Mg₉₆Zn₂Y₂合金チップ連続押出固化成形体の機械的性質

抄録

The authors examined the properties of Mg₉₆Zn₂Y₂ alloy bars made through continuous consolidation of chip using a newly developed single screw extrusion machine designed for magnesium alloy chip. Surface conditions as well as microstructure of the consolidated Mg₉₆Zn₂Y₂ alloy varied depending on the die conditions. With a die inner diameter of 49 mm and die temperature of 723 K, severe plastic deformation in the die produced a fine-grain microstructure in the consolidated Mg₉₆Zn₂Y₂ alloy bar. The compounds such as Mg₁₂YZn and Mg₃Y₂Zn₃ in the bar were also dispersed finely. Owing to its randomized crystal orientation, a secondary extruded bar made from the consolidated Mg₉₆Zn₂Y₂ alloy bar showed a higher ductility than that of ingot-extruded bar. The fine-grain consolidated Mg₉₆Zn₂Y₂ alloy bar exhibited an elongation of 308% at 723 K. Furthermore, the deformation characteristics were examined with the consolidated Mg₉₆Zn₂Y₂ alloy bar for the purpose of determining its suitability as hot-processing material billets. The fine-grain consolidated Mg₉₆Zn₂Y₂ alloy bar was compressed without cracking up to 623 K while Mg₉₆Zn₂Y₂ ingot cracked. It was found that smaller grain diameter made the m-value higher.