Rational Selection of Mg Concentration Specifications for 319-Type Alloys

Previous studies on the effect of Mg on the hardness of 319-type alloys are contradictory. The present study was conducted in an attempt to resolve this confusion and allow for a more rational choice of Mg concentration specifications. Four 319-type alloys were prepared with the following target Mg concentrations: 0.00, 0.15, 0.35 and 0.45 wt%. The addition of only 0.15 wt% Mg had a significant effect on the hardness of the alloy but further incremental additions of Mg did not produce the expected trends in hardness. Two hypotheses for this unexplained behavior are presented. This work suggests that the Mg concentration can be allowed to vary between 0.15 wt% and 0.45 wt% without significantly impacting the aging response (hardness) of the alloy.