scholarly journals Significantly fast spinodal decomposition and inhomogeneous nanoscale martensitic transformation in Ti–Nb–O alloys

2020 ◽  
Vol 321 ◽  
pp. 11049
Author(s):  
Yuya ISHIGURO ◽  
Yuhki TSUKADA ◽  
Toshiyuki KOYAMA
Keyword(s):  
Heat Treatment ◽  
Martensitic Transformation ◽  
Spinodal Decomposition ◽  
Treatment Temperature ◽  
Phase Field Method ◽  
Isothermal Heat Treatment ◽  
Phase Decomposition ◽  
Rate Condition ◽  
Continuous Cooling ◽  
Β Phase

The β phase spinodal decomposition during continuous cooling in Ti‒Nb‒O alloys is investigated by the phase-field method. Addition of only a few at.%O to Ti‒23Nb (at.%) alloy remarkably increases the driving force of the β phase spinodal decomposition. During isothermal heat treatment at 1000 K and 1100 K in Ti‒23Nb‒3O (at.%) alloy, the β phase separates into β1 phase denoted as (Ti)1(O, Va)3 and β2 phase denoted as (Ti, Nb)1(Va)3, resulting in the formation of nanoscale concentration modulation. The phase decomposition progresses in 0.3‒20 ms. In Ti‒23Nb‒XO alloys (X = 1.0, 1.2, 2.0), the spinodal decomposition occurs during continuous cooling with the rate of 500 K s‒1, indicating that the spinodal decomposition occurs during water quenching in the alloys. It is assumed that there is a threshold value of oxygen composition for inducing the spinodal decomposition because it does not occur during continuous cooling in Ti‒23Nb‒0.6O (at.%) alloy. The concentration modulation introduced by the β phase decomposition has significant effect on the β→α” martensitic transformation. Hence, it seems that for controlling microstructure and mechanical properties of Ti‒Nb‒O alloys, careful control of heat treatment temperature and cooling rate condition is required.

scholarly journals Effect of Heat Treatment Temperature on Martensitic Transformation and Superelasticity of the Ti49Ni51 Shape Memory Alloy

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2539 ◽  
Author(s):  
Peiyou Li ◽  
Yongshan Wang ◽  
Fanying Meng ◽  
Le Cao ◽  
Zhirong He
Keyword(s):  
Heat Treatment ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Thermal Hysteresis ◽  
Treatment Temperature ◽  
Heat Treated ◽  
Different Temperatures ◽  
Tini Phase ◽  
Rapidly Solidified

The martensitic transformation and superelasticity of Ti49Ni51 shape memory alloy heat-treatment at different temperatures were investigated. The experimental results show that the microstructures of as-cast and heat-treated (723 K) Ni-rich Ti49Ni51 samples prepared by rapidly-solidified technology are composed of B2 TiNi phase, and Ti3Ni4 and Ti2Ni phases; the microstructures of heat-treated Ti49Ni51 samples at 773 and 823 K are composed of B2 TiNi phase, and of B2 TiNi and Ti2Ni phases, respectively. The martensitic transformation of as-cast Ti49Ni51 alloy is three-stage, A→R→M1 and R→M2 transformation during cooling, and two-stage, M→R→A transformation during heating. The transformations of the heat-treated Ti49Ni51 samples at 723 and 823 K are the A↔R↔M/A↔M transformation during cooling/heating, respectively. For the heat-treated alloy at 773 K, the transformations are the A→R/M→R→A during cooling/heating, respectively. For the heat-treated alloy at 773 K, only a small thermal hysteresis is suitable for sensor devices. The stable σmax values of 723 and 773 K heat-treated samples with a large Wd value exhibit high safety in application. The 773 and 823 K heat-treated samples have large stable strain–energy densities, and are a good superelastic alloy. The experimental data obtained provide a valuable reference for the industrial application of rapidly-solidified casting and heat-treated Ti49Ni51 alloy.

Study of α”-Martensitic Transformation in Ti35NbxSn Alloys Subjected to Cryogenic Heat Treatment

2020 ◽  
Vol 1158 ◽  
pp. 17-26
Author(s):  
Abraão Silva ◽  
Thiago Figueiredo Azevedo ◽  
Weslley Rick Viana Sampaio ◽  
Luiz Carlos Pereira ◽  
Sandro Griza
Keyword(s):  
Heat Treatment ◽  
Elastic Modulus ◽  
Martensitic Transformation ◽  
Cryogenic Treatment ◽  
Quenching Temperature ◽  
High Mechanical Strength ◽  
Quenching Medium ◽  
Β Phase ◽  
Low Elastic Modulus ◽  
Cryogenic Heat Treatment

