Formation of ultrafine structure in as cast Ti7CuXSn alloys

The purpose of the present study was to investigate the microstructure and microhardness of novel Ti7CuXSn alloys. Ti7CuXSn alloys with x=0, 1, 2.5 and 5 wt-% were synthesised using a well developed arc melting and casting method. The microstructure was analysed by means of optical microscopy, SEM and X-ray diffraction methods. The cellular grain size d(G), lamellar spacing lambda(L), volume fraction of Ti2Cu phases f(v) and microhardness H-V were measured. The addition of Sn content into the Ti7Cu alloy can effectively increase the solubility of Cu in the eutectoid microstructure (alpha-Ti+Ti2Cu), induce transformation of ultrafine alpha' martensite microstructure and increase the volume fraction of the Ti2Cu phase f(v). Especially, ultrafine microstructures have been produced in as cast Ti7Cu5Sn alloys. The value of H-V increases with the increasing values of d(G)(-0.5), lambda(-0.5)(L) and f(v).