EFFECT OF HEAT TREATMENT AND STRAINING RATE ON FRACTURE AND CORROSION OF Zn-22 Al SUPERPLASTIC ALLOY.

The effect of heat treatment (annealing at 250 to 400 degree C for 1 h, followed by water quenching) and the rate of straining (4. 2 multiplied by 10** minus **4 minus 4. 1 multiplied by 10** minus **1s** minus **1) at 18 degree C on mechanical properties and corrosion of Zn-22Al in sulfuric acid were studied. The results obtained showed that there is a critical rate of straining at which the specimen fracture occurs at lower tensile strain levels although the ultimate tensile strength increases with increasing straining rate. The hardness of heat-treated specimens increased with the heat treatment temperature. The corrosion of heat-treated specimens in sulfuric acid demonstrated that there is a critical heat treatment temperature (about 330 degree C) which results in minimum corrosion. The corrosion rate in sulfuric acid increases at a higher rate in the concentration range of 0. 1-1 N sulfuric acid.