Microstructural evolution and mechanical properties of TiC/Ti6Al4V composites manufactured by selective laser melting after solution and aging treatments

Abstract

In this study, selective laser melting (SLM) technology was utilized to fabricate Ti6Al4V and TiC/Ti6Al4V composites. We then investigated the effect of the solution heat treatment temperature and aging time on the microstructural and mechanical properties of both the Ti6Al4V alloy and the TiC/Ti6Al4V composites. The findings showed that with an increase in the solution heat treatment temperature, the acicular martensite in the matrix of the Ti6Al4V alloy and the composites progressively transitioned into the plate-bar α phase. Concurrently, there was a distinct irregularity in the morphology of the β columnar grain boundaries, accompanied by an evenly enhanced and distributed β phase. With respect to hardness, the microhardness of Ti6Al4V initially displayed a slight drop with an increase in the solution temperature, followed by a significant increase, reaching a peak of 430 HV. In contrast, the composite materials exhibited an initial minor increase in microhardness followed by a substantial surge, with a maximum value of 607 HV. Post the aging treatment, the microhardness of the composite samples was observed to decrease from 463.2 HV to 362.7 HV. The aging time had a notable influence on the α + β structure, where the size of the martensitic α phase was constrained by the size of the β phase. This study revealed that an extension in the aging time resulted in an increased size of the strengthening phase, subsequently leading to a substantial reduction in the composite’s microhardness. This underscored the pivotal role of aging time in defining the mechanical properties of the composites.

Keywords

• Ti6Al4V alloy
• Selective laser melting
• TiC
• Heat treatment
• Mechanical properties