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B. Wilshire

Bio: B. Wilshire is an academic researcher from Swansea University. The author has contributed to research in topics: Creep & Ceramic. The author has an hindex of 14, co-authored 23 publications receiving 1141 citations.

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13 May 1993

190 citations

Journal ArticleDOI
TL;DR: In this paper, normal creep curves are recorded over extended stress ranges at 686-823 K for fine-grain copper and the observed behaviour patterns suggest that dislocation processes are dominant at all stress levels.
Abstract: Normal creep curves are recorded over extended stress ranges at 686–823 K for fine-grain copper. Analyses of the curve shape variations, together with the results of stress change experiments, do not support the view that a transition from dislocation to diffusional creep mechanisms occurs with decreasing stress. Instead, the observed behaviour patterns suggest that dislocation processes are dominant at all stress levels. However, strain accumulation within the grains becomes progressively less important as deformation is increasingly confined to the grain boundary zones when the stress is reduced below the yield stress at the creep temperature. New approaches are then introduced for rationalization of creep rate and creep life measurements, which account for the data trends taken as evidence for major mechanism changes when the creep properties are described using power law relationships.

138 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a methodology to predict the minimum creep rates, the times to various strains and the creep lives for stress-temperature conditions causing failure in 100 000 h and more.
Abstract: Although a transition from transgranular to intergranular fracture occurs and the tempered bainite microstructure evolves during creep exposure, new relationships allow rationalisation and extrapolation of the multibatch creep data sets reported for 1Cr–1Mo–0·25V steel. Specifically, analyses of results from tests lasting only up to 5000 h accurately predict the minimum creep rates, the times to various strains and the creep lives for stress–temperature conditions causing failure in 100 000 h and more. Validation of this new methodology would therefore offer the prospect of cost effective acquisition of long term creep design data.

80 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a procedure for rationalization and extrapolation of multi-batch creep and fracture data, based on relationships which involve only the activation energy for matrix diffusion (300kJ−mol−1) and the ultimate tensile stress values at the creep temperatures, allowing straightforward prediction of the 100,000h creep rupture strengths of 11Cr−2W−0.4Mo−1Cu−Nb-V steel (Grade 122).

71 citations


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Journal ArticleDOI
TL;DR: The current understanding of the fundamentals of recrystallization is summarized in this paper, which includes understanding the as-deformed state, nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recystallization, particle effects, and texture.
Abstract: The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section.

1,797 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of impurities and dispersoids on the constitutive equations for Al alloys are briefly discussed and compared with carbon, micro-alloyed, tool and stainless steels and to ferritic steels which usually do not exhibit DRX.
Abstract: Constitutive equations including an Arrhenius term have been commonly applied to steels with the objective of calculating hot rolling and forging forces. The function relating stress and strain rate is generally the hyperbolic-sine since the power and exponential laws lose linearity at high and low stresses, respectively. In austenitic steels, the equations have been used primarily for the peak stress (strain) associated with dynamic recrystallization (DRX) but also for the critical and steady state stresses (strains) for nucleation and first wave completion of DRX. Since the peak strain is raised by the presence of solutes and fine particles, the stress is raised more than by simple strain hardening increase, thus causing a marked rise in activation energy in alloy steels. In contrast, large carbides, inclusions or segregates, if hard, may lower the peak strain as a result of particle stimulated nucleation. Due to the linear relation between stress and strain at the peak, flow curves can be calculated from the constitutive data with only one additional constant. Maximum pass stresses can also be calculated from a sinh constitutive equation determined in multistage torsion simulations of rolling schedules. Comparison is made between carbon, micro-alloyed, tool and stainless steels and to ferritic steels which usually do not exhibit DRX. Parallels to the effects of impurities and dispersoids on the constitutive equations for Al alloys are briefly discussed.

892 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.
Abstract: Considerable work has been performed on NiAl over the last three decades, with an extremely rapid growth in research on this intermetallic occurring in the last few years due to recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still in question. Part of this problem lies in the incomplete characterization of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure and the apparent difficulty in accurately measuring composition has made direct comparison between individual studies sometimes tenuous. Therefore, the purpose of this review is to summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.

705 citations

Journal ArticleDOI
TL;DR: A review of the state-of-the-art of the understanding of cavity formation during stages I and II (primary and secondary) creep in polycrystalline metals and alloys, particularly at elevated temperatures, can be found in this article.

312 citations

Journal ArticleDOI
TL;DR: In this article, a wide range of experimental data on the creep of ceramics was analyzed and it was shown that there is an enhanced role of diffusion creep, and in the power-law regime, Ceramics divide into two categories with stress exponents of ∼ 5 and ∼ 3, respectively.
Abstract: This review analyses a wide range of experimental data on the creep of ceramic materials and reveals many similarities with the creep of metals. It is demonstrated that there are two important differences in the creep behaviour of ceramics: (1) there is an enhanced role of diffusion creep, and (2) in the power-law regime, ceramics divide into two categories with stress exponents of ∼ 5 and ∼ 3, respectively. It is concluded that the behaviour with an exponent of ∼ 5 represents fully ductile behaviour as in f cc metals, whereas the behaviour with an exponent of ∼ 3 is due to dislocation climb from Bardeen-Herring sources under conditions where there is either a lack of five independent slip systems or, if five independent slip systems are available, a lack of interpenetration of these systems.

286 citations