Effect of Mn and Cr on structure and mechanical properties of Al-10%Mg-0.1%Ti alloy

This study examines the effect of different concentrations of Cr and Mn on the microstructure and mechanical properties of Al-10%Mg-0.1%Ti Alloy by using Al-10Cr and Al-10Mn master alloys. The microstructures were studied via the aid of an optical microscope (OM), X-ray diffraction (XRD) and energy dispersive X-ray (EDS) integrated with scanning electron microscopy (SEM). Cr and Mn contents promote the formation of Al7Cr and Al11Cr2, and Al6Mn phases in the structures of the alloy. The mechanical properties of the alloy increase with Mn content (0.5-3 wt%) due to grain refining and dispersion hardening effect of Al6Mn while higher Cr content precipitates deleterious secondary brittle phase of Al11Cr2. Cr and Mn contents beyond 1 and 3 wt% deteriorate the ultimate tensile strength (UTS) and percentage elongation of the as-cast alloy due to the presence of higher area fraction of brittle intermetallic phases. A direct relationship exists between hardness values and the addition of Cr and Mn contents. Low and high Cr and Mn contents show ductile and brittle fracture modes.