Effect of yttrium addition on mechanical behavior of powder metallurgy TP304 at elevated temperatures

摘要

It is well known that oxide dispersion strengthened (ODS) alloys, which are mechanically alloyed with yttria, possess excellent mechanical properties in comparison with conventional ingot metallurgy (IM) materials at elevated temperatures even higher than 1000°C (1,2). However, mechanical alloying may not be desired in view of production cost for the high temperature application where such high strength is not necessarily required. There is not an extensive literature dealing with mechanical properties at above 800°C of the fully dense powder metallurgy (PM) materials without mechanical alloying. In the PM TP304 consolidated by hot extrusion, it was revealed that PM materials showed shorter creeprupture life than IM materials and their creep rupture strengths decrease with increasing oxide inci sions originated mainly from oxidation of powder (3,4). It was also shown that the kinds of oxidte inclusions observed in the consolidated materials were strongly dependent on the contents of strorfg oxide former elements such as Al, Si and Mn in the melt before atomizing. The mechanical behavior at elevated temperature's were affected by those kinds of oxides to a greater extent in PM materials thaji in IM materials (5). In the present study, the melt of TP304 containing yttrium was atomized to form yttria on and in the powder. The effects of such oxide inclusions on high temperature tensile properties and creep rupture strengths are investigated, using TP304 fully dense materials consolidated by hot extrusion.