Grain Boundary Microstructure Dependent – Intergranular Fracture in Polycrystalline Molybdenum

1999 ◽  
Vol 586 ◽  
Author(s):  
Sadahiro Tsurekawa ◽  
Tadao Watanabe
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Intergranular Fracture ◽  
Fracture Stress ◽  
Polycrystalline Materials ◽  
Grain Boundary Character Distribution ◽  
Premature Failure ◽  
Petch Relation ◽  
Practical Applications ◽  
Polycrystalline Molybdenum

ABSTRACTThe intergranular brittleness in polycrystalline materials is a source of serious problem in material processing and practical applications. To obtain a fundamental knowledge of improvement in the brittleness, we have examined the relationship between fracture behaviour and grain boundary (GB) microstructures in polycrystalline molybdenum. Quantitative analyses of GB microstructures were performed by orientation microscopy (OIM), and followed by 4-points bending tests at 77K. Thereafter, crack propagation was analyzed in connection with GB microstructures. We found the fracture stress depends on the grain size in similar manner to the Hall-Petch relation. In addition, the Hall-Petch relation also depends on the grain boundary character distribution (GBCD). The fracture stress increases with increasing the frequency of low σ GBs at constant grain size. Conversely, random GBs seem to act as weak intrinsic defects and the interconnection among them may give rise to premature failure. Therefore, the connectivity of random GBs probably becomes important as well as the GBCD to suppress the intergranular fracture.

Prediction and Control of Grain Boundary Fracture in Brittle Materials on the Basis of the Strongest-Link Theory

2005 ◽  
Vol 482 ◽  
pp. 55-62 ◽  
Author(s):  
Tadao Watanabe ◽  
Sadahiro Tsurekawa
Keyword(s):  
Grain Boundary ◽  
Intergranular Fracture ◽  
Boundary Energy ◽  
Boundary Structure ◽  
Polycrystalline Materials ◽  
Grain Boundary Character Distribution ◽  
Grain Boundary Engineering ◽  
Grain Boundary Character ◽  
Grain Boundary Structure ◽  
Link Theory

This paper discusses micropstructural aspects of brittleness fracture of polycrystalline materials caused by intergranular fracture. Structure-dependent intergranular brittle fracture in bicrystals and polycrystals are discussed and predicted theoretically. Experimental evidence for the structure-dependent intergranular fracture is shown and some general features are discussed to demonstrate the relationship between grain boundary structure/character, grain boundary energy and intergranular fracture strength. Theoretical prediction of the fracture toughness based on the strongest-link theory is introduced for polycrystals with different grain boundary microstructures, primarily defined by the grain boundary character distribution, grain boundary connectivity. Finally recent achievements of successful control of intergranular brittleness by grain boundary engineering based on the strongest-link theory are introduced for different materials.

Morphology and atomic structure of segregated grain boundaries in Cu-Sb

1992 ◽  
Vol 50 (1) ◽  
pp. 254-255
Author(s):  
R. W. Fonda ◽  
D. E. Luzzi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Atomic Structure ◽  
Copper Alloys ◽  
Polycrystalline Materials ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

The properties of polycrystalline materials are strongly dependant upon the strength of internal boundaries. Segregation of solute to the grain boundaries can adversely affect this strength. In copper alloys, segregation of either bismuth or antimony to the grain boundary will embrittle the alloy by facilitating intergranular fracture. Very small quantities of bismuth in copper have long been known to cause severe grain boundary embrittlement of the alloy. The effect of antimony is much less pronounced and is observed primarily at lower temperatures. Even though moderate amounts of antimony are fully soluble in copper, concentrations down to 0.14% can cause grain boundary embrittlement.

Degradation of the Strength of a Grain and a Grain Boundary due to the Accumulation of the Structural Defects of Crystal

2018 ◽  
Author(s):  
Guoxiong Zheng ◽  
Yifan Luo ◽  
Hideo Miura
Keyword(s):  
Thin Film ◽  
Grain Boundary ◽  
Tensile Test ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Semiconductor Devices ◽  
Ebsd Analysis ◽  
Structural Defects ◽  
Polycrystalline Materials ◽  
Transgranular Fracture

