Microstructures and properties of nanocomposites obtained through SPTS consolidation of powders

Abstract

The microstructures and properties of copper-and aluminum-based nanocomposites processed through severe plastic torsional straining (SPTS) consolidation of metallic micrometer powders and ceramic nanopowders were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), microhardness and electrical resistivity measurements, and mechanical tests. It was shown that the SPTS consolidation of powders is an effective technique for fabricating metal-ceramic nanocomposites with a high density, ultrafine grain size, and high strength. Copper samples processed under a high pressure of 6 GPa exhibited high failure strength and strain as well as unusual strain hardening. Superplastic-like behavior was found in Al-Al 2 O 3 nanocomposite samples.

Properties and Nanostructures of Materials Processed by SPD Techniques

“…Cold rolling of the copper to a thickness reduction of 60% significantly increased the strength (curve 2), but dramatically decreased the elongation to failure. This is consistent with the classical mechanical behaviour of metals that are deformed plastically [22,23]. This tendency is also true for Cu subjected to two passes of ECAP (curve 3).…”

Microstructures and mechanical properties of ultrafine grained 7075 Al alloy processed by ECAP and their evolutions during annealing

“…The grain size distribution of the UFG sample was nonsymmetric with long tail (Figs. 7(a) and (b)), typical of a lognormal distribution [29]. The initial CG sample was composed of equiaxed grains with an average size of about 40 lm.…”

High-Pressure Torsion of Machining Chips and Bulk Discs of Amorphous Zr<SUB>50</SUB>Cu<SUB>30</SUB>Al<SUB>10</SUB>Ni<SUB>10</SUB>

“…1,2) The HPT is also applicable as a processing tool for consolidation of powders without sintering process. [3][4][5][6][7][8][9][10][11][12][13][14][15] The application includes the consolidation of metallic powders, [3][4][5] composites, [6][7][8][9][10][11][12] ball-milled powders, 13,14) amorphous powders, 15) amorphous ribbons, 16) and very recently machining chips. 17,18) Strain-induced amorphization was reported for some compounds, 19,20) whereas crystallization is detected in amorphous materials such as Cu 50 [21][22][23][24][25][26][27][28][29][30][31] It is well established that bulk amorphous materials have high strengths and high hardness [32][33][34]…”