AZ31鎂合金在3.5wt.% NaCl水溶液中之應力腐蝕行為

Stress-Corrosion Cracking Behavior of AZ31 Alloy in 3.5 Pct NaCl Solution

本研究是以商業化AZ31鎂合金，在1.33Pa真空下進行T4及退火之熱處理後，在3.5 wt0.%NaCl 溶液中進行慢速拉伸試驗（SSRT）以評估AZ31鎂合金的應力腐蝕行為。實驗結果顯示：此材料具有高敏感的應力腐蝕行為，其破斷面是屬於穿晶應力腐蝕破裂，並且晶粒劈裂面能明顯地觀察到雙晶變形所造成平行裂縫（double line），此雙晶變形與不連續析出Mg17Al12相是造成此合金高敏感應力腐蝕破裂的主要因素。

The stress corrosion cracking behavior of a commercialized AZ31 magnesium alloy after T4 and annealing heat treatments under a vacuum of 1.33 Pa has been evaluated via slow strain rate tensile tests (SSRT) in an aqueous 3.5 wt.% NaCl solution. The experimental results show that this material displays a high sensitivity to stress corrosion cracking. The fractured surface appears in a transgranular mode. Double-line cracking resulted from twinning can be readily spotted on the cleavage plane. The presence of such deformation twins accompanied by the discontinuous precipitates of Mg17Al12 is the main reason for the stress corrosion cracking susceptibility of this alloy.