Ti-28　at.%　Ta　powders　were　produced　by　rapid　solidification　via　plasma　rotating　electrode　process　(PREP).　It　is　found　that　microstructure,　morphology　and　phase　constituents　of　Ti-28Ta　powders　are　particle　size　dependent.　Small　powder　particle　exhibit　the　formation　of　predominant　martensitic　alpha　＇＇　and　minor　metastable　beta,　whilst　large　particles　consist　of　primary　metastable　beta　with　minor　martensitic　alpha　＇＇　phase.　The　amount　of　martensitic　alpha　＇＇　increases　while　the　amount　of　metastable　beta　phase　decreases　with　decreasing　the　particle　size.　The　martensitic　alpha　＇＇　lath　with　the　size　of　about　50　nm　wide　and　1　mu　m　long　are　formed　preferentially　at　the　beta　grain　boundaries.　The　martensitic　transformation　start　temperature　(M-s)　and　peak　temperature　(M-p)　are　similar　to　390　degrees　C　and　similar　to　340　degrees　C　respectively　for　the　Ti-28Ta　powders　with　the　particle　size　between　40　and　65　mu　m.　An　increased　Vickers　micro-hardness　is　obtained　and　is　associated　with　decreasing　particle　size.　(C)　2017　Elsevier　B.V.　All　rights　reserved.