Hot-tearing susceptibility of Al-Zn alloys
Abstract
The modern concepts of the causes of hot tearing are considered and the influence of the solid fraction growth rate of an alloy is studied. The hot-tearing susceptibility (HTS) of binary Al-(5-73) wt % Zn alloys is investigated using backbone tests. The HTS is found to be maximal at ~25 wt % Zn. This maximum cannot be explained by a change in the effective solidification range, since this range of the alloys decreases monotonically with increasing zinc content. The calculations of nonequilibrium solidification by the Scheil-Gulliver model and the solid fraction growth rate of the alloys under study demonstrate that the increase in the HTS induced by an increase in the zinc content from 5 to 25 wt % is related to the decrease in the solid fraction growth rate at the final stages of solidification. The decrease in the HTS at >25 wt % Zn is associated with an increase in the fraction of eutectic in the alloys (the solid fraction growth rate during the eutectic reaction tends toward infinity) and with a change in its morphology.
- Publication:
-
Russian Metallurgy
- Pub Date:
- September 2017
- DOI:
- 10.1134/S0036029517090026
- Bibcode:
- 2017RuMet2017..711B
- Keywords:
-
- hot-tearing susceptibility;
- solid fraction growth rate;
- effective solidification range;
- Scheil-Gulliver model;
- coherency point