Phase Transformation and Microstructure Evolution in Near-β Ti-7333 Titanium Alloy during Aging

2013 ◽  
Vol 747-748 ◽  
pp. 904-911 ◽  
Author(s):  
Qiong Hui ◽  
Xiang Yi Xue ◽  
Hong Chao Kou ◽  
Min Jie Lai ◽  
Bin Tang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Phase Transformation ◽  
Grain Boundaries ◽  
Parent Phase ◽  
Solution Treatment ◽  
Ageing Treatment ◽  
Β Phase ◽  
Α Phase ◽  
Nucleation Sites ◽  
Higher Temperature

A newly near-β titanium alloy Ti-7Mo-3Cr-3Nb-3Al (Ti-7333) was subjected to β phase solution treatment and ageing in the present work. The characteristics of α phase transformation in ageing treatment were studied. Results show that isothermal aging at a low temperature (350) will result in lots of ω particles with small size homogeneously distributing in the parent phase. These ω particles can act as nucleation sites for α phase and lead to the uniform precipitation of fine α phase within the β grain after further ageing treatment. However, when ageing at a higher temperature, the α phase tends to precipitate direct from the β matrix and the morphology of α phase is determined by the temperature and period of ageing treatment. After aging at 550 for 5min, acicular α phase precipitates in the β grains as well as along β grain boundaries and the size and quantity of α phase increase with the holding time. Note that Ti-7333 alloy has a quick ageing response. When aging at 700 for 1h, coarser α laths precipitate both on the grain boundary and within the grain. Increase the ageing temperature to 800, α phase precipitates within the β grain as short rod-like morphology. It is suggested that the driving force for α phase nucleation and the amount of defects in the intragranular decrease with the increasing of temperature, leading to the grain boundaries become the prior nucleation sites. Substantial α phase precipitate-free regions adjacent to β grain boundaries remained after ageing at 700 for 1h due to the rejection of β-stabilizer from coarse α lath on β grain boundaries. Aging at 800 for 1h resulted in pronounced continuous α-films along β grain boundaries.

Effect of Quenching and Reheating on Isothermal Phase Transformation in Ti-15Nb-10Zr Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 582-587 ◽  
Author(s):  
Sengo Kobayashi ◽  
Ryoichi Ohshima ◽  
Kiyomichi Nakai ◽  
Tatsuaki Sakamoto
Keyword(s):  
Phase Transformation ◽  
Solution Treatment ◽  
The Other ◽  
Matrix Microstructure ◽  
Iced Brine ◽  
Β Phase ◽  
Solution Treated ◽  
Α Phase ◽  
Other Hand ◽  
Means Of Transmission

Isothermal phase transformation in Ti-15Nb-10Zr (at%) alloys has been examined by mainly means of transmission electron microscopy. Specimens solution-treated at 1000°C in  phase field were directly held at temperatures between 350 and 450°C for 1.8-86.4ks, which are called "DH (direct holding)-specimen". On the other hand, some specimens solution-treated at 1000°C were quenched into iced brine and then aged at temperatures between 350 and 450°C, which are called "QA(quench and aging)-specimen". In the DH-specimen held at 400°C α phase formed in β matrix. Microstructure evolution of QA-specimen aged at 400°C, on the other hand, is as follows.  phase formed in β matrix after aging for 1.8ks and further aging led to growth of  phase. After prolonged aging, α phase started to form in β matrix. These experimental results indicate that process of the quenching and reheating promotes the formation of  phase. Specimen quenched into iced brine after solution treatment exhibited α'' phase formation. The α'' phase in the quenched specimen would transform into β phase during reheating to the aging temperature. Reversion process of α''  β phase could promote the formation of  phase in β. Microstructure formation in the DH- and QA-specimens at 350 and 450°C will also be explained.

Effect of Heat Treatment on the Microstructure Evolution of Ti-6Al-3Sn-3Zr-3Mo-3Nb-1W-0.2Si Titanium Alloy

2016 ◽  
Vol 879 ◽  
pp. 1828-1833 ◽  
Author(s):  
Xiao Yun Song ◽  
Wen Jing Zhang ◽  
Teng Ma ◽  
Wen Jun Ye ◽  
Song Xiao Hui
Keyword(s):  
Heat Treatment ◽  
Titanium Alloy ◽  
Microstructure Evolution ◽  
Solution Treatment ◽  
Treatment Temperature ◽  
Water Quenching ◽  
Air Cooling ◽  
Two Phase ◽  
Β Phase ◽  
Α Phase

