Evaluation of precipitation hardening in TiC-reinforced Ti2AlNb-based alloys
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Ti2AlNb-based alloys with 0.0wt%, 0.6wt%, and 2.0wt% carbon nanotube (CNT) addition were fabricated from spherical Ti–22Al–25Nb powder by sintering in the B2 single-phase region. Phase identification and microstructural examination were performed to evaluate the effect of carbon addition on the hardness of the alloys. Carbon was either in a soluble state or in carbide form depending on its concentration. The acicular carbides formed around 1050°C were identified as TiC and facilitated the transformation of α2 + B2 → O. The TiC was located within the acicular O phase. The surrounding O phase was distributed in certain orientations with angles of 65° or 90° O phase particles. The obtained alloy was composed of acicular O, Widmanstatten B2 + O, and acicular TiC. As a result of the precipitation of carbides as well as the O phase, the hardness of the alloy with 2.0wt% CNT addition increased to HV 429 ± 9.
KeywordsTi2AlNb alloy carbides microstructure precipitation hardening hardness
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The authors are grateful to the China National Funds for Distinguished Young Scientists (No. 51325401), the National Natural Science Foundation of China (Nos. 51474156 and U1660201), and the National Magnetic Confinement Fusion Energy Research Program of China (No. 2014GB125006) for financial support.
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