Fabrication of high ductility TZM-La2O3 alloy and characterization of microstructure and mechanical properties

Abstract

This study employs spark plasma sintering (SPS) to fabricate TZM alloy doped with 0.5 wt% La₂O₃ at three different temperatures: 1800 °C, 1900 °C, and 2000 °C, and systematically investigates the effect of sintering temperature on its microstructure and mechanical properties. At 1900 °C, the alloy exhibits an equiaxed grain structure, achieving an optimal balance between grain size (7.03 ± 3.8 μm) and relative density (98.2 %). This temperature effectively suppresses excessive grain growth while promoting densification. The alloy attains a peak hardness of 211.3 HV_0.2, an ultimate tensile strength (UTS) of 606 MPa, and an exceptional elongation (EL) of 24.3 %, representing a 148 % increase over the 1800 °C sintered sample (EL of 9.8 %) and an 18 % improvement over the 2000 °C sample (EL of 20.6 %). The corresponding product of strength and elongation (PSE) reaches 14.7 GPa·%, surpassing most previously reported TZM-based alloys in the literature. Fractographic analysis reveals that all samples exhibit ductile dimple fracture, though variations in the area proportion of dimpled regions lead to differences in EL. The 1900 °C sample displays the most favorable dimple morphology and highest ductility, attributed to its homogeneous microstructure and effective inhibition of grain boundary sliding by La₂O₃ particles. Results indicate that La₂O₃ nanoparticles strengthen the matrix through grain refinement and dislocation pinning, achieving an optimal combination of strength and ductility. Consequently, 1900 °C is identified as the ideal sintering temperature for the TZM-0.5 wt% La₂O₃ alloy.