scholarly journals Gradient Microstructure Induced by Surface Mechanical Attrition Treatment (SMAT) in Magnesium Studied Using Positron Annihilation Spectroscopy and Complementary Methods

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4002
Author(s):  
Konrad Skowron ◽  
Ewa Dryzek ◽  
Mirosław Wróbel ◽  
Paweł Nowak ◽  
Marianna Marciszko-Wiąckowska ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Electron Backscatter Diffraction ◽  
Electrochemical Corrosion ◽  
Positron Beam ◽  
Corrosion Current ◽  
Surface Mechanical Attrition Treatment ◽  
Mechanical Attrition ◽  
Gradient Microstructure ◽  
The Mean

Surface mechanical attrition treatment (SMAT) was used to generate a gradient microstructure in commercial grade magnesium. Positron annihilation lifetime spectroscopy and variable energy positron beam measurements, as well as microhardness tests, electron backscatter diffraction, X-ray diffraction, and electrochemical corrosion tests, were used to investigate the created subsurface microstructure and its properties. It was found that SMAT causes an increase in dislocation density and grain refinement which results in increased hardness of the subsurface zone. The mean positron lifetime values indicate trapping of positrons in vacancies associated with dislocations and dislocation jogs. The increase of the SMAT duration and the vibration amplitude influences the depth profile of the mean positron lifetime, which reflects the defect concentration profile. Electrochemical measurements revealed that the structure induced by SMAT increases the susceptibility of magnesium to anodic oxidation, leading to the enhanced formation of hydroxide coverage at the surface and, as a consequence, to the decrease in corrosion current. No significant effect of the treatment on the residual stress was found.

scholarly journals Gradient Microstructure Induced by Surface Mechanical Attrition Treatment in Grade 2 Titanium Studied Using Positron Annihilation Spectroscopy and Complementary Methods

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6347
Author(s):  
Konrad Skowron ◽  
Mirosław Wróbel ◽  
Michał Mosiałek ◽  
Léa Le Joncour ◽  
Ewa Dryzek
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Electrochemical Impedance ◽  
Positron Annihilation Spectroscopy ◽  
Surface Mechanical Attrition Treatment ◽  
Positron Annihilation Lifetime ◽  
Vacancy Clusters ◽  
Complementary Methods ◽  
Mechanical Attrition ◽  
Gradient Microstructure

Microstructural changes in grade 2 titanium generated by surface mechanical attrition treatment (SMAT) were studied using positron annihilation lifetime spectroscopy and complementary methods. A significant increase in the mean positron lifetime indicated many lattice defects introduced by SMAT. Two positron lifetime components were resolved in the positron lifetime spectra measured. The longer lifetime revealed the presence of vacancy clusters containing about 3 or 4 vacancies, while the shorter one was attributed to the annihilation of positrons trapped at dislocations. The changes of the positron lifetime indicated a decreasing dislocation density and the presence of a deeper layer with a higher concentration of vacancy clusters at the distance from the treated surface for which the microhardness approached the value for the strain-free matrix. Electrochemical impedance spectroscopy showed the positive effect of SMAT on the corrosion resistance of the titanium studied in a saline environment also after removal of the original oxide layer that was formed during the SMAT.

Positron spectroscopy of bulk and near-surface defects in semiconductors

1989 ◽  
Vol 67 (8) ◽  
pp. 813-817
Author(s):  
P. Hautojārvi
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Surface Defects ◽  
Positron Beam ◽  
Near Surface ◽  
Slow Positron ◽  
Positron Spectroscopy ◽  
Positron Lifetime Spectroscopy ◽  
Defects In Semiconductors ◽  
Ion Implanted

The use of positron annihilation to study defects in semiconductors is discussed. Positron-lifetime spectroscopy reveals As vacancies in as-grown GaAs and gives information on ionization levels. The vacancy profiles in ion-implanted Si are investigated by slow positron beam.

scholarly journals A Coupled EBSD/TEM Analysis of the Microstructure Evolution of a Gradient Nanostructured Ferritic/Martensitic Steel Subjected to Surface Mechanical Attrition Treatment

