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 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 Mo, V and Zr on the microstructure and mechanical properties of Ti2AlNb alloys

2020 ◽  
Vol 321 ◽  
pp. 08003
Author(s):  
Yujun Du ◽  
Xianghong Liu ◽  
Jinshan Li ◽  
Wenzhong Luo ◽  
Yongsheng He ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Melting Process ◽  
Phase Region ◽  
Arc Furnace ◽  
Micro Hardness ◽  
Β Phase ◽  
Before And After ◽  
B2 Phase ◽  
O Phase

Small button ingots of Ti2AlNb alloys with different contents of Mo, V and Zr were melted by vacuum non-consumable arc furnace. Due to the rapid cooling rate during melting process, only β grains without precipitation were observed in most of the button ingots and no regular phenomenon was found. However, when the samples were heated to β phase region and then furnace cooled to room temperate, different morphologies and quantities of primary α phase and second O phase formed from the β grains of different samples. It is suggested that the morphology of α phase was changed from lamellar to quadrilateral with increasing V and the lath O increased with increasing Zr. Besides, the residual β/B2 phase increased with increasing Mo and V. The EDS results showed that Al and Zr were enriched in α phase whereas Nb, Mo and V were enriched in β/B2 phase. The micro-hardness of these samples before and after heat treatment was detected and the micro-hardness increased with increasing Zr and decreasing Mo and V.

Effect of Alloying and Thermal Processing on Mechanical Properties of TiAl Alloys

2016 ◽  
Vol 258 ◽  
pp. 501-505
Author(s):  
Alice Chlupová ◽  
Milan Heczko ◽  
Karel Obrtlík ◽  
Přemysl Beran ◽  
Tomáš Kruml
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Thermal Processing ◽  
Lamellar Microstructure ◽  
High Strength ◽  
Fatigue Behaviour ◽  
Tial Alloys ◽  
Working Temperature ◽  
Β Phase ◽  
Strength And Ductility

Two γ-based TiAl alloys with 7 at.% of Nb, alloyed with 2 at.% Mo and 0.5 at.% C, were studied. A heat treatment leading to very fine lamellar microstructure was applied on both alloys. Microstructure after the heat treatment was described and mechanical properties including fatigue behaviour were measured. The as-received material alloyed with C possesses high strength and very limited ductility, especially at RT. After application of selected heat treatment it becomes even more brittle; therefore, this process could be considered as not appropriate for this alloy. On the contrary, in the case of Mo alloyed material, both strength and ductility are improved by the heat treatment at RT and usual working temperature (~750 °C). Presence of the β phase is responsible for this effect. The selected heat treatment thus can be an alternative for this alloy to other thermomechanical treatments as high temperature forging.

Development and Characterization of New Ti-25Ta-Zr Alloys for Biomedical Applications

2021 ◽  
Vol 1016 ◽  
pp. 137-144
Author(s):  
Pedro Akira Bazaglia Kuroda ◽  
Fernanda de Freitas Quadros ◽  
Mycaela Vieira Nascimento ◽  
Carlos Roberto Grandini
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Elastic Modulus ◽  
Biomedical Applications ◽  
Solution Heat Treatment ◽  
High Hardness ◽  
Microstructural Characterization ◽  
Β Phase ◽  
Cp Ti ◽  
Microscopy Techniques

This paper deals with the study of the development, structural and microstructural characterization and, selected mechanical properties of Ti-25Ta-50Zr alloy for biomedical applications. The alloy was melted in an arc furnace and various solution heat treatments were performed to analyze the influence of the temperature and time on the structure, microstructure, microhardness and elastic modulus of the samples. The structural and microstructural results, obtained by X-ray diffraction and microscopy techniques, showed that the solution heat treatment performed at high temperatures induces the formation of the β phase, while solution heat treatment performed at low temperatures induces the formation of the α” and ω metastable phases. Regarding the effect of time, samples subjected to heat treatment for 6 hours have only the β phase, indicating that lengthy treatments suppress the α” phase. Regarding the hardness and elastic modulus, the alloy with the α” and ω phases, after treatment performed at a temperature of 500 °C, has a high hardness value and elastic modulus due to the presence of the ω phase that hardens and weakens alloys. The titanium alloys developed in this study have excellent mechanical properties results for use in the orthopedic area, better than many commercial materials such as cp-Ti, stainless steel and Co-Cr alloys.

