scholarly journals Effects of B on the Hot Ductility of Fe-36Ni Invar Alloy

2019 ◽  
Vol 38 (2019) ◽  
pp. 380-388 ◽  
Author(s):  
Yaxu Zheng ◽  
Fuming Wang ◽  
Changrong Li ◽  
Zhanbing Yang ◽  
Yutian He
Keyword(s):  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Secondary Phase ◽  
Grain Boundary Sliding ◽  
Hot Ductility ◽  
Temperature Range ◽  
Area Reduction ◽  
The Poor ◽  
Thermo Calc Software ◽  
Bearing Alloy

AbstractThis work conducted systematic studies on the effect of B on the hot ductility behavior of Fe-36Ni alloy over the temperature range of 900–1,200 °C by use of Gleeble-3500 thermal simulator, Thermo-Calc software, transmission electron microscopy and secondary ion mass spectroscopy. The influencing factors and mechanisms are also discussed in the present work. Results show that all the values of area reduction of the investigated alloy samples are below 60 % in the temperature range of 900–1,000 °C, indicating the poor hot ductility of the investigated alloys in this temperature range. When the grain boundary sliding occurs during the hot tensile processes, the fine secondary phase particles at grain boundaries prevent the occurrence of dynamic recrystallization and promote the nucleation and propagation of cracking simultaneously, resulting in the poor hot ductility of the investigated alloys in this temperature range. In the B bearing alloy, the segregation of B atoms around austenite grain boundaries promotes the solute dragging effects at grain boundaries and strongly inhibits the occurrence of dynamic recrystallization, which increases the brittle temperature to 1,000 °C. When the temperature exceeds 1,050 °C, the occurrence of dynamic recrystallization improves the hot ductility significantly. However, the coarsening of recrystallized grains and the formation of inter dendritic cracks decrease the hot ductility of the alloy gradually when the temperature increases from 1,100 °C to 1,200 °C.

Effect of Rare Earth Yttrium on the Hot Ductility of Fe-36Ni Invar Alloy

2014 ◽  
Vol 33 (6) ◽  
pp. 531-537 ◽  
Author(s):  
Y. C. Yu ◽  
H. T. Liu ◽  
W. Q. Chen ◽  
H. G. Zheng
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Testing Temperature ◽  
Grain Boundary Sliding ◽  
Substantial Improvement ◽  
Grain Structure ◽  
Invar Alloy ◽  
Hot Ductility ◽  
Temperature Range ◽  
Boundary Sliding

AbstractThe hot ductility of Fe-36Ni invar alloy doped with and without yttrium was investigated using a Gleeble-3800 thermal-mechanical simulator over the temperature range 850–1050 °C and the improvement mechanism of the hot ductility was analysed with a combination of SEM, EDS and OM. The results showed that Fe-36Ni invar alloy had a poor hot ductility below 1050 °C, which was mainly attributed to the presence of the grain boundary sliding and weak grain boundaries. The addition of 0.048% yttrium had a substantial improvement in the hot ductility of Fe-36Ni invar alloy over the whole testing temperature range especially at 950–1000 °C. At 850–900 °C, the improvement of the hot ductility was mainly associated with the grain boundary strengthening and the restriction of the grain boundary sliding because the addition of yttrium could reduce the segregation of sulfur at grain boundaries and refine the grain structure. At 950–1000 °C, the hot ductility was highly improved, which was owed to the acceleration and occurrence of dynamic recrystallization as a result of the refinement of the grain structure by addition of yttrium.

Influence of Ti on the Hot Ductility of High-manganese Austenitic Steels

2017 ◽  
Vol 36 (7) ◽  
pp. 725-732
Author(s):  
Hongbo Liu ◽  
Jianhua Liu ◽  
Bowei Wu ◽  
Xiaofeng Su ◽  
Shiqi Li ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Austenitic Steel ◽  
Testing Machine ◽  
Constant Strain Rate ◽  
Austenitic Steels ◽  
Hot Ductility ◽  
High Manganese ◽  
Thermo Calc Software ◽  
Simulation Testing ◽  
Ti Addition

AbstractThe influence of Ti addition (~0.10 wt%) on hot ductility of as-cast high-manganese austenitic steels has been examined over the temperature range 650–1,250 °C under a constant strain rate of 10−3 s−1 using Gleeble3500 thermal simulation testing machine. The fracture surfaces and particles precipitated at different tensile temperatures were characterized by means of scanning electron microscope and X-ray energy dispersive spectrometry (SEM–EDS). Hot ductility as a function of reduction curves shows that adding 0.10 wt% Ti made the ductility worse in the almost entire range of testing temperatures. The phases’ equilibrium diagrams of precipitates in Ti-bearing high-Mn austenitic steel were calculated by the Thermo-Calc software. The calculation result shows that 0.1 wt% Ti addition would cause Ti(C,N) precipitated at 1,499 °C, which is higher than the liquidus temperature of high-Mn austenitic steel. It indicated that Ti(C,N) particles start forming in the liquid high-Mn austenitic steel. The SEM–EDS results show that Ti(C,N) and TiC particles could be found along the austenite grain boundaries or at triple junction, and they would accelerate the extension of the cracks along the grain boundaries.

