IMPROVEMENT IN HEAT RESISTANCE OF ALUMINIUM ALLOYS BY ADDITION OF ZIRCONIUM-(1)
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The wrought aluminium alloys currently used can be classified into two main groups; age-hardenable alloys and the alloys hardened by cold working. The strength of the former, however, will be greatly reduced by overaging which takes place above 200°C. The latter, too, will lose its strength at high temperatures due to softening caused by recrystallization, but there would be the possibility to bring the latter to be stronger than the former at the higher temperatures if the effect of cold working should be retained up to the temperature by means of preventing recrystallization by the addition of a suitable alloying element.From this point of view, the alloying element has been searched for by the author which can enhance the recrystallization temperature of aluminium.As it was timely discovered by Dr. M. Yanagisawa that the small addition of zirconium can raise its recrystallization temperature higher than 400°C, a series of experiments has been carried out to observe the softening behaviers of various aluminium alloys with 0.5% Zr at high temperatures.The results obtained with Al-3%Mg, Al-1.2%Mn, Al-4%Cu and Al-6%Zn-2%Mg alloys has been reported here from among the experimental data hitherto obtained.The softening behaviors due to annealing for an hour at the respective temperatures have been shown in Figs. 1-8 and the changes of Vickers hardness during heating at the respective temperatures after cold rolling of 50 or 75% have been illustrated in Figs. 9-12 for Al-Mg and Al-Mn alloys. Vickers hardness values have been tabulated in Table. 1, measured at room temperature for the four alloys held for an hour at the respective temperatures, followed by quenching.As the results, Al-3% Mg alloy added with 0.5% Zr has been found to be the best, which retained its Vickers hardness of about 90 even after 100 hours at 400°C, and Al-Zn-Mg-Zr Alloy follows. Zirconium, however, has been found to have no effect its Al-Mn alloy system.Addition of zirconium has been carried out by using the master alloy of Al-10%Zr prepared by powder metallurgy from zirconium powder containing hafnium and aluminium powder. The loss of zirconium has been found to be scarce; only 1-5% except in the case of Al-Mn system. The procedure has also the advantage to utilize low grade zirconium sponge, zirconium scrap as well as zirconium powder.Though creep test above 300°C will be necessary before conclusion, extensive use of aluminium alloys can be expected in the field of the structural materials for supersonic aircraft as well as for nuclear reactors, if heat resistance can be enhanced through the study.
- 一般社団法人 軽金属学会の論文
一般社団法人 軽金属学会 | 論文
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