B、Ni3B2、Ni23B6、Ni3Si、Ni5Zr和Ni5Hf)的相稳定性、弹性常数、硬度及相应的电子结构。相稳定性计算结果表明,二元共晶沉淀相结构稳定性变化趋势由高到低的顺序为Ni3Si、Ni5Zr、Ni2B、Ni5Hf、Ni3B、Ni3B2、Ni23B6,这意味着降熔元素Si形成的Ni3Si沉淀相稳定性强于降熔元素B、Zr和Hf形成的沉淀相。弹性力学计算表明,Ni3B2表现为很强的各向异性,Ni2B、Ni3B和Ni3Si表现出一定的各向异性,而Ni23B6、Ni5Zr和Ni5Hf则表现为较强的各向同性。二元共晶沉淀相B/G值均大于1.75,这意味着它们为延性相。硬度计算的由小到大的小趋势为Ni3B2、Ni3B、Ni23B6、Ni2B、Ni5Zr、Ni3Si、Ni5Hf,其与各相中Ni 3d与B 2p,Si 3p,Zr 4d和Hf 5d的原子轨道杂化强度密切相关。

Properties of Ni-M(B,Si,Zr and Hf)binary eutectic precipitates in TLP diffusion joint of nickel-base alloy

A systematic investigation concerned with phase stability,elastic properties,hardness and relevant electronic structure of Ni-M binary eutectic precipitates(Ni2B,Ni3B,Ni3B2,Ni23B6,Ni3Si,Ni5Zr and Ni5Hf)was carried out using first principles calculations.The calculated results show that the change trend of the structural stability follows Ni3Si>Ni5Zr>Ni2B>Ni5Hf>Ni3B>Ni3B2>Ni23B6,indicating that the stability of Ni3Si phase using Si as melting-point depressant is stronger than that using B,Zr and Hf as melting-point depressants.The calculated elastic constants indicate that Ni3B2 is significantly anisotropic,and Ni2B,Ni3B and Ni3Si exhibit some anisotropy,while Ni23B6,Ni5Zr and Ni5Hfshow a relatively isotropic character.The ratios of bulk modulus(B)to shear modulus(G)are more than 1.75 for all the Ni-M binary eutectic precipitates in this research,indicating their ductile nature.The trend of Vickers hardness of these Ni-M binary eutectic precipitates is as Ni3B2