The Ductile-Brittle Transition of Aluminium in the Presence of Hg-3% Zn or Sn-10% Zn Liquid

抄録

Aluminium was embrittled in Hg-3% Zn and Sn-10% Zn. With increasing temperature, the ductility was restored and a ductile-brittle transition was observed. The dependence of transition temperature on the grain size was different in two liquids; in Hg-3% Zn the transition temperature was higher as the grain size became smaller, and in Sn-10% Zn the tendency was reversed.
The results are discussed in terms of stress concentrations for crack nucleation (brittle fracture) and yielding at the tip of the piled-up dislocations. There is a discrepancy between prediction and experiment for the annealed specimen wetted with Hg-3% Zn. To explain this, an expression “stress for definite plastic flow” is newly introduced.
In a subsidary experiment on the pre-strained specimen, the stress introduced is made to be of the same order of magnitude as the yield stress which can be determined experimentally. The above prediction is in excellent agreement with the experimental results.