High strength titanium with a bimodal microstructure fabricated by thermomechanical consolidation of a nanocrystalline TiH₂ powder

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• 作者：Yifeng Zheng^a ; Xun Yao^a ; Yongjun Su^a ; D.L. Zhang^a ; ^b ; ^{zhangdeliang@mail.neu.edu.cn}
• 关键词：Titanium ; Dehydrogenation of titanium hydride ; Powder metallurgy ; High energy mechanical milling ; Bimodal microstructure ; Mechanical properties
• 刊名：Materials Science and Engineering: A
• 出版年：2017
• 出版时间：16 February 2017
• 年：2017
• 卷：686
• 期：Complete
• 页码：11-18
• 全文大小：1664 K
• 卷排序：686

文摘

A titanium rod with a novel bimodal microstructure consisting of α-Ti plates of 1–5 µm in width and 10–15 µm in length and ultrafine grained (UFG) α-Ti regions with grain sizes in the range of 100–300 nm was fabricated by in-situ dehydrogenation and thermomechanical consolidation of a nanocrystalline TiH2 powder. The consolidation process combined spark plasma sintering at 800 °C for 5 min and hot extrusion at 1100 °C, and took less than 15 min in total. The titanium rod had a high tensile yield strength of 1052 MPa and a limited elongation to fracture of 2.0%. The high yield strength of the titanium rod can be attributed to the high strength of the UFG regions due to grain boundary strengthening and the increased strength of the α-Ti plates due to O solid solution strengthening associated with the high O content of 0.85 wt% in the titanium rod. A microstructural evolution model involving nucleation and growth of the α-Ti plates, partition of H between α-Ti and β-Ti phases and Ti-H eutectoid reaction has been proposed to elucidate the mechanism for the formation of the bimodal microstructure.