MICROSTRUCTURE AND HIGH-TEMPERATURE MECHANICAL-PROPERTIES OF TIN

The mechanical properties of tin have been studied by tensile tests in the temperature range 293-463 K. Tensile rests were performed for cyl indrical samples at a constant strain rate and varying strain rates du ring deformation. In-situ-tensile tests also were conducted in ribbon- form samples. At the strain rates studied, deformation takes place pre ferentially by slip, although some scattered twins also were observed at lower temperatures. Strong grain growth occurs at the higher temper atures. Microstructural observations of deformed samples show that dyn amic recrystallization is not important in the temperature range inves tigated. The fracture surface of the cylindrical samples changes from a chisel type of fracture at the lower temperatures to a simple shear type of fracture at the higher temperatures. Both the tensile strength and ductility decrease with increasing temperature. An explanation is given for the loss of ductility at high temperatures. The activation energy for creep, obtained from strain-rate-change tests is 35 kJ mol( -1) and the stress exponent is about 6. These values are related to a slip mechanism controlled by pipe diffusion.