Evolution in Dislocation Configuration of Deformed Fe-40Ni-Ti Alloy during Isothermal Relaxation

2014 ◽  
Vol 609-610 ◽  
pp. 515-520 ◽  
Author(s):  
Shao Qiang Yuan ◽  
Xiao Juan Zhang
Keyword(s):  
Relaxation Curve ◽  
Ti Alloy ◽  
Precipitation Behavior ◽  
Simulation Test ◽  
Dislocation Configuration ◽  
Pinning Effect ◽  
Transmission Electron ◽  
Perfect Dislocation ◽  
Dislocation Cells ◽  
Three Stages

The thermo-simulation test and transmission electron microscopy (TEM) were applied to investigate the evolution of dislocation configuration and strain induced precipitation behavior during relaxation at 850°C in a deformed Fe-40Ni-Ti alloy. The stress relaxation curve can be divided into three stages, namely, the process of incubation, nucleation and growth, and the coarsening of strain-induced precipitates. The highly dense and twisted dislocations formed during the deformation develop into dislocation cells and finally, the sub-grains can be observed when relaxing to 1000s. The strain induced precipitates occur both onto the dispersed dislocations and dislocation cells. The precipitates pin the dislocations which results in retarding the progress of dislocation configuration evolution. As precipitates start to coarsen, the pinning effect weakens and the dislocations get rid of the pinning though bypassing mechanism. Adopting the same simulation test to bainitic steel, the optimum refinement could be obtained at 60-200s during relaxation processing, corresponding to the perfect dislocation cells formation of Fe-40Ni-Ti alloy.

Investigation on Dissolving and Strain Induced Precipitation Behavior in Nb-Bearing Microalloyed Steel

2011 ◽  
Vol 109 ◽  
pp. 3-6
Author(s):  
Shao Qiang Yuan ◽  
Guo Li Liang ◽  
Hui Bin Wu
Keyword(s):  
Relaxation Time ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Microalloyed Steel ◽  
Thermal Simulation ◽  
Holding Time ◽  
The Other ◽  
Precipitation Behavior ◽  
Simulation Test ◽  
Transmission Electron

Thermal simulation test, TEM(Transmission Electron Microscope) and nanobeam EDS techniques were used to investigate the dissolving and precipitation behavior in Nb-bearing mciroalloyed steel. The experimental results indicate that: there are two families of precipitates in the as forged samples. The larger precipitates of Nb(C,N) disappear after being held for 2h at 1300°C,while the inclusions of MnS formed from the solidification even remain for 48h held at that temperature. After 30% of predeformtion at 850°C and 900°C, the strain-induced precipitation occurs, that is, the other tiny precipitates. Compared with the samples relaxed at 850°C, the ones that are held at 900°C show larger particles by same holding time but demonstrate the same size when the relaxation time reaches 1000s.

Strain-Induced Precipitation in Nb-Bearing Low Carbon Multi-Microalloyed Steel

2010 ◽  
Vol 97-101 ◽  
pp. 560-564 ◽  
Author(s):  
Shao Qiang Yuan ◽  
Guo Li Liang ◽  
Xiao Juan Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Relaxation Process ◽  
Microalloyed Steel ◽  
Low Carbon ◽  
Precipitation Behavior ◽  
Simulation Test ◽  
Transmission Electron

Thermo-simulation test, transmission electron microscopy(TEM) and nanobeam EDS technique were used to investigate the strain induced precipitation behavior during relaxation process after deformed austenite in Mn-Mo-Nb-B low carbon multi-microalloyed Steel. The experiment results indicate that during isothermal held at 850 °Cand 900 °C after predeformation, the size of precipitates occurred in the Mn-Mo-Nb-B steel at different stage is smaller than that happened in the only Nb and Ti-bearing microalloyed steel. The ratio of Nb/Ti to precipitates increased with the relaxing time. After being held longer, Mo atoms would enter the lattice of (Nb,Ti)(C,N) precipitates and the amount in the precipitates increased with the relaxation as time prolonged.

