σ-相合金粉を用いた鉄基粒子分散合金の作製

Abstract

In this study, we investigated a method for producing iron-base particle dispersion alloys of Fe-13Cr-3W-0.5Ti-(0.17∼0.83)Y2O3(mass%) using σ-phase alloy powder as a starting material for mechanical alloying(MA). The alloy powder was prepared by crushing a Fe-43Cr-10W-1.7Ti(mass%) alloy containing brittle σ-phase. The powder obtained was mixed with iron and Y2O3 powders. The mixture was then subjected to MA, and the MA powder was consolidated by hot working. In the study, we especially examined the formation of σ-phase with heat-treatment conditions and the milling characteristics of σ-phase alloys. We also examined the MA characteristics of the mixture and the mechanical properties together with microstructure of the consolidated dispersion alloys.The formation of the σ-phase varied with heat-treatment temperature and time. Alloys containing more than 75 vol% of σ-phase could be easily pulverized by stamping and milling. The powder mixture consisting of iron, σ-phase alloy and Y2O3 powders exhibited excellent MA characteristics, and its MA was accomplished within 72 ks. Y2O3 particle addition inhibited recrystallization and resulted in the refinement of structure. TEM observation and EDS analysis revealed that dispersoids in the alloy consolidated at 1203 K were mainly composed of titanium and oxygen, but yttrium content was small. This fact was considered to cause the solid solution of Y2O3 particles into iron-base alloy during the MA process. The tensile strength of dispersion alloys increased markedly with increasing Y2O3 content, and their elongation decreased with an increase of the strength. The results of tensile tests carried out at 923 K were comparable or superior to those reported by other authors.