TO STUDY THE CORRELATION BETWEEN MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AL-MG-CR ALLOY AFTER WORK HARDENING

The effect of cold-work and heat treatment on the microstructure development and changes occurred in the mechanical properties of Al-Mg-Cr alloy has been studied at large. The samples were homogenized at 573 K for one hour and allowed to cool at room temperature. X-ray fluorescence spectroscopy (XRF) was employed to ensure the exact elemental composition of the alloy. The samples were cold worked under normal static load of 30 KN with time variation to get 1% to 7% reduction in thickness. After work hardening the samples were aged for four hours at 373K. Optical microscopy was used to study the microstructure. Vickers hardness test was carried out to study hardness, which was improved as a result of work hardening. The steady state creep rate was found to be decreased as a result of above-mentioned treatment. Aluminum- Magnesium- Chromium is a non-heat treatable alloy (1-2) that is generally known for its excellent corrosion resistance. The Al-Mg-Cr alloys have a wide range of strength, good forming and welding characteristics, and high resistance to corrosion as has been shown by Haszler et. al. (3). The work of Gholinia, et. al. (4) showed the conditions under which micron- scale structure can be developed in Al-Mg-Cr alloy. The Niikura, et. al. (5) related with the refinements of recrystallized grain and its effects on mechanical properties in Al-Mg alloys. For the purpose of obtaining aluminum P/M materials strengthened by solid solution of Mg and dispersion of transition metal compounds, Fujii, et. al. (6) worked on rapidly solidified Al- Transition metals with addition of Mg Rapid solidification (RS). Jian et. al. (7) Investigated the influence of chemical composition on the microstructure and mechanical properties of AI Mg alloys. The work of Taleff, et. al. (8) showed that the solute-drag creep was observed in many aluminum alloy containing magnesium concentration from as little as 2 wt%, to the limit of solubility. Kaigorodeva (9) worked on microstructure and mechanical properties evolution during long term aging of AI-Mg alloy by optical and transmission electron microscopy as well as tensile test and corrosion resistance decreased during aging which result from film like grain boundary B' and β phase precipitation. The work reported by Savas et. al. (10) covered a comparative investigation of the Aluminum-Magnesium cast alloys containing up to 10% Mg.