scholarly journals Influence of β-Stabilizers on the α-Ti→ω-Ti Transformation in Ti-Based Alloys

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1135
Author(s):  
Askar Kilmametov ◽  
Alena Gornakova ◽  
Mikhail Karpov ◽  
Natalia Afonikova ◽  
Anna Korneva ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Room Temperature ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Bulk Diffusion ◽  
Eutectoid Decomposition ◽  
Next Generation ◽  
Alloying Element ◽  
Ti Alloys ◽  
Ω Phase

The development of next generation Ti-based alloys demand completely new processes and approaches. In particular, the Ti-alloys of next generation will contain not only α-Ti and β-Ti phases, but also small amounts of ω-phase and intermetallic compounds. The β→ω phase transformation induced by high-pressure torsion (HPT) has been studied in detail recently. In this work, we investigated the HPT-induced α→ω phase transformation. For this purpose, we added various β-stabilizers into α-Ti matrix of studied Ti-alloys. Ti-alloys with 4% Fe, 2% Cr, 3% Ni, and 4% Co (wt. %) have been annealed at the temperatures below their point of eutectoid decomposition, from β-Ti to α-Ti, and respective intermetallics (TiFe, Ti2Co, Ti2Ni, TiCr2). Volume fraction of HPT-driven ω-phase (from ≤5 up to ~80%) depended on the amount of alloying element dissolved in the α-matrix. Evaluation of lattice parameters revealed accelerated mass transfer during HPT at room temperature corresponding to bulk diffusion in α-Ti at ~600 °С.

ω Phase Transformation and Mechanical Properties in Binary Zr-Nb Biomedical Alloy

2016 ◽  
Vol 879 ◽  
pp. 1969-1973 ◽  
Author(s):  
Mitsuharu Todai ◽  
Keisuke Fukunaga ◽  
Takayoshi Nakano
Keyword(s):  
Electrical Resistivity ◽  
Phase Transformation ◽  
Temperature Coefficient ◽  
Medical Devices ◽  
Room Temperature ◽  
Volume Fraction ◽  
Positive Temperature ◽  
Compression Tests ◽  
Resistivity Curve ◽  
Ω Phase

The athermal ω phase transformation, magnetic susceptibility and deformation behavior of Zr-xNb alloys (x = 10 and 14) for use in medical devices subjected to magnetic resonance imaging (MRI) were investigated using electrical resistivity measurements, transmission electron microscopy observations and compression tests. The alloy with x = 10 exhibited a positive temperature coefficient in the electrical resistivity curve and the presence of an athermal ω phase at room temperature. On the other hand, the alloy with x = 14 showed an anomalous negative temperature coefficient (NTC) in the resistivity curve. Similar NTCs also appear in β-Ti alloys, which is interpreted as the growth of an athermal ω phase and the appearance of lattice modulation. The ω phase and diffuse satellites, which are possibly related to lattice modulation, were confirmed in the Zr-14Nb alloy at room temperature. The volume fraction of the athermal ω phase and the appearance of lattice modulation are related to the operating deformation mode and Young’s modulus. Thus, controlling the ω phase transformation in Zr-Nb alloys is key to developing medical devices that can be used in MRI.

Magnetic Characterization of SUS316L Deformed by High Pressure Torsion

2011 ◽  
Vol 239-242 ◽  
pp. 1300-1303
Author(s):  
Hong Cai Wang ◽  
Minoru Umemoto ◽  
Innocent Shuro ◽  
Yoshikazu Todaka ◽  
Ho Hung Kuo
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Stainless Steel ◽  
Phase Transformation ◽  
Austenitic Stainless Steel ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Austenitic Matrix ◽  
Magnetic Characterization

SUS316L austenitic stainless steel was subjected to severe plastic deformation (SPD) by the method of high pressure torsion (HPT). From a fully austenitic matrix (γ), HPT resulted in phase transformation from g®a¢. The largest volume fraction of 70% a¢ was obtained at 0.2 revolutions per minute (rpm) while was limited to 3% at 5rpm. Pre-straining of g by HPT at 5rpm decreases the volume fraction of a¢ obtained by HPT at 0.2rpm. By HPT at 5rpm, a¢®g reverse transformation was observed for a¢ produced by HPT at 0.2rpm.

