scholarly journals Macro-mesoscale microstructural evolution modeling under hot forging of a Ti-17 alloy with a lamellar (α+β) starting microstructure

2020 ◽  
Vol 321 ◽  
pp. 13005
Author(s):  
Hiroaki Matsumoto ◽  
Kenta Yamanaka ◽  
Akihiko Chiba ◽  
Yoko Yamabe-Mitarai ◽  
Yoshio Itsumi
Keyword(s):  
Dynamic Recrystallization ◽  
Microstructural Evolution ◽  
Hot Forging ◽  
Fem Simulation ◽  
Constitutive Models ◽  
Fem Analysis ◽  
Dominant Mode ◽  
Strain Rates ◽  
Continuous Dynamic Recrystallization ◽  
Β Phase

Microstructural conversion mechanisms under hot forging process (at temperatures ranging from 750 °C to 1050 °C and strain rates ranging from 10–3 s–1 to 1 s–1) of a Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) alloy with a lamellar starting microstructure were experimentally identified in this work. After that, constitutive formulae for predicting the microstructural evolution were established followed by calculation using finite-element (FEM) analysis. In the α phase, a lamellae kinking is the dominant mode in the higher strain rate region and dynamic globularization frequently occurs at higher temperatures. On the other hand, continuous dynamic recrystallization is the dominant mode below the transition temperature, Tβ (880~890 °C) in the β phase. And, at conditions of lower strain rates and higher temperatures, dynamic recovery tends to be more active. For microstructural prediction, a set of constitutive equations modeling the microstructural evolution and forging properties are established by optimizing the experimental data followed by implementation in the DEFORM-3D software package. Herein, microstructural evolution on dynamic globularization process, dynamic recrystallization behavior are predicted according to both approaches of physical model and artificial neural network model followed by FEM simulation. In these calculated results, there is a satisfactory agreement between the experimental and simulated results, indicating that the established series of constitutive models can be used to reliably predict the properties of a Ti-17 alloy after forging.

scholarly journals Microstructural Evolution and Refinement Mechanism of a Beta–Gamma TiAl-Based Alloy during Multidirectional Isothermal Forging

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2496 ◽  
Author(s):  
Kai Zhu ◽  
Shoujiang Qu ◽  
Aihan Feng ◽  
Jingli Sun ◽  
Jun Shen
Keyword(s):  
Dynamic Recrystallization ◽  
Microstructural Evolution ◽  
Lamellar Microstructure ◽  
Phase Region ◽  
Second Step ◽  
Electron Backscattered Diffraction ◽  
Isothermal Forging ◽  
Continuous Dynamic Recrystallization ◽  
Mixture Phase ◽  
Refinement Mechanism

Multidirectional isothermal forging (MDIF) was used on a Ti-44Al-4Nb-1.5Cr-0.5Mo-0.2B (at. %) alloy to obtain a crack-free pancake. The microstructural evolution, such as dynamic recovery and recrystallization behavior, were investigated using electron backscattered diffraction and transmission electron microscopy methods. The MDIF broke down the initial near-lamellar microstructure and produced a refined and homogeneous duplex microstructure. γ grains were effectively refined from 3.6 μm to 1.6 μm after the second step of isothermal forging. The ultimate tensile strength at ambient temperature and the elongation at 800 °C increased significantly after isothermal forging. β/B2→α2 transition occurred during intermediate annealing, and α2 + γ→β/B2 transition occurred during the second step of isothermal forging. The refinement mechanism of the first-step isothermal forging process involved the conversion of the lamellar structure and discontinuous dynamic recrystallization (DDRX) of γ grains in the original mixture-phase region. The lamellar conversion included continuous dynamic recrystallization and DDRX of the γ laths and bugling of the γ phase. DDRX behavior of γ grains dominated the refinement mechanism of the second step of isothermal forging.

scholarly journals Hot Deformation Behavior and Microstructure Evolution of 6063 Aluminum Alloy Modified by Rare Earth Y and Al-Ti-B Master Alloy

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4244 ◽  
Author(s):  
Wanwu Ding ◽  
Xiaoxiong Liu ◽  
Xiaoyan Zhao ◽  
Taili Chen ◽  
Haixia Zhang ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Rare Earth ◽  
Dynamic Recrystallization ◽  
Master Alloy ◽  
Hot Deformation ◽  
True Strain ◽  
Constitutive Models ◽  
Hot Workability ◽  
Continuous Dynamic Recrystallization ◽  
6063 Aluminum Alloy

