While magnesium alloys have the attractive attributes of low density, the application of the metal in transportation industries has been restricted by its low stiffness and strength. The aim of this study was to examine the possibility of lightweight railway car body construction using magnesium alloys from the structural and manufacturing perspectives. Extruded members, making up a car body, were designed employing a gradient-based optimization algorithm. And then, numerical simulations were conducted to confirm the structural performance of the newly designed car body. In addition, one of the designed members was extruded and joined with another via friction stir welding in order to verify its fabrication potential. The work demonstrated that, with just 85% of the weight of an aluminium car body currently in operation, a magnesium-based railway car body can be potentially constructed by extrusion followed by friction stir welding for the next generation rolling stocks; that is to say, the weight saving amount is 10% of the total bare frame weight, or 2% of its total rolling stock weight.

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