Patent ID: 6073677
Filing Date: 2000-06-13
Classification: C22C

Abstract:
A method of controlling the grain refinement of aluminium alloys, comprising the steps of:a) for the casting method used, establishing the grain sizes for different values of the grain growth index GGI, as represented by the formula:GGI=.SIGMA.m.sub.i C.sub.i (k.sub.i -1)=m.sub.1 C.sub.1 (k.sub.1 -1)+m.sub.2 C.sub.2 (k.sub.2 -1)+...where m.sub.i is the slope of the liquidus in the binary (Al-i) system, C.sub.i is the concentration of its dissolved solute in the alloy, and k.sub.i is the distribution coefficient of solute i between solid and liquid, and where m.sub.1, C.sub.1, k.sub.1, etc. represents the corresponding values for each alloy constituent;b) determining the GGI value for the particular aluminium base material by using the formula in a);c) using the data obtained in a) for calculating the grain size of the aluminium base material and how the concentration of grain size affecting agents in the aluminium melt should be changed in order to obtain an aluminium casting having a desired crystal grain size;d) adding the amount of grain size affecting agents calculated in c) to the melt; ande) optionally adding an amount of nucleating agents required.