Accession Number : AD0477650
Title : HIGH-TEMPERATURE PROPERTIES AND ALLOYING BEHAVIOR OF THE REFRACTORY PLATINUM-GROUP METALS
Descriptive Note : Final rept.
Corporate Author : BATTELLE MEMORIAL INST COLUMBUS OH
Personal Author(s) : Rudman, Peter S
Report Date : 17 Dec 1965
Pagination or Media Count : 7
Abstract : The occurrence of many phases in platinum-group metal alloys, or even more generally in transition metal alloys, correlates amazingly simply with electron/atom ratio or as we have preferred to call it, group number. One example is the HCP structure that occurs in alloys in the average group number range 7-8.5. The axial ratio, c/a, was a sensitive measure of the electronic state. The c/a-composition relationship in some 20 HCP alloys containing platinum-group metals was determined. The axial ratio appears to correlate well with phase stability: the smaller the axial ratio, the more stable the phase, with the HCP phase becoming unstable relative to cubic phases as c/a approaches 1.61. A theoretical study of Laves phases based on an elastic model was performed. A theoretical study of allotropism was initiated and is continuing. This study was very productive in providing clues to the phase-stabilizing factors. It has been tentatively concluded that the low temperature phases are generally characterized by a high density of states at the Fermi level and that the high temperature phases are characterized by high vibrational entropies.
Descriptors : *PHASE STUDIES , *TRANSITION METALS , *ALLOYS , PLATINUM , ATOMIC STRUCTURE , HEAT RESISTANT ALLOYS , PLATINUM ALLOYS , HEAT RESISTANT METALS , CRYSTAL LATTICES , CRYSTAL STRUCTURE , ELECTRONS
Subject Categories : Properties of Metals and Alloys
Atomic and Molecular Physics and Spectroscopy
Distribution Statement : APPROVED FOR PUBLIC RELEASE