scholarly journals Effects of Anisotropy and In-Plane Grain Boundary in Cu/Pd Multilayered Films with Cube-on-Cube and Twinned Interface

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Xiang Chen ◽  
Shayuan Weng ◽  
Xing Yue ◽  
Tao Fu ◽  
Xianghe Peng
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Multilayer Film ◽  
Polycrystalline Sample ◽  
Interfacial Structure ◽  
Necessary Condition ◽  
Strengthening Effect ◽  
Multilayered Films ◽  
Crystalline Materials ◽  
Dynamics Simulations

AbstractIn crystalline materials, grain boundary and anisotropy of crystal structure affect their mechanical properties. The effects of interfacial structure on the mechanical properties may be diverse when the multilayer film is loaded along different directions. In this work, we performed a series of molecular dynamics simulations of the tension of in-plane single and polycrystalline Cu/Pd multilayered films with cube-on-cube (COC) and twinned interfaces to explore the effects of the interfacial structure, loading direction and in-plane grain boundaries on their mechanical properties. The interfacial misfit dislocation lines become bent after relaxation, and the high temperature of 300 K was found as a necessary condition. When stretched along 〈110〉 direction, the strengthening effect of the COC interface is more noticeable; however, when stretched along 〈112〉 direction, the twin interface's strengthening effect is more visible, showing the anisotropic effect of interfacial structure on mechanical properties. However, in the in-plane honeycomb polycrystalline sample, the twin interface showed a pronounced strengthening effect, and no jogged dislocations were observed.

scholarly journals On the Effect of Local Grain-Boundary Chemistry on the Macroscopic Mechanical Properties of a High Purity Y2O3-Al2O3-Containing Silicon Nitride Ceramic

2004 ◽  
Vol 839 ◽  
Author(s):  
A. Ziegler ◽  
J.M. McNaney ◽  
M. J. Hoffmann ◽  
R. O. Ritchie
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Oxygen Content ◽  
High Purity ◽  
Interfacial Structure ◽  
Crack Advance ◽  
Transgranular Fracture ◽  
Boundary Films ◽  
Boundary Chemistry

ABSTRACTThe effects of grain-boundary chemistry on the mechanical properties of a high-purity silicon nitride ceramics were investigated, with specific emphasis on the role of oxygen. Variations in the grain-boundary oxygen content, through control of oxidizing heat treatments and sintering additives, was found to result in a transition in fracture mechanism from transgranular to intergranular fracture, with an associated increase in fracture toughness. This phenomenon is correlated to an oxygen-induced change in grain-boundary chemistry that appears to affect fracture by “weakening” the interface, facilitating debonding and crack advance along the boundaries, thereby enhancing the toughness by grain bridging. It is concluded that if the oxygen content in the thin grain-boundary films exceeds a lower limit, which is ∼0.87 equiv% oxygen content, then the interfacial structure and bonding characteristics favor intergranular debonding during crack propagation; otherwise, transgranular fracture ensues, with consequent low toughness.

scholarly journals Coupled Strengthening Effects by Lattice Distortion, Local Chemical Ordering, and Nanoprecipitates in Medium-Entropy Alloys

2021 ◽  
Vol 8 ◽  
Author(s):  
Wenqiang Cheng ◽  
Fuping Yuan ◽  
Xiaolei Wu
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Lattice Distortion ◽  
Dislocation Line ◽  
High Entropy Alloys ◽  
Strengthening Effect ◽  
Sliding Velocity ◽  
High Entropy ◽  
Chemical Ordering ◽  
Dynamics Simulations

