Experimental investigation on temperature-dependent uniaxial ratchetting of AZ31B magnesium alloy

Uniaxial strain- and stress-controlled cyclic tests were performed at five prescribed temperatures (i.e., 25, 100, 150, 200 and 250 degrees C) to investigate the temperature-dependent uniaxial cyclic deformation (especially for ratchetting) of extruded AZ31B magnesium alloy. The results show that AZ31B magnesium alloy presents a remarkable temperature-dependent cyclic deformation, that is: obvious tension-compression asymmetry is observed at room temperature, but it becomes weaker and weaker and eventually disappears with the increase of test temperature; significant cyclic hardening occurs at low temperatures (lower than 150 degrees C), but a cyclic softening is eventually observed as the test temperature increases to a certain critical value (e.g., 150 degrees C); the ratchetting in the tensile direction becomes more significant as the test temperature increases, while the ratchetting in the compressive direction is relatively temperature-insensitive when the test temperature is below 150 degrees C; the effect of different peak/valley stresses on the ratchetting also depends on the test temperature, and is more significant at the temperatures lower than 200 degrees C. Such a specific ratchetting of AZ31B magnesium alloy originates from different mechanisms of plastic deformation presented at different temperatures.