Effects of grain size and crystal orientation on tensile properties of pure titanium thin wires

To clarify the effects of the grain size and crystal orientation on the tensile properties of pure titanium thin wires, tensile and stepwise tensile tests were conducted on pure titanium wires with diameters of approximately 180 μm and different average grain sizes (52, 37, 23, and 3.8 μm). When the grain size was large, the fracture strain was significantly smaller, the variation in tensile strength was larger, and the grain size threshold for such properties was a grain-size ratio to wire diameter of 0.13 or greater. For larger grain sizes, the slip system with the highest modified Schmid factor (MSF), which is the Schmid factor divided by the critical resolved shear stress of each slip system, was activated in all 15 grains whereas for smaller grain sizes, the percentage of slip systems activated with the highest MSF was slightly lower. In addition, the fracture location in a thin wire with larger grain sizes was highly correlated with the average MSF of the grains in the cross-section.