Structural Characterisation and Mechanical Properties of Nanocomposite Al-based Alloys

Abstract

Nanocomposite Al-based alloys can be obtained with a combination of amorphous, crystalline and quasicrystalline phases. In order to understand the correlation between the nanostructure and the mechanical behaviour, four nanocomposite alloys with different characteristics were studied: two alloys from the Al-Fe-Cr-Ti system consisting of a spherical nanoquasicrystalline phase in an α-Al matrix; one alloy from the Al-Fe-V-Ti system consisting of a mixture of amorphous and α-Al phases; and one alloy from the Al-Mn-Cr-Cu system consisting of nanocrystalline particles embedded in an α-Al matrix. Melt-spun samples were prepared and the structure was characterised by means of X-ray diffraction and transmission electron microscopy. Differential scanning calorimetry was used to study the thermal stability and the transformation processes. Tensile tests, fractographic analysis and Vickers microhardness at room temperature were performed in order to evaluate the mechanical behaviour. A combination of solid solution, particle dispersion and grain refinement strengthening was responsible for the high strength of the alloys. The microstructure of the alloy Al 93 Fe 3 Cr 2 Ti 2 (at%) remained acceptably stable up to 703 K, due to the slow coarsening rate of the icosahedral phase.

Nanoquasicrystalline Al–Fe–Cr-based alloys. Part II. Mechanical properties

“…The microhardness value measured for the Ti-containing alloy is in agreement with the results from Ref. [1], which reported a value as high as 396 lHV 100 for the same melt-spun alloy. The relatively high microhardness values of the ternary and the V-containing alloy with respect to the Nb-or Ta-containing alloys could be related to the lower total solute content in the aAl matrix of the Nb-or Ta-containing alloys (see Table 3).…”

“…No plastic behaviour was observed on the tensile curves of the as-spun alloys. Audebert et al [1] also carried out tensile tests on melt-spun ribbons of the Al 93 Fe 3 Cr 2 Ti 2 alloy and found fracture stresses and total strains (elastic and plastic) typically of 510-575 MPa and 3-3.5%, respectively. The different values reported in the literature for the tensile tests at room temperature of as-spun ribbons could be due to the large influence of defects in the very small cross-section of the test specimens, and the different solute contents retained in the a-Al matrix.…”

“…However, nanostructured materials with high strength generally suffer from insufficient ductility and reduced toughness compared with conventional microcrystalline materials [1]. On the other hand, a metal matrix nanocomposite, the nanoquasicrystalline Al 93 Fe 3 Cr 2 Ti 2 (at.%) alloy, showed an excellent balance of mechanical properties at elevated temperature [2,3], with higher strength and elongation at high temperature than commercial Al alloys such as AA-2618 or hypereutectic Al-Si-based alloys [2,3].…”

Multicomponent and High Entropy Alloys

“…The ternary alloy had the largest icosahedral particle size, ~200 nm, which reduced to 70-100 nm for the Ti, V, Nb and Ta alloys. [35]. Figure 17 shows a more detailed (a) transmission electron micrograph; (b) selected area electron diffraction pattern and (c) energy dispersive X-ray analysis from an icosahedral particle embedded in melt spun Al93Fe3Cr2Nb2.…”

“…Galano, Audebert, Stone, Prima, Tomut and Cantor [35][36][37][38][39][40][41][42][43][44][45] investigated the structure of a wide range of melt spun alloys in the AlFeCrTiVNbTa system. The alloys were based on the generic formula Al93Fe3Cr2ETM2 where ETM is an early transition metal.…”