Orientation and temperature effects on indentation creep mechanisms in magnesium

This study investigates how crystal orientation and temperature affect the indentation creep behavior of pure magnesium at 25 ˚C, 100 ˚C, and 180 ˚C using in-situ indentation and post-test EBSD analyses. The integrated approach enables simultaneous evaluation of orientation-dependent activation parameters ( and ), athermal flow strength , and the contribution of deformation twinning. Results show that creep is primarily governed by obstacle-limited dislocation glide, with twinning contributing at lower temperatures at orientations where slip is limited. At lower temperatures, indentation depth and lattice rotation around the indents are strongly orientation-dependent, while at 180 ˚C these effects are less pronounced, suggesting more homogeneous deformation. The activation energy (0.56–1.09 eV) and volume (10.28 –21.56 ) increase with temperature but are unaffected by orientation, indicating a consistent creep mechanism. The evolution of athermal flow strength reflects a balance between strain hardening and dislocation recovery, with recovery dominating at higher temperatures. Twinning, particularly {10 }< > extension twins, was active at 25 ˚C and 100 ˚C but suppressed at 180 ˚C, and was shown to evolve during the creep hold, confirming its role in accommodating strain under constant load. These findings reveal that creep in Mg results from a temperature-dependent interplay between dislocation glide, evolving internal obstacles, and twinning, offering new insight into the mechanistic basis of time-dependent plasticity in hexagonal metals. The methodology presented in this paper provides a robust framework for investigating time-dependent plasticity in Mg and can be extended to Mg alloys with more complex microstructures.