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 140 ◽  
Author(s):  
Wenbo Liu ◽  
Xiao Jin ◽  
Bo Zhang ◽  
Di Yun ◽  
Piheng Chen
Keyword(s):  
Grain Boundaries ◽  
Transition Zone ◽  
Microstructure Evolution ◽  
Electron Backscatter Diffraction ◽  
Surface Region ◽  
Surface Mechanical Attrition Treatment ◽  
Ultrafine Grain ◽  
Tem Analysis ◽  
Mechanical Attrition ◽  
Rafm Steel

Surface mechanical attrition treatment (SMAT) was performed on a reduced ferritic/martensitic (RAFM) steel to form a nanostructured (NS) layer on the surface of the sample. Both electron backscatter diffraction (EBSD) and TEM were used to investigate the microstructure evolution during SMAT. The experimental results showed that there were three different zones after SMAT: (i) The “ultrafine grain” (UFG) zone, observed at the top-most surface region, (ii) the “transition zone” in which the original grains were fragmented under the severe plastic deformation and (iii) the “deformed zone” in which the original grains were simply deformed. The average grain sizes increased rapidly with the increase of depth, while the Vickers hardness decreased with the increase of depth, and this phenomenon could be explained in terms of boundary strengthening and dislocation strengthening. The number fractions of medium-angle grain boundaries (MAGBs) and medium-high-angle grain boundaries (MHAGBs) in UFG zones were larger than those in the transition zone and the deformed zone. However, the number fraction of the low-angle grain boundaries (LAGBs) was extremely small in all the zones after SMAT, especially in the transition zone.

scholarly journals Gradient Microstructure Design in Stainless Steel: A Strategy for Uniting Strength-Ductility Synergy and Corrosion Resistance

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2356
Author(s):  
Qiong He ◽  
Wei Wei ◽  
Ming-Sai Wang ◽  
Feng-Jiao Guo ◽  
Yu Zhai ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Strength ◽  
Back Stress ◽  
High Yield ◽  
Surface Mechanical Attrition Treatment ◽  
Steel Sheets ◽  
Mechanical Attrition ◽  
Gradient Microstructure ◽  
Nano Grains

Martensite transformation and grain refinement can make austenitic stainless steel stronger, but this comes at a dramatic loss of both ductility and corrosion resistance. Here we report a novel gradient structure in 301 stainless steel sheets, which enables an unprecedented combination of high strength, improved ductility and good corrosion resistance. After producing inter-layer microstructure gradient by surface mechanical attrition treatment, the sheet was annealed at high temperature for a short duration, during which partial reverse transformation occurred to form recrystallized austenitic nano-grains in the surface layer, i.e., introducing extra intra-layer heterogeneity. Such 3D microstructure heterogeneity activates inter-layer and inter-phase interactions during deformation, thereby producing back stress for high yield strength and hetero-deformation induced (HDI) hardening for high ductility. Importantly, the recrystallized austenitic nano-grains significantly ameliorates the corrosion resistance. These findings suggest an effective route for evading the strength–ductility and strength–corrosion tradeoffs in stainless steels simultaneously.

scholarly journals Analysis of Surface Properties of Nickel Alloy Elements Exposed to Impulse Shot Peening with the Use of Positron Annihilation

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7328
Author(s):  
Agnieszka Skoczylas ◽  
Kazimierz Zaleski ◽  
Radosław Zaleski ◽  
Marek Gorgol
Keyword(s):  
Surface Layer ◽  
Positron Annihilation ◽  
Nickel Alloy ◽  
Shot Peening ◽  
Positron Lifetime ◽  
Experimental Studies ◽  
Maximum Increase ◽  
Small Surface ◽  
The Mean ◽  
The Impact

