M. Narisawa et al., HIGH-TEMPERATURE CREEP AND RESULTANT ANISOTROPY IN ULTRASONIC VELOCITY IN ISOTROPIC GRAPHITE, Journal of Materials Science, 29(3), 1994, pp. 708-713
Plastic deformation of isotropic graphite in the vicinity of 2500-degr
ees-C was studied using an Instron-type testing machine. The load-defl
ection curve was found to show a proportional limit at high temperatur
e. Creep curves of graphite were also measured and were simulated by a
n empirical equation based on parabolic creep. Following the creep tes
ts, ultrasonic velocity in the elongated graphite was measured. The ve
locity showed 5%-20% decrease after the creep. Below 2500-degrees-C, t
he rate of velocity decrease along the elongation axis was always larg
er than that across the elongation axis. Above 2500-degrees-C, this be
haviour was reversed with the rate of velocity decrease across the elo
ngation axis being the larger. The rate of decrease appeared to depend
firstly on temperature and secondly on stress.