Effects of Sn additions on the tensile properties of two-phase TiAl al
loys in the lamellar form have been investigated in the hope that the
tensile ductility of the alloys would be improved by alloying with Sn
which is expected to soften the alpha(2) phase and thereby decreases s
train incompatibility between the gamma and alpha(2) phases. Microstru
ctural observations of the alloys investigated are summarized as follo
ws: (i) Ti3Al and Ti3Sn are completely soluble in each other; (ii) a w
ide gamma + alpha(2) two-phase field exists in the Ti-Al-Sn system; (i
ii) in the two-phase field, the Sn content in the alpha(2) phase is fo
ur times higher than that in the gamma phase. Hardness measurements in
dicate that the alpha(2) phase is indeed softened when its Sn content
exceeds 10 at%, whereas the hardness of the gamma phase increases with
increasing Sn content. All these results are in line with our predict
ions. However, any significant improvement in tensile ductility has no
t been observed upon alloying binary two-phase TiAl alloys with Sn. Po
ssible reasons for this are discussed based on the results obtained.