Microstructure and properties of (diamond + TiC) reinforced Ti6Al4V titanium matrix composites manufactured by directed energy deposition

Abstract

In this study, (diamond + TiC) reinforced Ti6Al4V titanium matrix composites (DT-TMCs) were fabricated using the directed energy deposition (DED) technique to enhance multiple properties of the Ti6Al4V alloy. The phase composition, microstructure, microhardness, wear resistance, and thermal conductivity of the composites were investigated. The findings demonstrate that the DT-TMCs consist of diamond, in-situ formed TiC (including eutectic TiC and primary TiC), α-Ti and β-Ti. The formation of in-situ TiC is attributed to the partial dissolution of the diamond into the Ti6Al4V matrix during the DED process. The superior hardness of in-situ TiC, compared to that of Ti6Al4V alloy, plays a pivotal role in enhancing the overall hardness of the DT-TMCs. Owing to the high hardness and excellent thermal conductivity of diamond, the wear resistance and thermal conductivity of the DT-TMCs are superior to those of the unmodified Ti6Al4V alloy. With the diamond volume fraction increasing from 0% to 15%, the microhardness of the DT-TMCs raises from 333.99 HV0.2 to 438.15 HV0.2, the wear rate decreases from 207.514 × 10−5 mm³·N−1·m−1 to 2.256 × 10−5 mm³·N−1·m−1, and the thermal conductivity increases from 6.686 W·m−1·K−1 to 13.613 W·m−1·K−1. Additionally, the in-situ TiC exhibits superior thermal conductivity compared to the Ti6Al4V alloy, which also contributes to the improved thermal conductivity of the DT-TMCs.

Keywords

• Directed energy deposition
• Diamond
• Wear resistance
• Thermal conductivity