Abstract
Magnesium, the lightest structural metal, is difficult to form at room temperature due to an insufficient number of deformation modes imposed by its hexagonal structure and a strong texture developed during thermomechanical processes. Although appropriate alloying additions can weaken the texture, formability improvement is limited because alloying additions do not fundamentally alter deformation modes. Here we show that magnesium can become super-formable at room temperature without alloying. Despite possessing a strong texture, magnesium can be cold rolled to a strain at least eight times that possible in conventional processing. The resultant cold-rolled sheet can be further formed without cracking due to grain size reduction to the order of one micron and inter-granular mechanisms becoming dominant, rather than the usual slip and twinning. These findings provide a pathway for developing highly formable products from magnesium and other hexagonal metals that are traditionally difficult to form at room temperature.
Highlights
Magnesium, the lightest structural metal, is difficult to form at room temperature due to an insufficient number of deformation modes imposed by its hexagonal structure and a strong texture developed during thermomechanical processes
Alloying additions can reduce the stress required to activate more deformation modes and/or weaken the basal texture to allow easier plastic deformation[8,9,10,11,12,13]. While such efforts have achieved some success in terms of formability improvement, they have not developed any magnesium products that are super-formable at room temperature
We report a breakthrough in the design and development of formable magnesium–polycrystalline pure magnesium can be tailored to be super-formable at room temperature by conventional processes
Summary
The lightest structural metal, is difficult to form at room temperature due to an insufficient number of deformation modes imposed by its hexagonal structure and a strong texture developed during thermomechanical processes. Specimens extruded at or below 80 °C do not fracture during compression at room temperature and a strain rate of 10−3 s-1 (Fig. 1a, b). As a further demonstration of the super-formability of the extruded polycrystalline pure magnesium, specimens extruded at 80 °C were rolled at room temperature without any intermediate annealing.
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