Relation between deformability and microstructures in a commercial pure Ti sheet subjected to dual-temperature square-shaped deep drawing

Abstract

Recent studies indicated that the deep drawing process at dual-temperatures could extend the drawability in many materials. This paper reports the study of commercial pure Titanium (CP-Ti)(α-Ti) heated to the temperature range of 25-400°C and deep-drawn by water-cooled square-shaped punch. The CP-Ti exhibits almost triple drawability when the temperature is increased from room temperature to 400°C. The location of the fracture point of CP-Ti sheets is on the corner of the cup wall near the die throat. The poor drawability at low temperature is due to the strain-hardening caused by reorientation bands (RBs). The active slip system at elevated temperature promotes the drawability of CP-Ti. The X-ray diffraction studies show the tendency of slip system to be active on the prismatic plane at approx. 200°C and on the pyramidal plane at approx. 400°C. The process at 400°C shows the microstructure with the micro-shear bands (MSBs) intersection induced by the heated die and the cooled punch. The MSB-MSB intersection prevents the further thinning of the cup wall and results in the superior deep drawability by virtue of better ductility.