Various brittle fractures have been found to occur at grain boundaries in polycrystalline materials. In thin film interconnections used for semiconductor devices, open failures caused by electro- and strain-induced migrations have been found to be dominated by porous random grain boundaries that consist of a lot of defects. Therefore, it is very important to explicate the dominant factors of the strength of a grain boundary in polycrystalline materials for assuring the safe and reliable operation of various products. In this study, both electron back-scatter diffraction (EBSD) analysis and a micro tensile test in a scanning electron microscope was applied to copper thin film which is used for interconnection of semiconductor devices in order to clarify the relationship between the strength and the crystallinity of a grain and a grain boundary quantitatively. Image quality (IQ) value obtained from the EBSD analysis, which indicates the average sharpness of the diffraction pattern (Kikuchi pattern) was applied to the crystallinity analysis. This IQ value indicates the total density of defects such as vacancies, dislocations, impurities, and local strain, in other words, the order of atom arrangement in the observed area in nano-scale. In the micro tensile test system, stress-strain curves of a single crystal specimen and a bicrystal specimen was measured quantitatively. Both transgranular and intergranular fracture modes were observed in the tested specimens with different IQ values. Based to the results of these experiments, it was found that there is the critical IQ value at which the fracture mode of the bicrystal specimen changes from brittle intergranular fracture at a grain boundary to ductile transgranular fracture in a grain. The strength of a grain boundary increases monotonically with IQ value because of the increase in the total number of rigid atomic bonding. On the other hand, the strength of a grain decreases monotonically with the increase of IQ value because the increase in the order of atom arrangement accelerates the movement of dislocations. Finally, it was clarified that the strength of a grain boundary and a grain changes drastically as a strong function of their crystallinity.

Grain size and grain boundary character distribution in ultra-fine grained (ECAP) nickel

2008 ◽  
Vol 491 (1-2) ◽  
pp. 1-7 ◽  
Author(s):  
K. Sitarama Raju ◽  
M. Ghanashyam Krishna ◽  
K.A. Padmanabhan ◽  
K. Muraleedharan ◽  
N.P. Gurao ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundary Character Distribution ◽  
Boundary Character ◽  
Fine Grained ◽  
Grain Boundary Character ◽  
Character Distribution ◽  
Boundary Character Distribution

Electrical Resistivity as a Characterization Tool for Nanocrystalline Metals

1999 ◽  
Vol 581 ◽  
Author(s):  
J.L. McCrea ◽  
K.T. Aust ◽  
G. Palumbo ◽  
U. Erb
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Electrical Resistivity ◽  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Elevated Temperatures ◽  
Polycrystalline Materials ◽  
Grain Growth Kinetics ◽  
Insight Into ◽  
Grain Boundary Resistivity

ABSTRACTThe electrical resistivity as a function of temperature (4K to 673K) of several electrodeposited nanocrystalline materials (Ni, Ni-Fe, Co) has been examined. The contribution of the grain boundaries to the electrical resistivity was quantified in terms of a specific grain boundary resistivity, which was found to be similar to previously reported values of specific grain boundary resistivity for copper and aluminum obtained from studies involving polycrystalline materials. In the high temperature range, the resistivity of the nanocrystalline samples was monitored as a function of time. The observed time dependence of the resistivity at elevated temperatures was correlated to microstructural changes in the material. The study has shown that electrical resistivity is an excellent characterization tool for nanocrystalline materials giving useful information regarding grain size and degree of thermal stability, as well as some insight into the grain growth kinetics at various temperatures.

SEM-ECP Analysis of Grain-Boundary Character Distribution in Polycrystalline Materials

1996 ◽  
Vol 54 ◽  
pp. 354-355
Author(s):  
Tadao Watanabe
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Polycrystalline Materials ◽  
Grain Boundary Character Distribution ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
Character Distribution ◽  
Boundary Character Distribution

As demonstrated early 1980’s (1), the scanning electron rnicrocopy-electron channelling pattern (SEM-ECP) technique is very powerful in determination of orientation of individual grains and the character of grain boundaries in polycrystalline materials. Figure 1(a) and (b) show SEM and ECP images of a grain boundary in polycrystal line iron-6.5 mass % silicon ribbon produced by rapid solidification and subsequent annealing. We can intuitively recognize from the SEM-ECP image that the character of the boundary is of <100> tilt type with about 7° misorientation angle. This kind of direct observation is very useful for a study of grain boundary migration and grain growth.This paper discusses advantages of the SEM-ECP technique for the precise determination of the character of grain boundary and for statistical analysis of grain boundaries to bridge roles of individual grain boundaries and bulk properties in a polycrystal. The new microstructural parameter associated with grin boundary termed “grain boundary character distribution (GBCD)” which was introduced by the present author (2,3) and has been utilized in designing and engineering grain boundaries in order to produce desirable and/or high bulk performance in polycrystalline materials (4,5). GBCD describes the type and the frequency of different types of grain boundaries, ie. random general boundaries and special boundaries like low-angle boundaries and low Σ coincidence boundaries.

