Microstructural study of Ti aluminide multilayered sheets fabricated by hot rolling Part I : formation behavior of intermetallic phases

The objective of this study is to analyze microstructures of multilayered Ti aluminide sheets fabricated by self-propagating high-temperature synthesis (SHS) reaction using hot rolling. Multilayered Ti/Al sheets were prepared by stacking thin Ti and Al sheets alternatively, and had a good Ti/Al interfacial bonding after pre-rolling at 500 degree C. When these sheets were heat-treated at 1000 degree C, spheroidal TiAl3 phases were formed by SHS reaction at Ti/Al interfaces and inside Al layers. This formation continued until Al was completely consumed, and the Ti/Al multilayers turned into the Ti/TiAl3 multilayers. Microstructural analysis on the hot-rolled, multilayered Ti/TiAl3 sheets indicated that intermetallic phases such as TiAl2, TiAl, and Ti3Al were formed at Ti/TiAl3 interfaces due to interaction between Ti and TiAl3, and that pores formed in TiAl3 layers were significantly reduced during hot rolling. These findings suggested that the SHS reaction using hot rolling was economical and useful for the continuous fabrication of the multilayered Ti/Ti aluminide sheets