Effects of Sr on microstructure and corrosion resistance in simulated body fluid of as cast Mg–Nd–Zr magnesium alloys

Mg–2·2Nd–xSr–0·3Zr alloys (wt-%, x = 0, 0·4, 0·7 and 2·0) were prepared by gravity casting to study the effects of Sr addition on the microstructure and corrosion resistance of Mg–Nd–Zr alloys in simulated body fluid (SBF). Phases were identified by X-ray diffraction, and microstructure was observed with optical microscopy and scanning electron microscopy. Corrosion resistance of the alloys was determined by evaluating mass loss and hydrogen evolution during immersion in SBF. Mg₁₇Sr₂ phase was formed, and the grain size decreased with additional Sr addition. For the grain refinement and more continuous second phase, which could improve the corrosion resistance, the alloy with 0·7 wt-%Sr showed the slowest corrosion rate, whereas the alloy with 2·0 wt-% showed the fastest corrosion rate due to the increased volume fraction of Mg₁₇Sr₂, which led to severe local microgalvanic corrosion.