مقاله جوشکاری با عنوان :Resistance-Spot-Welded AZ31 Magnesium Alloys:Part I. Dependence of Fusion Zone Microstructureson Second-Phase ParticlesL. XIAO, L. LIU, Y. ZHOU, and S. ESMAEILIچکیده:A comparison of microstructural features in resistance spot welds of two AZ31 magnesium(Mg) alloys, AZ31-SA (from supplier A) and AZ31-SB (from supplier B), with the same sheetthickness and welding conditions, was performed via optical microscopy, scanning electronmicroscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM).These alloys have similar chemical composition but different sizes of second-phase particles dueto manufacturing process differences. Both columnar and equiaxed dendritic structures wereobserved in the weld fusion zones of these AZ31 SA and SB alloys. However, columnar dendriticgrains were well developed and the width of the columnar dendritic zone (CDZ) was muchlarger in the SB alloy. In contrast, columnar grains were restricted within narrow strip regions,and equiaxed grains were promoted in the SA alloy. Microstructural examination showed thatthe as-received Mg alloys contained two sizes of Al8Mn5 second-phase particles. SubmicronAl8Mn5 particles of 0.09 to 0.4 lm in length occured in both SA and SB alloys; however, largerAl8Mn5 particles of 4 to 10 lm in length were observed only in the SA alloy. The weldingprocess did not have a great effect on the populations of Al8Mn5 particles in these AZ31 welds.The earlier columnar-equiaxed transition (CET) is believed to be related to the pre-existence ofthe coarse Al8Mn5 intermetallic phases in the SA alloy as an inoculant of a-Mg heterogeneousnucleation. This was revealed by the presence of Al8Mn5 particles at the origin of some equiaxeddendrites. Finally, the columnar grains of the SB alloy, which did not contain coarse secondphaseparticles, were efficiently restrained and equiaxed grains were found to be promoted byadding 10 lm-long Mn particles into the fusion zone during resistance spot welding (RSW).
مقاله جوشکاری با عنوان :Resistance-Spot-Welded AZ31 Magnesium Alloys:Part I. Dependence of Fusion Zone Microstructureson Second-Phase ParticlesL. XIAO, L. LIU, Y. ZHOU, and S. ESMAEILIچکیده:A comparison of microstructural features in resistance spot welds of two AZ31 magnesium(Mg) alloys, AZ31-SA (from supplier A) and AZ31-SB (from supplier B), with the same sheetthickness and welding conditions, was performed via optical microscopy, scanning electronmicroscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM).These alloys have similar chemical composition but different sizes of second-phase particles dueto manufacturing process differences. Both columnar and equiaxed dendritic structures wereobserved in the weld fusion zones of these AZ31 SA and SB alloys. However, columnar dendriticgrains were well developed and the width of the columnar dendritic zone (CDZ) was muchlarger in the SB alloy. In contrast, columnar grains were restricted within narrow strip regions,and equiaxed grains were promoted in the SA alloy. Microstructural examination showed thatthe as-received Mg alloys contained two sizes of Al8Mn5 second-phase particles. SubmicronAl8Mn5 particles of 0.09 to 0.4 lm in length occured in both SA and SB alloys; however, largerAl8Mn5 particles of 4 to 10 lm in length were observed only in the SA alloy. The weldingprocess did not have a great effect on the populations of Al8Mn5 particles in these AZ31 welds.The earlier columnar-equiaxed transition (CET) is believed to be related to the pre-existence ofthe coarse Al8Mn5 intermetallic phases in the SA alloy as an inoculant of a-Mg heterogeneousnucleation. This was revealed by the presence of Al8Mn5 particles at the origin of some equiaxeddendrites. Finally, the columnar grains of the SB alloy, which did not contain coarse secondphaseparticles, were efficiently restrained and equiaxed grains were found to be promoted byadding 10 lm-long Mn particles into the fusion zone during resistance spot welding (RSW).