High-temperature compressive properties and microstructural evolution of in situ reacted Nano-SiC whisker/ Ti6Al4V composites manufactured by selective laser melting

Abstract

A V-shaped stirring mixing method was utilised to prepare SiCw/Ti6Al4V composite powder, followed by selective laser melting (SLM) to fabricate SiCw/Ti6Al4V matrix composites. Then, the thermal compression behaviour of the Ti6Al4V-SiCw composites and Ti6Al4V alloy were analysed at a deformation of 60%, temperature of 900 °C, and strain rate of 1 s−1. The flow stress of Ti6Al4V-SiCw composites was always higher than that of Ti6Al4V alloys throughout the deformation stage and the high-temperature compressive resistance improved mainly due to the in-situ generation of TiC reinforcing phases during the forming process leading to grain refinement and dislocation reinforcement, thereby enhancing the composite's high-temperature compressive resistance. The composites showed flow softening behaviour after the peak of flow stress during hot pressing attributed to the presence of nanoscale TiC to enhance the composite recrystallisation. Moreover, microstructural analysis after hot pressing showed that the bonding between the TiC reinforcing phase in the composites and the matrix was still strong, and the matrix remains intact without any visible cracks. These results revealed that the in-situ introduction of reinforcing phases increased the dislocation density of the composites and refined the grain size ,which is the main reason for the improvement of the mechanical properties of the composites.

Keywords

• Ti6Al4V alloy
• SiCw/TiC/Ti6Al4V titanium matrix composites
• High-temperature compression
• Dynamic recrystallisation
• Microstructure