Grain Boundary Sliding as a Deformation Process in Creep and Superplasticity

In this review the investigations of deformation process development are discussed which were carried out by tension and creep in the temperature range Т<0.4Tm (here Тm is the absolute melting point of material) for nanostructured metals produced by the methods of severe plastic deformation. The contribution of grain boundary sliding to the total deformation in the above temperature interval is also considered. An analysis is made of the effect of grain size and grain boundary state on the evolution of grain boundary sliding and cooperative grain boundary sliding in nanostructured metals.

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Deformation Characteristics of Quasicrystalline Al–Cu–Fe Alloys

Journal of Materials Research ◽

10.1557/jmr.1997.0274 ◽

1997 ◽

Vol 12 (8) ◽

pp. 2043-2047 ◽

Cited By ~ 13

Author(s):

J. E. Shield ◽

M. J. Kramer

Keyword(s):

Grain Size ◽

High Temperature ◽

Grain Boundary ◽

Deformation Process ◽

Microstructural Analysis ◽

Grain Boundary Sliding ◽

High Temperature Creep ◽

Deformation Characteristics ◽

Boundary Sliding ◽

Fe Alloys

The deformation characteristics of icosahedral Al–Cu–Fe quasicrystals were determined by high temperature creep experiments between 680 and 720 °C and 15 and 41 MPa. The deformation process was determined to be controlled by grain boundary mechanisms. Both the stress and grain size sensitivity exponents were found to be 2, suggesting that grain boundary sliding was the rate-controlling deformation mechanism. Microstructural analysis supported this conclusion, as no intragranular defects were produced during the deformation experiments.

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Systematic Study of Polycrystalline Flow during In Situ Tension Test by SEM of Pb-50%Sn at Room Temperature

Materials Science Forum ◽

10.4028/www.scientific.net/msf.793.113 ◽

2014 ◽

Vol 793 ◽

pp. 113-118 ◽

Cited By ~ 2

Author(s):

A.J. López-Ramírez ◽

Juan Daniel Muñoz-Andrade ◽

E. Garfias-García ◽

M. Aguilar-Sánchez

Keyword(s):

Activation Energy ◽

Grain Boundary ◽

Deformation Process ◽

Room Temperature ◽

Grain Boundary Sliding ◽

Tension Test ◽

Irreversible Deformation ◽

Chatelier Effect ◽

Boundary Sliding

Microstructural evolution during in situ tension test at constant crosshead velocity of 0.38 mm/min, at room temperature of polycrystalline Pb-50%Sn alloy are reported. Direct observation during four steps of deformation, with a total deformation (εT) of 0.684, allows establish that the trajectories of grains during irreversible deformation process obey a sigmoidal motion. Such behaviour is related with dynamic recrystallization phenomenology and associated with grain boundary sliding between neighbouring grains and subsequent cavitation in order to allow emerging grains from the inner volume to free surface of Pb-50%Sn, as the main mechanisms of superplastic flow. The curve of true stress versus true deformation presented several fluctuations during irreversible deformation process in a similar way of the Portevin Le Chatelier effect. Also is observed in the early steps of plastic flow, hardening deformation, up to 27 MPa associated with the maximum stress. The activation energy values for polycrystalline flow, calculated in this work are between 67.5 to 68.07 kJ/mol and there are in a closed agreement with the activation energy of 65.7 kJ/mol, for grain boundary diffusion.

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Examination of Fracture Interfaces in Silicon Nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113925 ◽

1975 ◽

Vol 33 ◽

pp. 60-61

Author(s):

Nancy J. Tighe

Keyword(s):

Silicon Nitride ◽

Grain Boundary ◽

Crack Growth ◽

Subcritical Crack Growth ◽

Slow Crack Growth ◽

Ceramic Materials ◽

Grain Boundary Sliding ◽

Boundary Phase ◽

Turbine Engines ◽

Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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