EBSD Analysis of Hot Deformation Behavior of Oxide-Doped Molybdenum Alloys

Abstract

Hot compression tests of Mo−1.5 wt% Al2O3/ZrO2 molybdenum alloys were carried out using the Gleeble−1500 simulator at 0.01 s−1−5 s−1 strain rates and 1000–1500 °C deformation temperatures. The microstructural changes of the alloy at 1000–1500 °C were studied. The changes in the hot deformation process for the Mo−1.5 wt% Al2O3/ZrO2 molybdenum alloys were analyzed by means of EBSD. The ZrO2 particles had a greater effect on improving the thermal deformation resistance of molybdenum alloys than did the Al2O3 particles. The activation energy of the molybdenum alloy doped with ZrO2 (403.917 kJ/mol) was lower than that of the molybdenum alloy doped with Al2O3 (440.314 kJ/mol). Due to the occurrence of recrystallization, the intensity of {100} the texture first increased and, then, dropped down with increase in the temperature, while the change law of {111} texture was the opposite. Above 1200 °C, the higher deformation temperature made the texture more random by lowering the texture intensity. The dislocation density was sacrificed to promote recrystallization. When dynamic recrystallization occurred, the sub−grain boundaries absorbed dislocations and transformed them into high−angle grain boundaries, resulting in a decrease in dislocation density and an increase in high−angle grain boundaries at high temperatures and low strain rates. At 0.01 s−1 strain rate, the average grain size of Mo−1.5wt% ZrO2 alloy increased from 2.38 μm to 4.67 μm, and the proportion of large angle grain boundaries increased from 59.8% to 86.6%.