特集 粉末の成形・加工 ＡＺ９１マグネシウム合金切粉押出し材の押出し比と機械的性質との関係

Abstract

Relationship between extrusion ratio and mechanical properties was examined on hot extruded machined-chip of AZ91 magnesium alloy so as to establish a technology to recycle magnesium alloys from machined chips by a simple method. High tensile strength was achieved when the machined chips were extruded at an extrusion ratio of 4.9 or more compared with a material extruded at a ratio of 1.8 or a hot pressed material because the machined chips were completely bonded to each other and microstructure such as grains and Al12Mg17 precipitates was refined by severe plastic deformation of the machined chips during hot extrusion. A material extruded at a ratio of 44 showed the highest tensile strength of 373MPa, while the strength decreased when the extrusion ratio increased up to 100 owing to recovery of the microstructure. On the other hand, fracture strain increased with increasing extrusion ratio; 7.3% or more fracture strain was achieved especially when the extrusion ratios were 44 or 100 because initiation and growth of cracks were suppressed by the refined microstructure.