Ti-6Al-3Sn-3Zr-3Mo-3Nb-1W-0.2Si (BTi-6431S) alloy is a novel two-phase high temperature titanium alloy for short-term using in aerospace industry up to 700°C. The effects of heat treatment on the microstructure evolution of BTi-6431S alloy bar were investigated through optical microscopy (OM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The results show that solution treatment in β region at 1010°C followed by water quenching results in the formation of orthorhombic martensite α′′ phase, while air cooling leads to the formation of hexagonal martensite α′ phase. When solution-treated in α+β phase field at temperatures from 900°C to 980°C following by water quenching, the content of primary α phase decreases with the increase of heat treatment temperature. For the alloy subjected to identical heat treatment, the content of Al in α phase is much higher than that in β phase, while the contents of Nb, Mo and W elements in α phase are much less than those in β phase.

scholarly journals TiFe Precipitation Behavior and its Effect on Strengthening in Solution Heat-Treated Ti-5Al-3.5Fe During Isothermal Aging

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 875 ◽  
Author(s):  
Hye-Jeong Choe ◽  
Jong Won ◽  
Yong-Taek Hyun ◽  
Ka Lim ◽  
Seog-Young Yoon
Keyword(s):  
Phase Transformation ◽  
Isothermal Aging ◽  
Nucleation Site ◽  
Precipitation Kinetics ◽  
Precipitation Behavior ◽  
Β Phase ◽  
Α Phase ◽  
Nucleation Sites ◽  
Heat Treated ◽  
Interphase Boundaries

We investigated the TiFe precipitation behavior of solution heat-treated Ti-5Al-3.5Fe during isothermal aging, quantified the effect of precipitation on strengthening by evaluating the hardness, and compared it to the effect of Ti3Al precipitation in Ti-6Al-4V. TiFe precipitates formed both at grain boundaries (GBs) and within the grain matrices. Phase transformation from the β to α phase also occurred during isothermal aging; this transformation generated lamellar interphase boundaries between the transformed α phase and remaining β phase in prior β grains. These interphase boundaries enabled the formation of in-grain TiFe precipitates by acting as a nucleation site. GB precipitation did not require prior β → α phase transformation to generate nucleation sites (i.e., interphase boundaries), so TiFe precipitation could occur immediately upon isothermal aging. Thus, GB precipitation proceeded more quickly than in-grain precipitation; as a result, precipitates were larger and more spherical at the GBs than in grains. The strengthening behavior exhibited by TiFe precipitation differed obviously from that caused by Ti3Al precipitation in Ti-6Al-4V because of its differing precipitation kinetics and related microstructural evolution.

Microstructural Analysis and Wear Behavior of Cryogenically Treated Ti-6Al-4V Alloy

2014 ◽  
Vol 592-594 ◽  
pp. 1331-1335 ◽  
Author(s):  
Haider Nasreen ◽  
S. Beer Mohamed ◽  
S. Rasool Mohideen
Keyword(s):  
Grain Boundaries ◽  
Wear Behavior ◽  
Cryogenic Treatment ◽  
Microstructural Analysis ◽  
Wear Loss ◽  
Β Phase ◽  
Α Phase ◽  
Treated Sample

This paper helps in understanding the effects of cryogenic treatment on microstructural variation, hardness and wear behavior of Ti-6Al-4V alloy. The microstructure indicates white β-phase dispersed on the grain boundaries of dark α-phase. Cryogenic treatment at-186 °C for 10 h led to the transformation from β-phase to α-phase, resulting in coarsening of α. Hardness of the cryogenically treated sample was observed to decrease and wear loss was observed to increase; this can be attributed to the coarsening of α-phase.

Influences of Solution Temperatures on Microstructure and Mechanical Properties of near α Titanium Alloy

2021 ◽  
Vol 1035 ◽  
pp. 89-95
Author(s):  
Chao Tan ◽  
Zi Yong Chen ◽  
Zhi Lei Xiang ◽  
Xiao Zhao Ma ◽  
Zi An Yang
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
High Temperature ◽  
Room Temperature ◽  
Solution Temperature ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Β Phase ◽  
Α Phase ◽  
New Type

A new type of Ti-Al-Sn-Zr-Mo-Si series high temperature titanium alloy was prepared by a water-cooled copper crucible vacuum induction melting method, and its phase transition point was determined by differential thermal analysis to be Tβ = 1017 °C. The influences of solution temperature on the microstructures and mechanical properties of the as-forged high temperature titanium alloy were studied. XRD results illustrated that the phase composition of the alloy after different heat treatments was mainly α phase and β phase. The microstructures showed that with the increase of the solution temperature, the content of the primary α phase gradually reduced, the β transformation structure increased by degrees, then, the number and size of secondary α phase increased obviously. The tensile results at room temperature (RT) illustrated that as the solution temperature increased, the strength of the alloy gradually increased, and the plasticity decreased slightly. The results of tensile test at 650 °C illustrated that the strength of the alloy enhanced with the increase of solution temperature, the plasticity decreased first and then increased, when the solution temperature increased to 1000 °C, the alloy had the best comprehensive mechanical properties, the tensile strength reached 714.01 MPa and the elongation was 8.48 %. Based on the room temperature and high temperature properties of the alloy, the best heat treatment process is finally determined as: 1000 °C/1 h/AC+650 °C/6 h/AC.

