Nucleation Mechanism of IGF in the HAZs of Ti-Killed HSLA Steel

2014 ◽  
Vol 898 ◽  
pp. 161-163
Author(s):  
Dong Ming Duan ◽  
Meng Xia Tang ◽  
Run Wu ◽  
Yong Bu ◽  
Xiao Chen
Keyword(s):  
Electron Microscope ◽  
Driving Force ◽  
Hsla Steel ◽  
High Strength ◽  
Nucleation Mechanism ◽  
Titanium Oxides ◽  
Lattice Matching ◽  
Transmission Electron ◽  
Thermodynamic Driving Force ◽  
Inert Substrate

The weldability of the steel can be improved by formation of intra-granular ferrite (IGF) in heat affected zones (HAZs) on the edge of weld bead. The nucleation mechanism of IGF of Ti-killed high strength low alloyed (HSLA) steel has already been investigated with the aid of transmission electron microscope. Titanium oxides (Ti2O3) particles with the diameter of 0.4μm and Si-rich complex inclusions (Ti3O5+MnS) with that of 0.5μm can serve as the nuclei of IGF. The nucleation mechanism of IGF is proposed as follows: (1) inclusions are inert substrate. (2) The depletion of the austenite former Mn local to the inclusion increases the thermodynamic driving force of γα for transformation. (3) Lattice matching between inclusion and ferrite reduces the interfacial energy of opposing nucleation.

scholarly journals High Strength Nano Silica Based Concrete

2020 ◽  
Vol 9 (7) ◽  
pp. 1150-1155
Keyword(s):  
Electron Microscope ◽  
High Strength ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Hardened Concrete ◽  
Nano Silica ◽  
Nano Structure ◽  
Transmission Electron

There is a substantial curiosity in academia, the investment community and among manufacturers about the exhilarating opportunities offered by nano materials. Although a lot of applications for nanotechnology remain hypothetical, construction is one area where numerous ‘here and now’ applications have already emerged. While existing use is restricted, the market is likely to approach more than 500 million dollars within ten years. Concrete is most likely exceptional in the construction field, that it is the distinct material exclusive to business and hence, is the recipient of a reasonable quantity of research and development capital from the construction industry. SiO2 (Silica) usually is an integral part of concrete in the normal mix. On the other hand, one of the innovations made by the study of concrete at nano scale level is that particle stuffing in concrete can be enhanced by means of adding nano silica (NS), which results in the densification of the micro and nano structure of cementitious composite resulting in enhanced mechanical properties. In this research paper, the result of a thorough investigational analysis on the utilization of NS in addition to cement so that the strength and quality of concrete can improve has been achieved. The effect of various proportions of NS in concrete has been premeditated to evaluate the properties of NS based hardened concrete according to the standard concrete. The obtained outcomes after testing indicate that the addition of NS together with concrete has improved the mechanical behavior of concrete. The NS blended high strength concrete (HSC) shows a better compressive strength (CS) of 66.00 N/mm2 (MPa) after standard twenty eight days, which is an exceptional development over standard concrete. Each and every mixture containing NS in various proportions gave enhanced outcomes in comparison with the standard predictable concrete. RH (Rebound Hammer), UPV (Ultrasonic Pulse Velocity), SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope) examinations further authenticate the above results.

scholarly journals Investigation of Interfacial Layer for Friction Stir Scribe Welded Aluminum to Steel Joints

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Kaifeng Wang ◽  
Piyush Upadhyay ◽  
Yuxiang Wang ◽  
Jingjing Li ◽  
Xin Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Driving Force ◽  
Bond Formation ◽  
Welding Process ◽  
High Strength ◽  
Bimaterial Interface ◽  
Joint Interface ◽  
Friction Stir ◽  
Transmission Electron ◽  
Steel Joints

