Microstructure evolution and mechanical properties of TiC/Ti6Al4V medical composite processed by severe plastic deformation

Abstract Gradient materials can achieve both external strengthening and internal toughening, which has great potential to break the strong plastic tradeoff. Titanium carbide (TiC) particle is conducive to form a wearable surface in biomedical Titanium (Ti) alloy. In this work, gradient TiC/Ti6Al4V composites were successfully prepared by friction stir processing (FSP). Microstructure, texture and mechanical properties of the material were systematically characterized. Scanning electron microscopy (SEM) showed that the equiaxed grains near the machined surface were transformed into elongated grains inside. The results of energy spectrum analysis (EDS) showed that there was element aggregation near TiC particles. X-ray diffraction (XRD) indicated martensitic transformation in the stir zone and in the transition zone. The results of nano indentation showed that the hardness of stir zone was higher. In order to promote recrystallization and improve the hardness of the transition zone, high temperature rapid heat treatment was carried out after FSP. When the sample was heated at 700°C and cooled in the furnace, the hardness increased to the maximum. In the process of rapid heating, the dissolution of elements near TiC particles also led to the increase of hardness. This study provides a new idea for surface modification of gradient titanium alloy by using FSP method to improve its mechanical properties.