Effect of Mn/S Ratio on the Hot Ductility of Eco-friendly Bi-S based Free Cutting Steel

2014 ◽  
Vol 33 (6) ◽  
pp. 553-561 ◽  
Author(s):  
Haitao Liu ◽  
Yanchong Yu ◽  
Weiqing Chen ◽  
Qingxian Wang ◽  
Guangshun Wang
Keyword(s):  
Melting Point ◽  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Hot Rolling ◽  
Crack Development ◽  
Hot Ductility ◽  
Secondary Phases ◽  
Temperature Range ◽  
Fe Content ◽  
Formation Of Cracks

AbstractThe hot ductility of eco-friendly Bi-S based free cutting steels with different Mn/S ratios was studied using a Gleeble-1500 thermal–mechanical simulator. The hot ductility of the steel was found to depend on the Mn/S ratio, and the Mn/S ratio of the steel should be greater than 3.5 for hot rolling of billets without crack development. The low Mn/S ratio would inhibit the occurrence of the dynamic recrystallization and cause the formation of the low melting point sulfide Fe-rich (Fe,Mn)S as secondary phases, which could obviously reduce the strength of the grain boundary and resulted in the formation of cracks along the grain boundary. The higher the Mn/S ratio in the steel, the lower the Fe content in the Fe-rich (Fe,Mn)S phases. When the Mn/S ratio in the steel was high enough, the sulfide phases in the steel were mainly MnS as primary inclusions and the low melting point sulfide phases could be effectively avoided forming. While the Mn/S ratio could influence the hot ductility of the steel over the whole temperature range of 900–1200 °C, the segregation of bismuth along grain boundary could be harmful to the hot ductility in addition to the lower Mn/S ratio for the temperature was no more than 1050 °C.

Phase mixing in upper mantle shear zones: Olivine nucleation during dynamic recrystallization of orthopyroxene and clinopyroxene porphyroclasts

2020 ◽  
Author(s):  
Sören Tholen ◽  
Jolien Linckens
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Upper Mantle ◽  
Shear Zones ◽  
Grain Boundary Sliding ◽  
Diffusion Creep ◽  
Phase Assemblage ◽  
Secondary Phases ◽  
Phase Mixing

<p>Small grain size and a well-mixed phase assemblage are key features of upper mantle (ultra)mylonitic layers. In those layers, Zener pinning inhibits grain growth, which could lead to diffusion creep. This increases the strain rate for a given stress significantly. Prerequisite is phase mixing which can occur by dynamic recrystallization (dynRXS) plus grain boundary sliding (GBS), metamorphic or melt/fluid-rock reactions, creep cavitation plus nucleation, or by a combination of those processes. In order to get insights into the interplay of phase mixing and dynRXS we investigate microfabrics (EBSD, optical microscopy) displaying the transition from clasts to mixed assemblages. Samples are taken from the Lanzo peridotite shear zone (Italy).</p><p>Olivine dynamically recrystallizes from protomylonitic to ultramylonitic samples. Its grain size varies systematically between monomineralic (~20µm) and polymineralic layers (~10µm). Olivine is the dominant mixing phase for both, dynamically recrystallizing orthopyroxene (ol~55vol.%) and clinopyroxene clasts (ol~45vol.%). In contrast, recrystallizing olivine clasts show little evidence of phase mixing. In phase mixtures, olivine neoblasts show weak (J-index ~1.8) C-Type and weak (J-Index ~1.5) B-type CPO’s. Both types suggest the presence of water during deformation.</p><p>Isolated, equiaxial orthopyroxene clasts are present in all samples. DynRXS of opx starts in mylonites. Some clasts and tips of extensively elongated opx bands (max. axial ratios 1:50) are bordered by fine-grained (min. ECD~5µm) mixtures of olivine, opx ± anorthite/ cpx/ pargasite. Mixing intensities seem to depend on the connection to the olivine-rich matrix. Clast grain boundaries are highly lobate with indentations of secondary phases (mostly olivine). Opx neoblasts have no internal deformation and show large misorientations close to their host clast (misorientation angle >45° at ~20µm distance). Their grain shape is either flat and elongated or equiaxial. Both shapes have lobate boundaries. Their CPO depends on the host clast orientation. In ultramylonites, opx bands disappeared completely.</p><p>Clinopyroxene porphyroclasts dynamically recrystallize in protomylonite to ultramylonite samples. Olivine is the dominant mixing phase (~45vol.%). Cpx mixed area grain sizes tend to be coarser (~10µm) than in corresponding opx areas (~6µm). Ultramylonitic cpx-ol assemblages have a higher mixing percentage (phase boundaries/grain boundaries ~70%) than mylonitic assemblages (~40%). In the mylonitic layers, clusters of cpx neoblasts form ‘walls’ parallel to their host grain borders. Olivine neoblasts between these clusters show no CPO. The overall cpx CPO varies from [001] perpendicular and [010] parallel to the foliation with (J -Index ~2.5) to [100] perpendicular and [001] parallel to the foliation (J-Index ~1.2).</p><p>Beside few thoroughly mixed areas, bands of cpx+ol and of opx+ol are still distinguishable in ultramylonitic layers. This suggests their origin to be dynamically recrystallized opx and cpx clasts. Therefore, phase mixing is assumed to occur simultaneously to clast recrystallization. Beside a small gradient of opx/cpx abundance depending on the distance from their host clast there is little evidence for phase mixing by dynRXS+GBS only. High abundances of olivine neoblasts at grain boundaries of recrystallizing clasts and their instant mixed assemblage with host phase neoblasts suggest phase mixing being strongly dependent on olivine nucleation during dynRXS of opx and cpx.</p>

