Effect of In addition on microstructure and mechanical properties of Sn-40Bi alloys

The effect of In on melting property, microstructure and mechanical properties of Sn-40Bi-xIn (x = 0, 1, 2, 4, 6, 8 wt%, respectively) alloys was investigated by means of differential scanning calorimetry, scanning electron microscope, X-ray diffraction and tensile test. The results show that the solidus temperature and the liquidus temperature decrease with the increase in In content. The 1In, 2In and 4In alloys are composed of Sn-Bi eutectic and beta-Sn dendrites with In atoms dissolved, whereas 6In and 8In alloys composed of Sn-Bi eutectics, BiIn-Sn metastable phases, Bi particles and primary beta-Sn phases. At room temperature, 6In exhibits the maximum ultimate tensile strength of 77 MPa, while 4In displays a more outstanding elongation rate of 42%. Moreover, 2In alloy exhibits an even outstanding elongation behavior (above 300%) at temperatures of 100 and 120 degrees C.