Fabrication and Characterization of Nanostructured Surface Layer of 38CrSi Steel

2007 ◽  
Author(s):  
Shi-Ning Ma ◽  
De-Ma Ba ◽  
Chang-Qing Li ◽  
Fan-Jun Meng
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Surface Layer ◽  
Grain Refinement ◽  
Fine Particles ◽  
Nanostructured Surface ◽  
Cell Structures ◽  
Strain And Strain Rate ◽  
Transmission Electron ◽  
Average Grain Size

A nanocrystalline surface layer was fabricated on a 38CrSi Steel with tempered sorbite structure by using Supersonic Fine Particles Bombarding (SFPB). The microstructural evolution of SFPB-treated specimens under different processing conditions was characterized by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Experimental evidence showed severe plastic deformation and obvious grains refinement were observed and a nanocrystalline surface layer (grain size < 100nm) was found after SFPB treatment. The thickness of nanostructured surface layer varies from a few to about 25μm as treated time increasing from 80s to 240s, but the grain size varies slightly. For the sample treated for 240s, the average grain size of equiaxed nanocrystallites with random crystallographic orientations on the top surface layer is about 16nm. The indexing of diffraction rings indicates nanostructured surface layer consists of ferrite and cementite phases without any evidence of a new phase. The structure size increases gradually from nano-scale to original-scale with an increase of the distance from the top surface layer. In the region about 20–30μm deep from the top surface, the microstructures are mainly composed of 60–100nm roughly equiaxed grains and subgrains. Some subbounsaries are composed of dense dislocation walls (DDWs). In this regime some cell structures are also seen, which are separated by dislocation lines (DTs) and some DDWs. Experimental analysis indicate coarse-grains are gradually refined into nano-sized grains by dislocations activity with gradual increase of strain and strain rate from matrix to treated surface. Both ferrite and cementite phases occur grain refinement. Grain refinement of 38CrSi sample is mainly attributed to the movement of dislocation.

The Investigation of Surface Nanocrystallization of Structural Steel Induced by Supersonic Fine Particles Bombarding

2008 ◽  
Vol 373-374 ◽  
pp. 811-814
Author(s):  
De Ma Ba ◽  
Shi Ning Ma ◽  
Fan Jun Meng ◽  
C.Q. Li
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Carbon Steel ◽  
Alloy Steel ◽  
Fine Particles ◽  
Medium Carbon Steel ◽  
Nanostructured Surface ◽  
Medium Carbon ◽  
Silicon Alloy ◽  
Cell Structures

The nanostructured surface layers were fabricated on a hardened and tempered chrome-silicon alloy steel and a normalized medium carbon steel by mean of Supersonic Fine Particles Bombarding (SFPB). The microstructure features in the treated surface layer were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. Experimental results show the nanostructured surface layer is fabricated on both samples after SFPB treatment. The microstructure of the top surface is characterized by uniformly distributed nano-scale grains with equiaxed shape and random crystallographic orientations. The mean size of equiaxed nanocrystallites on the top surface layer is approximately 15-20nm for the SFPB treated medium carbon steel and Chrome-silicon alloy steel. During severe deformation the grain refinement in ferrite and cementite phases is observed, the cementite phases are exposed to breaking and dissolution due to mechanical alloying resulting in the formation of a supersaturated solid solution of carbon in α-Fe matrix. In the ferrite phase, the grains are refined by the process of dislocation actives and forming cell structures separated by dense dislocation walls (DDWs), as well as evolution of dislocation to subboundaries and grain boundaries.

Synthesis and Characterization of Plasma Synthesized Nanostructured Magnesia-Yttria Based Nanocomposites

2007 ◽  
Vol 1056 ◽  
Author(s):  
Jafar F. Al-Sharab ◽  
Rajendra Sadangi ◽  
Vijay Shukla ◽  
Bernard Kear
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Chemical Mapping ◽  
X Ray Diffraction ◽  
Fine Grained ◽  
Transmission Electron ◽  
Spray Method ◽  
Average Grain Size

ABSTRACTPolycrystalline Y2O3 is the material of choice for IR windows since it has excellent optical properties in the visible, and near infra-red band. However, current processing methods yield polycrystalline Y2O3 with large grain size (> 100 μm), which limits the hardness and erosion resistance attainable. One way to improve strength is to develop an ultra-fine grained material with acceptable optical transmission properties. To realize a fine-grained ceramic, one approach is to develop a composite structure, in which one phase inhibits the growth of the other phase during processing. In this study, Y2O3-MgO nanocomposite with various MgO content (20, 50 and 80 mol%) were synthesized using plasma spray method. Extensive characterization techniques including x-ray diffraction, scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy Dispersive spectrometry (EDS) were employed to study the synthesized powder as well as the consolidated sample. Transmission Electron Microscopy, as well as EDS chemical mapping, revealed that the consolidated sample have bi-continuous MgO-Y2O3 nanostructure with an average grain size of 200 nm.