Friction stir scribe (FSS) welding as a recent derivative of friction stir welding (FSW) has been successfully used to fabricate a linear joint between automotive Al and steel sheets. It has been established that FSS welding generates a hook-like structure at the bimaterial interface. Beyond the hook-like structure, there is a lack of fundamental understanding on the bond formation mechanism during this newly developed FSS welding process. In this paper, the microstructures and phases at the joint interface of FSS welded Al to ultra-high-strength steel were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that both mechanical interlocking and interfacial bonding occurred simultaneously during the FSS welding process. Based on SEM observations, a higher diffusion driving force in the advancing side was found compared to the retreating side and the scribe swept zone, and thermally activated diffusion was the primary driving force for the interfacial bond formation in the scribe swept region. The TEM energy-dispersive X-ray spectroscopy (EDXS) revealed that a thin intermetallic compound (IMC) layer was formed through the interface, where the thickness of this layer gradually decreased from the advancing side to the retreating side owing to different material plastic deformation and heat generations. In addition, the diffraction pattern (or one-dimensional fast Fourier transform (FFT) pattern) revealed that the IMC layer was composed of Fe2Al5 or Fe4Al13 with a Fe/Al solid solution depending on the weld regions.

Large plasticity in magnesium mediated by pyramidal dislocations

Science ◽  
2019 ◽  
Vol 365 (6448) ◽  
pp. 73-75 ◽  
Author(s):  
Bo-Yu Liu ◽  
Fei Liu ◽  
Nan Yang ◽  
Xiao-Bo Zhai ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Electron Microscope ◽  
Plastic Strain ◽  
Crystal Size ◽  
High Stress ◽  
High Strength ◽  
High Plasticity ◽  
Transmission Electron ◽  
Small Crystal Size

Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for widespread applications is the limited ductility of magnesium, which has been attributed to 〈c+a〉 dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that 〈c+a〉 dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more 〈c+a〉 dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.

Study on Precipitation Behavior of High Strength Steel Plate Strengthened Complexly by Titanium and Molybdenum

2011 ◽  
Vol 217-218 ◽  
pp. 812-818
Author(s):  
Hong Bin Wang ◽  
Sheng Li Li ◽  
Li Li ◽  
Peng Cheng Ma
Keyword(s):  
Electron Microscope ◽  
Steel Plate ◽  
High Strength ◽  
Optical Microscope ◽  
Steel Plates ◽  
Transmission Electron ◽  
Cold Rolled ◽  
Hot Rolled ◽  
Hot Rolled Steel ◽  
Energy Disperse Spectroscopy

The precipitation behaviors of hot rolling and cold rolled annealing steel plates strengthened complexly by titanium and molybdenum were studied in the paper. The microstructures and precipitate phases were analyzed using optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) with energy disperse spectroscopy (EDS). The results showed that the coarsening square TiN phase and the fine roundness (Ti,Mo)C phase were precipitated mostly in the hot rolled steel plate. As the finishing temperature decreased and coiling holding time increased, the quantity of fine precipitates increased. And also the fine round precipitates increased, dispersion expanded and shape of the phase being uniformed as the annealing temperature increased. Therefore, the strengthen effects can be improved effectively by a reasonable control toward titanium and molybdenum precipitation behaviors.

Microstructure and Mechanical Properties of Twinning M/A Islands in a X100 High Strength Pipeline Steel

2017 ◽  
Vol 896 ◽  
pp. 182-189 ◽  
Author(s):  
Ji Ming Zhang ◽  
Qiang Chi ◽  
Ling Kang Ji ◽  
Hui Feng ◽  
Yan Hua Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
High Strength ◽  
Pipeline Steels ◽  
Transmission Electron ◽  
Fine Microstructure ◽  
X100 Pipeline Steel ◽  
Deformation Hardening