The paper presents the results of experimental studies on the impact of impulse shot peening parameters on surface roughness (Sa, Sz, Sp, Sv), surface layer microhardness, and the mean positron lifetime (τmean). In the study, samples made of the Inconel 718 nickel alloy were subjected to impulse shot peening on an originally designed stand. The variable factors of the experiment included the impact energy, the diameter of the peening element, and the number of impacts per unit area. The impulse shot peening resulted in changes in the surface structure and an increase in surface layer microhardness. After the application of impulse shot peening, the analyzed roughness parameters increased in relation to post-milling values. An increase in microhardness was obtained, i.e., from 27 HV 0.05 to 108 HV 0.05 at the surface, while the maximum increase the microhardness occur at the depth from 0.04 mm to 0.08 mm. The changes in the physical properties of the surface layer were accompanied by an increase in the mean positron lifetime τmean. This is probably related to the increased positron annihilation in point defects. In the case of small surface deformations, the increase in microhardness was accompanied by a much lower increase in τmean, which may indicate a different course of changes in the defect structure consisting mainly in modification of the dislocation system. The dependent variables were subjected to ANOVA analysis of variance (it was one-factor analysis), and the effect of independent variables was evaluated using post-hoc tests (Tukey test).

scholarly journals Low cycle fatigue of 316L stainless steel processed by surface mechanical attrition treatment (SMAT)

2018 ◽  
Vol 165 ◽  
pp. 15002
Author(s):  
Zhidan Sun ◽  
Jianqiang Zhou ◽  
Delphine Retraint ◽  
Thierry Baudin ◽  
Anne-Laure Helbert ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
316L Stainless Steel ◽  
Electron Backscatter Diffraction ◽  
Low Cycle Fatigue ◽  
Surface Mechanical Attrition Treatment ◽  
Cycle Fatigue ◽  
Microstructure Change ◽  
Cyclic Behaviour ◽  
Mechanical Attrition

In this work, the effect of surface mechanical attrition treatment (SMAT) on the cyclic behaviour of a 316L stainless steel under low cycle fatigue (LCF) is investigated. The LCF results are presented in the form of cyclic stress amplitude evolution for both untreated and SMATed samples. In order to better understand the microstructure change due to cyclic loading, electron backscatter diffraction (EBSD) is used to characterize the microstructure of the SMATed samples before and after fatigue tests. A microstructure gradient is highlighted for samples after SMAT from the top surface layer in nanocrystalline grains to the interior region non-affected by impacts. Under LCF loading, new slip systems are activated in the work hardened region, whereas no plastic slip is activated in the nanostructured layer. The residual stresses generated by SMAT are measured using X-ray diffraction (XRD), and their relaxations under cyclic loading are studied by taking into account the microstructure change. The cyclic behaviour of the samples in different material states is interpreted based on these investigations.

Electron Backscatter Diffraction and Transmission Kikuchi Diffraction Analysis of an Austenitic Stainless Steel Subjected to Surface Mechanical Attrition Treatment and Plasma Nitriding

2015 ◽  
Vol 21 (4) ◽  
pp. 919-926 ◽  
Author(s):  
Gwénaëlle Proust ◽  
Delphine Retraint ◽  
Mahdi Chemkhi ◽  
Arjen Roos ◽  
Clemence Demangel
Keyword(s):  
Stainless Steel ◽  
Surface Properties ◽  
Electron Backscatter Diffraction ◽  
Plasma Nitriding ◽  
Surface Mechanical Attrition Treatment ◽  
Material Surface ◽  
Mechanical Attrition ◽  
Electron Backscatter ◽  
Nanocrystalline Layer ◽  
Backscatter Diffraction

AbstractAustenitic 316L stainless steel can be used for orthopedic implants due to its biocompatibility and high corrosion resistance. Its range of applications in this field could be broadened by improving its wear and friction properties. Surface properties can be modified through surface hardening treatments. The effects of such treatments on the microstructure of the alloy were investigated here. Surface Mechanical Attrition Treatment (SMAT) is a surface treatment that enhances mechanical properties of the material surface by creating a thin nanocrystalline layer. After SMAT, some specimens underwent a plasma nitriding process to further enhance their surface properties. Using electron backscatter diffraction, transmission Kikuchi diffraction, energy dispersive spectroscopy, and transmission electron microscopy, the microstructural evolution of the stainless steel after these different surface treatments was characterized. Microstructural features investigated include thickness of the nanocrystalline layer, size of the grains within the nanocrystalline layer, and depth of diffusion of nitrogen atoms within the material.

