Effects of grain size and dendrite arm spacing on tensile properties of continuous-cast 6061 aluminum alloy billets

A method to control grain size and DAS (secondary dendrite arm spacing) independently was established by the vertical semi-continuous casting process with a heat insulating mold, and the effects of grain size and DAS on the tensile properties of 6061 aluminum alloy billets were investigated. The grain size and DAS were controlled by changing casting rate and additional amount of a grain refiner. The Hall-Petch relation is obtained between grain size and 0.2% proof stress, but it's not obtained between DAS and 0.2% proof stress. DAS affects significantly the elongation, and the elongation increases as DAS decreases, but the effect of DAS on the elongation diminishes as a homogenization proceeds.