Microstructural changes as a result of temperature gradients in the Al-Al < inf> 3 Ni eutectic

Document Type

Article

Publication Date

2-1980

Department

Department of Materials Science and Engineering

Abstract

The microstructural changes accompanying exposure of the Al-Al3Ni eutectic to temperature gradients have been studied. It is observed that at high temperatures microstructural coarsening, as measured by transverse fiber density, is less during gradient as opposed to isothermal exposure. The converse holds to a much less degree at lower temperatures. The differences between the fiber densities during gradient and isothermal exposure are directly related to the temperature, the temperature gradient, and the time of exposure. Microchemical analysis was performed in an attempt to determine if there was redistribution of Al3Ni along the temperature gradient during such exposure. Experimental results were not entirely conclusive, but do suggest that the Al3Ni content is higher at the hot and cold ends in comparison to that in the center of the specimen. Numerical analysis was employed to test several theories relating to particle migration during elevated temperature exposure. It was found that a model of fiber migration controlled by diffusion along the fiber-matrix interfaces could account well for the observed values of fiber density and apparent redistribution of Al3Ni along the specimen length. Moreover, if reasonable values of the heat of transport of Ni in aluminum are assumed, the diffusion coefficient necessary to predict observed results agrees well with recently determined interfacial diffusion coefficients in a comparable (Al-CuAl2) system.

Publication Title

Metallurgical Transactions A

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