Investigation on the Grain Growth of Fe-40Ni-Ti Austenitic Steel in Heating Process

2014 ◽  
Vol 788 ◽  
pp. 272-276 ◽  
Author(s):  
Shao Qiang Yuan ◽  
Xiao Juan Zhang ◽  
Yue Hui Yang ◽  
Guo Li Liang
Keyword(s):  
Grain Growth ◽  
Room Temperature ◽  
Optical Microscope ◽  
Growth Behavior ◽  
Heating Process ◽  
Dislocation Configuration ◽  
Transmission Electron ◽  
The Matrix ◽  
Dislocation Cells ◽  
Grain Growth Behavior

Fe-40Ni alloy, keeping face-centred cubic structure (FCC) at room temperature, possesses similar stacking fault energy to that of austenite in steels at wide temperatures. The grain growth behavior of Fe-40Ni-Ti alloy at high temperatures was investigated by optical microscope and transmission electron microscopy (TEM). The results show that the grains grow very slowly from 880°C to 1160°C at holding time of 150min. At about 1220°C, the grain growing tendency can be clearly observed. At 1300°C, the rain size increases rapidly and coarsens when hold for 30min.TiN precipitates forms during the solidification and and strain induced precipitates can dissolve into the matrix, resulting in the grain boundaries moving easily. The evolution of dislocation configuration is retarded by the strain induced precipitates, which enhances the stabilization of dislocation cells.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

Precipitation in Al-Li-Cu Alloys

1981 ◽  
Vol 39 ◽  
pp. 44-45
Author(s):  
J. E. O'Neal ◽  
K. K. Sankaran
Keyword(s):  
Electron Microscopy ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Zone Formation ◽  
Specific Strength ◽  
Hardening Behavior ◽  
Cu Alloys ◽  
High Specific Strength ◽  
Transmission Electron ◽  
Structural Applications

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

Carbo-Nitride Precipitation in Tempered Martensite - Computer Simulation and Experiment

2012 ◽  
Vol 706-709 ◽  
pp. 1586-1591 ◽  
Author(s):  
Sabine Zamberger ◽  
Ernst Kozeschnik
Keyword(s):  
Computer Simulation ◽  
Precipitation Behavior ◽  
Tempered Martensite ◽  
Extraction Replica ◽  
Transmission Electron ◽  
Simulation And Experiment ◽  
Precipitate Microstructure ◽  
Means Of Transmission ◽  
Quenched And Tempered Steel ◽  
Good Agreement

In the present work, the precipitation behavior of a V-microalloyed, quenched and tempered steel with 0.3wt % C is investigated experimentally and by computer simulation. The specimens are analyzed by means of transmission electron microscopy using selected area diffraction (SAD) and energy dispersive x-ray spectroscopy (EDX). The analysis is done on electropolished foils and on extraction replica. The numerical simulation is performed with the thermokinetic software package MatCalc, where the precipitation kinetics is examined for the experimentally applied thermo-mechanical cycles. Good agreement between experiment and simulation is obtained and the experimentally observed precipitate microstructure can be well explained on the basis of these simulations.

Effect of Final Rapid Cooling Temperature on Ultra-Fine Carbides of Ti-Mo Ferrite Matrix Microalloyed Steel

2018 ◽  
Vol 926 ◽  
pp. 3-10
Author(s):  
Zhi Chen Yu ◽  
Zhen Li Mi ◽  
Qing Wu Cai ◽  
Jin Guo ◽  
Na Gong
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Microalloyed Steel ◽  
Ferrite Matrix ◽  
Precipitation Behavior ◽  
Rapid Cooling ◽  
Cooling Temperature ◽  
Interphase Precipitation ◽  
Transmission Electron ◽  
Scanning Electron

The size and distribution of nanoscale precipitate particles in Ti-Mo ferrite matrix microalloyed steel under three different final rapid cooling temperatures were studied by scanning electron microscopy(SEM), transmission electron microscope(TEM) and microhardness test. The results show that the interphase precipitation could be weakened by the excessive final rapid cooling temperature. A higher supersaturated solid solubility and high-density dislocation in ferrite matrix can be obtained under a relatively lower final rapid cooling temperature, which makes it easier to precipitate in ferrite. The related thermodynamic analysis indicated that the precipitation behavior was influenced by the final rapid cooling temperature during austenite/ferrite region. It is not conducive to get a large amount of small size precipitates in Ti-Mo ferrite matrix microalloyed steel when the final rapid cooling temperature is too high or low.

scholarly journals Influence of Inclusions on the Mechanical Properties of RAFM Steels Via Y and Ti Addition

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 851 ◽  
Author(s):  
Qiu ◽  
Zhan ◽  
Li ◽  
Yang ◽  
Qi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Oxide Particle ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Pinning Force ◽  
Impact Properties ◽  
Pinning Effect ◽  
Austenite Grain ◽  
Transmission Electron ◽  
Rafm Steel

