Effects of Heat Treatment on the Microstructure and Mechanical Properties of TiAlSi-3.7Mo and TiAlSi-13.7 V Alloys Synthesized via in Situ Laser Alloying

Abstract Titanium aluminide (TiAl)-based alloys are high-temperature material with potential to replace heavier superalloys like Ni-based alloys. This is because of their lightweight which makes TiAl-based alloys favorable for aerospace engine application, but low ductility, and fracture toughness limit their structural applicability. Moreover, in material science and engineering research, it is essential to achieve adequate balance in terms of strength and ductility without sacrificing other important material properties. Thus, the aim of this study is to investigate the influence of heat treatment on the microstructure and mechanical properties of TiAlSi-3.7Mo and TiAlSi-13.7 V alloys synthesized using laser in situ alloying. Heat treatment was performed at 1200 °C and 1400 °C for 60 minutes, followed by furnace cooling (FC). The microstructure and composition were examined using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS); phases identification was carried out with the aid of an x-ray diffractometer (XRD) and electron backscattered diffraction (EBSD). The Anton Paar nanoindentation tester was used to investigate the nanomechanical properties, while the Vickers hardness tester was used to determine the microhardness values. It was observed that dual-phased (DP) and fully lamellar (FL) microstructures were present at 1200 °C and 1400 °C, respectively, with varying amounts of β 0 and ζ-Ti 5 Si 3 precipitating phases along the grain boundaries depending on the alloying element (Mo and V) present. The phase analysis reveals the presence of γ , α 2 , α , β 0 , and ζ-Ti 5 Si 3 phases in the as-built alloys. The β 0 -TiAl and ζ-Ti 5 Si 3 phases exhibit solid precipitation hardening and solution strengthening at grain boundaries due to Mo and Si interactions. The alloy with V inclusion showed improved mechanical properties, particularly after heat treatment, by increasing the formation of α 2 + γ lamellae. This study demonstrated that V and Mo additions to Ti-Al-Si alloy sample showed improved mechanical properties after heat treatments.