scholarly journals Microstructure Evolution and Mechanical Properties of AZ80 Mg Alloy during Annular Channel Angular Extrusion Process and Heat Treatment

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4223 ◽  
Author(s):  
Xi Zhao ◽  
Shuchang Li ◽  
Fafa Yan ◽  
Zhimin Zhang ◽  
Yaojin Wu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Microstructure Evolution ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Annular Channel ◽  
Mg Alloy ◽  
Strengthening Effect ◽  
Β Phase ◽  
Angular Extrusion

Microstructure evolution and mechanical properties of AZ80 Mg alloy during annular channel angular extrusion (350 °C) and heat treatment with varying parameters were investigated, respectively. The results showed that dynamic recrystallization of Mg grains was developed and the dendritic eutectic β-Mg17Al12 phases formed during the solidification were broken into small β-phase particles after hot extrusion. Moreover, a weak texture with two dominant peaks formed owing to the significant grain refinement and the enhanced activation of pyramidal <c + a> slip at relative high temperature. The tension tests showed that both the yield strength and ultimate tensile strength of the extruded alloy were dramatically improved owing to the joint strengthening effect of fine grain and β-phase particles as compared with the homogenized sample. The solution treatment achieved the good plasticity of the alloy resulting from the dissolution of β-phases and the development of more equiaxed grains, while the direct-aging process led to poor alloy elongation as a result of residual eutectic β-phases. After solution and aging treatment, simultaneous bonding strength and plasticity of the alloy were achieved, as a consequence of dissolution of coarse eutectic β-phases and heterogeneous precipitation of a large quantity of newly formed β-phases with both the morphologies of continuous and discontinuous precipitates.

scholarly journals In Situ Formation of a Metastable β-Ti Alloy by Laser Powder Bed Fusion (L-PBF) of Vanadium and Iron Modified Ti-6Al-4V

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1067 ◽  
Author(s):  
Florian Huber ◽  
Thomas Papke ◽  
Christian Scheitler ◽  
Lukas Hanrieder ◽  
Marion Merklein ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Homogeneous Element ◽  
Alloy Formation ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Β Phase ◽  
Stabilizing Effect

The aim of this work is to investigate the β-Ti-phase-stabilizing effect of vanadium and iron added to Ti-6Al-4V powder by means of heterogeneous powder mixtures and in situ alloy-formation during laser powder bed fusion (L-PBF). The resulting microstructure was analyzed by metallographic methods, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The mechanical properties were characterized by compression tests, both prior to and after heat-treating. Energy dispersive X-ray spectroscopy showed a homogeneous element distribution, proving the feasibility of in situ alloying by LPBF. Due to the β-phase-stabilizing effect of V and Fe added to Ti-6Al-4V, instead of an α’-martensitic microstructure, an α/β-microstructure containing at least 63.8% β-phase develops. Depending on the post L-PBF heat-treatment, either an increased upsetting at failure (33.9%) compared to unmodified Ti-6Al-4V (28.8%), or an exceptional high compressive yield strength (1857 ± 35 MPa compared to 1100 MPa) were measured. The hardness of the in situ alloyed material ranges from 336 ± 7 HV0.5, in as-built condition, to 543 ± 13 HV0.5 after precipitation-hardening. Hence, the range of achievable mechanical properties in dependence of the post-L-PBF heat-treatment can be significantly expanded in comparison to unmodified Ti-6Al-4V, thus providing increased flexibility for additive manufacturing of titanium parts.

