Effect of Heat Treatment on Microstructure and Corrosion

Noori Gareab, Suhayla; Muna Khedier Abbas, Dr.

	Effect of Heat Treatment on Microstructure and Corrosion
Iraqi journal of mechanical and material engineering
Article 1, Volume 0, Issue 0, 2010, Pages 278-295
Authors
Suhayla Noori Gareab; Dr. Muna Khedier Abbas
Abstract
This work aims to study the effect of the heat treatment (precipitation hardening) on microstructure and corrosion parameters of two alloys (Al- 4%Cu) and (Al- 4.1%Cu- 0.9%Mg). They were prepared by melting and casting in a metallic mold. Hot rolling at 450C° was carried out on ingots by 50% deformation of two alloys to get sheets. Many tests were conducted on these prepared alloys of cast and wrought conditions, including microstructure and hardness and corrosion test. Precipitation heat treatment was carried out which included solution heat treatment at 515C° and aging. Two types of aging, artificial aging at 190C° for 3hr and natural aging at 25C° for 7 days were carried out on prepared alloys in order to indicate the effect of these heat treatments on the microstructure and hardness. Electrochemical corrosion test by Tafel extrapolation method was carried out on all prepared samples of alloys in sodium chloride solution of 3.5% NaCl (PH=8.2) to determine corrosion parameters. such as corrosion potential ( Ecorr. ),corrosion current ( Icorr.) and corrosion rate (mpy). The results show that the corrosion rate of cast samples and homogenized treated was lower than that of wrought samples of two alloys (Al- 4%Cu) and (Al- 4.1%Cu- 0.9%Mg) in salt solution at room temperature. Precipitation heat treatment and artificial aging at 190C° for both cast and wrought conditions lead to increase corrosion rate. The results also show that the addition of Mg to (Al-4%Cu) alloys reduce corrosion current density( I corr .) and corrosion potential (E ) shifts to more noble direction in 3.5% NaCl solution for two alloys in cast and wrought conditions. corr

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