Deformation Mechanisms of NiP/Ni Composite Coatings on Ductile Substrates

NiP/Ni composite coatings with different thicknesses were prepared on coarse-grained Ni substrates by electrodeposition. The tensile tests show that compared with the substrate, the toughness and strength of the samples with multilayer composite coatings are greatly improved. The uniform elongation is increased from 24% to 43%, and the yield strength is increased from 108 to 172 MPa. In the deformation process, the geometrically necessary dislocations accumulate, resulting in long-range back stress, leading to strain hardening, showing synergistic strength and ductility. The mechanical properties of composite coatings are strongly affected by the layer thickness. Molecular dynamics studies show that there is a more uniform distribution of the shear strain in thinner coatings, and the propagation of shear transformation zones (STZs) is restrained, preventing the formation of a large shear band. With the decrease of thickness, the deformation of the NiP layer changes from shear fracture to the coexistence of uniform deformation and shear deformation. The interface resistance of the multilayer structure increases the resistance of crack propagation and alleviates the effects of NiP layer cracking on substrate cracking. Multilayer amorphous/crystalline coatings therefore may increase the toughness of the Ni substrate.

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Elucidating how correlated operation of shear transformation zones leads to shear localization and fracture in metallic glasses: Tensile tests on Cu Zr based metallic-glass microwires, molecular dynamics simulations, and modelling

International Journal of Plasticity ◽

10.1016/j.ijplas.2019.02.011 ◽

2019 ◽

Vol 119 ◽

pp. 1-20 ◽

Cited By ~ 4

Author(s):

K.F. Gan ◽

S.S. Jiang ◽

Y.J. Huang ◽

H.B.C. Yin ◽

J.F. Sun ◽

...

Keyword(s):

Molecular Dynamics ◽

Metallic Glass ◽

Molecular Dynamics Simulations ◽

Metallic Glasses ◽

Tensile Tests ◽

Shear Localization ◽

Shear Transformation ◽

Shear Transformation Zones ◽

Dynamics Simulations

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Mechanical Properties and Microstructure of a Duplex Nanostructure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.973 ◽

2010 ◽

Vol 667-669 ◽

pp. 973-978

Author(s):

L. Chen ◽

Ping Jiang ◽

Xiao Lei Wu ◽

Mu Xin Yang ◽

Chang Wang ◽

...

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Yield Strength ◽

Uniform Elongation ◽

Tensile Tests ◽

Coarse Grained ◽

Uniaxial Tensile ◽

Plastic Behavior ◽

Angular Pressing ◽

Elongation To Failure

The nanostructure was obtained in a duplex stainless steel (DSS) by means of equal channel angular pressing. The mechanical properties were characterized by uniaxial tensile tests, while the microstructure was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that the yield strength in a deformed nanostructure increased significantly from 402 MPa to 1461 MPa as compared to its coarse-grained counterpart. In contrast, the uniform elongation decreased significant to only 2% together with elongation to failure of 9.8%, much lower than those of 25.4% and 42.6%. After annealing at 700°C for 10 minute, however, uniform elongation increases to 5.3% with the yield strength of 1200 MPa. TEM observation exhibited that deformation twins prevail in the austenite phase whereas the dislocations of high density present in ferrite. The plastic behavior in both phases was analyzed based on the deformation twinning and the presence of dislocation. Finally, the effect of the microstructure on mechanical properties was discussed.

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Microstructure Evolution and Tensile Properties of 304L Stainless Steel Subjected to Surface Mechanical Attrition Treatment

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.175 ◽

2010 ◽

Vol 667-669 ◽

pp. 175-179 ◽

Cited By ~ 1

Author(s):

Ping Jiang ◽

Jian Lu ◽

Xiao Lei Wu

Keyword(s):

Mechanical Property ◽

Stainless Steel ◽

Uniform Elongation ◽

Tensile Tests ◽

Bulk Sample ◽

Coarse Grained ◽

Surface Mechanical Attrition Treatment ◽

Uniaxial Tensile ◽

304L Stainless Steel ◽

Mechanical Attrition

A gradient nanostructured layer (GNsL) was generated on the two sides of bulk sample in 304L stainless steel by means of the surface mechanical attrition treatment. The microstructure of the GNsL was characterized via TEM observation. The prominent microstructural features involve the intersection of multi-system twin operation, subdividing the original grains into blocks, a martensite transformation mainly occurring at the interface of the twins as well, and the randomly orientated nanocrystallites at the top of surface. After annealing at 750°C for 10 min, recovery had occurred and the dislocation density was much reduced. The vast majority of the grains at the top surface were in the nanocrystalline/ultrafine range, with some recrystallization regions. The uniaxial tensile tests were performed to obtain the mechanical property of bulk samples with GNsL. The yield strength was about 2 times higher than that of the coarse-grained counterpart, but with a decrease in uniform elongation and elongation to failure as well. The relationship between the microstructure and mechanical property was discussed in detail.

