From atomistics to macro-behavior: structural superplasticity in micro- and nano-crystalline materials

2003 ◽  
Vol 94 (10) ◽  
pp. 1046-1051 ◽  
Author(s):  
K. A. Padmanabhan
Keyword(s):  
Crystalline Materials ◽  
Structural Superplasticity ◽  
Nano Crystalline

scholarly journals Наноиндентирование и механические свойства материалов в субмикро- и наношкале. Недавние результаты и достижения (О б з о р)

2021 ◽  
Vol 63 (1) ◽  
pp. 3
Author(s):  
Ю.И. Головин
Keyword(s):  
In Situ Monitoring ◽  
Load Testing ◽  
Crystalline Materials ◽  
Nanomechanical Properties ◽  
Nano Crystalline ◽  
Transmission Electron ◽  
Low Load ◽  
Rfbr Grant ◽  
Wide Family

The review discusses the details of various materials mechanical behavior in submicro- and nanoscale. Significant advances in this scope result from the development of wide family of load based precise nanotesting techniques called nanoindentation. But nowadays, nanomechanical properties are studied not only by nanoindentation techniques in narrow sense, i.e. local loading of macro, micro and nanoscale objects. Nanomechanical load testing is discussed here within a wider scope employing precise deformation measurement with nanometer scale resolution caused by various types of low load application to the object under study including uniaxial compression or extension, shearing, bending or twisting, optionally accompanied by in situ monitoring sample microstructure using scanning and transmission electron microscopy and Laue microdiffraction technique. The main courses of experimental techniques development in recent ten years along with the results obtained using them in single, poly and nano crystalline materials, composites, films and coatings, amorphous solids and such biomaterials as tissues, living cells and macromolecules are described. Special attention is paid to deformation size effects and atomic mechanisms in nanoscale. This review is a natural continuation and development of the review published at Fiz.Tverd.Tela vol.50, issue 12, 2008 of the same author that discusses details of nanomechanical properties of solids. Current review includes wider range of nanomechanical testing concepts and recent achievements in the scope. The work was supported by RFBR grant for project #19-12-50235.

scholarly journals Modelling and Experimental Validation of the Porosity Effect on the Behaviour of Nano-Crystalline Materials

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 821
Author(s):  
Panagiotis Bazios ◽  
Konstantinos Tserpes ◽  
Spiros Pantelakis
Keyword(s):  
Numerical Model ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
Static Compression ◽  
Crystalline Materials ◽  
Nano Crystalline ◽  
Porosity Effect ◽  
Grain Diameter

Nano-crystalline metals have attracted considerable attention over the past two decades due to their increased mechanical properties as compared to their microcrystalline counterparts. However, the behaviour of nano-crystalline metals is influenced by imperfections introduced during synthesis or heat treatment. These imperfections include pores, which are mostly located in the area of grain boundaries. To study the behaviour of multiphase nano-crystalline materials, a novel fully parametric algorithm was developed. The data required for implementing the developed numerical model were the volume fraction of the alloying elements and their basic properties as well as the density and the size of randomly distributed pores. To validate the developed algorithm, the alloy composition 75 wt% tungsten and 25 wt% copper was examined experimentally under compression tests. For the investigation, two batches of specimens were used; a batch having a coarse-grained microstructure with an average grain diameter of 150 nm and a nanocrystalline batch having a grain diameter of 100 nm, respectively. The porosity of both batches was derived to range between 9% and 10% based on X-ray diffraction analyses. The results of quasi-static compression testing revealed that the nanocrystalline W-Cu material exhibited brittle behaviour which was characterised by an elastic deformation that led to fracture without remarkable plasticity. A compressive strength of about 1100 MPa was derived which was more than double compared to conventional W-Cu samples. Finite element simulations of the behaviour of porous nano-crystalline materials were performed and compared with the respective experimental compression tests. The numerical model and experimental observations were in good agreement.

