Effect of spark plasma sintering temperature on microstructure and mechanical properties of melt-spun TiAl alloys

A TiAl alloy from pulverized rapidly solidified ribbons with the composition of Ti-46Al-2Cr-4Nb-0.3Y (mole fraction, %) was processed by spark plasma sintering (SPS). The effects of sintering temperature on the microstructure and mechanical properties were studied. The results show that the microstructure and phase constitution vary with sintering temperature. Sintering the milled powders at 1200 degrees C produces fully dense compact. Higher sintering temperature does not improve the densification evidently. The dominant phases are gamma and alpha(2) in the bulk alloys sintered at 1200 degrees C. With higher sintering temperature, the fraction of alpha(2) phase decreases and the microstructure changes from equiaxed near gamma grain to near lamellar structure, together with a slight coarsening. The bulk alloy sintered at 1260 C with refined and homogeneous near lamellar structure reveals the best overall mechanical properties. The compressional fracture stress and compression ratio are 2984 MPa and 41.5%, respectively, at room temperature. The tensile fracture stress and ductility are 527.5 MPa and 5.9%, respectively, at 800 degrees C.