tion has decreased due to the presence of alloying elements. Following mechanical testing of
heat aff ected zone simulations per- formed on Eglin steel, these conclu-
sions were made: • Heat input does not have a sig- nifi cant eff ect on the mechanical
• Strength decreases in the subcrit- ical, intercriticial and fi ne-grain heat aff ected zones relative to the base metal, probably due to tem- pering and carbide coarsening as a result of the thermal cycle.
properties of heat aff ected zone thermal simulations.
• The yield strength of the coarse-grain heat affected zone is increased relative to the base metal, but the tensile strength and ductility are decreased, most likely due to the forma- tion of untempered martensite.
• A similar loss of toughness was seen throughout all regions of the heat affected zone in com- parison to the base metal.
• T e base metal has a mixed mode of fracture consisting of micro- void coalescence and cleavage. T e subcritical and intercritical heat aff ected zones exhibit a fracture surface consisting of only cleavage, whereas the fi ne-grain and coarse-grain heat aff ected zones exhibit a mixed mode of fracture of microvoid coalescence and cleavage.
• Heat treatment following casting is shown to yield similar mechan- ical properties to the heat treated wrought alloy.
• Toughness of the cast and heat treated Eglin steel is less than its wrought counterpart in all regions of the heat aff ected zone.
• Performing the full Eglin steel heat treatment following thermal simulation yields an increase in toughness in all heat aff ected zone conditions, but does not restore properties to that of the base metal.
After preliminary welding experi- ments performed on the PH marag- ing alloys, the following conclusions
were made: • T e hardness variations in the fusion zone and heat aff ected zone are most likely caused by the presence of precipitates which can be aff ected by the weld thermal cycle causing coarsening or dissolution.
• Post-weld heat treatments in- creased hardness in the fusion zone and eliminated drops in hardness in the heat aff ected zone, most likely due to re-precipitation.
T is article is based on a paper presented at the Steel Founders Society of America’s 67th Technical and Operating Conference in Chicago December 2013.
46 | METAL CASTING DESIGN & PURCHASING | Jan/Feb 2014
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