Diffusion-creep in magnesium alloys

Vickers, W.; Greenfield, Peter

doi:10.1016/0022-3115(67)90198-5

Cited by 37 publications

(5 citation statements)

References 11 publications

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“…3). This structure is analogous to that established during plastic deformation of a totally crystallised Mg-23.5Ni alloy [16] and very similar to the formation of denuded zones during creep in some magnesium alloys [17][18][19]. However, denuded zones have been reported at higher temperatures as well as at slower strain rates than those employed for the present Mg-23.5Ni alloy [17][18][19].…”

Section: Discussionsupporting

confidence: 58%

“…This structure is analogous to that established during plastic deformation of a totally crystallised Mg-23.5Ni alloy [16] and very similar to the formation of denuded zones during creep in some magnesium alloys [17][18][19]. However, denuded zones have been reported at higher temperatures as well as at slower strain rates than those employed for the present Mg-23.5Ni alloy [17][18][19]. Formation of Mg 2 Ni-free zones is not accompanied by the dissolution of the second phase particles at these regions but the preferential deformation of the magnesium phase localised at domain boundaries, which are favourably orientated to the tensile axis.…”

Section: Discussionmentioning

confidence: 63%

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Mechanical behaviour of amorphous Mg–23.5Ni ribbons

Pérez

Garcés

Adeva

2004

Journal of Alloys and Compounds

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 63%

Mechanical behaviour of amorphous Mg–23.5Ni ribbons

Pérez

Garcés

Adeva

2004

Journal of Alloys and Compounds

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“…Clearly, the appearance of the denuded zones in Figure 7 is consistent with the advent of diffusion creep, as depicted in Figure 2(b). Nevertheless, there are several observations of denuded zones in samples subjected to an annealing treatment but without any creep testing, [38,61,62] thereby demonstrating unequivocally that, as also concluded elsewhere, [32,63] the presence of denuded zones cannot be taken as conclusive evidence for the occurrence of diffusion creep.…”

Section: B Harper-dorn Creepmentioning

confidence: 85%

Creep at low stresses: An evaluation of diffusion creep and Harper-Dorn creep as viable creep mechanisms

Langdon

2002

Metall Mater Trans A

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High-temperature creep experiments often reveal a transition at very low stresses to a region where the stress exponent is reduced to a value lying typically in the range of ϳ1 to 2. This region is generally associated with the occurrence of a new creep mechanism, such as grain-boundary sliding, diffusion creep, and/or Harper-Dorn creep. Several recent reports have suggested that diffusion creep and Harper-Dorn creep may not be viable creep mechanisms. This article examines these two processes and demonstrates that there is good evidence supporting the occurrence of both creep mechanisms under at least some experimental conditions. I. HISTORICAL BACKGROUNDexperiments were undertaken to determine the precise functional relationship between the steady-state creep rate and CREEP deformation refers to the unrecoverable plastic external experimental parameters such as stress and temperastrain occurring in a material when it is subjected to a conture. This latter approach had two very significant advanstant applied stress (or a constant applied load) over an tages over the earlier attempts to develop constitutive extended period of time. Creep processes are diffusionrelationships as in the classic Andrade t 1/3 law. First, the controlled, and they become of particular importance in approach, when combined with theory, permitted an assessmaterials experiencing extensive periods of time at elevated ment of the precise atomistic processes occurring during temperatures, where these high temperatures are generally creep deformation, and thus it led to the concept of specific above ϳ0.4 T m , where T m is the absolute melting temperature and well-defined rate-controlling creep mechanisms. Secof the material.ond, the approach provided, for the first time and over at least The small-scale industries of the 19th century tended to a reasonable range of experimental conditions, a predictive operate at relatively low temperatures so that the occurrence capability of the effect of changes in the operating stresses of any creep deformation in mechanical parts was generally and temperatures. The many publications of this era are well neither appreciated nor of significant magnitude to seriously documented in the creep literature, and they culminated impair the industrial operation. However, this situation began in an extended and comprehensive overview of the creep to change in the very early days of the 20th century when behavior of a wide range of metals and metallic alloys. [4] there was a concerted effort to increase the operating temperThis article follows on from this more recent approach, atures, and therefore the overall efficiency, of conventional and it is concerned specifically with the significance of working plants, such as steam boilers. It is not surprising, steady-state creep and the interpretation of rate-controlling therefore, that the first scientific publication dealing exclucreep mechanisms at very low stress levels. As will be sively with creep deformation should appear almost exactly demonstrated, although the ...

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“…While oxide dispersoids have been used in aluminum and many other metallic systems for high-temperature strengthening, only a few, relatively old investigations on ODS-Mg materials exist [6][7][8], this is due in large part to the difficulty of using powder metallurgy for magnesium. A solution to this processing problem is to apply to magnesium the high-temperature melt infiltration technique used to fabricate creep-resistant DSC-Al.…”

Section: Introductionmentioning

confidence: 99%

Creep of magnesium strengthened with high volume fractions of yttria dispersoids

Han

Dunand

2001

Materials Science and Engineering: A

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Creep experiments were performed on dispersion-strengthened-cast magnesium (DSC-Mg), consisting of unalloyed magnesium with 1 mm grain size containing 30 vol.% of 0.33 mm yttria particles. Strain rates were measured for temperatures between 573 and 723 K at compressive stresses between 7 and 125 MPa. DSC-Mg exhibits outstanding creep strength as compared with other magnesium materials, but is less creep resistant than comparable DSC-Al and other dispersion-strengthened aluminum materials. Two separate creep regimes were observed in DSC-Mg, at low stresses (|B30 MPa), both the apparent stress exponent (n app :2) and the apparent activation energy (Q app :48 kJ mol − 1 ) are low, while at high stresses (|\34 MPa), these parameters are much higher (n app =9-15 and Q app =230-325 kJ mol − 1 ) and increase, respectively, with increasing temperature and stress. The low-stress regime can be explained by an existing model of grain-boundary sliding inhibited by dispersoids at grain-boundaries. The unexpectedly low activation energy (about half the activation energy of grain boundary diffusion in pure magnesium) is interpreted as interfacial diffusion at the Mg/Y 2 O 3 interface. The high-stress regime can be described by dislocation creep with dispersion-strengthening from the interaction of the submicron particles with matrix dislocations. The origin of the threshold stress is discussed in the light of existing dislocation climb, detachment and pile-up models.

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Diffusion-creep in magnesium alloys

Cited by 37 publications

References 11 publications

Mechanical behaviour of amorphous Mg–23.5Ni ribbons

Mechanical behaviour of amorphous Mg–23.5Ni ribbons

Creep at low stresses: An evaluation of diffusion creep and Harper-Dorn creep as viable creep mechanisms

Creep of magnesium strengthened with high volume fractions of yttria dispersoids

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