Effects of Rare Earth Lanthanum on the Solidification Structure and Hot Ductility of Fe-43Ni Expansion Alloy

2018 ◽  
Vol 37 (3) ◽  
pp. 261-269 ◽  
Author(s):  
Y. C Yu ◽  
S. H Zhang ◽  
H Li ◽  
S. B Wang
Keyword(s):  
Rare Earth ◽  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Size Distribution ◽  
Intermetallic Compounds ◽  
Testing Temperature ◽  
Solidification Structure ◽  
Hot Ductility ◽  
Temperature Range ◽  
Lanthanum Content

AbstractEffects of lanthanum content on the solidification structure and the hot ductility of Fe-43Ni expansion alloy were investigated, the corresponding mechanisms were also discussed. The results showed that the macrostructures of the alloys were first significantly refined with increasing lanthanum content in the range of 0~0.025 % and then became coarse again with lanthanum content up to 0.04 %. La2O2S inclusions can serve as the effective inclusions sites promoting the refinement of the macrostructures. The changes of the macrostructures were influenced by the quantity density and the size distribution of La2O2S inclusions. The addition of 0.01–0.025 % lanthanum can improve the hot ductility over the whole testing temperature range, especially at 1000–1050 °C. The improvement of the hot ductility was mainly associated with the grain boundary strengthening and the acceleration of dynamic recrystallization by adding lanthanum. With addition of 0.04 % lanthanum, the hot ductility of the alloy became deteriorated, which was owed to the presence of brittle Fe-Ni-La intermetallic compounds.

scholarly journals Microstructure Evolution of a High Nb Containing TiAl Alloy with (α2 + γ) Microstructure during Elevated Temperature Deformation

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 916 ◽  
Author(s):  
Yudong Chu ◽  
Jinshan Li ◽  
Lei Zhu ◽  
Yan Liu ◽  
Bin Tang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Lattice Rotation ◽  
Dislocation Creep ◽  
Temperature Deformation ◽  
Texture Intensity ◽  
Compression Deformation ◽  
Boundary Sliding

In order to verify the correctness of the transition of deformation mechanism with the change in deformation parameters and to reveal the types and mechanism of dynamic recrystallization of γ grains during compression deformation, microstructure characterization of Ti-43.5Al-8Nb-0.2W-0.2B (at. %) alloy after isothermal compression deformation were performed. When the alloy was deformed at 1000 °C/10−2 s−1, the initial γ grains are elongated and significantly refined and the fraction of low angle grain boundaries (LAGB) of γ grains is obviously increased and the texture intensity remains unchanged, which indicates that the compression deformation in dislocation creep region is dominated by intragranular deformation and dynamic recrystallization (DRX) of γ grains. Besides, the lattice rotation at grain boundary serrations may be responsible for the nucleation of new recrystallized γ grains, and the following growth process may be achieved by the migration of γ grain boundaries. However, when the alloy deformed at 1050 °C/10−4 s−1 and 1000 °C/10−4 s−1, the γ grains maintain equiaxed shapes and distribute more uniformly and the fraction of LAGB of γ grains is slightly raised and the texture sharpness decreases, which indicates that the compression deformation in grain boundary sliding (GBS) region is mainly controlled by GBS of γ grains and DRX occurs simultaneously within some coarse γ grains.

