CORROSION BEHAVIOR OF HOT WORK STEEL CONTAININGHIGH Co IN LIQUID MAGNESIUM ALLOY AZ91D

Corrosion behavior of a new hot work die seel containing high Co in liquid magnesium alloy AZ91D was analyzed by SEM and energy spectrum analysis.The results show that a chemical reaction occurred between the steel and liquid magnesium alloy forming a corrosion layer.On the earlier stage of the reaction,the layer was loose and protectiveless;With inreasing of the reaction time,the layer became thick and compact with protectiveness and in tern decreased the reaction rate.Elements such as Fe,Mn etc. in the steel react with elements Al,Mn in liquid magnesium alloy.The corrosion kinetics can be divided into three stages:fast reaction stage,passivating stage and stable reaction stage.