TiNbSn alloys have been extensively researched due to several properties they exhibit, including high mechanical strength, low elastic modulus, superelasticity, shape memory effect, biocompatibility. The present study evaluated the cryogenic heat treatment in the Ti35NbxSn alloys (x = 0.0; 2.5; 5.0; 7.5). The alloys were arc melted, cold formed and quenched in both water and liquid nitrogen at-198° C. The Ti35Nb2.5Sn alloy was also aged after exposed to both quenching medium. Microstructure and microhardness analyses were performed. Cryogenic treatment was not enough for transformation of primary β phase into martensitic α” in alloys containing 5 and 7.5% Sn. Cryogenic treatment provided β to α” transformation in alloys containing 0 and 2.5% Sn. The Sn-free alloy was more likely to α" transformation in both quenching medium. The alloys microhardness increased with decrease of both quenching temperature and Sn content. The increase of α" is also related to the increase of the alloy microhardness after aging.

scholarly journals Influence of heat treatment and stress state on the functional and mechanical properties of the [001]-oriented single crystals of fenicoalti alloy

2020 ◽  
pp. 132-140
Author(s):  
I.V. Kuksgauzen ◽  
◽  
Y.I. Chumlyakov ◽  
I.V. Kireeva ◽  
V.V. Poklonov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Stress State ◽  
Martensitic Transformation ◽  
Single Crystals ◽  
Maximum Increase ◽  
Β Phase ◽  
Tension And Compression ◽  
Aging Regime ◽  
The Difference

The effect of the γ'- and β-phase particles on the thermoelastic γ-α' martensitic transformation (MT) during cooling/heating and under stress was studied under tension and compression on the [001]-oriented single crystals of Fe-28%Ni-17%Co-11.5%Al-2.5%Ti (at.%) alloy. The effect of the aging regime on the Ms temperature was shown. Maximum increase in the Ms temperature by 100 K was found with the simultaneous precipitation of the γ'- and β-phase particles after two-stage aging of 4+4h at 873 K, in comparison with single-stage aging for 8h. In crystals with γ' and γ'+β-phases particles the difference (asymmetry) of the stresses for the stress-induced γ-α' MT σcr and value α = d σcr/ dT under tension and compression were not observed. The absence of asymmetry of the σ cr and value α = d σcr/ dT are due to close values of the shape memory effect (SME) and superelasticity (SE) under tension and compression. The values of SME and SE were decreased when β-phase particles are precipitated.

scholarly journals Effects of Heat-Treatment Temperature on the Microstructure and Mechanical Properties of Steel by MgO Nanoparticle Additions

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1707
Author(s):  
Yutao Zhou ◽  
Shufeng Yang ◽  
Jingshe Li ◽  
Wei Liu ◽  
Anping Dong
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Acicular Ferrite ◽  
Heat Treatment Temperature ◽  
Treatment Temperature ◽  
Formation Mechanisms ◽  
Isothermal Heat Treatment ◽  
Mgo Nanoparticles ◽  
Intragranular Acicular Ferrite ◽  
Mgo Nanoparticle

The characteristics and formation mechanisms of intragranular acicular ferrite (IAF) in steel with MgO nanoparticle additions were systematically investigated for different isothermal heat-treatment temperatures, and its influence on mechanical properties was also clarified. The results indicate that the inclusions were finely dispersed and refined after adding MgO nanoparticles. In addition, with decreasing heat-treatment temperature, the microstructure changed from grain boundary ferrite (GBF) and polygonal ferrite (PF) to intragranular acicular ferrite. Moreover, the steel with MgO additions had excellent mechanical properties in the temperature range of 973 to 823 K and an average Charpy absorbed energies value of around 174 J at 873 K due to the significant refinement of the microstructure and nucleation of intragranular acicular ferrite.

scholarly journals Evolution and Evaluation of Duplex Grain of As-cast 30Cr2Ni4MoV Steel during Heat Treatment

2020 ◽  
Vol 26 (3) ◽  
pp. 281-286
Author(s):  
Xiuzhi ZHANG ◽  
Zhilong LIU ◽  
Jiansheng LIU ◽  
Shue DANG
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Isothermal Holding ◽  
Optical Microscope ◽  
Treatment Temperature ◽  
Heating Process ◽  
Isothermal Heat Treatment ◽  
Austenite Grains ◽  
Different Grain Size ◽  
Heat Preservation

As the main microstructure flaw of heavy forging, duplex grain (the grain size is non-uniform) may result in producing a reject. In this paper, the influences of heat treatment temperature and isothermal holding time on the duplex grains evolutions of as-cast 30Cr2Ni4MoV steel were studied using optical microscope and scanning electron microscope aided with XRD and EDS. It is shown that the globular austenite grains appear at 750 °C and the austenite grains in the regions rich in C, Cr, Ni, and Mo are smaller than that in other regions. Duplex grains appear in the heating process. Moreover, in the isothermal heat treatment process, grains with different grain size number also developed at all of the temperatures performed in the study. But the distribution of the grains with different sizes cannot be evaluated precisely using proper method commonly used now. On the basis of analysis of the sizes of the duplex grains, a new approach for evaluating the level of the mixture of different size grains was proposed, the result obtained are consistent with the experimental results. The microstructure of 30Cr2Ni4MoV could be more uniform by increasing the temperature and extending the heat-preservation time.

