Effect of LPSO phases and aged-precipitations on corrosion behavior of as-forged Mg–6Gd–2Y–1Zn–0.3Zr alloy

Abstract

This paper analyzed the effect of long period stacking ordered phases (LPSO) and aged-precipitations on corrosion behavior of Mg–6Gd–2Y–1Zn–0.3Zr magnesium alloys. As-forged alloys were subjected to aging at 225°C for a period of 4 and 12h such as to acquire the required microstructure. For these as-forged Mg alloys, some structures of LPSO phases were broken and replaced by fine dynamic recrystallized grains. After undergoing the aging treatment for a 4h period, these alloys demonstrated a higher number of recrystallized grains and lesser LPSO phases. However, the 12 aging of the alloys produced the least number of LPSO phases, but produced a considerable amount of aged-precipitations on the recrystallized grains. During the period of 120h immersion in 0.1mol NaCl solution, the corrosion behavior of the alloys was mainly determined by the decreased volume fraction of LPSO phases and the increased volume fraction of aged-precipitations. Alloys after aging for a 12h period, displayed the most critical corrosion rate owing to the severe micro-galvanic corrosion between high voltage aged-precipitations or LPSO phases and Mg-matrix, whereas, the alloys after aging for a 4h period, displayed the best corrosion resistance due to the lesser volume fraction of LPSO phases. As-forged alloys with the most amount of volume fraction of LPSO phases displayed a moderate corrosion resistance.