Creep microstructures and creep behaviors of pure molybdenum sheet at 0.7 Tm

• The creep microstructures and properties of pure molybdenum sheet were investigated
• The high-temperature deformation behaviors of pure molybdenum at 0.7 Tm were investigated by direct ohmic heating
• Creep rate is found to be 7.34 × 10− 6 to 2.83 × 10− 5 and 1.53 × 10− 4 s− 1 under a constant stress of 5, 10 and 20 MPa stress
• The stress exponent (n) is estimated to be 3.85–3.98 and strain activation energy (Q) creep is 362–413 kJ/mol

The creep behavior of high purity molybdenum (99.995 wt.%) is investigated at temperatures of 1600 to 2000 °C (0.61–0.77 Tm) by direct ohmic heating. The stress and temperature dependency of creep strain and rupture time are described through optical microstructure observations. Under low load and low temperature conditions, coarse secondary recrystallized grains caused by dynamic recrystallization are observed far from the crack tip. In contrast, under high load and high temperature conditions, coarse secondary recrystallized grains are only fully formed near the crack tip, while coarse secondary recrystallized grains and small primary recrystallized grains coexisted further away from the tip. The recrystallized grain size of the Mo-B sheet is smaller than that of the Mo-A sheet, and small primary and large secondary recrystallized grains are mixed throughout whole specimens of the Mo-B sheet. Mo-A sheet shows elongated ductile fracture, but Mo-B sheet shows irregular brittle fracture under the same conditions. The steady-state creep strain rate at 1800 °C is found to be 7.34 × 10− 6, 2.83 × 10− 5 and 1.53 × 10− 4 s− 1 under a constant stress of 5, 10 and 20 MPa, respectively. The stress exponent is estimated to be 3.85–3.98 and the strain activation energy for steady state creep is 362–413 kJ/mol.