scholarly journals Cracking and Toughening Mechanisms in Nanoscale Metallic Multilayer Films: A Brief Review

2018 ◽  
Vol 8 (10) ◽  
pp. 1821 ◽  
Author(s):  
Qing Zhou ◽  
Yue Ren ◽  
Yin Du ◽  
Dongpeng Hua ◽  
Weichao Han
Keyword(s):  
Fracture Toughness ◽  
High Strength ◽  
Plastic Instability ◽  
Multilayer Films ◽  
Fracture Mechanisms ◽  
Toughening Mechanisms ◽  
Individual Layer ◽  
Practical Applications ◽  
Mechanical Responses ◽  
The Individual

Nanoscale metallic multilayer films (NMMFs) have captured scientific interests on their mechanical responses. Compared with the properties of monolithic films, multilayers possess unique high strength as the individual layer thickness reduces to the nanoscale, which is benefited from the plentiful hetero-interfaces. However, NMMFs always exhibit a low fracture toughness and ductility, which seriously hinders their practical applications. While there have been reviews on the strengthening and deformation mechanisms of microlaminate, rapid developments in nanotechnology have brought an urgent requirement for an overview focused on the cracking and toughening mechanisms in nanoscale metallic multilayers. This article provides an extensive review on the structure, standard methodology and fracture mechanisms of NMMFs. A number of issues about the crack-related properties of NMMFs have been displayed, such as fracture toughness, wear resistance, adhesion energy, and plastic instability. Taken together, it is hoped that this review will achieve the following two purposes: (1) introducing the size-dependent cracking and toughness performance in NMMFs; and (2) offer a better understanding of the role interfaces displayed in toughening mechanisms. Finally, we list a few questions we concerned, which may shed light on further development.

Self-Assembly of Inorganic/Organic Multilayer Films

1994 ◽  
Vol 351 ◽  
Author(s):  
Astrid C. Zeppenfeld ◽  
Catherine J. Page
Keyword(s):  
Self Assembly ◽  
Grazing Angle ◽  
Multilayer Films ◽  
Silicon Wafers ◽  
Initial Surface ◽  
X Ray Diffraction ◽  
Individual Layer ◽  
X Ray ◽  
Influence Of Substrate ◽  
The Individual

ABSTRACTIn order to investigate the influence of substrate functionalization on the subsequent selfassembly of multilayer films, multilayers composed of alternating hafnium and 1,10-decanediylbis(phosphonic) acid (DBPA) have been grown on three different substrates. Substrates studied include gold wafers functionalized with 4-mercaptobutylphosphonic acid, silicon wafers functionalized using a hafnium oxychloride solution, and silicon wafers coated with an octadecylphosphonate LB-template layer. The nature of these films is probed using ellipsometry and grazing angle x-ray diffraction. These studies indicate that the overall order and the individual layer thickness can vary substantially from sample to sample and depend strongly on the initial surface functionalization prior to multilayer growth.

X-ray Fractographic Study on Alumina and Zirconia Ceramics

1990 ◽  
Vol 34 ◽  
pp. 719-727 ◽  
Author(s):  
Sumio Tanaka ◽  
Yukio Hirose ◽  
Keisuke Tanaka
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Fracture Surface ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Tests ◽  
Fracture Mechanisms ◽  
Zirconia Ceramics ◽  
X Ray ◽  
Fractographic Study

The residual stress left on the fracture surface is one of the important parameters in X-ray fractographic study. It has been used to analyze fracture mechanisms in fracture toughness and fatigue tests especially of high strength steels.In this paper, X-ray fractography was applied to brittle fracture of alumina (Al2O3) and zirconia (ZΓO2) ceramics.

GMR and Structure in Sputtered Co90Fe10/Ag Multilayers

1995 ◽  
Vol 403 ◽  
Author(s):  
J. D. Jarratt ◽  
J. A. Barnard
Keyword(s):  
Magnetic Properties ◽  
Multilayer Structure ◽  
Giant Magnetoresistance ◽  
Multilayer Films ◽  
X Ray Diffraction ◽  
Individual Layer ◽  
X Ray ◽  
The Individual

AbstractGiant magnetoresistance (GMR), structure, and magnetic properties of sputtered (Co90Fe10 X Å/Ag Y Å) multilayer films have been investigated. Distinct GMR behaviors including granulartype (GGMR) and ‘discontinuous’ (DGMR) are observed which are strongly dependent on the individual CoFe and Ag layer thicknesses; however, standard multilayer GMR and the associated antiferromagnetic (AFM) coupling is absent. The multilayer structure, individual layer thicknesses, and growth texture were investigated using high and low angle x-ray diffraction (HXRD & LXRD).

