Complete mechanical characterization of nanocrystalline Al–Mg alloy using nanoindentation

In an effort to explore alternate means of mechanical characterization of small material volumes, a nanocrystalline Al–Mg alloy synthesized via cryomilling and consolidated by cold isostatic pressing with subsequent extrusion was subjected to nanoindentation testing. The data collected from these tests was subjected to two different data analysis techniques (one proposed by Dao et al. (2001) and one proposed by Ogasawara et al. (2006)) in an effort to investigate the capabilities of such techniques in full, accurate elastoplastic characterization. A commercially available, coarse-grained sample of this same Al–Mg alloy was also tested to investigate these models’ capabilities of distinguishing between the two types of material. Nanoindentation, as expected, proved to accurately predict the elastic modulus of a tested material. Also, these methods provided evidence that through determination of strain-hardening exponent and yield stress, they could reasonably estimate the plastic properties of a tested material. Both models seemed to slightly overestimate the strength of the nanocrystalline material (according to previously reported values for similar material). In terms of the coarse-grained material, Ogasawara’s model appeared to overestimate the strength while Dao’s model provided estimations closer to values reported in literature. Finite element analysis was used as a verification mechanism for the property values extracted from the nanocrystalline material, and initial results show signs of good accuracy of characterization.

► Al-Mg nanocrystalline alloy is fully characterized using nanoindentation. ► Elastic modulus, hardness, hardening exponent and yield strength are reported. ► A comparison of two proposed models (Dao et al. and Ogasawara et al.) is done. ► This comparison shows that accuracy of these two models vary in different ranges.