Synthesis and Characterization of Nanocrystalline 316-Stainless Steel Coatings by High Velocity Oxy-Fuel Spraying

1998 ◽  
Author(s):  
M.L. Lau ◽  
H.G. Jiang ◽  
E.J. Lavernia
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Stainless Steel ◽  
High Velocity ◽  
Polished Surface ◽  
316 Stainless Steel ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Stainless Steel Coatings

Abstract The present paper describes the synthesis of nanocrystalline 316-stainless steel coatings by high velocity oxy-fuel (HVOF) thermal spraying. The feedstock powders were synthesized by mechanical milling to produce flake-shaped agglomerates with an average grain size of less than 100 nm. The powders were introduced into the HVOF spray to successfully produce nanocrystalline coatings. X-ray diffraction analysis and transmission electron microscopy were used to determine the average grain size of the milled powders. Scanning electron microscopy and transmission electron microscopy were used to study the morphology of the nanometric particles and the microstructure of the as-sprayed coatings. The properties of various coating materials were characterized by microhardness measurements performed on the polished surface of the cross section.

Evolution of Microstructure and Texture during Annealing of a Copper Processed by ECAE

2005 ◽  
Vol 495-497 ◽  
pp. 845-850 ◽  
Author(s):  
Anne Laure Etter ◽  
Denis Solas ◽  
Thierry Baudin ◽  
Richard Penelle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Equal Channel Angular Extrusion ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Angular Extrusion ◽  
Evolution Of Microstructure ◽  
Electron Back Scattered Diffraction

A submicron-grained (SMG) microstructure, with an average grain size of ~0.4 µm was produced by equal channel angular extrusion (ECAE). The SMG microstructure was composed of large dynamic recrystallized grains within a matrix of deformed elongated cells. Samples were annealed for various times at 473 K and then examined using transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). The results specify that a large recovery takes place during the first annealing times. Moreover, MET investigations show nucleation of grains which orientations are found in the recrystallized texture. The EBSD measurements established that, after 7min30s at 473 K, the microstructure is equiaxed and stable with an average grain size of about 2 µm.

Direct Conversion of TiO2 Sol to Nanocrystalline Anatase at 85 °C

2002 ◽  
Vol 17 (6) ◽  
pp. 1507-1512 ◽  
Author(s):  
K. I. Gnanasekar ◽  
V. Subramanian ◽  
J. Robinson ◽  
K. I. Gnanasekar ◽  
K. I. Gnanasekar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fine Particles ◽  
Anatase Phase ◽  
Direct Conversion ◽  
Scanning Calorimetry ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Tio2 Sol ◽  
Diffraction Patterns

Nanocrystalline TiO2 anatase with particle size in the range of 5–7 nm has been prepared by in situ cracking of the sol at 85 °C, thereby avoiding the intermediate gel formation process. Hydrolysis of Ti(O-isoPr)4 was carried out in excess of 2-propanol to keep the suspension of fine particles from agglomeration. Differential thermal analysis, thermogravimetric analysis, differential scanning calorimetry, powder x-ray diffraction (XRD), and electron microscopy have been used to characterize the samples. Gel to crystalline conversion, which requires a temperature of at least 400 °C, can be achieved by digesting the TiO2 sol at 85 °C. XRD and selected area electron diffraction patterns show the presence of a small amount of brookite phase along with the major anatase phase. High-resolution transmission electron microscopy shows that the average grain size of TiO2 particle remains around 5–9 nm even when heated at 510 °C.

Microstructural Evolution of Friction Stir Treated WE43 Alloy

2014 ◽  
Vol 788 ◽  
pp. 74-77
Author(s):  
Xu Dong Wang ◽  
Jiong Li Li ◽  
Zheng Lu ◽  
Xian Feng Zhang ◽  
Zhi Feng Ma ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
High Resolution Electron Microscopy ◽  
Traverse Speed ◽  
Friction Stir ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Average Grain Size ◽  
Super Plastic ◽  
We43 Alloy

Mg-Y-Nd (WE43) plate in 3mm thickness was friction stir welded (FSW) under a tool rotation rate of 800rpm and a traverse speed of 100 mm/min. The super plastic deformation structure was obtained in as-FSWed WE43 alloy. Coarse equiaxed recrystallized microstructure in extruded WE43 alloy with the average grain size of over 50μm changed into fine equiaxed recrystallized grains with the average grain size of under 5μm in the FSW core zone. The formation and evolution of hardening precipitates in WE43 alloy during ageing at 210oC is characterized by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) observations. It was indicated that the microstructure of as-FSWed WE43 always contain β’’ phase even without heat treatment. The hardening is mainly associated with the β’’→β’ transformation.

