Role of Ti3AlC2 MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part IV: mechanical properties

Abstract

In this study, the 4^th part of a series of publications on the sintering and characterization of TiAl-Ti₃AlC₂ composite materials, the mechanical properties were measured and discussed. For this purpose, different contents of synthesized Ti₃AlC₂ reinforcement (10, 15, 20, 25, and 30 wt%) were added to metallic Ti and Al powders, then ball-milled and manufactured by spark plasma sintering (SPS) for 420 s at 900 ºC under 40 MPa. Flexural strength, fracture toughness and Vickers hardness were measured by 3-point technique, SENB method, and indentation technique, respectively. Increasing the Ti₃AlC₂ content resulted in improvement of the mechanical properties, so that TiAl-25 wt% Ti₃AlC₂ composite showed the best flexural strength and Vickers hardness (270 MPa and 4.11 GPa, respectively). Increasing amount of Ti₃AlC additive had no significant effect on fracture toughness. Densification improvement, in-situ formation of Ti₂AlC, and limitation of grain growth were recognized as the reasons of mechanical properties enhancement. In contrast, further addition of Ti₃AlC₂ (30 wt%) decreased the mechanical properties due to the reduction of density and formation of more Ti₂AlC agglomerates in grain boundaries.