抄録
In order to determine the optimum aging temperature to give superior toughness to an age-hardening alloy, a comparison of the experimental values of ductility in the under- and over-aged states having similar strength was made using various kinds of iron and aluminum alloys, for example, Fe-Cu, Fe-Cr, Fe-Ni-Cu, Fe-Ni-Mo-C, Fe-Co-Cr-W, Al-Si and Al-Ag alloys. The following conclusions have been drawn from the data by the authors and other investigators: (1) In general, the under-aged alloy has a higher ductility, a lower yield point and a larger strain hardening exponent than those in the over-aged alloy having similar tensile strength. (2) In the alloys strengthened by precipitation of G.P. zone or by decomposition into two phases, in other words, having a coherent second phase, premature fracture often takes place in the under-aged state. (3) In the heavily cold worked alloys and secondary-hardened high alloy steels, the superior toughness may be obtained after slight over-aging.
