Effect of Heat Treatment on the Microstructure and Mechanical Properties of a Ti-TiAl Laminate Composite

The effect of an innovative two-step heat-treatment process on the microstructure and mechanical properties of a Ti-TiAl laminate composite fabricated by hot-pack rolling was studied in this paper. After heat treatment, the fracture toughness of the composite was enhanced and the elongation of the composite was almost twice that of the initial one. These changes were due to the dislocations and substructures stored in the Ti-43Al-9V alloy being decreased, the microstructure of the DsTi700 alloy turning to a duplex structure, the acicular alpha(2) phase being precipitated at the interfacial region and the residual stresses stored in interfacial region being eliminated. The precipitation of dual-scale silicides was the main reason for the slightly reduced strength. Compared with the initial composite, the tensile strength of the heat-treated composite at 25 degrees and 700 degrees only reduced by 2.7% and 4%, respectively. The primary annealing temperature had a huge impact on the mechanical properties of the composite. However, with the change in secondary annealing temperature, the mechanical properties of the composite were not changed significantly. After heat treatment at 940-960 degrees C/2 h/AC + 725-750 degrees C/6 h/AC, the composite might possess high, comprehensive mechanical properties.