Effects of Relative High Density Preparation of Interfacial Coated Pb(Zr0.52Ti0.48)O3 on CaCu3Ti4O12 with Short Sintering Time on its Dielectric Properties

2012 ◽  
Vol 557-559 ◽  
pp. 1838-1843
Author(s):  
Rajabtabar Darvishi Ali ◽  
Wei Li Li ◽  
Sheikhnejad Bishe Ommeaymen ◽  
Li Dong Wang ◽  
Zhe Liu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Grain Boundary ◽  
Relative Density ◽  
Sol Gel ◽  
Composite Particles ◽  
Composite Ceramics ◽  
Practical Applications ◽  
Cold Press ◽  
Sintering Time

Pb(Zr0.52Ti0.48)O3was coated on the surface of CaCu3Ti4O12particles that prepared using sol-gel method. Then the composite particles were sintered into composite ceramics using cold press with the two different pressures and pressing time to achieve sufficient higher relative density after sintering. Afterward, the composite particles were sintered into composite ceramics with various sintering time at the same temperature to reach smaller grain size and higher relative density. The results show that the ceramics are composed of Pb(Zr0.52Ti0.48)O3and CaCu3Ti4O12phases, and Pb(Zr0.52Ti0.48)O3phase is mainly exist at the grain boundary even the composite particles sintered for 2h before pellet making. The results exhibit when density of CaCu3Ti4O12/Pb(Zr0.52Ti0.48)O3composite ceramic is kept in higher level using this simple technology, not only The dissipation loss in these giant-dielectric constant materials was reduced to a considerable level of practical applications but also dielectric constant enhance to very high level in the large frequency range. The results show that the improvement of the dielectric loss and dielectric constant enhancing mainly comes from the increase in the density of the CaCu3Ti4O12/Pb(Zr0.52Ti0.48)O3composite ceramics using suitable pressure in cold press, suitable short sintering time that lead to smaller grain size and sufficient grain boundary.

Ductility of Nanostructured Materials

MRS Bulletin ◽  
1999 ◽  
Vol 24 (2) ◽  
pp. 54-58 ◽  
Author(s):  
C.C. Koch ◽  
D.G. Morris ◽  
K. Lu ◽  
A. Inoue
Keyword(s):  
Grain Size ◽  
Fracture Stress ◽  
Size Dependence ◽  
Polycrystalline Materials ◽  
Mechanical Instability ◽  
Percent Elongation ◽  
Ductile Brittle Transition Temperature ◽  
Engineering Materials ◽  
And Performance ◽  
Reduction In Area

Ductility is defined as the ability of a material to change shape without fracture. It is of critical importance for engineering materials for both manufacturability and Performance. Measures of ductility include percent elongation (uniform plastic flow prior to mechanical instability—necking—or fracture) and percent reduction in area. Fracture toughness is also some measure of potential ductility. Engineering materials exhibit wide variations in ductility which can often limit their application.Ductility is a property of nanocrystalline materials which might be predicted to be enhanced by extrapolation of its grain-size dependence in conventional polycrystalline materials. It has been predicted that extrapolation of the grain size, or the scale of the microstructure, to the nanoscale will lead to both strengthening and an increase in ductility. As far as failure and ductility are concerned, this idea is based on experience with conventional materials, where the yield and fracture stress show different dependencies on the grain size. The fracture stress typically increases faster than the yield stress with decreasing grain size such that ductile/brittle transitions can occur. For example, the ductile / brittle transition temperature in mild steel can be lowered about 40°C by reducing the grain size by a factor of five. In terms of how ductility may be affected by the extreme grainsize reduction to the nanoscale, we consider the following. Firstly, it may be recalled that obtaining ductility relies simply on plastic deformation occurring without the catastrophic onset of failure mechanisms, and therefore we can examine possibilities of changing ductility in terms of avoiding failure.

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