Further comments on grain boundary wetting in liquid phase sintered Fe-Cu alloys
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The authors are indebted to Professor B. M. Korevaar for stimulating discussions.
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Further Comments on Grain Boundary Wetting in Liquid Phase Sintered Fe-Cu Alloys A.N. NIEMI and T. H. COURTNEY In this communication we wish to clarify and, in one case, correct observations reported in a previous publication.~ In the work cited it was observed that certain 7Fe grain boundaries in liquid phase sintered Fe-Cu alloys were penetrated by the liquid copper after having been sintered at various temperatures, cooled to room temperature, and then reheated to a liquid phase sintering temperature lower than the original one. Moreover, we reported that one sample, cooled below the solidus by removing it from the furnace hot zone and then reheated slightly above the liquidus by reinsertion into the hot zone, also showed evidence of such boundary wetting. These observations led us to conclude that the "secondary wetting" was the result of liquid penetration along low angle boundaries formed by particle coalescence events at the higher temperature. S. Takajo, 2 in discussing these phenomena with us, suggested we were observing penetration of liquid copper along high angle 7/7 grain boundaries formed by cycling through the 7 ~ a transformation in Fe. Although we originally believed the sample cooled below the solidus temperature did not experience a temperature below 7 / a transformation temperature, it turns out this belief is wrong and Takajo's interpretation is correct. We have determined this by showing that cooling below the allotropic transformation temperature is required for subsequent boundary "rewetting." For example, liquid phase sintering (LPS) a 0.7 Fe-Cu (70 volume pct Fe, 30 volume pct Cu) at 1423 K for 24 hours followed by a one hour LPS treatment at 1403 K did not result in wetting of t
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