Zrの高温硬さに及ぼすAl, Sn, Moの影響

Abstract

In order to improve the strength of zirconium at elevated temperature, the binary alloys of zirconium with aluminium, tin and molybdenum were melted in non-consumable argon arc furnace and their hot-hardness has been investigated. The results obtained are summerized as follows: (1) About 3% of tin or 4% of molybdenum, at least, has to be added to zirconium in order to improve the strength of zirconium at elevated temperature. On the other hand, addition of 2% of aluminium hardness zirconium more than any of the above elements. Generally, below 400°, molybdenum is the most effective among the three in hardening zirconium, but above 600°, aluminium is the most effective. (2) By quenching from α range, alloys are hardened less than by slow-cooling them from the same temperature. On the contrary, by quenching from β range, they are more hardened. (3) The hot-hardness of alloys which are slow-cooled decreases with increasing temperature, but there is an abnormal hardening range between 300° and 400° in the Zr-Mo alloys when quenched from 900°. A similar phenomenon is also found in the case of tempered Zr-Mo alloys after quenching at the same condition, that is, the hardness rises to the maximum at about 400°. It seems that these phenomena are related with the precipitation of ω in β phase reported by H. A. Robinson et al.