Ion beam irradiation induced effects on microstructure and mechanical properties of molybdenum

Molybdenum is used as a plasma-facing component (PFC) in tokamaks where it is exposed to high-energy neutrons and plasma particles (He and H ions). This study examines the effects of high-energy copper ion beam with varying doses (0.108, 1.08, and 10.8 dpa) on the microstructure and mechanical properties of molybdenum samples, to emulate the impact of high-energy particle cascade damage. Following exposure to high-energy copper ion beams, changes in microstructure, crystal size, lattice constant, micro-strain (%), and surface morphology were observed. Lower ion dose (0.108 dpa) resulted in severe cracking as shown in SEM images, attributed to a high dislocation density as a result of increased micro-strain (%) and decreased crystal size. Features like dents, melt craters, and a rough surface were observed at high ion doses of 1.08 and 10.8 dpa.Initially, crystal size decreased (fragmentation) at low ion dose of 0.108 dpa. However, at higher ion doses of 1.08 and 10.8 dpa an increase in crystal size (growth) was observed and the microstrain was dropped to lower values. Decrease in lattice constant seems linear with the ion dose as clear from XRD results, indicating the progressive radiation damage. The change in hardness with increasing dose was nonlinear. Hardness was observed to increase first at lower ion dose (0.108 and 1.08 dpa), however at higher ion doses of 10.8 dpa, a decrease in hardness is observed due to crystal size coarsening and structure recovery/recrystallization effects.