Microstructural Nano-Scale Evolution at Inter-Particles Bonding Interface of Cold-Sprayed Ti6Al4V Deposits During Heat Treatment

The inter-particle bonding (IPB) mechanism of cold-sprayed titanium alloy during heat treatment (HT) is not clear. The interfacial microstructure and bonding characteristics at the interface of cold-sprayed Ti6Al4V after HT were studied at the micro- and nano-scale. As a result, the nanocrystallization at IPB during cold spray (CS) cannot cause obvious metallurgical bonding between Ti6Al4V particles. The average Young’s modulus of CS Ti6Al4V is 57% higher than that of powder, but the average Young’s modulus of HT sample decreases by 16%. The internal stress and dislocation distribution of interfacial microstructure can lead to various microstructure features and non-uniform rates of microstructure growth at deformed transition layer and IPB during HT. The nanograins at the IPB grow into micron-equiaxed grains. On the contrary, the micron martensitic laths at deformed transition layer adjacent to IPB show the characteristics of equiaxed nanograins transformation under the action of grain boundary bulges induced by dislocation entanglement.