Growth Kinetics of Intermetallic Phases in Transient Liquid Phase Bonding Process (TLPB) in Al /Ni System

Abstract

New processes and materials are vital nowadays, since specific features of materials are essential to accomplish the more demanding technological and environmental requirements. Al/Ni system has stimulated a large number of phase equilibrium, thermodynamic, diffusion and related studies. Its relevance relays on first principle features as well as technological importance. Transient Liquid Phase Bonding (TLPB) process is presented in this work due to the advantages of this method above others. Low temperatures of processing are needed, to obtain stable intermetallic phases (IPs) suitable for high temperatures of service. The aim of this research is to investigate the impact of temperature on the IPs growth and formation mechanisms, completing previous works on microstructure and kinetics characterization of IPs in Al/Ni system at 720°C. The results of SEMEDS/ WDS analyses of the cross-sections of the bonds showed the presence of Al3Ni and Al3Ni2 at the beginning of the interaction between Al and Ni, which are consistent with the phase equilibrium diagram. The Al3Ni2 layer growth showed linear correlation with time at 800°C, whereas at 900 and 1000°C it suggested a diffusive growth. Inert markers experiments allowed distinguishing individual growth. Vickers micro-hardness was determined obtaining values for Ni and Al3Ni2 of about 100 and 800 HV/ 0.025, respectively.