Electronic International Standard Serial Number (EISSN)
The effect of microstructure and strain rate on the room-temperature (RT) and 700 °C compression deformation behavior of a powder metallurgy processed γ-TiAl intermetallic alloy, Ti-45Al-2Nb-2Mn (at.%)-0.8 (vol%) TiB2, was investigated. Samples were heat-treated to obtain a duplex two-phase α2+γ microstructure and two nearly fully-lamellar α2+γ microstructures with different lamellar spacings and γ-phase volume fractions. Compression experiments were performed to a minimum deformation of 10% true strain under strain rates of 10-2, 10-3, 10-4, and 10-5 s-1. The compression strength, strain rate sensitivity, colony size, interlamellar spacing, and microhardness were dependent on microstructure. The nearly fully-lamellar microstructures exhibited higher compression strengths than the duplex microstructure for all the testing conditions. The strain rate sensitivity index (m), tended to increase with increasing temperature, and for the 700 °C deformation, m increased with increasing true strain. The apparent activation volumes, decreased with increasing true strain at 700 °C. Scanning electron microscopy observations showed that cracking preferentially occurred within the γ phase and the extent of cracking increased with increased temperature, strain, and strain rate. Overall, the RT deformation was considered to be controlled by dislocation glide, while at elevated temperature, the likely thermally activated process controlling dislocation glide was associated with the forest junctions acting as pinning points.