Dynamic Softening and Hardening Behavior and the Micro-Mechanism of a TC31 High Temperature Titanium Alloy Sheet within Hot Deformation

TC31 is a new type of α+β dual phase high temperature titanium alloy, which has a high specific strength and creep resistance at temperatures from 650 °C to 700 °C. It has become one of the competitive candidates for the skin and air inlet components of hypersonic aircraft. However, it is very difficult to obtain the best forming windows for TC31 and to form the corresponding complex thin-walled components. In this paper, high temperature tensile tests were carried out at temperatures ranging from 850 °C to 1000 °C and strain rates ranging from 0.001 s−1 to 0.1 s−1, and the microstructures before and after deformation were characterized by an optical microscope, scanning electron microscope, and electron back-scatter diffraction. The dynamic softening and hardening behaviors and the corresponding micro-mechanisms of a TC31 titanium alloy sheet within hot deformation were systematically studied. The effects of deformation temperature, strain rate, and strain on microstructure evolution were revealed. The results show that the dynamic softening and hardening of the material depended on the deformation temperature and strain rate, and changed dynamically with the strain. Obvious softening occurred during hot tensile deformation at a temperature of 850 °C and a strain rate of 0.001 s−1~0.1 s−1, which was mainly caused by void damage, deformation heat, and dynamic recrystallization. Quasi-steady flowing was observed when it was deformed at a temperature of 950 °C~1000 °C and a strain rate of 0.001 s−1~0.01 s−1 due to the relative balance between the dynamic softening and hardening. Dynamic hardening occurred slightly with a strain rate of 0.001 s−1. Mechanisms of dynamic recrystallization transformed from continuous dynamic recrystallization to discontinuous dynamic recrystallization with the increase in strain when it was deformed at a temperature of 950 °C and a strain rate of 0.01 s−1. The grain size also decreased gradually due to the dynamic recrystallization, which provided an optimal forming condition for manufacturing thin-walled components with the desired microstructure and an excellent performance.

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

Materials ◽

10.3390/ma13163623 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3623 ◽

Cited By ~ 2

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).

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Analysis of Hot Deformation Dynamics of TC18 Titanium Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.878 ◽

2013 ◽

Vol 747-748 ◽

pp. 878-884 ◽

Cited By ~ 1

Author(s):

Qing Rui Wang ◽

Ai Xue Sha ◽

Xing Wu Li ◽

Li Jun Huang

Keyword(s):

Titanium Alloy ◽

Phase Transformation ◽

Flow Stress ◽

Strain Rate ◽

Hot Deformation ◽

Deformation Temperature ◽

Relationship Model ◽

Deformation Dynamics ◽

Deformation Mechanics ◽

Versus Strain

The effect of strain rate and deformation temperature on flow stress of TC18 titanium alloy was studied through heat simulating tests in 760~960 with temperature interval and the strain rate interval in 0.01~10s-1. Relationship model of flow stress versus strain was established and hot deformation mechanics of TC18 titanium alloy was analyzed. The results show that the flow stress reduces obviously as the deformation temperature increases or the strain rate decreases. Dynamic recovery occurs at high strain rate above phase transformation point, while dynamic recrystallization occurs at low strain rate as well as at the temperature below phase transformation point.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1035.305 ◽

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

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Constitutive Relationship for Hot Deformation of TB18 Titanium Alloy

Advances in Materials Science and Engineering ◽

10.1155/2020/5716548 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Qiang Fu ◽

Wuhua Yuan ◽

Wei Xiang

Keyword(s):

