Growth morphology and microstructural characterization of nonstoichiometric Ti2AlC bulk synthesized by self-propagating high temperature combustion synthesis with pseudo hot isostatic pressing

• Of most importance, the SHS/PHIP process has a significant effect on the microstructures of Ti2AlC.
• There are high-density lattice defects in Ti2AlC bulk synthesized by SHS/PHIP.
• The high-density vacancies and stacking faults are both contributed to its nonstoichiometry, with many nano pores.
• The large-scale Ti2AlC bulk with Φ150 × 25 mm2 was fabricated successfully, and the relative density was raised.

Ti2AlC bulk pellets, Φ150 × 25 mm2 in size, were fabricated by self-propagating high temperature combustion synthesis with pseudo hot isostatic pressing (SHS/PHIP). The growth morphology and microstructures were investigated in detail by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The used SHS/PHIP process results in some unusual microstructures. The relative density increases to over 98% when increasing the size of the used pellet. The as-fabricated Ti2AlC has many lattice defects, contributing to its low phonon thermal conductivity. Interestingly, many nanopores were present in Ti2AlC grains. Of much importance, a high density of vacancies contributes to the nonstoichiometry of Ti2AlC synthesized by the SHS/PHIP process. Ti2AlC synthesized by the SHS/PHIP process is deformed with high residual stress, due to fast cooling and grain growth.