Analyses of Eutectoid Phase Transformations in Nb–SilicideIn SituComposites

2004 ◽  
Vol 10 (4) ◽  
pp. 470-480 ◽  
Author(s):  
B.P. Bewlay ◽  
S.D. Sitzman ◽  
L.N. Brewer ◽  
M.R. Jackson
Keyword(s):  
Crystal Structure ◽  
Phase Transformation ◽  
High Temperature ◽  
Room Temperature ◽  
Bulk Composition ◽  
High Strength ◽  
Eutectoid Decomposition ◽  
Quaternary Alloys ◽  
Temperature Fracture

Nb–silicide in situ composites have great potential for high-temperature turbine applications. Nb–silicide composites consist of a ductile Nb-based solid solution together with high-strength silicides, such as Nb5Si3and Nb3Si. With the appropriate addition of alloying elements, such as Ti, Hf, Cr, and Al, it is possible to achieve a promising balance of room-temperature fracture toughness, high-temperature creep performance, and oxidation resistance. In Nb–silicide composites generated from metal-rich binary Nb-Si alloys, Nb3Si is unstable and experiences eutectoid decomposition to Nb and Nb5Si3. At high Ti concentrations, Nb3Si is stabilized to room temperature, and the eutectoid decomposition is suppressed. However, the effect of both Ti and Hf additions in quaternary alloys has not been investigated previously. The present article describes the discovery of a low-temperature eutectoid phase transformation during which (Nb)3Si decomposes into (Nb) and (Nb)5Si3, where the (Nb)5Si3possesses the hP16 crystal structure, as opposed to the tI32 crystal structure observed in binary Nb5Si3. The Ti and Hf concentrations were adjusted over the ranges of 21 to 33 (at.%) and 7.5 to 33 (at.%) to understand the effect of bulk composition on the phases present and the eutectoid phase transformation.

scholarly journals Effect of Quasi-Hydrostatic Pressure on Deformation Mechanism in Ti-10Mo Alloy

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1387
Author(s):  
Baozhen Jiang ◽  
Satoshi Emura ◽  
Koichi Tsuchiya
Keyword(s):  
Phase Transformation ◽  
Hydrostatic Pressure ◽  
Deformation Mechanism ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Mechanical Twinning ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Ω Phase ◽  
Dominant Deformation Mechanism

The deformation mechanisms of Ti-10Mo (wt.%) alloy subjected to different quasi-hydrostatic pressure values were investigated under constrained compression using stage of high-pressure torsion apparatus. Deformation products contain {332}<113> mechanical twinning, stress-induced α″ martensitic phase and stress-induced ω phase. A volume expansion accompanied stress-induced α″ martensitic phase transformation is 2.06%. By increasing the applied pressure from 2.5 GPa to 5 GPa, the dominant deformation mechanism underwent a transition from stress-induced α″ martensitic phase transformation to {332}<113> mechanical twinning.

Plasticity-Induced Martensitic Phase Transformation in Fatigue of Unnotched SUS304 Plates

2005 ◽  
Vol 297-300 ◽  
pp. 1152-1157
Author(s):  
Yoshifumi Iwasaki ◽  
Yuji Nakasone
Keyword(s):  
Phase Transformation ◽  
Fatigue Life ◽  
Room Temperature ◽  
Volume Fraction ◽  
Tensile Tests ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Air Volume ◽  
Maximum Value ◽  
Residual Fatigue

The present study has investigated plasticity-induced martensitic phase transformation in fatigue of unnotched SUS304 plates. Martensitic phase transformation occurred in uunotched SUS304 plate specimens fatigued at room temperature in air. Volume fraction Va’ of a’ martensite in the uunotched portion of fatigued specimens was measured by ferrite scope. The relations between the maximum value of Va’, Va’max, and the number of load cycles N were represented by reverse sigmoidal curves for all the applied stress range Ds levels tested in this study. For the most portion of fatigue life, the value of Va’max remained almost constant. This value was increased with increase in the value of Ds. The spatial distribution of Va’ in the specimens varied with N: i.e., continued cycling of stress made a’ transformation localized near the central portion of specimens where the Va’ value reached as high as 35-40%. This value is more than doubled compared to the highest Va’ value found in the tensile tests of SUS304 at room temperature in air. Invisible cracks of 200µm in length were found in the high Va’ value region. These results imply that the measurement of Va’ in fatigued SUS304 components may detect crack initiation sites and may predict residual fatigue life.

Phase Transformation and Annealing Behavior of SUS 304 Austenitic Stainless Steel Deformed by High Pressure Torsion

2010 ◽  
Vol 654-656 ◽  
pp. 334-337 ◽  
Author(s):  
Innocent Shuro ◽  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Seiji Yokoyama
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
Phase Transformation ◽  
Austenitic Stainless Steel ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Two Phase ◽  
Annealing Behavior ◽  
304 Austenitic Stainless Steel ◽  
Deformed State

SUS 304 austenitic stainless steel was subjected to severe plastic deformation (SPD) by the method of high pressure torsion (HPT). From a fully austenitic matrix (γ), HPT resulted in phase transformation to give a two phase structure of austenite (γ) and martensite (α') by the transformation γα'. The phase transformation was accompanied by an increase in hardness (Hv) from 1.6 GPa in the as annealed form to 5.4 GPa in the deformed state. Subsequent annealing in temperature range 250oC to 450oC resulted in an increase in both α' volume fraction and hardness (6.4 GPa). Annealing at 600oC resulted in a decrease in α' volume fraction hardness.

