The effect of calcium on the texture, microstructure and mechanical properties of extruded Mg-Mn-Ca alloys

Research highlights: → Observation of characteristic 'rare earth' texture resulting from the addition of Ca. → Improvement in the tension compression asymmetry due to Ca addition. → Solution treatment prior to extrusion is shown to have a marked effect on the extrusion force, but minimal effect on the extruded grain size. → TEM analysis has shown that the Mn particles and Mg2Ca eutectic phase both exist in the microstructure. Mn and Ca do not form an additional phase. - Abstract: The effect of Ca concentration on the texture, microstructure and mechanical properties of extruded ternary Mg-1.3Mn-xCa alloys has been examined. The ternary alloys have been benchmarked against Mg-1.3Mn and binary Mg-Ca alloys. The extruded microstructures contained stringers of Mg2Ca eutectic with individual particle sizes of up to 2 μm. Fine Mn-rich particles with a size range of 20-50 nm were also present. The addition of Ca to the ternary alloys weakened the extrusion texture, and it is shown that Ca behaves in a similar manner to rare earth elements when alloyed with magnesium, and this attributed to its large atomic radius. The texture weakening improved the tension compression asymmetry, however, this did not correlate to improved tensile ductility. The drop in uniform elongation observed with increasing Ca concentration is attributed to the presence of large Mg2Ca particles.