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

• Published in: The International journal of pressure vessels and piping Vol. 159; pp. 93 - 100
• Main Authors: Maruyama, K., Abe, F., Sato, H., Shimojo, J., Sekido, N., Yoshimi, K.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2018
• Subjects: Aging; Creep fracture; Creep life prediction; Modelling of creep rupture life; Time-temperature parameter analysis; Aging; Time-temperature parameter analysis; Creep life prediction; Creep fracture; Modelling of creep rupture life
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2017.11.013

Larson-Miller (LM) and Orr-Sherby-Dorn (OSD) parameters are widely used when formulating and predicting creep rupture life tr. The LM constant C and the activation energy Q in the OSD parameter characterize temperature dependence of tr. Q = QLSD (QLSD: activation energy for lattice self-diffusion) and C = 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 determining C and Q of each dataset. Based on the correlation between C and Q among similar materials, it is discussed what is the C value equivalent to Q = QLSD. It is also examined how the C value changes with melting temperature of the material. The value of C equivalent to Q = QLSD varies from 14 to 9.5 depending on average values of log(rupture life) and of reciprocal temperature of the dataset. These values of C point out that C = 20 is not equivalent to Q = QLSD. The equivalent C values are similar in all the materials independently of their melting temperatures. Larson-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.