INVESTIGATION OF SOLIDIFICATION OF HIGH-STRENGTH STEEL CASTINGS
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF METALLURGY AND MATERIALS SCIENCE
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Analytical and experimental work on microsegregation and dendrite structure in a series of iron base alloys is summarized. Experimental work is on iron-nickel alloys, iron-4 phosphorous alloy, iron-25 copper alloy, and iron-nickel carbon alloys. A new computer analysis for microsegregation is presented, with detailed numerical results given for iron-26 nickel alloy, iron-10 nickel alloy, and iron-4 phosphorous alloy. Results agree reasonably well with experiment provided the dendrite arm spacing used in calculation is less by a constant correction factor, g, than that measured for example g nearly equal to 0.40 for cylinder model, secondary dendrite arm spacing. It is concluded the need for the correction factor arises primarily because the model employed for calculation does not account for ripening during solidification. Structures of the various alloys studied are presented in some, the dendrite morphology is strongly plate-like in others, it is fibrous. Over a range of cooling rates from 0.001 Csec to nearly 1,000,000 Csec dendrite arm spacing of iron-26 nickel alloy is linearly related to a single power of cooling rate. It is concluded that the dependency results from the predominant effect of coarsening in determining final dendrite arm spacing.
- Fabrication Metallurgy