EFFECT OF IMPOSING A VERY HIGH STRAIN ON THE STRESS-STRAIN BEHAVIOR OF A Zn-22 Al ALLOY

摘要

Specimens of the Zn-22% Al eutectoid alloy were processed by equal channel angular pressing (ECAP) at 473 K through various numbers of passes up to a maximum of 24 passes. Tensile specimens were machined from unpressed and as-pressed billets and tested at strain rates of 1.0 x 10~(-3) and 1.0 x 10~(-2) s~(-1) at room temperature. The tensile results show that higher elongations are recorded in the specimens processed by ECAP. However, samples processed through very large numbers of passes show essentially the same yield stresses and the same high fracture strains as samples processed though only a relatively small number of passes. The result is attributed to the low melting temperature of the alloy because room temperature corresponds to an homologous temperature close to ～0.43 T_m where T_m is the absolute melting temperature. An optimum elongation of ～280% was recorded at the lowest strain rate for a sample pressed through 12 passes.