scholarly journals Temperature Dependence of Fracture Characteristics of Variously Heat-Treated Grades of Ultra-High-Strength Steel: Experimental and Modelling

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5875
Author(s):  
Jaroslav Pokluda ◽  
Ivo Dlouhý ◽  
Marta Kianicová ◽  
Jan Čupera ◽  
Jana Horníková ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Temperature Dependence ◽  
High Stress ◽  
Stress Triaxiality ◽  
High Strength ◽  
Fracture Mechanisms ◽  
Temperature Range ◽  
Heat Treated ◽  
Shape Ratio ◽  
Standard Steel

The temperature dependence of tensile characteristics and fracture toughness of the standardly heat-treated low-alloyed steel OCHN3MFA along with three additionally heat-treated grades was experimentally studied. In the temperature range of ⟨−196; 22⟩ °C, all the additional heat treatments transferred the standard steel from a high- to ultra-high strength levels even with improved tensile ductility characteristics. This could be explained by a reduction of the inclusion content, refinement of the martensitic blocks, ductile retained austenite content, and homogenization of the shape ratio of martensitic laths as revealed by metallographic, X-ray, and EBSD techniques. On the other hand, the values of the fracture toughness of all grades were found to be comparable in the whole temperature range as the cause of a high stress triaxiality in the pre-cracked Charpy V-notch samples. The values of the fracture toughness of the standard steel grade could be predicted well using the fracture model proposed by Pokluda et al. based on the tensile characteristics. Such a prediction failed in the case of additionally heat-treated grades due to the different temperature dependence of the fracture mechanisms occurring in the tensile and fracture-toughness tests. While the tensile samples fractured in a ductile-dimple mode at all temperatures, the fracture-toughness specimens exhibited a transition from the ductile to quasi-brittle fracture mode with decreasing temperature. This transition could be interpreted in terms of a transfer from the model proposed by Rice and Johnson to the model of Tvergaard and Hutchinson.

Ballistic performance of multi-metal systems

2020 ◽  
Vol 11 (3) ◽  
pp. 379-410 ◽  
Author(s):  
Prabhani Ranaweera ◽  
Dakshitha Weerasinghe ◽  
PLN Fernando ◽  
Sudharshan N Raman ◽  
Damith Mohotti
Keyword(s):  
High Strength ◽  
Areal Density ◽  
Fracture Mechanisms ◽  
Low Density ◽  
Ballistic Performance ◽  
Comprehensive Review ◽  
Practical Applications ◽  
Ballistic Resistance ◽  
Optimum Arrangement ◽  
Metallic Plates

Ballistic resistance enhancement of armours and structures has been a prominent area of research over the years. Monolithic metallic plates have been the preferred choice for armours against high-velocity projectiles. High-strength steel is a popular choice for such systems. However, the high areal density deters in accommodating such systems in practical applications which require lightweight products. On the contrary, multi-metallic systems produced by the combination of low-density materials with similar or superior ballistic resistance as their monolithic counterparts have become attractive candidates in defence applications. However, only a limited number of comprehensive studies on the ballistic performance of multi-metal multi-layered targets are available in the literature. Moreover, these studies have drawn contradictory conclusions on the optimum arrangement of different layers and materials within the systems. In addition, existing knowledge in this area is scattered in the literature and there is a need to collate them to enhance the development of multi-metal multi-layered ballistic-resistant plate systems in order to be optimised for ballistic-related armour. This article aims to provide a comprehensive review of the effect of different metals, thickness, fracture mechanisms, feasibility of the connection types and the order of the metallic plates within targets on the ballistic performance.

Analysis of Notch Effect in Fracture Micromechanisms

2012 ◽  
Author(s):  
Sergio Cicero ◽  
Virginia Madrazo ◽  
Isidro Carrascal ◽  
Roman Cicero
Keyword(s):  
Fracture Toughness ◽  
Aluminum Alloy ◽  
Critical Radius ◽  
High Strength ◽  
Fracture Mechanisms ◽  
Notch Effect ◽  
Progressive Change ◽  
Load Bearing Capacity ◽  
Notched Specimens ◽  
Apparent Fracture Toughness

This paper presents an analysis of the notch effect in fracture micromechanisms. To this end, experimental results obtained in notched specimens are presented, together with the corresponding stress field at fracture and the SEM fractographies. The specimens comprise three materials (structural steel S275JR, high-strength aluminum alloy Al7075-T651 and Polymethyl methacrylate-PMMA) and notch radii varying from 0 mm (cracks) up to 2.5 mm. The results show how the stress relaxation caused by the notch effect is accompanied by a progressive change in the fracture mechanisms, from basically brittle ones in cracked conditions (for the three materials analyzed) to non-linear mechanisms observed for high notch radii, which explain the increase caused by the notch effect in both the load bearing capacity and the apparent fracture toughness. Also the concept of critical radius, that one below which the notch effect is negligible, is justified by SEM observations.

