Mechanical Properties of the Nanoquasicrystalline Al-based Alloys

M GALANO; F AUDEBERT; A. GARCIA ESCORIAL; I STONE; B CANTOR

Congreso; Nanomat 2003; 2003

Nanostructured Al-based alloys have been studied intensively for the last decade. In particular nanoquasicrystalline Al-based alloys showed to have promising mechanical properties at elevated temperature compared with commercial Al-based alloys. In a previous work on the nanoquasicrystalline Al93(Fe3Cr2)7 and Al93Fe3Cr2X2 (at%) (with X= Ti, V, Nb Ta) alloys, produced by melt spinning, it was found that the early transition metals led to improve the thermal stability of the microstructure in the following order: Ti, V, Nb and Ta. In the present work the mechanical properties at elevated temperature of these nanoquasicrystalline alloys were studied by tensile tests at a constant strain rate. Tests were designed in order to compare the mechanical behaviour at different test temperatures. The fracture surface of the tensile samples was analysed by scanning electron microscopy. The activation energy was found to be close to the self diffusion in grain boundaries and lattice for pure Al in the ternary alloy and in the V and Ti containing alloys. Whereas, the activation energy of the alloy containing Ta was three times higher than of the rest of the alloys. All the alloys show similar sensitivity to the strain rate in the range of 10-3 to 10-6 s-1 at 350 0C and the true stress exponent was n~7, which can be associated to a deformation process controlled by dislocation mechanisms. A mechanical characterisation at room temperature was done by microhardness tests as well and the results were compared to the ones for samples heat treated at 550 0C. The microhardness of the heat treated samples was lower than that of the rapid solidified samples. The heat treated alloy containing Ti showed the higher microhardness and tensile strength values than the rest of the alloys.