Method of relieving residual stresses in light metal articles

Abstract

Abstract Light metal articles i.e. of aluminium or magnesium or their alloys, are stress relieved by chilling to below -100 DEG F. and then directing a current of a condensable vapour at a temperature not lower than the boiling point of water over the entire surface at a velocity sufficient to sweep away droplets of liquid condensate. The articles may be chilled in dry ice, a mixture of dry ice with acetone, ether, or thrichlorethylene, liquid isopentane, liquid air, liquid nitrogen or liquid helium. When using a liquid gas it is preferable to cool preliminarily to -100 to -200 DEG F. in some other bath. Such vapours as steam, alcohol, glycerine, glycols and their alkyl substituted products may be used, and the articles are exposed to the vapour at over 240 DEG F. for less than one minute. Precipitation hardenable alloys are chilled before the inception of hardening.

Inventors

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