APPLICATIONS FOR THE STRONTIUM TREATMENT OF WROUGHT AND DIE-CAST AL

Strontium is well known for its ability to modify the eutectic silicon phase in aluminum-silicon foundry alloys. More recently, however, it has been established that strontium also stabilizes the move desirable alpha iron-bearing intermetallic phase in 6XXX series wrought aluminu m alloys. As a result, lengthy billet homogenization times that ave no rmally required to transform the acicular beta iron-bearing intermetal lic phase to the alpha phase can be shortened significantly. In the ca se of the foundry alloys, strontium additions to a 380 alloy were foun d to increase the pressure tightness of high-pressure die castings by as much as 60%. This improvement is believed to occur as a result of i mproved metal flow with the strontium addition causing a reduction in the size of the entrapped air pores and the refinement of sludge parti cles.