Microstructural modifications in a dynamically consolidated microcrystalline nickel titanium alloy powder

Abstract

Spherically shaped, microcrystalline NiTi alloy powder with both nonhomogeneous particle-size distribution (2 to 60μm diameter) and chemical composition, was consolidated with a shock input energy of 316 kJ kg%^(−1). Upon shock compaction, the two-phase NiTi powder particles (containing 45wt% Ti and 65 wt% Ti) were bonded together, generally by interparticle melting and subsequent welding. The melted material at interparticle regions was observed to have rapidly solidified to largely amorphous and/or microcrystalline phases. Particle interiors were also subjected to extensive plastic deformation which resulted in deformation twinning, grain elongation and some recrystallization to defect-free grains. Unique microstructural modifications occurring due to inhomogeneous thermal and mechanical processing during the dynamic consolidation process, are reported here.