Bulk Texture Analysis in Powder Extruded Ti-6Al-4V alloy containing extra high oxygen

Over the last few decades, there has been a desire to expand the market for Ti-6Al-4V alloy from aerospace applications to more general applications. However, the high cost of Ti-6Al-4V produced by conventional ingot metallurgy is a barrier. Consequently, there is a lot of interest in the utilisation of powder metallurgy (PM) as an affordable alternative that can produce near-net shape components. One major concern associated with conventional PM techniques is the presence of post-processing residual porosity and relatively high interstitial impurities resulting from cheaper starting powders that can lead to inferior properties. Although the development of innovative thermo-mechanical powder consolidation processes, such as powder compact extrusion has provided a nearly fully dense material introduction of severe deformation during processing means significantly complex evolution of microstructure showing anisotropic behaviour. Hence analysing the microstructural variations and crystallographic texture of constituent phases (hcp α and bcc β) across cross-sections and along the length of extruded material is rather important and no such study has been performed for powder-extruded Ti-6Al-4V. The knowledge of texture is essential to achieve desirable mechanical properties through heat treatments despite the presence of high interstitial impurities in relative cheap final components that can be utilised in many non-critical ‘fit for purpose applications.

近数十年来，工业界与学界一直期望将Ti-6Al-4V钛合金（Ti-6Al-4V）的应用市场从航空航天领域拓展至更广泛的通用场景。然而，传统铸锭冶金法制备的Ti-6Al-4V钛合金成本高昂，成为其推广应用的核心障碍。因此，粉末冶金（powder metallurgy, PM）作为一种成本可控、可制备近净成形构件的替代工艺，受到了广泛关注。但传统粉末冶金工艺存在一大显著弊端：由于使用成本较低的原始粉末，成品易存在后处理残余孔隙以及较高的间隙杂质，进而导致材料性能劣化。尽管诸如粉末坯挤压成形这类新型热机械粉末固结工艺已可制备出接近全致密的材料，但加工过程中引入的强变形会使微观组织发生显著复杂的演化，使其呈现各向异性行为。因此，对挤压成形构件的横截面及全长范围内的微观组织演变与组成相（密排六方（hcp）α相和体心立方（bcc）β相）的晶体织构进行分析，具有重要的研究价值；而目前尚无针对粉末挤压成形Ti-6Al-4V的此类研究。尽管低成本最终构件存在较高的间隙杂质，但通过调控织构并辅以热处理以获得理想力学性能，仍是这类构件应用于诸多非关键"适配用途"场景的核心前提。