Analysis of Splitting and Martensitic Transformation of AlNi Intermetallic Obtained by Transient Liquid Phase Bonding

This study investigates the characteristics of the AlNi intermetallic formed in a Ni/Al/Ni couple obtained by the Transient Liquid Phase Bonding (TLPB) process. The crystal structure and orientation of the AlNi intermetallic phase were evaluated through SEM-EDS EBSD and its mechanical properties were analyzed by means of instrumented hardness. The results showed that AlNi intermetallic splits into two layers, with different Al content and the same crystal structure and orientation. EBSD mapping revealed that there is no grain boundary along the split line, suggesting that a chemical partition takes place without the need of nucleation, like in a spinodal decomposition. A martensitic layer formed at the Ni-rich AlNi split side was identified by indexing the measured Kikuchi patterns. Instrumented hardness showed that the mechanical properties of AlNi phase change markedly depending on its chemical composition. These results provide experimental data that contribute to the understanding of the solid-state transformations occurring in the central portion of the Al-Ni phase diagram under isothermal conditions.