Novel fabrication of bulk Al with gradient grain size distributions via powder metallurgy

作者：Yang Hanry; Lavernia Enrique J; Schoenung Julie M^*

来源：Philosophical Magazine Letters, 2015, 95(3): 177-186.

DOI：10.1080/09500839.2015.1028504

• nanograined structures
• aluminium alloys
• gradient cryomilling
• microstructural characterization

We describe a novel approach to synthesize gradient microstructures, defined hereafter as containing a broad but continuous distribution of grain sizes. These microstructures extend the concept of a bimodal grain size distribution and the ability to design with multiple length scales. We demonstrate the proposed approach via experiments involving cryogenic ball milling of Al-4.5Mg-0.4Mn-0.05Fe and Al-50Mg powder followed by subsequent consolidation. Our results reveal that the grains in the consolidated powder present a gradient size distribution ranging from 3 mu m. Moreover, phase composition analysis revealed a unique "interfingered" structure where the two starting phases were intermixed in a complex three-dimensional mesh. Hardness studies of this gradient microstructure show average Vickers hardness values of 200 +/- 2.6, 204 +/- 4.3 and 266 +/- 50 for macrohardness, microhardness and nanoindentation, respectively. The standard deviation values highlight that the gradient microstructure is disordered locally, but homogenous macroscopically.

• 出版日期2015-3-4