Process developed at the National Metallurgical Laboratory: Modification of Aluminium Silicion alloys - India Patents No. 76415

Abstract

SILICON is one of the most widely used alloying elements in aluminium and aluminium-silicon alloys occupy a unique position in the light alloys of today so much so that nearly 75% of the light alloy castings belong to this group. Excellent casting characteristics such as good fluidity permitting production of intricate castings even in thin sections reproducing the finest details, freedom from shrinkage and hot tear, good pressure tightness along with good corrosion and wear resistance render them eminetly suitable for the manufacture of various items in the automobile, aircraft, architectural, marine and several other engineering fields by sand, permanent mould or die casting processes. The aluminium-silicon alloys can be classified into 3 groups : the hydro-eutectic, the eutectic and the hypereutectic. The hypo-eutectic alloys contain silicon below 11.7%; the eutectic alloys contain 11.7% silicon but sometimes they may have commercially silicon as high as 13. The hyper-eutectic alloys contain silicon above 11.7% but more specifically 170/" to 230/1, Addition of other alloying elements like Cu, Mg, Ni, Mn; Cr, Co in small percentages are also made to all these alloys to get certain desired properties.