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Three different carbon steels, namely ASTM 516 Gr70 PVQ plate, G40.21 350 WT plate and G40.21 350 AT plate, were tensile tested at temperatures from ambient to 623 K over a range of strain rates (l.48 × 10–5–1.48 × 10–3 s–1). Particular attention was paid to behaviour that was indicative of dynamic strain aging, namely (i) serrated yielding, (ii) negative strain rate dependence of the ultimate tensile strength and (iii) increase of the ultimate tensile strength measured at elevated temperatures compared with that measured at ambient temperature. The three steels displayed different strain aging behaviours and these differences are discussed in terms of their respective nitrogen and carbon contents. Resume Trois aciers differents so us forme de plaques ASTM 516 Gr70 PVQ, G40.21 350 WT et G40.21 350 AT, ont ete soumis a des essais de traction a des temperatures allant de l'ambiante jusqu'a 623 K selon des taux de deformation compris entre 1.48 × 10–5 et 1.48 × 10−3 s−1. Une attention particuliere et...

The primary and steady-state creep behaviour of 310-type stainless steel has been investigated over the temperature range 500–700°C (0.46–0.58 Tm ). The steady-state stress exponent, n, increased slightly with increasing grain size, d, from n= 5.9 at d = 40 μm to n = 6.4 at d = 100 μm at a test temperature T = 600°C. The activation energy for steady-state creep, Q c, determined at σ = 300 MPa was 250±6.4 kJ mol−1 for d = 40 μm. This value of Q c is approximately equal to that for the volume self-diffusion of iron (280 kJ mol−1). The activation energy determined for primary creep is almost the same as that for secondary creep. The grain diameter parameter, m, in the equation ec = Aσn d m exp (− Q c/RT) was determined to be –1.67 for σ = 300 MPa and T = 600°C. This value is slightly different from a previously published value of m= −2, which was obtained at a lower applied stress. Using the strain-time data obtained in these tests, constitutive equations have been developed to describe both the pri...

This paper discusses the development of transient creep theories with respect to their physical bases. A simple derivation for the periodic or oscillating type of creep is presented which is based on a combination of the thermal fluctuation of dislocation density model and the exhaustion model. Resume Cet article discute des developpements des theories du fluage transitoire au niveau des principes physiques de base. On presente une approche simple du flage de type periodique ou oscillatoire, basee sur la combinaison de modeles d'epuisement et de modeles de fluctuation thermique de la densite de dislocations.

Canadian manufactured pressure vessel quality steel plate, namely, ASTM 516 Gr. 70 PVQ, was tensile tested at temperatures from ambient to 573 K over a range of strain rates. The mechanical properties determined included: yield strength, ultimate strength and total elongation. There was an increase in ultimate tensile strength, relative to the ambient temperature strength, over a certain range of temperatures. The strain rate dependence of the strength changed from positive to negative at relatively high temperatures and switched back to a positive dependence again at even high temperatures. This increase in the strength and change in strain rate dependence, are attributed to dynamic strain aging. The degree of strain aging can be correlated with an increase in the magnitude of work hardening relative to that at ambient temperature. In general, a finer grain size leads to a higher degree of strain aging. There is a range of temperatures-strain rates over which strain aging is a maximum. The result...

Metal hydrides provide an efficient and safe method for storing hydrogen. Hydrogen can be stored indefinitely and released as needed for a number of energy usages. The commercially available alloys for storage are LaNi5-based, FeTi-based, and Mg-based alloys. In this paper we conduct an overall review of these alloys and compare them with other alloys, and in particular with zirconium based binaries and pseudobinaries. Also described in this paper is the apparatus required for hydrogen absorption and desorption experiments.

A critical review is presented of all published data on phase transformation in zirconium and its alloys. Topics discussed include: The α → β transformation; factors affecting the stability of α and β zirconium; transformations in the β-phase including ω-phase formation, eutectoidal decomposition and strain induced transformations; transformations in the α-phase including the tempering of martensite and supersaturated alpha, and peritectoid formation of ordered Zr3Al. The review concludes with examples of phase transformations in commercial zirconium alloys and the effects of these transformations on the mechanical properties of the alloys. Resume Une revue critique de toutes les donnees publiees sur les transformations de phase du zirconium et de ses alliages est presentee. Les sujets traites sont: la transformation α → β, les facteurs influencant la stabilite des phases α et β, les transformations ayant lieu dans la phase β incluant la formation de la phase ω, la decomposition eutectoidique et ...

The anisotropy of mechanical properties as measured by Knoop microhardness in Zircaloy-4 nuclear fuel cladding containing a range of oxygen and nitrogen impurity contents is related to the heat treatment schedule experienced in simulated brazing treatments. With increasing (0 + N) contents there was an increase in the overall Knoop hardness value but no significant effects on the degree of mechanical anisotropy. The effect of the brazing cycle (short times at temperatures ≥1050°C) is to lower the overall micro hardness value and to reduce the degree of anisotropy. However, no simulated brazing cycle entirely eliminated the anisotropy and the general orientations of the “hard” and “soft” directions remained the same. An annealing treatment of 1h at 850°C produced the highest degree of mechanical isotropy. Resume L'anisotropie des proprietes mecaniques d'un cladding de Zircalloy-4 destine a combustible nucleaire contenant diverses teneurs d'oxygene et d'azote a ete mesuree par microdurete Knoop et ...