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Outstanding Tensile Properties and Their Origins in Twinning-Induced Plasticity (TWIP) Steels with Gradient Substructures

Materials ◽

10.3390/ma13051184 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1184 ◽

Cited By ~ 3

Author(s):

Huihui Zhi ◽

Cheng Zhang ◽

Zihui Guo ◽

Stoichko Antonov ◽

Yanjing Su

Keyword(s):

Yield Strength ◽

Back Stress ◽

Tensile Tests ◽

Coarse Grained ◽

High Yield ◽

Uniaxial Tensile ◽

High Ductility ◽

Strengthening Mechanisms ◽

High Yield Strength ◽

Twip Steels

The low yield strength (~300 MPa) of twinning-induced plasticity (TWIP) steels greatly limits their structural applications in the industrial field. Conventional strengthening mechanisms usually cause an enhancement of yield strength but also a severe loss of ductility. In this research, gradient substructures were introduced in the Fe-22Mn-0.6C TWIP steels by different pre-torsional deformation in order to overcome the above limitations. The substructure evolution, mechanical properties, and their origins in gradient-substructured (GS) TWIP steels were measured and compared by electron backscattered diffraction (EBSD), monotonous and loading-unloading-reloading (LUR) tensile tests. It was found that a simple torsional treatment could prepare gradient twins and dislocations in coarse-grained TWIP steel samples depending on torsional strain. The uniaxial tensile tests indicated that a superior combination of high yield strength, high ultimate strength, and considerable ductility was simultaneously obtained in the GS samples. The high yield strength and high ultimate tensile strength were attributed to synergetic strengthening mechanisms, viz., dislocation strengthening, due to the accumulation of high density of dislocations, and very high back stress strengthening due to gradient substructure distribution, which was accommodated through pile-ups of extra geometrically necessary dislocations (GNDs) across the sample-scale. Additionally, high ductility originated from gradient substructure-induced back stress hardening. The present study is also beneficial to the design efforts of high strength and high ductility of other heterogeneous-structured TWIP alloy systems.

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Comparison on Tensile Characteristics of Plain C–Mn Steel with Ultrafine Grained Ferrite/Cementite Microstructure and Coarse Grained Ferrite/Pearlite Microstructure

Materials ◽

10.3390/ma14092309 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2309

Author(s):

Yan Tian ◽

Mingchun Zhao ◽

Wenjian Liu ◽

Jimou Zhang ◽

Min Zhang ◽

...

Keyword(s):

Uniform Elongation ◽

Tensile Tests ◽

Total Elongation ◽

Microstructural Change ◽

Coarse Grained ◽

Lower Yield ◽

Thermal Component ◽

Ultrafine Grained ◽

Athermal Component ◽

Mn Steel

This work investigated the tensile characteristics of plain C–Mn steel with an ultrafine grained ferrite/cementite (UGF/C) microstructure and coarse-grained ferrite/pearlite (CGF/P) microstructure. The tensile tests were performed at temperatures between 77 K and 323 K. The lower yield and the ultimate tensile strengths were significantly increased when the microstructure was changed from the CGF/P to the UGF/C microstructures, but the total elongation and the uniform elongation decreased. A microstructural change from the CGF/P microstructure to the UGF/C microstructure had an influence on the athermal component of the lower yield and the ultimate tensile strengths but not on the thermal component. The UGF/C microstructure with a higher carbon content provided a higher strength without losing ductility because cementite particles restrained necking.