The hot deformation behaviors of the new 6063 aluminum alloy modified by rare earth Y and Al-Ti-B master alloy were studied through isothermal hot compression experiments on the Gleeble-3800 thermal simulator. By characterizing the flow curves, constitutive models, hot processing maps, and microstructures, we can see from the true stress–true strain curves that the flow stress decreases with the increase of deformation temperature and the decrease of strain rate. Through the calculation of the constitutive equation, we derived that the activation energy of the new composite modified 6063 aluminum alloy is 224.570 KJ/mol. we roughly obtained its excellent hot processing range of temperatures between 470–540 °C and the strain rates of 0.01–0.1 s−1. The verification of the deformed microstructure shows that with the decrease of lnZ, the grain boundary changes from a low-angle one to a high-angle one and the dynamic recrystallization is dominated by geometric dynamic recrystallization and continuous dynamic recrystallization. Analysis of typical samples at 480 °C/0.01 s−1 shows that the addition of rare earth Y mainly helps form Al3Y5 and AlFeSiY phases, thus making the alloy have the performance of high-temperature recrystallization, which is beneficial to the hot workability of the alloy.

Dynamic Recrystallization of Zircaloy-4 during Working within the Upper α-Range

2004 ◽  
Vol 467-470 ◽  
pp. 1151-1156 ◽  
Author(s):  
Cédric Chauvy ◽  
Pierre Barbéris ◽  
Frank Montheillet
Keyword(s):  
Dynamic Recrystallization ◽  
Large Strain ◽  
Large Angle ◽  
Rate Sensitivity ◽  
Large Strains ◽  
Strain Rates ◽  
Compression Tests ◽  
Continuous Dynamic Recrystallization ◽  
Ebsd Technique ◽  
Continuous Dynamic

Compression tests were used to simulate simple deformation paths within the upper a-range of Zircaloy-4 (i.e. 500°C-750°C). The mechanical behaviour reveals two different domains : at low temperatures and large strain rates, strain hardening takes place before flow softening, whereas this first stage disappears at lower flow stress levels. Strain rate sensitivity and activation energy were determined for both domains. Dynamic recrystallization was investigated using the Electron BackScattering Diffraction (EBSD) technique. It appears that the mechanism involved here is continuous dynamic recrystallization (CDRX), based on the increasing misorientation of subgrain boundaries and their progressive transformation into large angle boundaries. At low strains (e £ 0.3), CDRX kinetics are similar whatever the deformation conditions, while higher temperatures and lower strain rates promote recrystallization at large strains.

scholarly journals Tensile Properties and Microstructural Evolution of an Al-Bearing Ferritic Stainless Steel at Elevated Temperatures

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 86 ◽  
Author(s):  
Ying Han ◽  
Jiaqi Sun ◽  
Yu Sun ◽  
Jiapeng Sun ◽  
Xu Ran
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Ferritic Stainless Steel ◽  
Microstructural Evolution ◽  
Deformation Mechanism ◽  
Strain Rates

The influence of temperature and strain rate on the hot tensile properties of 0Cr18AlSi ferritic stainless steel, a potential structural material in the ultra-supercritical generation industry, was investigated at temperatures ranging from 873 to 1123 K and strain rates of 1.7 × 10−4–1.7 × 10−2 s−1. The microstructural evolution linked to the hot deformation mechanism was characterized by electron backscatter diffraction (EBSD). At the same strain rate, the yield strength and ultimate tensile strength decrease rapidly from 873 K to 1023 K and then gradually to 1123 K. Meanwhile, both yield strength and ultimate tensile strength increase with the increase in strain rate. At high temperatures and low strain rates, the prolonged necking deformation can be observed, which determines the ductility of the steel to some extent. The maximum elongation is obtained at 1023 K for the strain rates of 1.7 × 10−3 and 1.7 × 10−2 s−1, while this temperature is postponed to 1073 K once decreasing the strain rate to 1.7 × 10−4 s−1. Dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX) are found to be the main softening mechanisms during the hot tensile deformation. With the increase of temperature and the decrease of strain rate (i.e., 1123 K and 1.7 × 10−4 s−1), the sub-grain coalescence becomes the main mode of CDRX that evolved from the sub-grain rotation. The gradual decrease in strength above 1023 K is related to the limited increase of dynamic recrystallization and the sufficient DRV. The area around the new small recrystallized grains on the coarse grain boundaries provides the nucleation site for cavity, which generally results in a reduction in ductility. Constitutive analysis shows that the stress exponent and the deformation activation energy are 5.9 and 355 kJ·mol−1 respectively, indicating that the dominant deformation mechanism is the dislocations motion controlled by climb. This work makes a deeply understanding of the hot deformation behavior and its mechanism of the Al-bearing ferritic stainless steel and thus provides a basal design consideration for its extensive application.

