On the physical basis of a Larson-Miller constant of 20

摘要

AbstractLarson-Miller (LM) and Orr-Sherby-Dorn (OSD) parameters are widely used when formulating and predicting creep rupture lifetr. The LM constantCand the activation energyQin the OSD parameter characterize temperature dependence oftr.Q?=?QLSD(QLSD: activation energy for lattice self-diffusion) andC?=?20 are often assumed in the formulation. Creep rupture datasets of 11 heats of nickel alloy A617, 304H and 304J1 stainless steels, 6 heats of A3004N aluminum alloy and four Mg-Al alloys are formulated with the parameters for determiningCandQof each dataset. Based on the correlation betweenCandQamong similar materials, it is discussed what is theCvalue equivalent toQ?=?QLSD. It is also examined how theCvalue changes with melting temperature of the material. The value ofCequivalent toQ?=?QLSDvaries from 14 to 9.5 depending on average values of log(rupture life) and of reciprocal temperature of the dataset. These values ofCpoint out thatC?=?20 is not equivalent toQ?=?QLSD. The equivalentCvalues are similar in all the materials independently of their melting temperatures.HighlightsLarson-Miller constant C is correlated to Orr-Sherby-Dorn constant Q by an equation.?C takes about 12 when Q is equal to activation energy for lattice diffusion.?C is proved to be insensitive to melting temperature of the material.?Q decreases to activation energy for lattice diffusion in long-term creep.]]>