The TC4/AlSi12 bimetallic structures (BS) with Nb interlayer transition were fabricated by laser additive manufacturing (LAM). The results showed that the TC4/AlSi12 BS with Nb interlayer prepared with optimized process parameters can be divided into three regions (the TC4 region, Nb region and the AlSi12 region) and two interfaces (the TC4/Nb interface and the Nb/AlSi12 interface). The high melting point (Ti, Nb) solid solution formed in the Nb region acted as a diffusion barrier between the TC4 alloy and the AlSi12 alloy, thereby effectively inhibiting the formation of Ti-Al intermetallic compounds (IMCs). With the decrease of the laser output power for AlSi12 deposition, the NbAl₃ IMC changed from layered to dispersed distribution, while γ-TiAl and Ti₅Si₃ IMC disappeared, thus significantly reducing the crack susceptibility of the BS deposited layer. The tensile strength of TC4/AlSi12 BS with Nb interlayer was about 128MPa, and the fracture was located near the Nb/AlSi12 interface.

Ti/Al bimetallic structure (BS) has a good development prospect and broader application potential in aerospace engineering. Considering the limitation that dissimilar welding is only applicable to the thin plate, it is necessary to explore a new manufacturing process for Ti/Al BS. In this study, a TC4/AlSi12 BS was prepared by laser additive manufacturing (LAM). TC4 zone, AlSi12 zone and transition zone were formed in the LAM process. Due to the sufficient diffusion reaction, the transition zone with a width of about 0.8 mm was obtained. At the same time, a few micro-cracks were found in the transition zone. The microstructure and phase composition of the transition zone had been emphatically studied. Research results showed that the presence of Si element made the phase composition of the transition zone more complicated. The structure evolution from TC4 to AlSi12 was: α-Ti → Ti₃Al → TiAl+(TiAl+Si) → Ti₅Si₃ → TiAl₃+(α-Al+Si) → α-Al+Si+TiAl₃+(α-Al+Si) → α-Al+Si+(α-Al+Si). The hardness distribution of BS was uneven, with the highest value reaching 524 HV. The tensile strength of the TC4/AlSi12 BS was about 110Mpa, and the fracture location was located in the transition zone.

The bimetallic structure formed by TC4 and Inconel718 has broad potential applications in aerospace. Based on the laser deposition manufacturing technique, a TC4/Inconel718 bimetallic structure was fabricated via the Ta/Cu transition layer. The test results indicated that a Ta/Cu transition region with a width of 475.0 μm was formed. The microstructure of the transition region changed from a reticular to a rod structure, and the corresponding phase compositions were β-Ta + Ti₂Cu + TiCu and TiCu+γ-Cu + Cr₂Ta. Owing to the formation of Ti–Cu and Cr–Ta phases in the transition region, the Vickers hardness reached 444.0 HV. The ultimate tensile strength was 280 MPa, and the fracture morphology presented a quasi-cleavage fracture, which occurred in the Ta/Cu transition region where Ti–Cu brittle phases exist.

Stellite-6+VC 混合粉末激光熔覆性能的研究 * 徐国建 1 杨文奇 1 杭争翔 1 刘祥宇 2 迟海龙 2 欧雪松 2 (1. 沈阳工业大学材料科学与工程学院 沈阳 110870； 2. 南京中科煜宸激光技术有限公司 南京 210038) 摘要：小功率脉冲激光下飞机叶片的强化是现在急需解决的问题，本试验通过采用光纤传输 300 W Nd:YAG 脉冲激光熔覆系 统，在低碳钢(SM400B)上熔覆 Co 基合金(Stellite-6)和碳化钒(VC)混合粉末(VC 的质量分数变化范围为 0～100%)，并对熔覆 层的性能进行了研究，从而探究小功率脉冲激光下飞机叶片强化的工艺。试验结果表明，随着 VC 质量分数的增加，熔覆层

A bimetallic structure (BS) made of Inconel625 (IN625) nickel-base superalloy with excellent high temperature properties and Ti6Al4V (TC4) titanium alloy with a light weight and a high strength has broad application prospects in aerospace engineering. However, the integrated manufacturing of the IN625/TC4 BS is a difficult research topic in the industry. In this work, the laser melting deposition (LMD) technology was used to prepare an IN625/TC4 BS without cracks and other metallurgical defects by adding Cu/V interlayers. The results show that the IN625/TC4 BS structure from the IN625 side to the TC4 one can be divided into four regions: IN625 region (region A) → Interlayers/IN625 transition region (region B) → TC4/Interlayers transition region (region C) → TC4 region (region D). The phase compositions of these regions are: γ-Ni + laves → (Ni, Cu)ss + (V, Cr)ss + TiNi → α-Ti + β-Ti + Ti₂Ni → α-Ti + β-Ti. The Vickers hardness distribution is uneven in all regions, and the highest value (about 590.0 HV) is achieved in region B. The tensile strength of the IN625/TC4 BS with Cu/V interlayers reaches nearby 514.5±9.5 MPa at room temperature, and fractures are initiated in region B.