Universal method for evaluating work-hardening exponent of metals using ultra-microhardness tests

The method for evaluating the work-hardening exponent (n) of Cu using an ultra-microhardness technique, which was proposed by the present authors, is checked up for Al and Ni, and a universal equation relating n to the ultra-microhardness (Hum) or the Vickers hardness (Hv), which does not depend on the specific metal, is proposed for f.c.c. metals. To this end, tensile tests and measurements of Hv and Hum were carried out on Cu, Ni and Al. The previous method is also valid for Al and Ni. The ratio of Hum/Hum₀ or Hv/Hv₀ can be well scaled solely by n, where Hum₀ and Hv₀ are respectively the values of Hum and Hv of each metal showing no working-hardening, and the ratio is independent of the specific metal. The universal equation can be essentially explained in terms of a constitutive equation for polycrystalline metals together with the isotropic continuum approximation.