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- Crystallization (2)
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- Aluminum alloy (1)
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- Cold rolling (1)
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The stability of microstructure and the microhardness of a NiCoCrAlY alloy was studied after thermal treatment at high temperatures and subsequent quenching into ice water. The alloy revealed mainly two ordered phases, a gamma' phase with L12 lattice structure and a beta phase with B2 structure. The gamma' phase is shown to become unstable in the temperature range between 1073 K and 1373 K where it undergoes an order-disorder phase transformation. The low transformation temperature compared to pure Ni3Al is ascribed to deviations from the Ni3Al stoichiometry and to the additional alloying elements Co and Cr. The gamma'-gamma order-disorder transformation is shown to be attended by a decrease in microhardness of about 30 %.
Texture formation in amorphous Al86Ni6Y4.5La1.5Co2 splats by thermal and mechanical treatment
(2016)
The crystallization behavior of amorphous Al86Ni6Y4.5La1.5Co2 splats was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Rietveld refinement was used to analyze the preferred orientation of fcc aluminum nanocrystals in the residual amorphous matrix after annealing. Fiber textures in [200] and [220] directions were found after heating to 360 C. The influence of cold rolling on the preferred crystal orientation was studied as a function of the thickness reduction of the specimen. It was found that cold rolling significantly increases the (220) texture, while the (200) texture remains unchanged. Based on the experimental results the formation of (220) and (200) texture during the crystallization of the amorphous splats was ascribed to two different processes, internal stresses induced during splat formation or cold-rolling.