Optimized combination of room-temperature formability and high-temperature creep property in a dilute-alloyed Mg sheet via tailoring Nd solute segregation

Abstract

The synergy of room-temperature formability and high-temperature creep property has been a long-term problem in the manufacturing of Mg alloy sheets. Aiming at saving rare-earth resource and providing a widely applicable approach to realize the synergy, this study focuses on the effects of preparation conditions on these two properties in Mg alloyed by dilute Nd (0.8 % in weight percent). Through comparing the mechanical behaviors of the samples prepared by different treatments, including low-temperature and long-time solution (Sample #1), high-temperature and short-time solution (Sample #2), and hot deformation for grain refinement (Sample #3), the best combination of stretch formability and creep property was successfully achieved in the Sample #1. The key reason was the conspicuous Nd solute segregation along grain boundaries after solution treated under the low-temperature and long-time condition. Such segregation behavior allowed dislocations moving freely in grain interiors but inhibited dislocations moving across grain boundaries. Finally, the stretch formability related to free dislocation slip in grain interiors and the creep property related to strong grain boundaries were synchronously enhanced. Thus, the low-temperature and long-time solution treatment is recommended for developing dilute Mg–Nd based alloy sheet used in the environment of alternating temperature changes.