MICROSTRUCTURE, MECHANICAL PROPERTIES AND ANYSOTROPY OF PURE TI PROCESSED BY TWIST EXTRUSION AND COLD ROLLING

摘要

It is investigated UFG structure formation in CPTi bulks processed by SPD (cold Twist Extrusion (TE), true strain e approx 5.1, with the following Cold Rolling (CR), true strain e approx 0.7). Evolution of microstructure and tensile mechanical properties in the CP Ti were investigated under room temperature. After the TE, in transversal section it is formed structure fragments with size less 1 mu m. Strength increased on 80 percent; elongation was 3.4 percent. Following low-temperature annealing (300 deg C, 1 hour) leaded to increasing in both strength and ductility properties. In longitudinal section, specimens' strength properties increased slightly. Elongation was about 6 percent. The following low-temperature annealing practically did not influence on the strength but improved elongation to 7.2 percent. The additional CR leaded to forming severe deformed structure. Average size of fragments was 50-500 nm. It was observed elimination of anisotropy and equalization of strength. In both directions ultimate tensile strength became about 780-800 MPa and ductility properties remained the same as in the original.