Microstructure Evolution of near α Titanium Alloy during Multi-Step Thermomechanical Deformation Process

2021 ◽  
Vol 1035 ◽  
pp. 305-311
Author(s):  
Qing Shan Liu ◽  
Bo Long Li ◽  
Tong Bo Wang ◽  
Cong Cong Wang ◽  
Peng Qi ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Strain Curve ◽  
Optical Microscope ◽  
Phase Content ◽  
Β Phase ◽  
Α Phase ◽  
Gleeble 3500

A new type of near α high temperature titanium alloy of Ti-Al-Sn-Zr-Mo-Si-Er was studied. The samples with different primary α phase content were prepared by solid solution at 950 °C/1 h—1010 °C/1 h. The multi-step hot compression experiments were carried out by Gleeble-3500 in a sequence of upper region of α + β phase, then followed by lower region of α + β phase. The effects of primary α phase content and deformation temperature on the microstructure of the alloy were studied by means of true stress-strain curve and optical microscope. The results show that the content of primary α phase gradually decreases from 45.4% at 950°C to 0% at 1010°C. As the deformation temperature decreases from 940°C to 900°C, the content of α phase increases gradually from 65% to 94%, which is changed from dynamic recrystallization to deformed structure elongated along RD direction. It is found that the arrangement of α phase along RD direction is the longest at 920°C. With the increase of the deformation temperature in the multi-step high temperature region from 970°C to 990°C, the width of deformed α phase decreases from 3.64 μm at 970°C to 2.71 μm at 990°C. The optimized microstructure is composed of 20% primary α phase arranged along RD direction. This process has a certain potential in the process of hot deformation of the alloy. Key words: high temperature titanium alloy, primary α phase, multi-step hot deformation

scholarly journals High-Temperature Deformation Behavior and Microstructural Characterization of Ti-35421 Titanium Alloy

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3623 ◽  
Author(s):  
Danying Zhou ◽  
Hua Gao ◽  
Yanhua Guo ◽  
Ying Wang ◽  
Yuecheng Dong ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Deformation Temperature ◽  
Phase Region ◽  
Temperature Deformation ◽  
Β Phase ◽  
Α Phase

A self-designed Ti-35421 (Ti-3Al-5Mo-4Cr-2Zr-1Fe wt%) titanium alloy is a new type of low-cost high strength titanium alloy. In order to understand the hot deformation behavior of Ti-35421 alloy, isothermal compression tests were carried out under a deformation temperature range of 750–930 °C with a strain rate range of 0.01–10 s−1 in this study. Electron backscatter diffraction (EBSD) was used to characterize the microstructure prior to and post hot deformation. The results show that the stress–strain curves have obvious yielding behavior at a high strain rate (>0.1 s−1). As the deformation temperature increases and the strain rate decreases, the α phase content gradually decreases in the α + β phase region. Meanwhile, spheroidization and precipitation of α phase are prone to occur in the α + β phase region. From the EBSD analysis, the volume fraction of recrystallized grains was very low, so dynamic recovery (DRV) is the dominant deformation mechanism of Ti-35421 alloy. In addition to DRV, Ti-35421 alloy is more likely to occur in continuous dynamic recrystallization (CDRX) than discontinuous dynamic recrystallization (DDRX).

scholarly journals Formation of Large Size Precipitate-Free Zones in β Annealing of the Near-β Ti-55531 Titanium Alloy

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 544 ◽  
Author(s):  
Xueqi Jiang ◽  
Xiaoqiang Shi ◽  
Xiaoguang Fan ◽  
Qi Li
Keyword(s):  
Titanium Alloy ◽  
Phase Transformation ◽  
Heterogeneous Nucleation ◽  
Isothermal Heat Treatment ◽  
Precipitate Free Zone ◽  
Mode Iii ◽  
Slow Cooling ◽  
Free Zone ◽  
Large Size ◽  
Α Phase

Large size (>10000 μm2) precipitate-free zones in the absence of microsegregation were observed in the near-β Ti-55531 titanium alloy after furnace cooling from high temperature and longtime annealing in the single-β phase field. To reveal the formation mechanism of the large size precipitate-free zone, continuous cooling and isothermal heat treatment were carried out to investigate the β-α phase transformation process. It was found that the large size precipitate free zone is attributed to the heterogeneous nucleation of α phase. The nucleation site evolves in three different modes: I-random nucleation inside the β grain, II-network nucleation inside the β grain and, III-heterogeneous nucleation on the precipitated α phase. Modes I and II lead to homogeneous transformed structure while Mode III results in the large size precipitate-free zone. Both modes II and III are promoted at high annealing temperature, rapid cooling above 600 °C or slow cooling below 600 °C. Mode II is common as it can minimize the strain energy in phase transformation. As a result, the formation of the large size precipitate-free zone is not deterministic.

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