Characterization based analysis on TiAl3 intermetallic phase layer growth phenomenon and kinetics in diffusion bonded Ti/TiAl3/Al laminates

Abstract

In this article, new insights towards the layer growth phenomenon of TiAl3 phase in alternative Ti/Al based multilayer metal intermetallic laminate is discussed. Ti/Al multilayered metal intermetallic laminates were prepared at two different temperatures of 550 and 575 °C using solid-state diffusion bonding technique. TiAl3 was the only intermetallic layer formed along the Ti/Al metallic layer interfaces at the processed temperatures. The TiAl3 intermetallic layer grows (thickens) in two stages with respect to diffusion duration with each stage controlled by different growth phenomena viz. chemical reaction-controlled and diffusion-controlled growth respectively. The initial nucleation of TiAl3 grains takes place by chemical reaction between Ti and Al atoms without any specific nucleation sites in the intermix zone. Whereas, the triple junctions of the initially nucleated TiAl3 grains acts as a preferred TiAl3 nucleation site for further layer growth during reaction-controlled growth stage. During diffusion-controlled growth, the preferred nucleation site shifts to Ti/TiAl3 and Al/TiAl3 interfaces which makes the TiAl3 layer growth to be predominantly controlled by the diffusivities of Ti and Al atoms. The growth kinetics study exhibits higher layer growth rate during diffusion-controlled growth stage which is mainly due to faster Al diffusion and higher TiAl3 nucleation rate at Ti/TiAl3 interface.