Phase transformation kinetics of ω-phase in pure Ti formed by high-pressure torsion

2015 ◽  
Vol 51 (5) ◽  
pp. 2608-2615 ◽  
Author(s):  
Nozomu Adachi ◽  
Yoshikazu Todaka ◽  
Kenshu Irie ◽  
Minoru Umemoto
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
High Pressure Torsion ◽  
Transformation Kinetics ◽  
Ω Phase ◽  
Phase Transformation Kinetics ◽  
Kinetics Of

Anomalous Property Evolution during Annealing in HPTed SUS 304 Austenitic Stainless Steel

2010 ◽  
Vol 667-669 ◽  
pp. 589-592
Author(s):  
Innocent Shuro ◽  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Ho Hung Kuo ◽  
Hong Cai Wang
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Room Temperature ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Peak Hardness ◽  
Scanning Calorimetry ◽  
Matrix Deformation ◽  
Magnetization Saturation ◽  
304 Austenitic Stainless Steel

SUS 304 austenitic stainless steel (ASS) was deformed by high pressure torsion (HPT) to obtain 100% volume fraction of martensite (α') from a fully austenitic (γ) matrix. Deformation caused an increase in hardness (Hv) from 1.6 GPa in the as annealed state to 6.4 GPa　after HPT. Deformed samples were then annealed in the range 200 – 600oC and peak hardness of 7.8 GPa was observed after annealing at 400oC for 1 hour. Differential scanning calorimetry (DSC) and electrical resistivity tests showed that the deformed alloy undergoes a two stage phase transformation on heating from room temperature up to 700oC. The first stage of transformation was associated with hardening behavior while the second one which is reverse α' → γ transformation resulted in a reduction in hardness. Annealing at 400oC after deformation was found to increase the magnetization saturation (Msat) values.

Phase Transformation in Ni-Ti Shape Memory and Superelastic Alloys Subjected to High Pressure Torsion

2010 ◽  
Vol 123-125 ◽  
pp. 1007-1010 ◽  
Author(s):  
Karimbi Koosappa Mahesh ◽  
Francisco M. Braz Fernandes ◽  
Gheorghe Gurau
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Shape Memory ◽  
High Pressure Torsion ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
One Stage ◽  
Heating And Cooling ◽  
Ti Alloys ◽  
M Phase

A systematic study on the phase transformation of Ni-Ti shape memory and superelastic alloys subjected to Severe Plastic Deformation (SPD) – High Pressure Torsion (HPT) technique has been carried out. Ni-Ti alloys of three compositions were chosen for the study. Specimens of these alloys in as-received (AR) condition and after HPT have been subjected to Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) analyses. In this study, while comparing the results of DSC thermograms and XRD spectra for the same sample conditions, some differences were observed. In the case of NiTi-H alloy after HPT, there appeared one stage phase transformation with DSC both while heating and cooling suggesting Martensite↔Austenite transformation but, with respect to XRD spectra while cooling, at the intermediate temperature of 55°C, the R-phase peaks corresponding to (1 1 2)R and (3 0 0)R planes appeared. In the thermogram obtained for the NiTi-B alloy subjected to HPT, it is observed that, while cooling, the Austenite to R-phase transformation is merged with R-phase to Martensite transformation. The results of the XRD obtained at -180°C show the presence of R-phase along with M-phase. The DSC curve of the NiTi-S alloy subjected to HPT corresponds to one stage phase transformation both while heating and cooling but, the diffractogram of the sample obtained at -180°C corresponds to the presence of both R-phase and M-phase.

scholarly journals The Phase Transformations Induced by High-Pressure Torsion in Ti–Nb-Based Alloys

2021 ◽  
pp. 1-7
Author(s):  
Anna Korneva ◽  
Boris Straumal ◽  
Askar Kilmametov ◽  
Lidia Lityńska-Dobrzyńska ◽  
Robert Chulist ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Phase Transformations ◽  
High Pressure Torsion ◽  
Chemical Compositions ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Nb Content ◽  
Long Time

The study of the fundamentals of the α → ω and β → ω phase transformations induced by high-pressure torsion (HPT) in Ti–Nb-based alloys is presented in the current work. Prior to HPT, three alloys with 5, 10, and 20 wt% of Nb were annealed in the temperature range of 700–540°C in order to obtain the (α + β)-phase state with a different amount of the β-phase. The samples were annealed for a long time in order to reach equilibrium Nb content in the α-solid solution. Scanning electron microscope (SEM), transmission electron microscopy, and X-ray diffraction techniques were used for the characterization of the microstructure evolution and phase transformations. HPT results in a strong grain refinement of the microstructure, a partial transformation of the α-phase into the ω-phase, and a complete β → ω phase transformation. Two kinds of the ω-phase with different chemical compositions were observed after HPT. The first one was formed from the β-phase, enriched in Nb, and the second one from the almost Nb-pure α-phase. It was found that the α → ω phase transformation depends on the Nb content in the initial α-Ti phase. The less the amount of Nb in the α-phase, the more the amount of the α-phase is transformed into the ω-phase.

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