STRESS-RELAXATION AND CREEP-BEHAVIOR OF SOME RAPIDLY SOLIDIFIED MAGNESIUM ALLOYS

Application of rapid solidification to magnesium alloys generally increases the mechanical properties by a factor of 2-2.5 compared with conventional wrought magnesium alloys. This is mainly due to a smaller grain size. What is the creep behaviour of these high strength magnesium alloys? Planar flow cast magnesium alloys have been cast and extruded. The mechanical properties in tension and compression, the stress-relaxation in compression and the tensile creep properties have been tested at temperatures from RT to 150-degrees-C. Traditionally one would expect poor creep resistance in a small grained material. In some rapidly solidified aluminium alloys, however, the creep resistance is good, due to fine particles pinning grain boundaries and impeding dislocation movements. In the magnesium alloys tested there is a big difference in the creep resistance depending on the microstructure of the alloys. The on-going study focuses on the optimal microstructure for good mechanical properties and creep resistance.