Development Program for Improving Foundry and Repair Welding Techniques for ZE41-type Magnesium Alloy Castings.

摘要

This report describes a development program for improved foundry and repair welding techniques for large complex ZE41-type magnesium castings, such as currently specified by the designers of next generation of army aircraft (e.g. the AAH, UTTAS, etc.). This one year program was directed at resolving the weld cracking problem in ZE41 magnesium alloy combiner housing casting for the HLH aircraft, and making it a high quality reproducible part. The results on one HLH combiner housing casting poured with a chemical composition between that of EZ33 and ZE41 alloys, showed that the tensile properties of the machined test bars taken from various section thicknesses and chill/riser/neutral locations were similar, and that the tensile properties of welded and nonwelded areas were comparable. Two step heat treatment (625 F or 675 F for two (2) hours, air cool, 340 F for twelve (12) hours) provided effective stress relief. Thus for large complicated magnesium castings, such as the HLH combiner housing, the cracking in the weld areas during welding as well as delayed cracking in the weld areas can be overcome by the proper selection of chemical composition and heat treatment.