The Microstructure And Mechanical Properties Of Binary Ti-Sn Alloys

The most important reason that restricts wide application of titanium in the civilian market was the high cost. The effective methods for reducing the cost were the addition of low-cost agent and near net shape. Tin(Sn) had much lower cost compared with some elements, such as Nb and V, and it could improve the mechanical property of titanium. In this paper, the microstructure and properties for a series of as-cast (below said with AC) Ti-Sn alloys and that prepared by powder metallurgy (below with PM said) were studied. The analyzing results were compared and shown as followsAC Ti-Sn alloys(1)The Ti-Sn(0-20wt.%) alloys exhibited hcp a structures according to the results of XRD. The samples exhibited lamellar a phase structure when Sn contents was lower than10wt.%. As Sn contents exceeded10wt.%, it showed a fine, acicular martensite structure.(2)The addition of Sn could improve the UTS, microhardness and lower the impact toughness obviously, elongation of the pure titanium lightly. The curves of variable trend for microhardness appeared a turning point at the Sn content of10wt.%, which indicated that the microhardness of acicular a martensite was higher than that of lamellar a structure. PM Ti-Sn alloys(1)With the increasing Sn content, the density of PM Ti-Sn alloys decreased, the tensile strength and microhardness increased. The elongation decreased when Sn content was over8wt.%and the variation was not obvious for samples with Sn content lower than8wt.%.The tensile strength of Ti-20Sn was lower than that when the Sn content was from8wt.%to15wt.%for the larger porosity and Ti-8Sn has the best mechanical properties.(2)The optimal process parameters was pressure for500MPa, milling time for5min, sintering temperature for1350℃, sintering time for4h in PM Ti and Ti-8Sn.(3)AC Ti-Sn alloys had larger grain size compared with PM and the microstructure was lamellar a structure. On contrary, the grain of sintered compaction was equiaxed. The PM samples had higher tensile strength and microhardness than that of AC Ti-Sn alloys. The tensile strength of PM Ti-8Sn was747MPa, which was35percent higher than that by casting and the elongation was equal. The microhardness of Ti-8Sn sintered compaction was276.8HV which was29percent higher than that by casting. (4)The microtopography of fracture surfaces for AC Ti-8Sn and Ti-20Sn was characteristics of ductile fracture, and so was PM Ti-8Sn. The microtopography of fracture surfaces of PM Ti-20Sn alloys\exhibited brittle fracture.