Abstract
The aluminium specimens subjected to various cooling treatments were tensile-tested in the temperature range from room temperature to 240°C, in the presence of 3% Zn amalgam.
The yield stresses of these dry specimens increased with an increase in cooling rate. The temperature dependence of the yield stress was almost the same for each specimen, but that of the wetted brittle fracture stress decreased with an increase in cooling rate.
The observed ductile-brittle transition temperature increased with an increase in cooling rate, i.e., the transition temperature of the quenched specimen was higher by 70°C than that of the annealed specimen.
Since the increase in yield stress is due to point defects, secondary defects and thermal stress, the effect of cooling rate on the transition temperature can be evaluated in terms of this sort of hardening, without any interference of interstitial precipitation which is considered to have an important role in the transition of body centered cubic metals.