FINITE ELEMENT MODELING OF DAMPING CAPACITY IN NANO-CRYSTALLINE MATERIALS

2010 ◽  
Vol 01 (03) ◽  
pp. 421-433 ◽  
Author(s):  
M. YADOLLAHPOUR ◽  
S. ZIAEI-RAD ◽  
F. KARIMZADEH
Keyword(s):  
Finite Element ◽  
Energy Dissipation ◽  
Grain Boundary ◽  
Composite Model ◽  
Grain Structure ◽  
External Loading ◽  
Damping Capacity ◽  
Crystalline Materials ◽  
Nano Crystalline ◽  
Local Plastic Strain

Plastic deformation of materials is a major source of energy dissipation during external loading. In nano-crystalline (NC) materials, local plastic strain may arise even if the overall external load is below the yield stress of the material because of the grain structure. In this paper, the damping capacity of nano-crystalline materials is modeled by considering the grain structure. First, the grains are modeled by using a composite model. The composite model takes each oriented crystal and its immediate boundary to form a pair. Next, the finite element method in conjunction with the composite model is employed to evaluate the energy dissipation of nano-crystalline material under cyclic loading. The influence of the grain size and the external loading on the energy dissipation is investigated numerically. Energy dissipation in each of the two parts (i.e. grain and grain boundary) is also calculated as an attempt to understand the effect of grain boundary on energy dissipation.

Pulsed Electric Current Sintering of Nano-Crystalline Iron-Base Powders

2007 ◽  
Vol 534-536 ◽  
pp. 589-592
Author(s):  
Yuan Yuan Li ◽  
Yan Long ◽  
Xiao Qiang Li ◽  
Yun Zhong Liu
Keyword(s):  
Electric Current ◽  
High Energy ◽  
Sintered Specimen ◽  
Iron Matrix ◽  
Crystalline Materials ◽  
Densification Temperature ◽  
Nano Crystalline ◽  
Average Grain Size ◽  
Pulsed Electric Current ◽  
Particulate Size

A new process of pulsed electric current sintering was developed. It combines compaction with activated sintering effectively and can manufacture bulky nano-crystalline materials very quickly. Pulsed electric current sintering of high-energy ball-milled nano-crystalline iron-based powders is investigated in this work. A nanostructured steel is obtained with high relative density and hardness by this process. The average grain size of iron matrix is 58nm and the carbide particulate size is less than 100nm. The densification temperature of ball-milled powders is approximately 200°C lower than that of blended powders. When the sintering temperature increases, the density of as-sintered specimen increases but the hardness of as-sintered specimen first increases and then decreases. Microstructure analysis results show that the decrease of hardness is caused by the dramatic grain growth of iron matrix.

Effect of Hydrostatic Pressure on Nano Crystalline Materials Behavior

2012 ◽  
Vol 18-19 ◽  
pp. 27-42 ◽  
Author(s):  
Reza Jafari Nedoushan ◽  
Mahmoud Farzin
Keyword(s):  
Grain Size ◽  
Hydrostatic Pressure ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Crystalline Materials ◽  
Nano Crystalline ◽  
Tension And Compression ◽  
Boundary Sliding ◽  
Tension Compression Asymmetry ◽  
Effect Of Hydrostatic Pressure

One of the Remarkable Differences between Mechanical Behavior of Nano-Crystalline and Coarse-Grained Materials Is Tension Compression Asymmetry that Has Been Experienced in Nano-Crystalline Materials. In this Paper a Constitutive Model Is Proposed which Considers Dominant Operative Deformation Mechanisms of Nano-Crystalline Materials Including Grain Interior Plasticity, Grain Boundary Diffusion and Grain Boundary Sliding. A Grain Size Dependent Taylor Type Polycrystalline Model Is Used to Predict Grain Interior Deformation. Three Dimensional Relationships Are Proposed to Relate Macro Stress and Strain Rate in Grain Boundary Mechanisms. The Effect of Normal Stress Acting on a Boundary Is Also Considered in Grain Boundary Sliding, Therefore, Effect of Hydrostatic Pressure Is Included in the Model. The Proposed Model Is Used to Predict Strength of Nano-Crystalline Copper in both Tension and Compression and Good Results Are Obtained Comparing with Experimental Data. The Model Also Predicts Various Behaviors of Nano-Crystalline Materials Observed in Literature's Experiments and Molecular Dynamic Simulations. Some Examples Are: Inverse Hall-Petch Effect; Tension and Compression Maximum Strength Grain Sizes; Tension Compression Asymmetry and its Change Vs. Grain Size and Strain Rate and the Yield Locus Shape.

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