Effect of Calcium on Structure, Phase Composition and Hardening of Al-Zn-Mg Alloys Containing up to 12wt.%Zn

The influence of calcium on structure and phase composition of the aluminum alloys, containing additions of zinc up to 12 wt.% and magnesium (3.5 wt.%) was studied. The increase of Zn content leads to formation of Al4Ca primary crystals at lower concentrations of calcium. Zinc is distributed between aluminum solid solution and intermetalic phases (Ca-containing and T-Al2Mg2Zn3) in the alloys of the Al-Zn-Mg-Ca system. The eutectic (Al)+Al4Ca has fine structure and particles of Al4Ca are capable to spheroidization during heat treatment at 500 degrees C The maximal level of hardness observed on calcium containing alloys was higher than 200 HB, what gives a reason to expect good strength properties. Due to summarized results it is seen that the Al-Zn-Mg-Ca system is promising for development of new eutectic type high-strength aluminum alloys.