Mfg. intermetallic phases with non-congruent m.pts. - by calcio:thermal redn. of homogeneous mixt. of alloy components with mean particle size up to 75 microns, followed by tempering

摘要

Mfr. of single phase intermetallic phases with incongruent melting points between 900-2000 K and upto 10 atom.% homogeneity at room temp. involves calciothermal redn. of a fine, homogeneous mixt. of the alloy components, one of which exists as an oxide, followed by diffusion of the alloy components. then sepn. of the resultant calcium oxide and, where necessary, excess calcium. The novelty is that a) Adjustment of the exothermic heat of reaction of calciothermal redn. by altering oxide content of the reaction mixt., the compsn. of which corresponds to the desired single phase alloy is achieved by fulfilment of the temp. condition Tm is where TR is at least 0.9Tm (in K), in which Tm is the m.pt. of the intermetallic phase and temp. b) Use of a reaction mixt., the components of which (apart from Ca) have a mean particle size upto 75 microns. c) On completion of the exothermic reaction, tempering of reaction prods. at a temp. within the range 0.7-0.95 times the m.pt., Tm, of the desired single phase alloy (in K) for a period of time adequate for diffusion of the components. ADVANTAGE - Starting materials are oxides, redn. and alloy formation occur in one process step in economically viable time frame, a powdered product is formed, and the process is performed without complicated machinery