scholarly journals Mechanical Property of Duplex Stainless Steel with Nanostructured Layer by Surface Mechanical Attrition Treatment

2011 ◽  
Vol 682 ◽  
pp. 123-130 ◽  
Author(s):  
Liu Chen ◽  
Xiao Lei Xu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Property ◽  
Stainless Steel ◽  
Tensile Test ◽  
Duplex Stainless Steel ◽  
Electron Backscatter Diffraction ◽  
Annealed Sample ◽  
Surface Mechanical Attrition Treatment ◽  
Mechanical Attrition ◽  
Deformed Layer

A grain size gradient layer material was produced by means of surface mechanical attrition treatment on a UNS S32304 duplex stainless steel. In this study, the mechanical property was characterized by tensile test, while microstructure was investigated by transmission electron microscopy, scanning electron microscopy and electron backscatter diffraction. The deformed layer enhanced both the yield strength and maximum strength with large ductility retained, as revealed by tensile test that the yield stress of 30 minutes processed sample was 702 MPa as compared with 454 MPa of as-annealed sample. The elongation to failure, however, decreased from 0.41 to 0.27.

Investigation of defects and nanoparticles with martensitic phase transformation in surface nanostructured 316L stainless steel by slow-positron beam

2010 ◽  
Vol 25 (3) ◽  
pp. 587-591 ◽  
Author(s):  
Xiaowei Wang ◽  
Liangyue Xiong ◽  
Xiaoguang Liu ◽  
Gang Liu ◽  
Chunlan Zhou ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Phase Transformation ◽  
316L Stainless Steel ◽  
Positron Beam ◽  
Martensite Phase ◽  
Surface Mechanical Attrition Treatment ◽  
Annihilation Radiation ◽  
Slow Positron ◽  
Mechanical Attrition ◽  
Line Shape Parameter

In this article, we investigated the defects introduced by surface mechanical attrition treatment by Doppler-broadening spectroscopy of positron annihilation radiation in surface-nanostructured 316L stainless steel. Through the measurement of different thinning layers in the samples treated for 15 min, the slope of line shape parameter S versus wing parameter W curves showed three different values with depth responding to the change of defect configuration. An unusual change of S and W parameters near the surface was mainly from the effect of quantum-dot-like state caused by the formation of nanoparticles. Based on the change of S ˜ W with depth, the martensite phase transformation induced by strain could be estimated to occur within a depth of 35 μm.

scholarly journals EXPERIMENTAL INVESTIGATION ON THE EFFECTS OF SURFACE MECHANICAL ATTRITION TREATMENT ON THE SURFACE OF THE ALUMINUM ALLOY

2021 ◽  
Vol 10 (1) ◽  
pp. 101-108
Author(s):  
Pham Quang Trung ◽  
To Dinh Kha
Keyword(s):  
Plastic Deformation ◽  
Shot Peening ◽  
Optical Microscope ◽  
Surface Mechanical Attrition Treatment ◽  
Mechanical Attrition ◽  
Experimental Parameters ◽  
Aluminum Sample ◽  
Ultrasonic Shot Peening ◽  
The Mean ◽  
Steel Balls

Surface mechanical attrition treatment (SMAT) or ultrasonic shot peening method improves mechanical properties of metallic materials by causing the plastic deformation on their surface layer of the workpiece. In this research, an ultrasonic generator, an ultrasonic booster, a sonotrode, one hundred steel balls with the mean diameter of 1 mm, an optical microscope, an automatic roughness meter, and other supporting accessories are employed to conduct the experiment. The effect of shot peening time of the ultrasonic shot peening method on the surface coverage and the roughness of the treated aluminum sample A7075 is systematically investigated. The study reveals that shot peening time has a significant effect on the coverage and the surface roughness of the treated samples. The surface of sample is rougher with the increasing of shot peening time and the surface is full coverage after shot peening in 35s. The results of this study indicate that the method of surface mechanical attrition (SMAT) or ultrasonic shot peening is an effective method to induce the plastic deformation on the material. It also shows that this is a promising method to investigate the effects of experimental parameters on the microstructure, properties, and fatigue life of the material.

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