Composition and Performance of an Improved Magnesium AS41 Alloy 890205
Standard salt spray corrosion tests have been used with die cast AS41 samples of controlled purity to define the critical iron, nickel, and copper contaminant levels, up to which excellent corrosion performance can be obtained, and beyond which the corrosion rates accelerate rapidly. As previously observed with magnesium alloys AZ91 and AM60, the critical iron content is dependent upon the manganese content of the alloy, so that the critical factor is the iron:manganese ratio rather than the iron alone. While the iron:manganese tolerance is lower for the AS41 alloy, the tolerance for the nickel and copper contaminants lie between those of AZ91 and AM60. When each of the contaminants is less than the critical level, the salt spray corrosion performance was found to be equal to or better than that of die cast 380 aluminum. This represents a dramatic improvement over that normally associated with AS41 alloy in the past.
Creep tests were also conducted which confirm the improved performance of the alloy relative to die cast AZ91.