Titanium Alloy ◽

Flow Stress ◽

Dynamic Recrystallization ◽

Strain Rate ◽

Hot Deformation ◽

Flow Behavior ◽

Peak Stress ◽

Constitutive Relationship ◽

Flow Localization ◽

Phase Zone

In the present work, the hot deformation behavior of TB18 titanium alloy was investigated by isothermal hot compression tests with temperatures from 650 to 880°C and strain rates from 0.001 to 10 s−1. The flow curves after friction and temperature correction show that the peak stress decreased with the temperature increase and the strain rate decrease. Three typical characteristics of flow behavior indicate the dynamic softening behavior during hot deformation. At a strain rate of 0.001∼0.01 s−1, the flow stress continues to decrease as the strain rate increases after the flow stress reaches the peak stress; the flow softening mechanism is dynamic recovery and dynamic recrystallization at a lower temperature and dynamic recrystallization at a higher temperature. The discontinuous yielding phenomenon could be seen at a strain rate of 1 s−1, dynamic recrystallization took place in the β single-phase zone, and flow localization bands were observed in the α + β two-phase zone. At a higher strain rate of 10 s−1, the flow instabilities were referred to as the occurrence of flow localization by adiabatic heat. Constitutive equation considering the compensation of strain was also established, and the results show high accuracy to predict the flow stress with the correlation coefficient of 99.2% and the AARE of 6.1%, respectively.

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A STUDY OF DYNAMIC RECRYSTALLIZATION IN TA15 TITANIUM ALLOY DURING HOT DEFORMATION BY CELLULAR AUTOMATA MODEL

International Journal of Modern Physics B ◽

10.1142/s0217979209060269 ◽

2009 ◽

Vol 23 (06n07) ◽

pp. 934-939 ◽

Cited By ~ 2

Author(s):

DONG HE ◽

JING CHUAN ZHU ◽

YANG WANG ◽

YONG LIU

Keyword(s):

Titanium Alloy ◽

Flow Stress ◽

Dislocation Density ◽

Cellular Automata ◽

Dynamic Recrystallization ◽

Strain Rate ◽

Hot Deformation ◽

Temperature Filed ◽

Ca Model ◽

Grain Growth Model

The dynamic recrystallization (DRX) of TA 15 ( Ti -6 Al -2 Zr -1 Mo -1 V ) titanium alloy during the hot deformation process was studied by the Cellular Automata (CA) model which is base on the dislocation density theory. To build the CA model, the dislocation density model, dynamic recovery model, nucleation model and grain growth model were introduced and developed. The influences of strain rate on the microstructure evolution and flow stress character were investigated which shows that high strain rate leads to later DRX appearance, high flow stress peak value, small mean size of recrystallizing grains( R -grains) and low DRX percentage, but they have the similar Avrami curve. The characteristic of DRX process in a modeling non-uniform temperature filed (NTF) has been studied. All the simulation results show good agreement with the pioneer's work and experimental results.

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Microstructural Variation and a Physical Mechanism Model for a Ti-55511 Alloy during Double-Stage Hot Deformation with Stepped Strain Rates in the β Region

Materials ◽

10.3390/ma14216371 ◽

2021 ◽

Vol 14 (21) ◽

pp. 6371

Author(s):

Dao-Guang He ◽

Gang Su ◽

Yong-Cheng Lin ◽

Yu-Qiang Jiang ◽

Zhou Li ◽

...

Keyword(s):

High Temperature ◽

Dynamic Recrystallization ◽

Strain Rate ◽

Hot Deformation ◽

Physical Mechanism ◽

Nucleation Mechanism ◽

Strain Rates ◽

Mechanism Model ◽

Flow Features ◽

Variation Characteristics

The microstructural variation and high-temperature flow features of a Ti-55511 alloy in the β region are studied by utilizing double-stage compression with a stepped strain rate. The results demonstrate that the stresses in the latter stage of hot compression markedly reduce as the strain at the previous stage or the strain rate at the previous/latter stage drops. Moreover, the annihilation/interaction of substructures is promoted, and the distinct refinement of the dynamic recrystallization (DRX) in the β grain can be found. However, the coarsening of the β grain and the consumption of dislocation substructures are accelerated at high temperatures. Furthermore, the principal DRX nucleation mechanism of the Ti-55511 alloy during double-stage compression with a stepped strain rate in the β region is discontinuous DRX. Additionally, by using the microstructural variation characteristics related to the forming parameters, a physical mechanism equation is modeled to forecast the forming features, the DRX fraction, and the size of the β grain in the investigated alloy. The forecasted results are in accordance with the tested results, indicating that the established model can accurately forecast the microstructure variation and flow features of the studied alloy.