Fine microstructure of twinning Martensite/austenite (M/A) islands in a X100 high strength pipeline steel were analyzed by the scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM), and a uniaxial compressive experiment of micro-pillar for a twinning M/A island was conducted in present paper. The experimental results showed that M/A islands in X100 pipeline steels were consisted of retained austenite and nanoscale twins with sizes of less than ten nanometers. There were a few small blocks of nanoscale twins in an M/A island. Volume fraction of twinning M/A islands had an important effect on mechanical properties of X100 pipeline steels, with the increase of twinning M/A islands fraction, yield strength of X100 pipeline steel increased, and impact toughness of X100 pipeline steel decreased. The micro-pillar compression showed that the nanoscale twinning M/A island exhibited the higher deformation hardening during the compressive test, and its uniaxial compressive strength could up to 1.35GPa ultrahigh stress level.

scholarly journals Stem-EDX and FIB-SEM Tomography of ALLVAC 718Plus Superalloy

2016 ◽  
Vol 61 (2) ◽  
pp. 535-542 ◽  
Author(s):  
A. Kruk ◽  
G. Cempura ◽  
S. Lech ◽  
A. Czyrska -Filemonowicz
Keyword(s):  
Electron Microscope ◽  
Focused Ion Beam ◽  
Electron Tomography ◽  
Ion Beam ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Scanning Transmission Electron Microscope ◽  
Particle Analysis ◽  
Transmission Electron ◽  
Scanning Transmission

Abstract Allvac 718Plus (718Plus) is a high strength, corrosion resistant nickel- based superalloy used for application in power generation, aeronautics and aerospace industry. The 718Plus microstructure consists of a γ matrix with γ’-Ni3(Al,Ti) and some δ- Ni3Nb phases as well as lamellar particles (η-Ni3Ti, η*-Ni6AlNb or Ni6(Al,Ti)Nb) precipitated at the grain boundaries. The primary strengthening mechanism for this alloy is a precipitation hardening, therefore size and distribution of precipitates are critical for the performance of the alloy. The aim of this study was to characterize precipitates in the 718Plus superalloy using Scanning Transmission Electron Microscope combined with Energy Dispersive X-ray Spectroscopy (STEM-EDX) and Focused Ion Beam Scanning Electron Microscope (FIB-SEM). The STEM-EDX and FIB-SEM tomography techniques were used for 3D imaging and metrology of the precipitates. Transmission electron microscopy and EDX spectroscopy were used to reveal details of the 718Plus microstructure and allow determine chemical composition of the phases. The study showed that electron tomography techniques permit to obtain complementary information about microstructural features (precipitates size, shape and their 3D distribution) in the reconstructed volume with comparison to conventional particle analysis methods, e.g. quantitative TEM and SEM metallography

Influence of Carbon Content on the Microstructure and Precipitates of the V-N Microalloyed Steels

2011 ◽  
Vol 335-336 ◽  
pp. 645-649
Author(s):  
Jia Yan Ma ◽  
Xian Zhong Zhang ◽  
Yun Guan ◽  
Zhao Jun Deng
Keyword(s):  
Electron Microscope ◽  
Carbon Content ◽  
Driving Force ◽  
Local Area ◽  
Microalloyed Steels ◽  
Cooling Process ◽  
Intragranular Ferrite ◽  
Transmission Electron ◽  
Ferrite Nucleation ◽  
Strength Effect

The microstructure and precipitates of the V-N microalloyed steels whose carbon content were respectively 0.27% and 0.35%, were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that the microstructures of the test steels are all composed of ferrite and pearlite, the area percent of ferrite decreases from 49% to 40% and the grain size also descends from 8.96μm to 8.61μm with the increase of carbon content. TEM results show that the precipitates in two kinds of steels all include a large amount of 10~20nm dispersion distribution irregular flake VC, the part of fibrous VC that grows toward to intragranular ferrite along the grain boundary in the local area, and only a small amount of spherical VN or V (C, N). When the carbon content increases from 0.27% to 0.35%, the number of the spherical VN or V(C,N) increases obviously and the size of it varies from 20~100nm to 45~105nm, while the number of flake VC and fibrous VC decreases significantly and the length of fibrous VC shortens from several micrometers to nanometer size. Experimental results indicate that most of the spherical VN or V (C, N) firstly appear in austenite, then the flake VN and fibrous VN with precipitation strength effect emerge in ferrite during the following γ→α transformation and cooling process. The increase of carbon content can lead to the increase of driving force that VN or V (C, N) firstly appear in austenite, which results in the significant increase of ferrite nucleation rate and the refinement of microstructure.

