Study Of Process Of Rolling And Heat Treatment On Multilaminated Ti-B₄ C/Al Sheets

As an excellent high temperature performance material, TiAl-based alloy has been applied widely in aviation and automotive industries. Research of TiAl-based alloy plate is very important in theoretical and practical value. In this paper, boron carbide particle reinforced aluminum matrix composite (B₄Cp/Al) sheet and pure-titanium plate are used for raw materials, and the process of multi-layer combined rolling deformation and heat treatment is studied. Phase composition, reaction kinetics and reaction mechanism of the reaction layer during heat treatment process are also studied by SEM and XRD.B₄Cp/Al composite with particle volume fraction of 5%, 10%, 15% are prepared by powder metallurgy technique. The optimum temperature of hot pressing and rolling of the multi-layered plate is determined to be 500℃, by comparing the deformability of Ti and B₄Cp/Al composite after hot pressed. After 80% reduction in thickness by rolling, compatibility of deformation is reached basically.After heat treatment at 650℃, the reaction layer of multi-layered Ti/Al sheets is TiAl₃ phase, and a small amount of Al and Ti remains. After heat treatment at650℃fro 50h, the multi-layered plate changed to Ti–TiAl₃–(B₄Cp/Al).During high temperature heat treatment of the Ti–TiAl₃–(B₄Cp/Al) plate, the reaction layer is composed of Ti₃Al, TiAl, TiAl₂ and TiAl₃ phases and a gradient distribution of the elements exist in the reaction layer at the beginning stage after the 950℃heat treatment. The reaction layer is still composed of Ti₃Al, TiAl, TiAl₂ and TiAl₃ phases and a gradient distribution of the elements get smaller in the reaction layer after heat treatment at 1100℃. After two steps of heat treatment of 650℃×50h and 1100℃×40h, the multi-layered Ti-B₄Cp/Al sheets have transformed to Ti₃Al–TiAl–TiAl₂–(B₄Cp/Al) sheet.The growth of reaction layer of multi-layered Ti- (B₄Cp/Al) plate during the heat treatment follows a reaction-diffusion mechanism which is controlled by parabolic growth kinetics. Kinetic equation of the multi-layered Ti-(B₄Cp/Al) plate during the high temperature heat treatment is obtained in this paper.