Crystallization of amorphous Zr2Pd and Zr3Rh alloys

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Abstract
The thermal stability behavior of the metallic glasses a‐Zr2Pd and a‐Zr3Rh was studied by means of x‐ray diffraction, differential scanning calorimetry (DSC), and isothermal annealing. While several a‐Zr2Pd alloys each exhibit two exothermic peaks during the DSC heating sequence, three different types of exothermic behavior have been observed for a‐Zr3Rh alloys with nominally identical stoichiometries. These variations in DSC behavior are probably related to different conditions during the rapid quenching procedures. The three types of differential scanning calorimeter behavior shown by a‐Zr3Rh alloys include (1) two peaks of about 715 K and 790 K, (2) a single large peak at about 730 K, and (3) a strong peak at about 725 K with a much weaker peak at about 850 K. The a‐Zr3Rh alloys of type (1) crystallize to form a tetragonal lattice that is a newly identified Zr3Rh phase of the D0e structure type. The a‐Zr3Rh alloys of types (2) and (3) crystallize first to form a face‐centered cubic lattice which appears to be an E93‐type structure. Both the D0e and E93 phases are metastable and ultimately anneal to the Zr2Rh phase with the tetragonal C16‐type structure. The formation of the Zr2Rh phases with either the C16 or E93 structure is accompanied by α‐Zr. The a‐Zr2Pd alloys undergo a two‐step crystallization with the initial formation of a disordered body‐centered‐cubic phase followed by the tetragonal Zr2Pd phase with the C11b‐type structure.