- Email: [email protected]
Thermodynamics of ordered ß1-PdZn alloys
xxix
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
Vol. 9, No. 6
originates at larger misorientation grain boundaries. Segments of these boundaries migrate at a rate depending on temperature and time and consume the semicoherent matrix spinodal, leaving behind larger irregularly shaped semiReceived December 9, 1974 coherent particles in a cellular morphRevised January 30, 1975 plogy. The combined influence of a dominant driving force (reduction in total The resolution of lattice fringes interphase interfacial energy) and slugin ordered and partially ordered Cu3Au gish boundary migration rate promotes has been calculated using the dynamical additional coarsening among the boundary-fed particles, wherein their effecttheory of electron diffraction, taking into consideration the effects of such ive interparticle spacing (A 2) varies variables as foil thickness aad orient0.7 ation, objective lens defocus, degree as A 2 = k2t , compared to that of the of order and, for partially ordered 0.34 alloys, the position of small ordered matrix, ~ = kit . In both cases the rate of coarsening is greater in the domains in the foil. The experimental alloy of asyn~netrical composition than observations were found to be in exin the syn~netrical alloy. No satisfactcellent agreement with these calculaory account of Cu-Ni-Fe discontinuous tions. Lattice defects in ordered Cu3Au have been studied using this tech-coarsening reaction kinetics can be made nique. Thus, the domain wall thickness based upon current theories of thermally at transitional antiphase domain bound- activated growth processes. aries has been shown to be one or two atomic diameters and the antiphase 17. THERMODYNAMICS OF ORDERED ~l-PdZn boundary separating the pair of fundaALLOYS mental lattice dislocations which conS. Kou and Y. A. Chang stitute a superdislocation has been reMaterials Dept., College of Enginvealed. A clear distinction exists beeering and Applied Science, Univertween the lattice image contrast of sity of Wisconsin-Milwaukee, Milwaukpredominantly ordered and disordered Milwaukee, Wisconsin 53201. regions and this has been utilized to study partial long-range order and Received December I0, 1974 short-range order. Short-range order in this system is characterised by a disRevised March I0, 1975 persion of small highly ordered domains, Thermodynamic activities of Zn in ~15~ in diameter, in a predominantly ~l-PdZn alloys exhibiting the f.c. disordered matrix. tetragonal structure were determined at 12730K using the isopiestic technique. 16. DISCONTINUOUS COARSENING OF The experimental data are found to agree SPINODALLY DECOMPOSED Cu-Ni-Fe with the theoretical equations of Gyuk, ALLOYS Liang and Chang for describing the compositional dependence of the thermodynR. Gronsky and G. Thomas amic activity. The phase ~l-PdZn is Inorganic Materials Research Div., Lawrence Berkeley Lab. and Dept. of highly stable as evidenced by the critical transition temperature of 4546°K, Materials Science and Engineering, and a highly exothermic Gibbs free enerCollege of Engineering, University of California, Berkeley, Cal. 94720 gy of formation of -12 kcal/g.atom at 1273°K. The high stability of this phase is most likely due to the transfer of Received December 9, 1974 electrons from zinc to the d-band of Revised February 19, 1975 palladium. The trend in the stabilities of intermetallic phases formed between The coarsening behavior of two groups II and III metals with the group Cu-Ni-Fe alloys has been found to inVIII transition metals is discussed. clude a discontinuous reaction which Division, Lawrence Berkeley Lab., University of California, Berkeley, California. *Brown, Boveri and Cie. A.G., D-6800 Mannheim I, W. Germany.
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
Vol. 9, No. 6
originates at larger misorientation grain boundaries. Segments of these boundaries migrate at a rate depending on temperature and time and consume the semicoherent matrix spinodal, leaving behind larger irregularly shaped semiReceived December 9, 1974 coherent particles in a cellular morphRevised January 30, 1975 plogy. The combined influence of a dominant driving force (reduction in total The resolution of lattice fringes interphase interfacial energy) and slugin ordered and partially ordered Cu3Au gish boundary migration rate promotes has been calculated using the dynamical additional coarsening among the boundary-fed particles, wherein their effecttheory of electron diffraction, taking into consideration the effects of such ive interparticle spacing (A 2) varies variables as foil thickness aad orient0.7 ation, objective lens defocus, degree as A 2 = k2t , compared to that of the of order and, for partially ordered 0.34 alloys, the position of small ordered matrix, ~ = kit . In both cases the rate of coarsening is greater in the domains in the foil. The experimental alloy of asyn~netrical composition than observations were found to be in exin the syn~netrical alloy. No satisfactcellent agreement with these calculaory account of Cu-Ni-Fe discontinuous tions. Lattice defects in ordered Cu3Au have been studied using this tech-coarsening reaction kinetics can be made nique. Thus, the domain wall thickness based upon current theories of thermally at transitional antiphase domain bound- activated growth processes. aries has been shown to be one or two atomic diameters and the antiphase 17. THERMODYNAMICS OF ORDERED ~l-PdZn boundary separating the pair of fundaALLOYS mental lattice dislocations which conS. Kou and Y. A. Chang stitute a superdislocation has been reMaterials Dept., College of Enginvealed. A clear distinction exists beeering and Applied Science, Univertween the lattice image contrast of sity of Wisconsin-Milwaukee, Milwaukpredominantly ordered and disordered Milwaukee, Wisconsin 53201. regions and this has been utilized to study partial long-range order and Received December I0, 1974 short-range order. Short-range order in this system is characterised by a disRevised March I0, 1975 persion of small highly ordered domains, Thermodynamic activities of Zn in ~15~ in diameter, in a predominantly ~l-PdZn alloys exhibiting the f.c. disordered matrix. tetragonal structure were determined at 12730K using the isopiestic technique. 16. DISCONTINUOUS COARSENING OF The experimental data are found to agree SPINODALLY DECOMPOSED Cu-Ni-Fe with the theoretical equations of Gyuk, ALLOYS Liang and Chang for describing the compositional dependence of the thermodynR. Gronsky and G. Thomas amic activity. The phase ~l-PdZn is Inorganic Materials Research Div., Lawrence Berkeley Lab. and Dept. of highly stable as evidenced by the critical transition temperature of 4546°K, Materials Science and Engineering, and a highly exothermic Gibbs free enerCollege of Engineering, University of California, Berkeley, Cal. 94720 gy of formation of -12 kcal/g.atom at 1273°K. The high stability of this phase is most likely due to the transfer of Received December 9, 1974 electrons from zinc to the d-band of Revised February 19, 1975 palladium. The trend in the stabilities of intermetallic phases formed between The coarsening behavior of two groups II and III metals with the group Cu-Ni-Fe alloys has been found to inVIII transition metals is discussed. clude a discontinuous reaction which Division, Lawrence Berkeley Lab., University of California, Berkeley, California. *Brown, Boveri and Cie. A.G., D-6800 Mannheim I, W. Germany.