Evolution of Mechanical Properties of Ti-6Al-4V Alloy in the Temperature Range of 20 to-196 °C

Cryogenic cooling is becoming an attractive method for machining difficult-to-cut materials to extend their machinability. However, it's a challenging task to analyze the effect of cryogenic cooling on the machining. In order to better understand the various physical phenomena in the cryogenic cutting process, cryogenic impact test, and tensile test of titanium alloy Ti-6Al-4V were undertaken in this work. The impact and tensile properties of Ti-6Al-4V alloy in the temperature range of 20 to - 196 degrees C were investigated. Later on, the macroscopic and microscopic morphology of the produced fractures were analyzed. Findings have depicted a decreasing impact toughness and an increase of tensile and yield strength of Ti-6Al-4V alloy in the temperature range from 20 to - 196 degrees C. The impact fracture appeared as a tendency of becoming material brittle. Meanwhile, three kinds of zones of shear-lip, fiber, and radiation were found on the fracture morphology. Those zones correspond to the shear fracture zone, crack initiation zone, and crack extension zone, respectively. With the temperature decrease, the proportion of fiber zone was decreased, while a gradual increase in the radiation zone was observed. Besides, the fiber zone was observed for the macroscopic morphology of the fracture under the temperature of - 196 degrees C. Some dimples were found in the tensile fracture at - 196 degrees C indicating the ability of Ti-6Al-4V alloy to deform plastically under such low temperature. This work is a fundamental support to analyze the behavior of Ti-6Al-4V alloy under cryogenic cooling conditions.