The ternary Fe-6%B-x%Mo alloys have a composite microstructure consisting mainly of a complex boride Mo
2FeB
2 as a hard phase and a ferritic binder. The mechanism of liquid phase sintering of this alloy was investigated by means of dilatometry, differential thermal analysis, X-ray diffraction, and scanning electron microscopy. A fine composite microstructure of Mo
2FeB
2 and ferrite was produced from powders of Fe, Mo and FeB by a reaction sintering process involving two liquid phases. The hard phase Mo
2FeB
2 is produced in the compact prior to liquid formation. Above 1, 365K, considerable densification results from the initial stage rearrangement of the solid phases (austenite and Mo
2FeB
2) coexisting with the first formed liquid phase (L
1). Another liquid (L
2) which forms above 1, 415K, where Mo
2FeB
2 is the only coexisting solid phase, is required for complete densification. L2 having a high solubility for Mo
2FeB
2, provides for solution/reprecipitation process which characterize the intermediate stage of liquid phase sintering. The effective separation of the initial and intermediate stages by L
1 and L
2 is considered essential for the control of the sintered microstrucure of the ternary alloy.
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