Characterization of magnesium spot welds under tensile and cyclic loadings

Abstract

Resistance spot welds of a magnesium alloy were characterized in terms of microstructure, hardness and monotonic and cyclic properties. Microstructural features in base metal and different zones in the weld region were discussed and the mechanical behavior of spot welds in tensile-shear configuration was studied. Effects of welding parameters were investigated on the micro-and macroscale characteristics of magnesium spot welds. To this end, five sets of spot weld specimens were prepared, utilizing different welding parameters. The effect of cyclic loading was studied on microstructure and hardness of the base metal and the weld region, and it was shown that microstructural features do not change remarkably under cyclic loading. Fatigue crack initiation and propagation behavior was discussed for different specimen sets under both low and high cyclic loads. Fatigue cracks under high cyclic loading initiated close to the nugget edge, and decreasing the cyclic load nucleated the cracks farther from the nugget.The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.matdes.2011.06.001 © 2011 ABSTRACTResistance spot welds of a magnesium alloy were characterized in terms of microstructure, hardness and monotonic and cyclic properties. Microstructural features in base metal and different zones in the weld region were discussed and the mechanical behavior of spot welds in tensile-shear configuration was studied. Effects of welding parameters were investigated on the micro-and macro-scale characteristics of magnesium spot welds. To this end, five sets of spot weld specimens were prepared, utilizing different welding parameters. The effect of cyclic loading was studied on microstructure and hardness of the base metal and the weld region, and it was shown that microstructural features do not change remarkably under cyclic loading. Fatigue crack initiation and propagation behavior was discussed for different specimen sets under both low and high cyclic loads. Fatigue cracks under high cyclic loading initiated close to the nugget edge, and decreasing the cyclic load nucleated the cracks farther from the nugget.

Fatigue characterization and modeling of AZ31B magnesium alloy spot-welds

“…Nugget sizes were measured after monotonic testing as the average diameters of the bonding area, along and perpendicular to the loading direction. The work by Behravesh et al [16] provides a detailed discussion of the effect of process parameter on static and fatigue performance of Mg spot-welds.…”

“…This ratio in the work by Sheppard et al [36] is 30%. Another deficiency associated with the fracture mechanics approach is that the formulations are based on the assumption that the crack is along the faying surface; however, it has been shown that through-thickness cracking is more common for TS specimens [16,26,27,31].…”

“…Published research available regarding fatigue characterization of RSW of Mg alloys is limited to a very few studies. Behravesh et al [15,16] investigated the effect of nugget diameter on fatigue resistance of spot-welds, and showed that fatigue resistance within low cycle fatigue (LCF) regime may be enhanced by increasing nugget size; however, this effect diminishes in the high cycle fatigue (HCF) domain [15]. Depending on the cyclic load level, three different failure modes may occur in fatigue testing: interfacial, partially-interfacial and coupon failures [15,16] .…”

“…Behravesh et al [15,16] investigated the effect of nugget diameter on fatigue resistance of spot-welds, and showed that fatigue resistance within low cycle fatigue (LCF) regime may be enhanced by increasing nugget size; however, this effect diminishes in the high cycle fatigue (HCF) domain [15]. Depending on the cyclic load level, three different failure modes may occur in fatigue testing: interfacial, partially-interfacial and coupon failures [15,16] . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 Many researchers have focused on developing models to estimate the fatigue life of spot-welds.…”

Fatigue behaviour of dissimilar Al 5052 and Mg AZ31 resistance spot welds with Sn‐coated steel interlayer

“…However, limited studies are available on fatigue of Mg/Mg similar spot welds. Behravesh et al . investigated the fatigue behaviour of magnesium spot welds with different nugget sizes.…”