Nanoindentation Properties and the Microstructure of Grain Boundary Precipitate-Free-Zones (PFZs) in an AlCuSiGe Alloy.

V. RADMILOVIC; C. TAYLOR; Z. LEE; A. TOLLEY; D. MITLIN; U. DAHMEN

PHILOSOPHICAL MAGAZINE

TAYLOR AND FRANCIS

Año: 2007 vol. 87 p. 3905 - 3919

1478-6435

We have characterized the nano-scale mechanical properties of grain-boundary precipitate-free-zones (PFZ?s) in an AlCuSiGe alloy, using combined nanoindentation and in-situ atomic force microscopy (AFM). These mechanical properties were then correlated to the composition, precipitate distribution, and indirectly to the vacancy concentration within these regions, as analyzed by transmission electron microscopy and spectroscopy. Using these results we constructed a structure-zone-map of the area adjacent to the grain boundary, which relates the reduced elastic modulus and nanoindentation hardness of the alloy to its graded microstructure. Our analysis indicate that the worst mechanical properties  are found in the region where no precipitates are present at all, regardless of solute concentration. In regions where precipitation is different from that of the bulk, somewhat inferior mechanical properties are achieved, though they may be remedied by overaging the alloy.