Microstructure characterisation and mechanical properties of rapidly solidified Mg–Zn–Ca alloys with Ce addition

The rapidly solidified (RS) Mg–Zn–Ca based alloys with Ce addition were produced via atomising the alloy melt and subsequently splat quenching the atomised droplets on the water cooled copper twin rollers in the form of flakes. The alloys were characterised by XRD, SEM, HRTEM, DSC and microhardness. All the alloys are characteristic of fine grains in the size of 1–5 μm. The RS Mg–6Zn–5Ca ternary alloy is composed of α–Mg, Mg₂Ca, Ca₂Mg₆Zn₃ and a small quantity of Mg₅₁Zn₂₀, Mg₂Zn₃ and MgZn₂. With the increment of Ce, the Mg₁₂Ce phase in the alloy increases and the Mg₅₁Zn₂₀, Mg₂Zn₃ and Ca₂Mg₆Zn₃ phases decrease, seemly indicating that the proper Ce content is beneficial to the suppression of the latter phases. Moreover, the addition of Ce to the Mg–Zn–Ca alloy contributes to the enhanced thermal stability of the phases in the alloys, especially for the Mg–6Zn–5Ca–3Ce alloy. The microhardness of the RS alloys increases with the increment of Ce, and the strengthening mechanism is discussed.