AI 中文总结
该研究采用CALPHAD方法筛选确定铜基、铌基中间层，通过瞬时液相扩散连接实现了NiTi合金的高强度、近无金属间相接头，且保留了超弹性等功能性能。
AI 中文摘要
本研究探究瞬时液相（TLP）扩散连接作为连接镍钛（NiTi）合金的方法，旨在实现高接头效率，同时最小化接头区域内的化学变化。通过CALPHAD方法筛选三元合金中TLP的热力学判据，确定了两种连接中间层成分：铜基和铌基。随后，针对这两种体系，实验评估了它们对凝固动力学、接头区域微观结构以及准静态和循环拉伸载荷下性能的影响。对于两种中间层成分，接头区域的成分分布和微观结构均证实了等温凝固机制。此外，接头被发现完全致密，且最多含有1.2%的金属间相。拉伸测试显示，载荷可通过接头高效传递，铜基和铌基中间层的接头分别具有约4%的可恢复应变，马氏体起始应力达到未键合退火NiTi值的94%和89%。最后，两种成分的接头在循环载荷下均观察到稳定的超弹性响应，应变演化的空间变化与接头区域因铜和铌置换溶质导致的刚度和硬度提升相关，这一点通过纳米压痕测试得到证实。本研究表明，NiTi的TLP连接可产生高强度、几乎无金属间相的接头，且不会牺牲超弹性等功能性能。
英文摘要
Transient liquid phase (TLP) bonding was examined as an approach for joining NiTi to achieve a high joint efficiency while minimizing chemical variance within the joint region. Two bonding interlayer chemistries (Cu-base and Nb-base) were identified by screening thermodynamic criteria for TLP in ternary alloys using the CALPHAD method. These two systems were then experimentally evaluated with respect to their impact on solidification kinetics, microstructure in the joint region, and performance during quasistatic and cyclic tensile loading. For both interlayer chemistries, the composition profile and microstructure in the joint region confirmed an isothermal solidification mechanism. In addition, the joints were found to be fully dense and contain at most 1.2% intermetallic phases. Tensile testing showed excellent load transfer across the joints with approximately 4% recoverable strain and martensite onset stresses reaching 94% and 89% of the unbonded, annealed NiTi values for Cu-base and Nb-base interlayers, respectively. Lastly, a stable superelastic response was observed under cyclic loading for both bond chemistries, with spatial variation in the strain evolution linked to enhanced stiffness and hardness in the joint region arising from the substitutional Cu and Nb solutes, as confirmed via nanoindentation. This study demonstrates that TLP bonding of NiTi can produce high-strength and nearly intermetallic-free joints without sacrificing functional performance, such as the superelastic response.
Comments25 pages, 11 figures, 7 tables
