Creep deformation of a soft magnetic iron-cobalt alloy

TR Number
Date
1999-04-15
Journal Title
Journal ISSN
Volume Title
Publisher
American Institute of Physics
Abstract

The U.S. Air Force is in the process of developing magnetic bearings, as well as an aircraft integrated power unit and an internal starter/generator for main propulsion engines. These developments are the driving force for the new emphasis on the development of high saturation, low loss magnets capable of maintaining structural integrity in high stress and high temperature environments. It is this combination of desired material characteristics that is the motivation of this effort to measure, model, and predict the creep behavior of such advanced magnetic materials. Hiperco(R) Alloy 50HS, manufactured by Carpenter Technology Corporation, is one of the leading candidates for these applications. Material specimens were subjected to a battery of mechanical tests in order to study and characterize their behaviors. Tensile tests provided stress versus strain behaviors that clearly indicated: a yield point, a heterogeneous deformation described as Luders elongation, the Portevin-LeChatelier effect at elevated temperatures, and most often a section of homogeneous deformation that concluded with necking and fracture. Creep testing indicated three distinct types of behavior. Two types resembled a traditional response with primary, secondary, and tertiary stages; while the third type can be characterized by an abrupt increase in strain rate that acts as a transition from one steady-state behavior to another. The relationships between the tensile and creep responses are discussed. Analyses of the mechanical behavior include double linear regression of empirically modeled data, and constant strain rate testing to bridge the tensile and creep test parameters. (C) 1999 American Institute of Physics. [S0021-8979(99)77908-9].

Description
Keywords
Creep, Magnetic materials, Materials behavior, Materials properties, Testing procedures
Citation
Fingers, R. T., Coate, J. E., Dowling, N. E. (1999). Creep deformation of a soft magnetic iron-cobalt alloy. Journal of Applied Physics, 85(8), 6037-6039. doi: 10.1063/1.369074