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<p>The Ti-45Al-8Nb-0.2Si-0.3B alloy was fabricated by hot isostatic pressing (HIP) of pre-alloyed powders produced via electrode induction melting gas atomization (EIGA). The microstructures of the pre-alloyed powders and the effects of HIP temperature and post-HIP heat treatment on the microstructures and mechanical properties of the alloy were investigated. The results indicate that the pre-alloyed powders exhibit a particle-size range primarily between 65-260&#xa0;<i>μ</i>m with a median size (D<sub>50</sub>) of 131.75&#xa0;<i>μ</i>m. Large particles show cellular–dendritic surface morphology, whereas decreasing particle size leads progressively to a disordered surface morphology. The large-sized pre-alloyed powders primarily consist of the <i>γ</i> phase, with coarsened <i>α</i><sub>2</sub> grains regions observed in the microstructures of some large particles. In contrast, the fine pre-alloyed powders are mainly composed of the <i>α</i><sub>2</sub> phase. The microstructures of as-HIPed Ti-45Al-8Nb-0.2Si-0.3B alloy is composed of equiaxed near <i>γ</i> microstructure and dispersed Nb<sub>5</sub>Si<sub>3</sub> precipitates. The microstructures also contain the <i>α</i><sub>2</sub>-phase prior particle boundaries (PPBs) and local enrichment of the <i>α</i><sub>2</sub> phase, which is derived from the abnormally coarsened <i>α</i><sub>2</sub> grains in the large powders. Increasing HIP temperature together with post-HIPed heat treatment effectively eliminates PPBs, however, due to the local enrichment of the α<sub>2</sub> phase, the fully lamellar colonies obtained after heat treatment exhibit a typical bimodal distribution. Tensile test results indicate that the strength and ductility of the as-HIPed TiAl alloy are superior to those of the fully lamellar heat-treated TiAl alloy.The factors influencing the evolution of microstructures and tensile properties are discussed as well.</p>

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Microstructure and Tensile Properties of a Ti-45Al-8Nb-0.2Si-0.3B Alloy Fabricated by Hot Isostatic Pressing of Pre-alloyed Powders

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Gang Wang,
  • Bing Li,
  • Yang Liu,
  • Tianlong Yuan,
  • Yang Lu,
  • Pengyuan Qi,
  • Ming Yuan

摘要

The Ti-45Al-8Nb-0.2Si-0.3B alloy was fabricated by hot isostatic pressing (HIP) of pre-alloyed powders produced via electrode induction melting gas atomization (EIGA). The microstructures of the pre-alloyed powders and the effects of HIP temperature and post-HIP heat treatment on the microstructures and mechanical properties of the alloy were investigated. The results indicate that the pre-alloyed powders exhibit a particle-size range primarily between 65-260 μm with a median size (D50) of 131.75 μm. Large particles show cellular–dendritic surface morphology, whereas decreasing particle size leads progressively to a disordered surface morphology. The large-sized pre-alloyed powders primarily consist of the γ phase, with coarsened α2 grains regions observed in the microstructures of some large particles. In contrast, the fine pre-alloyed powders are mainly composed of the α2 phase. The microstructures of as-HIPed Ti-45Al-8Nb-0.2Si-0.3B alloy is composed of equiaxed near γ microstructure and dispersed Nb5Si3 precipitates. The microstructures also contain the α2-phase prior particle boundaries (PPBs) and local enrichment of the α2 phase, which is derived from the abnormally coarsened α2 grains in the large powders. Increasing HIP temperature together with post-HIPed heat treatment effectively eliminates PPBs, however, due to the local enrichment of the α2 phase, the fully lamellar colonies obtained after heat treatment exhibit a typical bimodal distribution. Tensile test results indicate that the strength and ductility of the as-HIPed TiAl alloy are superior to those of the fully lamellar heat-treated TiAl alloy.The factors influencing the evolution of microstructures and tensile properties are discussed as well.