Effect of Cl on microstructure and mechanical properties of in situ Ti/TiB MMCs produced by a blended elemental powder metallurgy method

• Published in: Journal of microscopy (Oxford) 1997-02, Vol.185 (2), p.157-167
• Main Authors: FAN, Z., NIU, H. J., CANTOR, B., MIODOWNIK, A. P., SAITO, T.
• Format: Article
• Language: English
• Subjects: mechanical properties; microstructure; MMCs; NaCl; powder metallurgy; Ti alloy
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1046/j.1365-2818.1997.d01-622.x

A modified blended elemental powder metallurgy (MBEPM) method has been developed for the production of low‐cost Ti alloys and in situ Ti/TiB MMCs for automobile components such as connecting rods and inlet and exhaust valves. The MBEPM method uses Ti sponge fines as raw material, which contain a substantial amount of Cl. The Cl refines the microstructure of the as‐sintered Ti–6Al–4V alloys, with a reduced prior β‐grain size and a reduced α‐lath size and aspect ratio. However, the grain refining effect of Cl is much less pronounced in as‐sintered Ti–6Al–4V–10%TiB MMCs. The Cl is present in the as‐sintered microstructure in three forms: (1) shells consisting of fine NaCl particles in macropores; (2) cuboidal NaCl precipitates in the alloy matrix; and (3) Cl and Na segregated to prior β‐grain boundaries. Increasing the Cl content increases the tensile ductility of both Ti–6Al–4V alloys and Ti–6Al–4V–10%TiB MMCs, but has little effect on strength.