Surface Nanocrystallization of Zircaloy-4 by Surface Mechanical Attrition Treatment

2010 ◽  
Vol 658 ◽  
pp. 452-455 ◽  
Author(s):  
Cong Hui Zhang ◽  
Xiao Ge Duan ◽  
Lian Zhou ◽  
Xin Zhe Lan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Surface Hardness ◽  
Surface Mechanical Attrition Treatment ◽  
Dislocation Slip ◽  
Transmission Electron ◽  
Mechanical Attrition ◽  
Average Grain Size ◽  
Mechanical Twins

A nanostructured surface layer was induced on zircaloy-4 by the method of surface mechanical attrition treatment (SMAT). X-ray diffraction and microhardness tester were applied to identify the average grain size and hardness of specimen processed for different duration, transmission electron microscopy and high-resolution transmission electron microscopy were adopted to observe the microstructure of specimen. The results showed that the surface hardness enhanced gradually and then stabilized with the processing duration increasing, while the average grain size declined gradually, to the minimum 20 nm at 15 min, then increased. The formation of nanocrystalline was due to the mechanical twins and dislocation slip.

scholarly journals Grain refinement at the nanoscale via mechanical twinning and dislocation interaction in a nickel-based alloy

2004 ◽  
Vol 19 (6) ◽  
pp. 1623-1629 ◽  
Author(s):  
N.R. Tao ◽  
X.L. Wu ◽  
M.L. Sui ◽  
J. Lu ◽  
K. Lu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Layer ◽  
Grain Refinement ◽  
Mechanical Twinning ◽  
Surface Mechanical Attrition Treatment ◽  
Dislocation Interaction ◽  
Inconel 600 ◽  
Transmission Electron ◽  
Refinement Mechanism

A nanostructured surface layer was formed on an Inconel 600 plate by subjecting it to surface mechanical attrition treatment at room temperature. Transmission electron microscopy and high-resolution transmission electron microscopy of the treated surface layer were carried out to reveal the underlying grain refinement mechanism. Experimental observations showed that the strain-induced nanocrystallization in the current sample occurred via formation of mechanical microtwins and subsequent interaction of the microtwins with dislocations in the surface layer. The development of high-density dislocation arrays inside the twin-matrix lamellae provides precursors for grain boundaries that subdivide the nanometer-thick lamellae into equiaxed, nanometer-sized grains with random orientations.

scholarly journals Effective Surface Nano-Crystallization of Ni2FeCoMo0.5V0.2 Medium Entropy Alloy by Rotationally Accelerated Shot Peening (RASP)

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1074 ◽  
Author(s):  
Ningning Liang ◽  
Xiang Wang ◽  
Yang Cao ◽  
Yusheng Li ◽  
Yuntian Zhu ◽  
...  
Keyword(s):  
Grain Size ◽  
Surface Layer ◽  
Grain Refinement ◽  
Shot Peening ◽  
Model Material ◽  
High Entropy Alloy ◽  
Transmission Electron Microscopy Analysis ◽  
High Entropy ◽  
Average Grain Size ◽  
Electron Microscopy Analysis

The surface nano-crystallization of Ni2FeCoMo0.5V0.2 medium-entropy alloy was realized by rotationally accelerated shot peening (RASP). The average grain size at the surface layer is ~37 nm, and the nano-grained layer is as thin as ~20 μm. Transmission electron microscopy analysis revealed that deformation twinning and dislocation activities are responsible for the effective grain refinement of the high-entropy alloy. In order to reveal the effectiveness of surface nano-crystallization on the Ni2FeCoMo0.5V0.2 medium-entropy alloy, a common model material, Ni, is used as a reference. Under the same shot peening condition, the surface layer of Ni could only be refined to an average grain size of ~234 nm. An ultrafine grained surface layer is less effective in absorbing strain energy than a nano-grain layer. Thus, grain refinement could be realized at a depth up to 70 μm in the Ni sample.

Study on Refinement Mechanism of Sc and Zr as-Cast Al-7.2Zn-2.2Mg-1.8Cu Alloys

2013 ◽  
Vol 372 ◽  
pp. 66-69
Author(s):  
Zhi Gang Wang ◽  
Jun Xu ◽  
Bao Li ◽  
Zhi Feng Zhang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Grain Size ◽  
Grain Refinement ◽  
Heterogeneous Nucleation ◽  
Composite Particles ◽  
Cast Ingot ◽  
Average Grain Size ◽  
Refinement Mechanism ◽  
Scanning Electron

The effect of trace Sc and Zr on grain refinement of Al-7.2Zn-2.2Mg-1.8Cu as-cast ingot was studied by using optical microscopy and scanning electron microscopy with EDS. The results show that addition of only 0.20% Zr or 0. 20% Sc to Al-7.2Zn-2.2Mg-1.8Cu alloy can refine grains to a certain degree, and the addition of 0.10% Sc+0.20%Zr leads to stronger grain refinement, the average grain size is only 10-15μm. Al3Sc/Al3Zr composite particles in the melt work as the nucleation of heterogeneous nucleation during solidification.

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