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Vol.34, No.4, 470 ~ 478, 1996

Title

Research Paper - Mechanical Behavior - : Effect of the Factors on the Formation of Luders Line in Al - Mg Alloys

한공Gong Han, 최일동Il Dong Choi, 강석봉Suk Bong Kang

Abstract

The formation of Lu¨ders lines was characterized in Al-4.5%Mg and Al-5.6%Mg alloys. All of the test specimens of Al-4.5%Mg and Al-5.6%Mg alloys showed type B Lu¨ders line in the strain rate range from 2×10^(-4)/sec to 2×10^(-1)/sec. Type B Lu¨ders line was identified as serration on stress-strain curves. However, type A Lu¨ders line was not observed. The critical strain(ε_c) for the occurrence of the Portevin Le Chatelier effect(type B Lu¨ders line) in Al-4.5%Mg alloy increased with increasing the strain rate. It was considered that dislocation locking was delayed at high strain rates because dislocations moved faster than solute atoms. Specimens were reheat-treated at 400℃, 450℃ and 500℃ for 30 minutes to study the effect of microstructure on the formation of type A Lu¨ders line. It was shown that Al-4.5%Mg alloy showed type A Lu¨ders line but Al-5.6%Mg alloy didn`t. It was considered that the formation of type A Lu¨ders line in Al-4.5%Mg alloy was caused by the grain refinement, increasing the quantity of soluble solute atoms and formation of cell structure after reheat-treatment.

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