マグネシウム合金の腐蝕(第6報)

焼鈍温度の影響

抄録

The effect of annealing at 120°, 200°, 290°, 380° and 470° on the corrosion of pure magnesium and its alloys, Mg-Al (1, 3, 7, 11%), Mg-Zn (2, 4, 7%), Mg-Sn (2, 4, 6%), Mg-Cd (2, 4, 6%), Mg-Si (0.62, 0.52%), Mg-Mn (0.90, 2.28%), Mg-Zn (4%)-Al (1, 3, 6%) and Mg-Zn (4%)-Al (1, 3, 6%)-Mn (0.3%) which cast in dry-sand-moulds, was studied. The change of micro-structure of those alloys by annealing was also observed. The following results were obtained. The rate of corrosion for pure magnesium, Mg-Zn (less than 2%), Mg-Cd, and Mg-Mn (less than 2%) alloys decreases with the rise of annealing temperature; for Mg-Si alloys it increases first by annealing and then decreases as temperature rises; for alloys containing aluminium the annealing at a temperature up to 290° has no effect, and above this temperature it is markedly harmful which is noticeable to an appreciable extent when aluminium content is low and this point appears at higher temperature as manganese content increases. The effect of annealing temperature on the corrosion of Mg-Zn, Mg-Sn, Mg-Cd and Mg-Mn alloys has a relation to its change in structure, but for pure magnesium, Mg-Si and alloys containing aluminium the effect is impossible to explain by change in structure.