Influence of grain boundary sliding near a nanovoid on crack growth in deformed nanocrystalline materials

2018 ◽  
Vol 144 ◽  
pp. 842-848 ◽  
Author(s):  
T.W. He ◽  
W.S. Xiao ◽  
Q.H. Fang ◽  
H.P. Zhu ◽  
M.L. Feng
Keyword(s):  
Grain Boundary ◽  
Crack Growth ◽  
Nanocrystalline Materials ◽  
Grain Boundary Sliding ◽  
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.

Mechanical Properties of Novel Nanocrystalline Materials

2001 ◽  
Author(s):  
J. Narayan ◽  
H. Wang ◽  
A. Kvit
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
High Surface ◽  
Grain Boundary Sliding ◽  
Boundary Shear ◽  
Functionally Gradient ◽  
Boundary Sliding ◽  
First Time ◽  
Critical Grain Size

Abstract We have synthesized nanocrystalline thin films of Cu, Zn, TiN, and WC having uniform grain size in the range of 5 to 100 nm. This was accomplished by introducing a couple of manolayers of materials with high surface and have a weak interaction with the substrate. The hardness measurements of these well-characterized specimens with controlled microstructures show that hardness initially increases with decreasing grain size following the well-known Hall-Petch relationship (H∝d−½). However, there is a critical grain size below which the hardness decreases with decreasing grain size. The experimental evidence for this softening of nanocrystalline materials at very small grain sizes (referred as reverse Hall-Petch effect) is presented for the first time. Most of the plastic deformation in our model is envisioned to be due to a large number of small “sliding events” associated with grain boundary shear or grain boundary sliding. This grain-size dependence of hardness can be used to create functionally gradient materials for improved adhesion and wear among other improved properties.

An energy analysis of nanovoid nucleation in nanocrystalline materials with grain boundary sliding accommodations

2014 ◽  
Vol 29 (2) ◽  
pp. 277-287 ◽  
Author(s):  
Lu Wang ◽  
Jianqiu Zhou ◽  
Shu Zhang ◽  
Yingguang Liu ◽  
Hongxi Liu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Energy Analysis ◽  
Grain Boundary Sliding ◽  
Boundary Sliding ◽  
Image Position

Abstract

Cooperative grain boundary sliding in nanocrystalline materials

2006 ◽  
Vol 86 (36) ◽  
pp. 5797-5804 ◽  
Author(s):  
A. V. Sergueeva ◽  
N. A. Mara ◽  
N. A. Krasilnikov ◽  
R. Z. Valiev ◽  
A. K. Mukherjee
Keyword(s):  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Grain Boundary Sliding ◽  
Boundary Sliding

Coupled effect of grain boundary sliding and dislocation emission on fracture toughness of nanocrystalline materials

2016 ◽  
Vol 01 (02) ◽  
pp. 1650008 ◽  
Author(s):  
Q. H. Fang ◽  
L. C. Zhang
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Crack Growth ◽  
Nanocrystalline Materials ◽  
Crack Tip ◽  
Grain Boundary Sliding ◽  
Dislocation Emission ◽  
Disclination Dipole ◽  
Coupled Effect ◽  
Wedge Disclination

This paper establishes a theoretical model to explore the coupled effect of grain boundary (GB) sliding deformation and crack tip dislocation emission on the critical stress intensity factor (SIF) for crack growth in ultrafine-grained and nanocrystalline materials (NCMs). The model postulates that the stress concentration near a crack tip initiates GB sliding. It is found that GB sliding leads to the formation of wedge disclination dipole at the triple junctions of grain boundaries. Under the external load and stress fields produced by wedge disclinations, dislocations are emitted from crack tips but will stop at the opposite GBs. The influence of the wedge disclination dipole and the dislocation emitted from crack tip on the critical SIF for crack growth is investigated. The model prediction shows that the critical SIF varies with the decrement of grain size, and that there is a critical grain size corresponding to a minimum value of SIF. Compared with the pure brittle fracture in NCMs at the grain sizes of tens of nanometers, the combined deformation mechanisms can bring an increase of the critical SIF for crack growth.

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