Effect of grain size on the elongation for 3004 aluminum alloy

In general, a fine grain structure may be produce an excellent elongation. However, the different tendency was observed with Al-Mg system alloys. In order to make clear a grain size dependence for elongation, a tensile test, a surface roughness measurement and a fractography were performed for 3004 aluminum alloy with various grain sizes from 18 to 121 μm. Then a total and a uniform elongation of 3004 aluminum alloy tensiled for a strain rate of 1.67 × 10-4 s-1 was plotted for grain size, a maximum elongation was obtained in 77μm of mean grain size. The total and the uniform elongation was proportional to a reciprocal square root of grain size. There is no change a local elongation for the reciprocal square root of grain size. In fine grain region below the 77 μm of grain size, grain size dependence for elongation was indicated a inverse Hall-Petch type by the effects of a work hardening exponent and an amplitude of serration. In the meantime, coarse grain region over the 77 μm of grain size, the grain size dependence for elongation was indicated a Hall-Petch type by the effects of a three dimensional stress and a surface roughness on the tensile specimen. The same grain size dependence for elongation was observed in the strain rate of l.67 × 10-3 and 1.67 × 10-5 s-1.