Extraordinary mechanical properties can be achieved in high-entropy alloys (HEAs) or medium-entropy alloys (MEAs) with nanoprecipitates. In the present study, the extra coupled strengthening effects by lattice distortion, local chemical ordering, and nanoprecipitates in the HEAs and MEAs with nanoprecipitates have been systematically investigated by large-scale molecular dynamics simulations. The moving of the dislocation can be slowed down, and the dislocation line shows a wavy configuration due to lattice distortion and local chemical ordering, resulting in strengthening. The degree of the wavy configuration increases and the sliding velocity of the dislocation decreases with increasing degrees of local chemical ordering. It is clearly indicated that the dislocation moves via nanoscale segment detrapping mechanism due to the effects of lattice distortion and local chemical ordering, resulting in roughened dislocation pathways for strengthening. The activated nanoscale segments are observed to be easier to detrap from the regions with stronger Co-Cr local chemical ordering and then propagate into the regions without such chemical ordering. These moving characteristics of the dislocation can delay the unpinning process from nanoprecipitates; thus, extra coupled strengthening effect has been revealed in the HEAs and MEAs with nanoprecipitates compared to pure Orowan’s strengthening.

Effects of Heat Treatment on Mechanical Properties of Ni-P-CNT Composite Coating

2015 ◽  
Vol 817 ◽  
pp. 493-497 ◽  
Author(s):  
Qin Shi ◽  
Wan Chang Sun ◽  
Jun Gao ◽  
Ying Wang ◽  
Miao Miao Tian
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Wear Resistance ◽  
Grain Boundary ◽  
Composite Coating ◽  
Friction Pair ◽  
Nanocomposite Coating ◽  
Nitrogen Atmosphere ◽  
Wear Loss ◽  
Strengthening Effect

Ni-P-CNT nanocomposite coating was successfully co-deposited by electroless plating and the heat treatment was carried out at 200°C, 400°C, 600°C in nitrogen atmosphere respectively for a holding period of 1 h. The effects of heat treatment on the microstructure and mechanical properties of Ni-P-CNT composite coating were investigated. The results indicate that the heat treatment at 400°C can greatly improve the hardness and wear resistance of the composite coating. The reason is that Ni3P hard phase is greatly precipitated after the heat treatment, which played a strengthening effect. On the other hand, the precipitated Ni, Ni3P crystalline phases in the coating result in an increase of the amount of grain boundary. The increased amount of grain boundary broke the spread of shear force during friction process, and reduced the wear loss caused by friction pair. Compared with as-deposited coating, the coatings after heat treatment possess higher microhardness and wear resistance.

scholarly journals Inapparent Strengthening Effect of Twin Interface in Cu/Pd Multilayered Films with a Large Lattice Mismatch

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1778 ◽  
Author(s):  
Shayuan Weng ◽  
Xiang Chen ◽  
Xing Yue ◽  
Tao Fu ◽  
Xianghe Peng
Keyword(s):  
Flow Stress ◽  
Maximum Stress ◽  
Lattice Mismatch ◽  
Interfacial Structure ◽  
Triangular Distribution ◽  
Strengthening Effect ◽  
Multilayered Film ◽  
Twin Interface ◽  
Modulation Period ◽  
Dynamics Simulations

It has been found that there are two kinds of interfaces in a Cu/Pd multilayered film, namely, cube-on-cube and twin. However, the effects of the interfacial structure and modulation period on the mechanical properties of a Cu/Pd multilayered film remain unclear. In this work, molecular dynamics simulations of Cu/Pd multilayered film with different interfaces and modulation periods under in-plane tension are performed to investigate the effects of the interfacial structure and modulation period. The interface misfit dislocation net exhibits a periodic triangular distribution, while the residual internal stress can be released through the bending of dislocation lines. With the increase of the modulation period, the maximum stress shows an upward trend, while the flow stress declines. It was found that the maximum stress and flow stress of the sample with a cube-on-cube interface is higher than that of the sample with a twin interface, which is different from the traditional cognition. This unusual phenomenon is mainly attributed to the discontinuity and unevenness of the twin boundaries caused by the extremely severe lattice mismatch.

A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

1992 ◽  
Vol 50 (2) ◽  
pp. 1024-1025
Author(s):  
Jun Liu ◽  
Katie E. Gunnison ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Ion Beam ◽  
Laminated Composite ◽  
Organic Matrix ◽  
Pearl Oyster ◽  
Interfacial Structure ◽  
Interfacial Region ◽  
Thin Sections ◽  
Organic Layers ◽  
Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

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