A dynamic lattice dislocation grain boundary sliding mechanism

1985 ◽  
Vol 51 (1) ◽  
pp. 71-78 ◽  
Author(s):  
Keith Reading ◽  
David A. Smith
Keyword(s):  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Lattice Dislocation ◽  
Sliding Mechanism ◽  
Boundary Sliding

Slip Induced Strain Rate Sensitivity for Superplastic Material?

2012 ◽  
Vol 735 ◽  
pp. 31-36 ◽  
Author(s):  
Hector Basoalto ◽  
Paul L. Blackwell
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Microstructural Parameters ◽  
Sliding Mechanism ◽  
Physically Based ◽  
Boundary Sliding

The conventional consensus has it that the magnitude of the strain rate sensitivity observed in superplastic materials is linked with grain boundary sliding. The grain boundary sliding mechanism is thought to theoretically produce a strain rate sensitivity exponent of 0.5, which is in good agreement with experimental data. The present paper argues that a rate sensitivity of 0.5 can be generated by dislocation slip under certain temperature and strain rate regimes that overlap with conditions representative of superplasticity. A physically based slip model that links the relevant microstructural parameters to the macroscopic strain rate is proposed.

Influence of Second Phases on the Superplasticity of Mg-Tm-Y-CeMM Alloys Containing LPSO-Phases

2016 ◽  
Vol 879 ◽  
pp. 1477-1482
Author(s):  
Pablo Pérez Zubiaur ◽  
Judith Medina ◽  
Gerardo Garcés ◽  
Paloma Adeva
Keyword(s):  
Grain Boundary ◽  
Earth Element ◽  
Volume Fraction ◽  
Grain Boundary Sliding ◽  
Metal Alloys ◽  
Lpso Phase ◽  
Transition Metal Alloys ◽  
Sliding Mechanism ◽  
Second Phases ◽  
Boundary Sliding

The effect of the nature of the second phases in extruded Mg-TM-Y-CeMM (TM refers to a transition metal) alloys reinforced by intermetallic MgRE (RE refers to a rare earth element) compounds and LPSO-phase on their superplasticity has been evaluated between 300 and 400°C at the strain rate of 10-4 s-1. The data have been compared with those of alloys containing a similar volume fraction of the LPSO-phase. The results evidence that no superplasticity below 350°C was found in the alloys containing exclusively the LPSO-phase while the alloys containing both MgRE compounds and LPSO-phase deform superplastically by grain boundary sliding from 300°C. These differences are related to the different behaviour of MgRE compounds and LPSO-phase in the course of superplastic regime. MgRE compounds assist to accommodate the deformation more easily than LPSO-phase, reducing tendency to develop cavities and extending the time for the occurrence of necking. The size and volume fraction of the respective phases are critical in order to promote enhanced superplastic behaviour. Maximum elongations are attained in the alloys combining similar volume fractions of MgRE compounds and LPSO-phase in which their size is reduced to the maximum. An increase in the particle size of the second phases, especially in the case of the LPSO-phase, hinders the grain boundary sliding mechanism in the alloys.

Superplastic Deformation Mechanisms in a Fine-Grained, Yttria-stabilized Tetragonal Zirconia Polycrystal (Y-TZP)

1990 ◽  
Vol 196 ◽  
Author(s):  
T. G. Nieh ◽  
J. Wadsworth
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Grain Growth ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Boundary Triple ◽  
Sliding Mechanism ◽  
Boundary Sliding

ABSTRACTConcurrent grain growth, and in particular, dynamic grain growth, was observed to take place during superplastic deformation of Y-TZP. As a result of this concurrent grain growth, the measured strain rate sensitivity was found to be lower than that measured under constantstructure conditions. In the present paper, data obtained from the superplastic deformation of YTZP under constant-structure conditions are presented. It is demonstrated that the strain rate sensitivity values are generally higher than 0.5, when measured from the grain size-compensated data; this result suggests a grain boundary sliding mechanism. Microstructures from samples prior to and after superplastic deformation reveal grains which are essentially equiaxed; this observation is also consistent with a grain boundary sliding mechanism. Both high-resolution images of grain boundary triple points using transmission electron microscopy, and fracture surface studies using Auger electron spectroscopy and X-ray photoelectron spectroscopy indicate that there is no evidence for the presence of glassy phases at grain boundaries in Y-TZP.

scholarly journals Grain boundary sliding mechanism during high temperature deformation of AZ31 Magnesium alloy

2016 ◽  
Vol 669 ◽  
pp. 171-177 ◽  
Author(s):  
Peiman Shahbeigi Roodposhti ◽  
Apu Sarkar ◽  
Korukonda Linga Murty ◽  
Harold Brody ◽  
Ronald Scattergood
Keyword(s):  
High Temperature ◽  
Magnesium Alloy ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Sliding Mechanism ◽  
Boundary Sliding

Examination of Fracture Interfaces in Silicon Nitride

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.

INTERNAL FRICTION PEAKS CONNECTED WITH GRAIN BOUNDARY SLIDING IN Al

1983 ◽  
Vol 44 (C9) ◽  
pp. C9-759-C9-764
Author(s):  
E. Bonetti ◽  
A. Cavallini ◽  
E. Evangelista ◽  
P. Gondi
Keyword(s):  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Boundary Sliding
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