Patent ID: 8591674

Claim:
A method of improving the room temperature tensile elongation of a magnesium-based alloy sheet with a thickness, the sheet having an initial annealed microstructure comprising strain-free grains of substantially uniform size, by forming in the sheet a microstructure comprising grains of two distinguishable size ranges, the method comprising: deforming the sheet, in a single rolling operation at a temperature no higher than about 160° C. to distribute, the deformation producing a substantially uniform distribution of closely-spaced, strained, portions of the sheet embedded in substantially undeformed sheet portions; and annealing the sheet at a temperature and for a time suitable for producing, in the strained, closely-spaced, embedded portions, grains larger than the grains in the substantially undeformed sheet portions to develop a microstructure in which the grain sizes comprise a bimodal distribution in which a majority of the grains have sizes which lie within one of two size ranges of between about 10 and 25 micrometers and between about 70 and 100 micrometers, the regions with grains of between about 70 and 100 micrometers developing in the previously-strained portions.