Effects of HIP Process on the Microstructure and Mechanical Properties of a Cast Superalloy

2017 ◽  
Vol 898 ◽  
pp. 476-479
Author(s):  
Jin Xia Yang ◽  
Yuan Sun ◽  
Dong Ling Zhou
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Room Temperature ◽  
Stress Rupture ◽  
Homogeneous Distribution ◽  
Standard Heat Treatment ◽  
Microstructure And Mechanical Properties ◽  
The Difference ◽  
Hip Process ◽  
Cast Superalloy

The effects of HIP process on microstructure and mechanical properties of IN792 cast superalloy were studied. The results showed that HIP process produced more uniform and finer cubic γ′ than standard heat treatment. The difference of the mechanical properties should be caused by the microstructure changes. HIP process leads the homogeneous distribution of γ′ at dendritic arm and interdendritic area, and improved UTS and YS of tested alloy at 550°C. However, it played no role in increasing UTS and YS at room temperature and stress-rupture lives of 760°C/662MPa and decreased stress-rupture lives of 982°C/186MPa.

scholarly journals Isochronal Phase Transformation in Bimodal Ti-55531

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 790 ◽  
Author(s):  
Fuwen Chen ◽  
Guanglong Xu ◽  
Kechao Zhou ◽  
Hui Chang
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Activation Energy ◽  
Phase Transformation ◽  
Microstructure Evolution ◽  
Continuous Heating ◽  
Interface Curvature ◽  
The Difference ◽  
Treatment Procedures ◽  
And Control

Bimodal microstructures where globular α and acicular α phases are embedded in the β matrix are commonly used in industry-relevant Ti-55531. To optimize the performance of Ti-55531 through heat treatment, it is crucial to understand and control the phase transformation in the as-received bimodal Ti-55531 as well as its microstructure evolution. In this work, the isochronal phase transformations and microstructure evolution in the bimodal Ti-55531 during the continuous heating were systematically studied by combining dilatometry, XRD phase analyses, and SEM observation. The β → α transformation occurred at 678 K only with the acicular α. When the temperature was higher than 788 K, α → β transformation took place in two separate stages (i.e., αacicular → β and αglobular → β transformation). The dissolution of αglobular occurred after the dissolution of αacicular was completed. Due to the difference in the chemical composition and interface curvature between αacicular and αglobular, the average activation energy for αacicular → β transformation was lower than that for the αglobular → β transformation. The isochronal phase transformation and microstructure evolution during continuous heating in the present work could be used to optimize heat treatment procedures for desired mechanical properties.

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.

Effects of Heat Treatment on Microstructures and Mechanical Properties of Ti-38644 Alloy for Aerospace Fasteners

2018 ◽  
Vol 913 ◽  
pp. 109-117 ◽  
Author(s):  
Qing Yun Zhao ◽  
Si Rui Cheng ◽  
Li Dong Wang ◽  
Li Min Dong ◽  
Feng Lei Liu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Tensile Strength ◽  
Solution Temperature ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Air Cooling ◽  
Β Phase ◽  
Α Phase

The effects of heat treatment on microstructure and mechanical properties of Ti-38644 alloy were investigated by scanning electron microscope (SEM) and transmission electron microscopy (TEM) as well as uniaxial tensile test. The results show that when the solution temperature is lower than 845°C, the microstructure of Ti-38644 alloy is equiaxed β phase with the grain size of 20μm, and the tensile strength is about 960MPa. As raising solution temperature to 860°C, the grain size of Ti-38644 alloy increases to 100μm and the tensile strength decreased to 870MPa. There are a large number of secondary α phase precipitated from the grain boundaries and within grain of β phase undergoing aging treatment. Secondary α phase coarsens with increasing the aging temperature, leading to the decrease of tensile strength. After solution treatment at 815°C for 1.5h, water quenching plus aging at 520°C for 10h, air cooling, Ti-38644 alloy shows a better mechanical property with the tensile strength 1330MPa, elongation and reduction of area 10% and 45% respectively.

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