Cu过渡层对激光增材制造TC4/IN718双金属结构组织性能的影响

Effect of Cu Interlayer on Microstructure and Properties of TC4/IN718 Bimetallic Structure Fabricated by Laser Additive Manufacturing

摘要:

钛合金和镍基合金各具有独特性能，二者的双金属结构在航空航天领域具有广泛的应用前景。由于两种金属的物理与化学性能差异较大，易在结合区域产生开裂。基于直接激光沉积（DLD）技术，分别制备了无过渡层和Cu过渡层的TC4/IN718双金属结构。测试分析结果表明，无过渡层双金属结构，结合区形成大量Ti-Ni脆性相，导致裂纹敏感性提高，产生开裂；Cu过渡层的双金属结构，在TC4与IN718之间形成Cu过渡区，限制TC4与IN718直接结合，降低裂纹敏感性，无裂纹等冶金缺陷产生，由于冶金反应与元素扩散的发生，在Cu过渡区中形成了少量Ti-Cu与微量Ti-Ni化合物相；化合物相在双金属结构中的产生，使Cu过渡区维氏硬度最高约为592 HV，但远低于无过渡层双金属结构的维氏硬度（最高约为845 HV）。

Abstract:

Titanium alloys and nickel-based alloys have unique properties. The bimetallic structure formed by them has a broad application prospect in the aerospace field. However, due to the large differences in physical and chemical properties between the two metals, cracking is easy to occur at the bonding zone. Based on directed laser deposition (DLD) technology, TC4/IN718 bimetallic structures without interlayer and Cu interlayer were fabricated, respectively. The resuslts of test and analysis results indicate that the TC4/IN718 bimetallic structure without interlayer has cracking due to the formation of the Ti-Ni brittle phases at the bonding zone, which leads to the increase of crack sensitivity. In the bimetallic structure with Cu interlayer, the Cu transition zone formed between TC4 and IN718, which inhibited the direct combination of TC4 and IN718 and reduced the crack sensitivity. Due to metallurgical reaction and element diffusion, a small amount of Ti-Cu and a very small amount of Ti-Ni compound phases are formed in the Cu transition zone. Due to the formation of the compound phase, the Vickers hardness of the transition zone of TC4/IN718 bimetallic structure with Cu interlayer is about 592 HV. However, it is much lower than the Vickers hardness of the bonding zone of TC4/IN718 bimetallic structure without Cu interlayer (about 845 HV).