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Characterization of Hot Deformation Behavior and Dislocation Structure Evolution of an Advanced Nickel-Based Superalloy

Metals ◽

10.3390/met10070920 ◽

2020 ◽

Vol 10 (7) ◽

pp. 920 ◽

Cited By ~ 2

Author(s):

Zhihao Yao ◽

Hongying Wang ◽

Jianxin Dong ◽

Jinglin Wang ◽

He Jiang ◽

...

Keyword(s):

Dynamic Recrystallization ◽

Strain Rate ◽

Hot Deformation ◽

Deformation Behavior ◽

Deformation Temperature ◽

Flow Instability ◽

Processing Condition ◽

Constitutive Relationship ◽

Structure Evolution ◽

Hot Deformation Behavior

The hot deformation behavior of an advanced nickel-based Haynes282 superalloy was systematically investigated employing isothermal compression tests in the sub-solvus and super-solvus temperature with various strain rates. The influence of deformation temperature and strain rate on the microstructure was studied by transmission electron microscope. The results reveal that the interaction between work hardening and dynamic softening did not reach equilibrium under lower deformation temperature and higher strain rate. The active energy of alloy is around 537.12 kJ/mol and its hot deformation constitutive relationship equation was expressed. According to the processing map and microstructure observations, two unsafe flow instability domains should be avoided. The optimum hot processing condition for homogeneous and fine dynamic recrystallization grains are obtained. TEM micrograph observations indicated that deformation temperature and strain rate affected recrystallization by affecting the evolution of dislocation substructures within the alloy. The nucleation and growth of DRX grains can be promoted by the relatively high deformation temperature and low strain rate. The main mechanism of dynamic recrystallization nucleation preferred to discontinuous dynamic recrystallization and the typical feature of discontinuous dynamic recrystallization showed grain boundary migration nucleation. The findings improve the understanding of hot deformation behavior and dislocation substructures evolution of the superalloy, which benefits the accurate control of microstructures of nickel-based superalloys, and tailors the properties of final components used in the land-based gas turbine.

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Flow Behavior and Microstructural Evolution of a 7039 Aluminum Alloy during Hot Deformation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.2395 ◽

2011 ◽

Vol 239-242 ◽

pp. 2395-2398 ◽

Cited By ~ 1

Author(s):

Hui Zhong Li ◽

Xiao Peng Liang ◽

Min Song ◽

Min Zeng

Keyword(s):

Aluminum Alloy ◽

Flow Stress ◽

Dynamic Recrystallization ◽

Strain Rate ◽

Microstructural Evolution ◽

Hot Deformation ◽

Deformation Temperature ◽

Flow Behavior ◽

Thermal Simulation ◽

Strain Rates

The flow behavior of a 7039 aluminum alloy and the corresponding microstructural evolution during hot deformation were studied by Gleeble-1500 thermal simulation tests, EBSD and TEM observations with temperatures ranging from 300 °C to 500 °C under strain rates from 0.01 s-1 to 10 s-1. It has been shown that the flow stress increases with the decrease in the deformation temperature and increase in the strain rate. The degree of dynamic recrystallization (DRX) increases with the increase in the deformation temperature and strain rate in 7039 aluminum alloy. The complete dynamic recrystallization occurs at 500 °C with a strain rate of 10 s-1.