The effects of the Y- and Ti-containing inclusions on the tensile and impact properties of reduced activation ferritic martensitic (RAFM) steels were evaluated. Four steels with different Y and Ti contents were produced via vacuum induction melting. The size and quantity of inclusions in the steels were analyzed using scanning electron microscopy, and the oxide particle formation mechanism was clarified. These inclusions helped to enhance the pinning effect of the austenite grain boundaries based on the Zener pinning force. The average prior austenite grain sizes, measured via the linear intercept method, were 12.34 (0 wt.% Ti), 9.35 (0.010 wt.% Ti), 10.22 (0.030 wt.% Ti), and 11.83 (0.050 wt.% Ti) μm for the four steels, in order of increasing Ti content, respectively. Transmission electron microscopy was conducted to observe the fine carbides. The strength and impact properties of the steel containing 0.010 wt.% Ti were improved, and the ductile-to-brittle-transition temperature was reduced to −70.5 °C. The tensile strength and impact toughness of the steel with 0.050 wt.% Ti were significantly reduced due to the coarsening of both the inclusions and grain size, as well as the precipitation of large TiN inclusions. The RAFM steel with approximately 0.015 wt.% Y and 0.010 wt.% Ti exhibited an optimized combination of microstructures, tensile properties, and impact properties among the four steels.

scholarly journals Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 901
Author(s):  
Shitian Su ◽  
Jixue Zhou ◽  
Shouqiu Tang ◽  
Huan Yu ◽  
Qian Su ◽  
...  
Keyword(s):  
Mechanical Milling ◽  
Sem Analysis ◽  
Submicron Particles ◽  
X Ray Diffraction ◽  
Az91 Magnesium Alloy ◽  
Magnesium Matrix ◽  
Pinning Effect ◽  
Sic Particles ◽  
Transmission Electron ◽  
Az91 Magnesium

The development of a magnesium matrix composite with a high content of dispersions using conventional liquid-phase process is a great challenge, especially for nanometer/submicron particles. In this work, mechanical milling was employed to prepare nanocrystalline AZ91 dispersed with 15 vol.% submicron SiC particles (SiCp/AZ91). AZ91 with no SiCp was applied as a comparative study with the same mechanical milling. In order to investigate the mechanism of dispersing, the morphology evolution of powders and the corresponding SiCp distribution were observed. As the scanning electron microscope (SEM) analysis exhibited, the addition of SiCp accelerated the smashing of AZ91 particles, which promoted the dispersion of SiCp in AZ91. Thus, after mechanical milling, 15 vol.% SiCp, which was smashed from 800 to 255 nm, got uniformly distributed in the Mg matrix. Based on X-ray diffraction (XRD) results, part of the Mg17Al12 precipitate got dissolved, and an Al-supersaturated Mg solid solution was formed. The transmission electron microscopy (TEM) results showed that the ultimate Mg grain (32 nm) of milled SiCp/AZ91 was much smaller than that of milled AZ91 (64 nm), which can be attributed to a pinning effect of submicron SiCp. After mechanical milling, the hardness of SiCp/AZ91 reached 185 HV, which was 185% higher than the original AZ91 and 33% higher than milled AZ91, due to fine Mg grain and submicron dispersions.

The Grain Growth of Austenitic Model Steel during Fast Heating

2014 ◽  
Vol 644-650 ◽  
pp. 4772-4775
Author(s):  
Shao Qiang Yuan ◽  
Guo Li Liang ◽  
Yue Hui Yang
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Ti Alloy ◽  
Parent Metal ◽  
Simulation Test ◽  
Fast Heating ◽  
Metallographic Observation ◽  
Welding Line ◽  
Quantitative Statistics ◽  
Different Parts

The metallographic observation, thermo-simulation test and quantitative statistics were used to investigate the grain growth on different parts of the samples for Fe-40Ni-Ti alloy. The experiment results demonstrate that: near the center of the sample corresponding to the summit point of the temperature, the grain grows rapidly in 5s when the temperature reaches 1350°C, whose size is about 180μm; While the grain size of parent metal and HAZ (4mm to the welding line) remains nearly unchanged, whose size is about 80μm. The size of TiN particles in the welding line is fine than that of the parent metal obviously and the hinder to the grain boundaries can be observed. With the aid of Fe-40Ni-Ti alloy, the austenitic grain growth in the steel can be simulated.

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