The AZX (X = calcium) series of magnesium alloys have recently been developed as lightweight incombustible alloys for use in automotive and railway vehicles. However, magnesium alloys containing Ca show inferior plastic deformation and poor formability. The tensile properties of rolled and annealed samples of Mg-3Al-1Zn-1Ca (AZX311) alloy were examined. Sheets of this alloy subjected to a rolling process of three passes at 473 K without reheating showed a 0.2% proof stress of 361 MPa and a tensile strength of 373 MPa. The high strength of the AZX311 alloy sheet was the result of the effective grinding of compounds and their fine dispersal in the magnesium phases, which occurred during rolling deformation and grain refinement. After annealing, the growth of compounds and grains was improved without extreme elongation, but the strength of the compounds was maintained owing to their fine dispersion. The thermal stability of this alloy was improved by adding only 1 mass% elemental Ca.

Effects of Al concentration and Zn addition on microstructures and mechanical properties of Mg-Al-(Zn)-Ca series magnesium (Mg) alloy medium plates were investigated. Concerning to mechanical properties of AMX (Mg-Al-Ca) alloys with various Al concentrations, which were processed by rolling at 523 K and final annealing at 473 K, good balance of tensile strength and failure elongation were obtained, when Al concentration was 8 mass%. When Al concentration was more than 9 mass%, however, both tensile strength and failure elongation were deteriorated due to coarsening of Al-Ca compounds. Concerning to mechanical properties of AZX (Mg-Al-Zn-Ca) alloys with various Al concentrations and 1 mass% Zn addition, which were processed by the same procedure with AMX alloys, enhancement of tensile strength without deterioration of failure elongation was attained at Al concentration of 6-8 mass%, when the tensile direction was parallel to the rolling direction. Clear deterioration in failure elongation compared with AMX alloys were observed, however, when the tensile direction was perpendicular to the rolling direction. 1 mass%Zn addition to AMX alloy promoted precipitation of fine Mg 17 Al 12 particles, which likely affected mechanical properties. In addition, solid solution of Zn in AMX alloy likely contributed to enhancement of tensile strength.

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The effects of Al concentration and Zn addition on the corrosion resistance of Mg-Al-(Zn)-Ca based magnesium (Mg) alloy rolled sheets were investigated. AXM (Mg-Al-Ca) alloys containing 1 mass%Ca, and AZX (Mg-Al-Zn-Ca) alloys containing 1 mass% of Ca plus 1 mass%Zn, both adjusted the Al concentration to 6, 7, 8, 9, 11 mass%, were prepared. The corrosion resistance of alloys in 5 mass%NaCl solution was evaluated by the weight loss and the penetration depth. Electrochemical method based on corrosion potential and impedance spectroscopy was applied to monitor the corrosion behavior. The surface film formed on the alloy surface was characterized by GD-OES and SEM/EDS. The corrosion rates were minimal for AXM alloy with Al content of around 8 mass%Al whereas AZX alloy showed the opposite result with the same content. The reason was interpreted in terms of the Al concentration in the matrix (α phase). The tendency of localized corrosion in high Al-containing Mg alloys was pointed out.

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