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Effect of Equal Channel Angular Pressing on the Dynamic Softening Behavior of Ti-6Al-4V Alloy in the Hot Deformation Process

Materials ◽

10.3390/ma14010232 ◽

2021 ◽

Vol 14 (1) ◽

pp. 232

Author(s):

Zhiyong Zhao ◽

Jun Gao ◽

Yaoqi Wang ◽

Yanling Zhang ◽

Hongliang Hou

Keyword(s):

Dynamic Recrystallization ◽

Strain Rate ◽

Equal Channel Angular Pressing ◽

Hot Deformation ◽

Deformation Process ◽

Hot Compression ◽

Deformation Condition ◽

Softening Behavior ◽

Angular Pressing ◽

Dynamic Softening

To investigate the effect of equal channel angular pressing (ECAP) on the deformation of Ti-6Al-4V alloy at a higher temperature, hot compression tests were conducted on alloys having two different initial microstructures (the original alloy (Pre-ECAP) and ECAP-deformed alloy (Post-ECAP)). Post-ECAP, the alloy showed a higher degree of dynamic softening during the hot deformation process due to its finer grain size and higher distortion energy. The flow stress of Post-ECAP alloy was higher than the Pre-ECAP alloy at 500 °C when ε˙= 0.003 s−1. However, the stress of the Post-ECAP alloy decreased rapidly with increasing temperature and strain rate, until the stress value was much lower than that of Pre-ECAP at 700 °C when ε˙= 0.03 s−1. The value of the dynamic softening coefficient revealed that the dynamic softening behavior of Post-ECAP was more pronounced than that of Pre-ECAP in the hot compression deformation process. The main dynamic softening mechanism of Pre-ECAP is dynamic recovery, while the dynamic recrystallization process plays a more important role in the deformation process of Post-ECAP alloy. The microstructures observation results showed that dynamic recrystallization was more likely to occur to Post-ECAP alloys under the same deformation condition. Almost fully dynamic recrystallization had occurred in the deformation process of Post-ECAP at 700 °C and a strain rate of ε˙= 0.01 s−1. The grains of Post-ECAP alloys were further refined. The Post-ECAP alloy exhibits better plastic deformation at temperatures higher than 600 °C due to its significant dynamic recrystallization.

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Thermal Deformation Behavior of Ti-6Mo-5V-3Al-2Fe Alloy

Crystals ◽

10.3390/cryst11101245 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1245

Author(s):

Lin Han ◽

Haoyu Zhang ◽

Jun Cheng ◽

Ge Zhou ◽

Chuan Wang ◽

...

Keyword(s):

Dynamic Recrystallization ◽

Strain Rate ◽

Hot Deformation ◽

Deformation Temperature ◽

Rate Sensitivity ◽

Hot Working ◽

Sensitivity Index ◽

Strain Rate Sensitivity Index ◽

Deformation Activation Energy ◽

New Type

The Gleeble-3800 thermal simulation machine was used to perform hot compression experiments on a new type of β alloy, Ti-6Mo-5V-3Al-2Fe (wt.%), at temperatures of 700–900 °C, strain rates of 5 × 10−1 to 5 × 10−4 s−1, and total strain of 0.7. Transmission and EBSD techniques were used to observe the microstructure. The results show that the deformation activation energy of the alloy was 356.719 KJ/mol, and dynamic recrystallization occurred during the hot deformation. The higher the deformation temperature was, the more obvious the dislocations that occurred and the more sufficient the dynamic recrystallization that occurred, but the effect of strain rate was the opposite. When the deformation temperature was higher than the phase transition point, the recrystallized grains clearly grew up. The calculated strain rate sensitivity index of the alloy was 0.14–0.29. The constitutive equation of hot deformation of Ti-6Mo-5V-3Al-2Fe alloy was established by using the Arrhenius hyperbolic sine equation. The dynamic DMM hot working diagram with the strain of 0.7 was constructed. The relatively good hot working area of the alloy was determined to be the deformation temperature of 700–720 °C and 0.0041–0.0005 s−1.

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