Characteristics of Embrittlement in Weather Resistant Steel in Austenite and γ-Ferrite Temperature Range

2011 ◽  
Vol 704-705 ◽  
pp. 847-852
Author(s):  
Xing Jian Gao ◽  
Deng Fu Chen ◽  
Li Wei Song ◽  
Hui Hu ◽  
Xing Lei Yang ◽  
...  
Keyword(s):  
Tensile Deformation ◽  
Flow Behavior ◽  
Strain Analysis ◽  
Casting Process ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Hot Ductility ◽  
Resistant Steel ◽  
Stress Strain ◽  
Temperature Range

The embrittlement of particular weather resistant steel has been investigated by thermal tensile tests using a Gleeble-1500D system at temperatures range from 600 to 1300°C and at a strain rate of 10-3/s. The specimen was reheated and cooled to the test temperature before the tensile deformation in order to get the mechanical properties subject to the continuous casting process. To make clear the plastic flow behavior in Austenite and γ-Ferrite temperature range of the weather resistant steel, the tensile tests were performed and the results indicate that the stress-strain curves as a function of temperature and with the temperature increased the stress became less, while the hot ductility changed significantly due to the work hardening and recrystallization. All of the strength indices (including yield strength, tensile strength and fracture strength) of the steel increased gradually with decreasing temperature, except for small fluctuations during the γ→α transformation occurred. Special emphases were placed on the hot ductility to clarify the sensitivity of surface cracking during unbending operation and the embrittlement zone occurred in the temperature range between 750 and 1050°C, in which the minimum %R of A was around 22% at 850°C. In the embrittlement zone, the specimens were fractured with little plastic deformation by either grain boundary sliding or by localization of strain in the film proeutectoid ferrite produced by the γ→α transformation. Keywords: Weather Resistant Steel, Embrittlement Zone, Stress-Strain Analysis, Hot Ductility, Fracture Surface.

Hot Ductility of 20Cr13 Steel at High Temperature

2017 ◽  
Vol 898 ◽  
pp. 778-782
Author(s):  
Fan Zhao ◽  
Ning Bo Zhou ◽  
Guang Lei Liu ◽  
Zhi Lin Wang ◽  
Ya Zheng Liu
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Hot Ductility ◽  
Temperature Range ◽  
Area Reduction ◽  
Tensile Process ◽  
Micro Hole ◽  
Two Phases ◽  
Fracture Morphologies ◽  
Scanning Electron

Hot ductility of 20Cr13 steel at high temperature was investigated through tensile test. The main phases of the steel in temperature range of 600-1400 °C were calculated with thermodynamic software. The fracture morphologies and microstructure were observed by scanning electron microscopy. The steel showed good hot ductility in temperature range of 1000-1200 °C, and the area reduction was 82 % or more. In temperature range of 800-950 °C, the M23C6 precipitated at the grain boundary of austenite, and it fractured in the tensile process. Thus the micro-crack or micro-hole formed at the grain boundary of austenite, and the area reduction was 52-68 %. The ferrite precipitated at 800 or 1250 °C, and the micro-voids formed at interface of ferrite and austenite because of the discordant deformation of two phases, which was harmful to hot ductility. Moreover, quasi-cleavage fracture happened at 800 °C because of the ferrite cleavage, which further decreased hot ductility of the steel.

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

scholarly journals Microstructural evolution during high-temperature tensile creep at 1,500°C of a MoSiBTiC alloy

2020 ◽  
Vol 39 (1) ◽  
pp. 136-145 ◽  
Author(s):  
Sojiro Uemura ◽  
Shiho Yamamoto Kamata ◽  
Kyosuke Yoshimi ◽  
Sadahiro Tsurekawa
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Grain Boundary Sliding ◽  
Primary Creep ◽  
Tensile Creep ◽  
Tertiary Creep ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic ◽  
Creep Regime

AbstractMicrostructural evolution in the TiC-reinforced Mo–Si–B-based alloy during tensile creep deformation at 1,500°C and 137 MPa was investigated via scanning electron microscope-backscattered electron diffraction (SEM-EBSD) observations. The creep curve of this alloy displayed no clear steady state but was dominated by the tertiary creep regime. The grain size of the Moss phase increased in the primary creep regime. However, the grain size of the Moss phase was found to remarkably decrease to <10 µm with increasing creep strain in the tertiary creep regime. The EBSD observations revealed that the refinement of the Moss phase occurred by continuous dynamic recrystallization including the transformation of low-angle grain boundaries to high-angle grain boundaries. Accordingly, the deformation of this alloy is most likely to be governed by the grain boundary sliding and the rearrangement of Moss grains such as superplasticity in the tertiary creep regime. In addition, the refinement of the Moss grains surrounding large plate-like T2 grains caused the rotation of their surfaces parallel to the loading axis and consequently the cavitation preferentially occurred at the interphases between the end of the rotated T2 grains and the Moss grains.

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