Automotive Mg Research and Development in North America

The friction stir weldability of a fine-grained high strength AZ31B magnesium alloy to A5083 Al alloy was evaluated at various welding conditions, by using a tool with shoulder diameter of 15 mm, pin diameter of 5 mm and pin length of 3.9 mm. A square butt dissimilar joint without any defect was obtained at the condition of welding speed 100 mm/min, tool rotating speed 500 rpm and offset 0 mm. Higher or lower welding speeds or rotating speeds led to either the formation of defect or lack of bonding in the joint. Defects occurred also in the case that the offset was not 0 mm, i.e. the insertion position of the probe was on either Mg side or Al side, when tool rotating speed was 500 rpm and welding speed was 100 mm/min. The maximum tensile strength of the dissimilar joints in the present study was about 115 MPa, lower than that of Al alloy base metal (about 308 MPa). Transmission electron microscopy showed that an intermetallic compound (IMC) layer, which consisted of Al 12 Mg 17 and Al 3 Mg 2 , formed at the bonding interface of the joints, and it was found that the formation and growth of the IMC were controlled by the react diffusion of Mg and Al atoms, instead of the eutectic reaction. The present study demonstrated that the tensile strength of the dissimilar joints was mainly affected by the thickness of IMC layer and the mechanical interlock between magnesium and aluminum alloys. The tensile strength decreased remarkably with the increase in the thickness of IMC layer, which made the mechanical interlock weaker.

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“…1) However, the poor mechanical properties of Mg alloys, such as low tensile strength and poor formability, limit their application area.…”

Section: Introductionmentioning

confidence: 99%

Effect of Intermetallic Compound Layer on Tensile Strength of Dissimilar Friction-Stir Weld of a High Strength Mg Alloy and Al Alloy

Yamamoto¹,

Liao²,

Watanabe

et al. 2009

Mater. Trans.

134

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“…[1] Magnesium alloy, the lightest structural metal, is a promising material for reducing the weight of automobiles; however, its automotive application is limited to a single-component level mainly due to its low strength and poor formability. [2] It is therefore important to improve the strength of magnesium alloys in order to broaden their application in the automotive field as well as other industries.…”

Section: Introductionmentioning

confidence: 99%

Effect of Dispersed Intermetallic Particles on Microstructural Evolution in the Friction Stir Weld of a Fine-Grained Magnesium Alloy

Liao

Yamamoto

Nakata

2009

Metall Mater Trans A

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A fine-grained Mg alloy with copious dispersed Al 6 Mn particles was friction stir (FS) welded, and microstructures at the stir zones (SZs) were investigated intensively and compared to those in a coarse-grained Mg alloy, which had identical chemical compositions with the fine-grained one but much less Al 6 Mn particles. It is found that the grain size at the SZs is a little coarser than that of the base material in the fine-grained alloy, while it becomes much finer in the coarse-grained one. Under the same welding conditions, however, the grain size at the SZs in the fine-grained alloy is much smaller than that in the coarse-grained one. These experimental results are explained in terms of a grain growth mechanism proposed in the present study. Transmission electron microscopy (TEM) examination shows that the dispersed Al 6 Mn particles can suppress grain growth via Zener pinning, and consequently result in smaller grains at the SZs in the fine-grained alloy.

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“…However, the use of die-cast magnesium alloys is currently limited due to the variations of local mechanical properties throughout a complex die-cast component [1][2][3][4]. A major goal in several research programmes in die-cast magnesium alloys is the predictive capability of these local mechanical properties [3][4][5][6]. Due to local mechanical property variations, die-casters currently design components using lowerthan-actual properties which results in larger sections, resulting in greater component mass, minimizing the advantages of die-cast magnesium alloys.…”

Section: Introductionmentioning

confidence: 99%