Effect of annealing temperature on microstructure, texture and properties of molybdenum foil in cross rolling
The microstructure, texture and mechanical properties of 0.06 mm thick molybdenum foil were studied by means of metallographic observation, electron backscatter diffraction (EBSD) analysis, tensile test at room temperature and microvickers hardness test. The results show that the yield strength and tensile strength of RD(0° with the main rolling direction) are higher than 900 MPa, followed by TD(90° with the main rolling direction), and the strength of 45°RD(45° with the main rolling direction) is the lowest. Due to the small particle size in 45° RD direction, the elongation in this direction is the highest (8.4%), followed by RD direction and TD direction (2.7%). The plane anisotropy index (IPA) of tensile strength is 8.5%, indicating that the tensile strength has good isotropy. The grain size of cross-rolled aluminum foil presents irregular cake shape in space and is stacked and staggered with {001} < 110 > texture, accounting for 78.9%. After annealing at 700 ~ 1050℃, the molybdenum foil mainly underwent continuous recrystallization with expansion and recovery. Compared with the classical recrystallization nucleation and growth process during low temperature annealing, the recrystallization mechanism at this annealing temperature was subcrystalline polymerization coarsing. With the increase of annealing temperature, the hardness of molybdenum foil samples decreases gradually, the degree of recrystallization increases, and the average layer width of molybdenum foil grains increases. The strength of molybdenum foil samples decreases linearly, and the IPA value of tensile strength drops to 4.4%, indicating that the isotropy degree of molybdenum foil materials is improved. After annealing at 1050℃, the yield strength and tensile strength in RD and TD direction decreased by 31%, while the elongation in 45° RD direction increased to 12.6% and TD direction increased to 7.4%, and the plasticity was significantly improved, due to the decrease of grain boundary area and small Angle boundary.