Microstructure and Stabiulty of TiB2 and Cu Multilayers

1990 ◽  
Vol 187 ◽  
Author(s):  
S. N. Basu ◽  
K. M. Hubbard ◽  
J-P. Hirvonen ◽  
T. E. Mitchell ◽  
M. Nastasi
Keyword(s):  
Driving Force ◽  
Multilayer Structure ◽  
Maximum Dose ◽  
Ion Irradiation ◽  
High Strength ◽  
Interfacial Reactions ◽  
Interfacial Stability ◽  
Thermodynamic Driving Force

AbstractThe Interfacial stability of a high strength TiB2/Cu multilayer structure was examined by subjecting the layers to ion irradiation by 400 keV Ne++ ions up to a maximum dose of 12×1015 ions/cm2. Even at the highest dose, with a maximum dpa value of 4.92, the TiB2/Cu interface did not show any mixing. This stability of the multilayers has been explained by examining the maximum thermodynamic driving force for Interfacial reactions in this system.

scholarly journals Characterization by Electron Diffraction of Two Thermodynamical Phases of Precipitation in Nb-Microalloyed Steels

2005 ◽  
Vol 480-481 ◽  
pp. 489-494 ◽  
Author(s):  
Manuel Gómez ◽  
S.F. Medina ◽  
Pilar Valles ◽  
Alberto Quispe
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Electron Diffraction Study ◽  
High Strength ◽  
Lattice Parameters ◽  
Microalloyed Steels ◽  
Mean Values ◽  
Transmission Electron ◽  
Analytical System

Excellent mechanical properties (high strength and toughness) of microalloyed steels are mainly caused by induced precipitation during thermomechanical treatment (TMT) and grain refinement. It has been recently found that TMT of Nb-microalloyed steels can give rise to two different kinds of precipitates, manifested by the double plateau in the statically recrystallised fraction (Xa) against time curves. This work presents an electron diffraction study performed in a transmission electron microscope, equipped with an EDS analytical system. Lattice parameters of a great deal of particles, smaller than 200 nm and with face cubic centred structure, have been measured. Frequency distribution of the values of lattice parameters shows that these are grouped in two sets whose mean values are close. Comparison of these values with those found in the literature for carbides, nitrides and carbonitrides usually present in microalloyed steels demonstrates that they are Nb carbonitrides with slight stoichiometric differences (NbCxNy).

scholarly journals High-resolution Transmission Electron Microscopy Characterization of the Structure of Cu Precipitate in a Thermal-aged Multicomponent Steel

2019 ◽  
Vol 32 (1) ◽  
Author(s):  
Lizhan Han ◽  
Qingdong Liu ◽  
Jianfeng Gu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Hsla Steel ◽  
Structural Evolution ◽  
High Strength ◽  
Transmission Electron ◽  
Alloy Steels ◽  
Bearing Alloy ◽  
Crystallographic Defects

Abstract High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening, and whereas usually lead to degraded toughness for especially ferritic steels. Hence, it is important to understand the formation behaviors of the Cu precipitates. High-resolution transmission electron microscopy (TEM) is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy (HSLA) steel. The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations. The Cu precipitates in the same aging condition have various structure of BCC, 9R and FCC, and the structural evolution does not greatly correlate with the actual sizes. The presence of different structures in an individual Cu precipitate is observed, which reflects the structural transformation occurring locally to relax the strain energy. The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe–Cu alloys with Ni or Mn additions. This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.

Sign in / Sign up

Export Citation Format

Share Document