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The Effect of Grain Size on Superplastic Deformation of Ti-6Al-4V Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.551-552.387 ◽

2007 ◽

Vol 551-552 ◽

pp. 387-392 ◽

Cited By ~ 4

Author(s):

Wen Juan Zhao ◽

Hua Ding ◽

D. Song ◽

F.R. Cao ◽

Hong Liang Hou

Keyword(s):

Grain Size ◽

Grain Growth ◽

Superplastic Deformation ◽

Initial Strain Rate ◽

Deformation Mode ◽

Tensile Tests ◽

Optical Microscope ◽

Coarse Grained ◽

Transmission Electron ◽

Grain Growth Model

In this study, superplastic tensile tests were carried out for Ti-6Al-4V alloy using different initial grain sizes (2.6 μm, 6.5μm and 16.2 μm) at a temperature of 920°C with an initial strain rate of 1×10-3 s-1. To get an insight into the effect of grain size on the superplastic deformation mechanisms, the microstructures of deformed alloy were investigated by using an optical microscope and transmission electron microscope (TEM). The results indicate that there is dramatic difference in the superplastic deformation mode of fine and coarse grained Ti-6Al-4V alloy. Meanwhile, grain growth induced by superplastic deformation has also been clearly observed during deformation process, and the grain growth model including the static and strain induced part during superplastic deformation was utilized to analyze the data of Ti-6Al-4V alloy.

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New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0180 ◽

2015 ◽

Vol 60 (2) ◽

pp. 605-614 ◽

Cited By ~ 2

Author(s):

T. Kvačkaj ◽

A. Kováčová ◽

J. Bidulská ◽

R. Bidulský ◽

R. Kočičko

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

Tensile Tests ◽

Coarse Grained ◽

Wear Behaviour ◽

Ofhc Copper ◽

Strain Rates ◽

Ultrafine Grained ◽

Reduction Of Area ◽

Pin On Disk

AbstractIn this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was subjected to two different processing methods, which made possible to study the influence of structure. The study of strain rate and microstructure was focused on progress in the mechanical properties after tensile tests. It was found that the strain rate is an important parameter affecting mechanical properties of copper. The ultimate tensile strength increased with the strain rate increasing and this effect was more visible at high strain rates$({\dot \varepsilon} \sim 10^2 \;{\rm{s}}^{ - 1} )$. However, the reduction of area had a different progress depending on microstructural features of materials (coarse-grained vs. ultrafine-grained structure) and introduced strain rate conditions during plastic deformation (static vs. dynamic regime). The wear behaviour of copper was investigated through pin-on-disk tests. The wear tracks examination showed that the delamination and the mild oxidational wears are the main wear mechanisms.

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Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.182 ◽

2008 ◽

Vol 584-586 ◽

pp. 182-187

Author(s):

Lilia Kurmanaeva ◽

Yulia Ivanisenko ◽

J. Markmann ◽

Ruslan Valiev ◽

Hans Jorg Fecht

Keyword(s):

Mechanical Properties ◽

Deformation Behavior ◽

Materials Science ◽

High Pressure Torsion ◽

Uniform Elongation ◽

Grain Structure ◽

Coarse Grained ◽

Ultrafine Grain ◽

Ultrafine Grained ◽

Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

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Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1517193112 ◽

2015 ◽

Vol 112 (47) ◽

pp. 14501-14505 ◽

Cited By ~ 437

Author(s):

Xiaolei Wu ◽

Muxin Yang ◽

Fuping Yuan ◽

Guilin Wu ◽

Yujie Wei ◽

...

Keyword(s):

Large Scale ◽

Low Cost ◽

High Strength ◽

Back Stress ◽

Coarse Grained ◽

Ultrafine Grain ◽

Asymmetric Rolling ◽

Dislocation Hardening ◽

Ultrafine Grained ◽

Lamella Structure

Grain refinement can make conventional metals several times stronger, but this comes at dramatic loss of ductility. Here we report a heterogeneous lamella structure in Ti produced by asymmetric rolling and partial recrystallization that can produce an unprecedented property combination: as strong as ultrafine-grained metal and at the same time as ductile as conventional coarse-grained metal. It also has higher strain hardening than coarse-grained Ti, which was hitherto believed impossible. The heterogeneous lamella structure is characterized with soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The unusual high strength is obtained with the assistance of high back stress developed from heterogeneous yielding, whereas the high ductility is attributed to back-stress hardening and dislocation hardening. The process discovered here is amenable to large-scale industrial production at low cost, and might be applicable to other metal systems.

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