THE BINARY-SYSTEM PD-SI

The Pd-Si phase diagram has been revised in details (178 alloys) on carefully annealed specimens by microprobe analysis, X-rays diffraction and DTA. The Pd2Si intermetallic phase (m.p. 1404-degrees-C) is confirmed to be stoichiometric with the C22-structure, but within the ranges of composition 33.3-33.9 and 34.5 at.% Si it diversifies in three very similar crystalline structures formed peritectically at 1053-1083 and 1072+/-2-degrees-C respectively. PdSi only exists in a very short range of temperature (888-908-degrees-C melting congruently), whereas Pd5Si (m.p. 856-degrees-C) disappears below 811-degrees-C, likewise producing four very narrow and similar phases at 16 at.% Si (below 811-degrees-C), 17.7 (below 795-degrees-C), 18.2 at.% Si (between 819 and 764-degrees-C) and 21.0 at.% Si (between 792 and 753-degrees-C), all these phases being formed by peritectoid transformations. The only Pd3Si-phase (congruent m.p. 1074-degrees-C) remains stable at low temperature.