The Influence of the Out-of-Plane Constraint on Fracture Toughness of High Strength Steel at Low Temperatures

2014 ◽  
Vol 224 ◽  
pp. 157-166 ◽  
Author(s):  
Andrzej Neimitz ◽  
Ihor Dzioba ◽  
Robert Pała ◽  
Urszula Janus
Keyword(s):  
Fracture Toughness ◽  
Critical State ◽  
Low Temperatures ◽  
High Strength Steel ◽  
Brittle Materials ◽  
High Strength ◽  
Specimen Thickness ◽  
Structural Element ◽  
Practical Applications ◽  
Out Of Plane

The values of JIC measured in laboratories, when used in practical applications, may lead to conservative results in assessing the critical state of a structural element. When the thickness of the structural element is less than required by standards the fracture toughness can be much higher than measured in the laboratory. In this paper the fracture toughness of brittle or semi-brittle materials is discussed. The out-of-plane constraint is characterized in this paper by other quantity then the specimen thickness. This quantity can be related to the thickness if the thickness is uniquely defined.

Precipitation in Al-Li-Zr alloys

1992 ◽  
Vol 50 (1) ◽  
pp. 186-187
Author(s):  
D.M. Vanderwalker
Keyword(s):  
Fracture Toughness ◽  
Precipitation Hardening ◽  
Weight Ratio ◽  
High Strength ◽  
Transmission Electron ◽  
Water Quench ◽  
Aluminum Lithium ◽  
Aluminum Lithium Alloys ◽  
Lithium Alloys ◽  
Zr Alloys

Aluminum-lithium alloys have a low density and high strength to weight ratio. They are being developed for the aerospace industry.The high strength of Al-Li can be attributed to precipitation hardening. Unfortunately when aged, Al-Li aquires a low ductility and fracture toughness. The precipitate in Al-Li is part of a sequence SSSS → Al3Li → AlLi A description of the phases may be found in reference 1 . This paper is primarily concerned with the Al3Li phase. The addition of Zr to Al-Li is being explored to find the optimum in properties. Zirconium improves fracture toughness and inhibits recrystallization. This study is a comparision between two Al-Li-Zr alloys differing in Zr concentration.Al-2.99Li-0.17Zr(alloy A) and Al-2.99Li-0.67Zr (alloy B) were solutionized for one hour at 500oc followed by a water quench. The specimens were then aged at 150°C for 16 or 40 hours. The foils were punched into 3mm discs. The specimens were electropolished with a 1/3 nitric acid 2/3 methanol solution. The transmission electron microscopy was conducted on the JEM 200CX microscope.

Phase separation in sol gel-derived ceramic films of silica-zirconia, alumina-zirconia, and titania-zirconia system

1994 ◽  
Vol 52 ◽  
pp. 646-647
Author(s):  
J. Tong ◽  
L. Eyring
Keyword(s):  
Fracture Toughness ◽  
Phase Separation ◽  
Sol Gel ◽  
Great Influence ◽  
High Strength ◽  
Chemical Durability ◽  
Separation Method ◽  
Toughening Mechanism ◽  
Ceramic Films ◽  
Zirconia Toughened Alumina

There is increasing interest in composites containing zirconia because of their high strength, fracture toughness, and its great influence on the chemical durability in glass. For the zirconia-silica system, monolithic glasses, fibers and coatings have been obtained. There is currently a great interest in designing zirconia-toughened alumina including exploration of the processing methods and the toughening mechanism.The possibility of forming nanocrystal composites by a phase separation method has been investigated in three systems: zirconia-alumina, zirconia-silica and zirconia-titania using HREM. The morphological observations initially suggest that the formation of nanocrystal composites by a phase separation method is possible in the zirconia-alumina and zirconia-silica systems, but impossible in the zirconia-titania system. The separation-produced grain size in silica-zirconia system is around 5 nm and is more uniform than that in the alumina-zirconia system in which the sizes of the small polyhedron grains are around 10 nm. In the titania-zirconia system, there is no obvious separation as was observed in die alumina-zirconia and silica-zirconia system.

Sign in / Sign up

Export Citation Format

Share Document