1993 年 42 巻 479 号 p. 990-996
Tensile properties and stress corrosion cracking (SCC) resistance of Al-8wt.% Zn-1wt.% Mg system alloys with various Cu and La contents were investigated. The influences of additional elements on mechanical properties and SCC life were discussed on the basis of experimental results. The results obtained in the present work are as follows;
(1) Additions of elements of Cu and La were effective to decrease the grain size of those materials. In particular, the grain sizes in alloys containing La contents of more than 1.7wt.% were small at 20μm, comparing with that in the master alloy.
(2) For the present alloys containing La, the second phase particles, consisting of Zn and La, have the capacity of hydrogen storage. These particles were between 5 and 10μm in size, and were dispersed in the matrix homogeneously.
(3) Tensile properties were improved with increasing Cu or La content. For the alloys with Cu and La, the tensile strength was from 450 to 500MPa, and the elongation between 14 and 17%.
(4) The alloys containing La had high resistance to SCC. Their SCC lives were about 15 times as long as that of the master alloy. In conclusion, the alloys added Cu more than 0.6wt.% and La 4.0wt.% were much superior to the master alloy in both the tensile properties and the SCC resistance.