Cast Al Alloys
Low melting temperature, good surface finish and insolubility to gases except H2 are characteristics of these alloys. Significant drawback of cast aluminium alloys is their shrinkage subsequent to solidification and thus careful mould design is named as for. Mechanical properties are inferior to wrought alloys not including in creep. Alloys can be, cold chamber pressure die cast and sand cast gravity die cast. Si, Cu, Mg and Sn raise fluidity while casting thin sections. A mechanical property of cast Al alloys is enhanced by adding Cu that induces age hardening to impart stability and hardness upto 250oC. Alloys utilized for die casting are as: 380 (Si, Al and 3.5 Cu) and 413 (11.5 Si, Al). Alloys chosen for permanent mould casting are as: 332 (1 Mg, 9 Si, Al, 3Cu,) and 319 (6 SI, Al, and 4 Cu). Y-alloy having 4% Cu and 2% Ni retain strength at high temperatures. This is utilize for piston and cylinders of IC engines.