MECHANICAL-PROPERTIES AND STRUCTURE OF IGNITION-PROOF MG-CA-ZR ALLOYSPRODUCED BY SQUEEZE CASTING

The effects of calcium and zirconium additions on the microstructures and mechanical properties have been investigated in the squeeze-cast i gnition-proof magnesium alloys. The marked grain refining is achieved by the combined addition of calcium and zirconium because calcium prom otes the dissolution of zirconium into the magnesium melt. The tensile strength and 0.2% proof stress of the magnesium alloys containing cal cium are increased by grain refining. The combined addition of calcium and zirconium is also effective for the grain refining in the Mg-Y al loys. The ignition-proof Mg-Y-Ca-Zr alloys have good room-temperature strength and elevated-temperature strength which are maintained up to 473 K. The combined addition of calcium and zirconium higher than abou t 1% causes remarkable grain refining and improvements in tensile stre ngth and 0.2% proof stress of the Mg-Zn alloys at room temperature.