VCrAl_(1.21)Ni_(0.93)Co_(1.85)高熵合金中间层真空扩散连接TC4钛合金和T2铜

Vacuum diffusion bonding of TC4 titanium alloy to T2 copper with VCrAl_(1.21)Ni_(0.93)Co_(1.85) high entropy alloy interlayer

根据伪二元合金设计策略和共晶高熵合金设计理念,设计并制备了VCrAl_(1.21)Ni_(0.93)Co_(1.85)共晶高熵合金中间层用于真空扩散连接TC4钛合金和T2铜,研究了不同连接温度对TC4/T2扩散连接接头微观组织和力学性能的影响规律.结果表明,所有接头界面结合良好无缺陷产生,在TC4侧的连接界面附近发生了部分相变,由α-Ti向β-Ti进行转变,并且形成了部分魏氏体组织.Ti_(2)(Co,Ni),Ti_(2)(V,Cr,Al),Ti(V,Cr,Co)和(V,Cr)(Al,Ni,Co)相形成在TC4/VCrAl_(1.21)Ni_(0.93)Co_(1.85)界面上,而VCrAl_(1.21)Ni_(0.93)Co_(1.85)/T2界面上形成了(V,Cr)(Al,Ni,Co)和(V,Cr)(Cu,Ni,Co)_(3)相.界面上形成高熵微观组织结构起到高熵固溶强化作用,扩散层Ⅰ和Ⅱ对应的生长激活能分别为229 kJ/mol和191 kJ/mol,接头抗剪强度在880℃时达到最大为194 MPa,接头主要沿着BCC基体相和B2相交替位置断裂,断口表面出现河流花样特征,属于一种典型的解理断裂模式.

VCrAl_(1.21)Ni_(0.93)Co_(1.85) eutectic high entropy alloy interlayer was designed based on the pseudo-binary strategy and design concept of eutectic high entropy alloy,which was used to join TC4 titanium alloy and T2 copper via vacuum diffusion bonding.The influence of bonding temperature on the microstructure and mechanical property of TC4/T2 diffusion bonded joint was investigated.The results showed that all the joint were well combined without defects.TC4 titanium alloy adjacent to the diffusion layer underwent a phase transition fromα-Ti to β-Ti,forming part of the Widmanstatten structure.Ti_(2)(Co,Ni),Ti_(2)(V,Cr,Al),Ti(V,Cr,Co)and(V,Cr)(Al,Ni,Co)phases appeared in the TC4/VCrAl_(1.21)Ni_(0.93)Co_(1.85) interface while(V,Cr)(Al,Ni,Co)and(V,Cr)(Cu,Ni,Co)_(3) phases formed in the VCrAl_(1.21)Ni_(0.93)Co_(1.85)/T2 interface.The high entropy microstructure formed in the interface,which played the role of high entropy solution strengthening.The growth activation energy of diffusion layer Ⅰ and Ⅱ was 229 kJ/mol and 191 kJ/mol,respectively.The maximum shear strength of joint at 880℃reached 194 MPa.The joint fracture was mainly along the BCC matrix phase and B2 phase alternately,and the fracture surface had the feature of river pattern,which belonged to a typical cleavage fracture mode.