Transformation Behavior of TiNiPt Thin Films Fabricated Using Melt Spinning Technique

2004 ◽  
Vol 842 ◽  
Author(s):  
Tomonari Inamura ◽  
Yohei Takahashi ◽  
Hideki Hosoda ◽  
Kenji Wakashima ◽  
Takeshi Nagase ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Martensitic Transformation ◽  
Heat Treatment Temperature ◽  
Melt Spinning ◽  
Bulk Material ◽  
Parent Phase ◽  
Treatment Temperature ◽  
Transformation Behavior ◽  
Scanning Calorimetry ◽  
Similar Chemical

ABSTRACTMartensitic transformation behavior of Ti50Ni40Pt10 (TiNiPt) melt-spun ribbons were investigated where the heat treatment temperature was systematically changed from 473K to 773K. A hot-forged bulk TiNiPt material with the similar chemical composition was also tested as a comparison. θ-2θ X-ray diffraction analysis and transmission electron microscopy observation revealed that the as-spun ribbons were fully crystallized. The apparent phases of as-spun ribbons at room temperature are both B19 martensite and B2 parent phase instead of B2 single phase for the hot-forged bulk material. No precipitates were found in as-spun and heat-treated ribbons. It was revealed by differential scanning calorimetry that all the specimens exhibit one-step transformation. The martensitic transformation temperatures of the TiNiPt as-spun ribbons are 100K higher than those of the hot-forged bulk material, and the martensitic transformation temperature decreases with increasing heat treatment temperature.

scholarly journals Fabrication and Crystallization of ZnO-SLS Glass Derived Willemite Glass-Ceramics as a Potential Material for Optics Applications

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Mohd Hafiz Mohd Zaid ◽  
Khamirul Amin Matori ◽  
Sidek Hj. Abdul Aziz ◽  
Halimah Mohamed Kamari ◽  
Wan Mahmood Mat Yunus ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Structural Evolution ◽  
Linear Shrinkage ◽  
Treatment Temperature ◽  
Isothermal Heat Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zinc Orthosilicate

Willemite glass-ceramics were successfully derived from conventional melt-quench ZnO-SLS precursor glass by an isothermal heat treatment process. The effect of heat treatment temperatures on the physical properties was investigated by Archimedes principle and linear shrinkage. The generation of willemite crystal phase and morphology with increase in heat treatment temperature was examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM) techniques. X-ray diffraction revealed that the metastableβ-Zn2SiO4and thermodynamically stable zinc orthosilicateα-Zn2SiO4phases can be observed at temperatures above 700°C. The experimental results indicated that the density and shrinkage of the glass-ceramic vary with increasing the sintering temperature. FTIR studies showed that the structure of glass-ceramic consists of SiO2and ZnO4units and exhibits the structural evolution of willemite glass-ceramics. The characteristic of strong vibrational bands can be related to theSiO44-tetrahedron corresponding to reference spectra of willemite.

A STUDY ON THERMO-OPTIC EFFECT OF β POLY(VINYLIDENE FLUORIDE) THIN FILMS PREPARED BY SOLUTION CASTING METHOD

2008 ◽  
Vol 15 (01n02) ◽  
pp. 175-181 ◽  
Author(s):  
YINGXUE XI ◽  
HUIQING FAN ◽  
WEIGUO LIU ◽  
CHEN YANG ◽  
XIAOLING NIU
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Infrared Imaging ◽  
Vinylidene Fluoride ◽  
Treatment Temperature ◽  
X Ray Diffraction ◽  
Long Wavelength ◽  
Β Phase ◽  
Poly Vinylidene Fluoride ◽  
Solution Casting Method

The Poly(vinylidene) fluoride (PVDF) thin films with a high content of β-phase were prepared by controlling heat-treatment temperature using casting from the poled solvents. The crystallite microstructure of thin films was depicted by the techniques of X-ray diffraction and FTIR. The results showed that heat treatment was favorable for inducing the β- and γ-phase formation of PVDF. The β phase films were obtained with heat treatment at temperatures ranging from 60°C to 120°C and annealing at 120°C after casting from DMF. The thermo-optical effect of β phase PVDF films was investigated using a spectroscopic ellipsometer. At temperatures ranging from 20°C to 100°C, the refractive index of PVDF was negatively correlated with the temperature between 350 and 1500 nm. The value of the t.o. coefficient of PVDF films was calculated at all temperatures. The maximum value of the t.o. coefficient was about 3.3 × 10-4/°C at the ascending stage of temperature and 3.0 × 10-4/°C at the descending stage of temperature. Therefore, it is possible to use the thermo-optic effect of the β phase PVDF for long wavelength infrared imaging.

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