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

2011 ◽  
Vol 239-242 ◽  
pp. 2395-2398 ◽  
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.

Continuous Dynamic Recrystallization in Dual-Phase Titanium Alloy in Superplasticity

2018 ◽  
Vol 385 ◽  
pp. 126-130 ◽  
Author(s):  
Keita Sekiguchi ◽  
Hiroshi Masuda ◽  
Hirobumi Tobe ◽  
Eiichi Sato
Keyword(s):  
Titanium Alloy ◽  
Dynamic Recrystallization ◽  
Early Stage ◽  
Continuous Dynamic Recrystallization ◽  
New Class ◽  
Β Phase ◽  
Α Phase ◽  
Slip Planes ◽  
The Difference ◽  
Continuous Dynamic

A new class of superplastic titanium alloy, Ti–4.5Al–2.5Cr–1.2Fe–0.1C–0.3Cu–0.3Ni, was deformed at 1073 K with strain rates of 1×10−4–1×10−1 s−1, and microstructures in the condition between superplastic regions II and III (= 1×10−2 s−1) were observed using scanning electron microscope and electron back-scattered diffraction. Continuous dynamic recrystallization was observed, resulting in grain refinement both in α and β phases. The grain size decreased significantly in α phase at the early stage of the deformation and in β phase at the later stage. In the recrystallized microstructure, the major sub-boundaries formed perpendicularly to slip directions <11−20> in α phase and parallel to slip planes {110} in β phase, which might be caused by the difference in the symmetry of the crystal structures.

Dynamic Recrystallization Behavior of Biomedical CCM Alloys in Hot Compression Process

2010 ◽  
Vol 654-656 ◽  
pp. 1275-1278 ◽  
Author(s):  
Yun Ping Li ◽  
Shingo Kurosu ◽  
Emi Onodera ◽  
Hiroaki Matsumoto ◽  
Akihiko Chiba
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Forging ◽  
Stacking Faults ◽  
Recrystallization Behavior ◽  
Compression Tests ◽  
Compression Process ◽  
Continuous Dynamic Recrystallization ◽  
Computer Aided ◽  
Dynamic Recrystallization Behavior ◽  
Continuous Dynamic

Dynamic recrystallization behavior of Co-29Cr-6Mo-0.16N alloy was analyzed in details. Compression tests were carried out in a computer aided Thermecmaster- Z hot forging simulator. The results showed that uniformly distributed superfine grain size could be obtained by continuous dynamic recrystallization (DRX) process; Texture-free microstructure with uniformly distributed equiaxed fine grains was obtained. The formation of profuse stacking faults and their subsequent intersections are considered to be the principle mechanisms of DRX.

Continuous Dynamic Recrystallization during Warm Deformation of Tempered Lath Martensite in a Medium Carbon Steel

2012 ◽  
Vol 508 ◽  
pp. 124-127 ◽  
Author(s):  
Un Hae Lee ◽  
Naoya Kamikawa ◽  
Goro Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Dynamic Recrystallization ◽  
Microstructural Evolution ◽  
Boundary Migration ◽  
Lath Martensite ◽  
Medium Carbon Steel ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Dynamic Recrystallization Behavior ◽  
Fine Grained Structure ◽  
Continuous Dynamic

To Understand the Mechanisms of Accelerated Dynamic Recrystallization Behavior during the Warm Deformation of Martensites, the Tempered Lath Martensite of 0.4C Steel (Fe-0.399%C-1.96%Mn in Mass %) Was Deformed at 650 °C in Compression to Different Reductions, and Microstructural Evolution Was Investigated. During the Deformation, an Initial Lath Martensite Structure with a Complicated Morphology Was Gradually Changed into More Equiaxed Structure. After 50% Reduction and above, an Equiaxed, Fine Grained Structure Mainly Surrounded by High-Angle Boundaries Was Uniformly Formed with Dislocation Substructures, where the Dislocation Density in the Grains Is Relatively Low. Since there Was No Significant Boundary Migration during this Process, this Microstructural Evolution Can Be Termed as Continuous Dynamic Recrystallization.

Analysis on Phases and Grain Evolution of TC4 Ti-Alloy in Hot Forming in Time and Space Based on Deform-3D

2016 ◽  
Vol 703 ◽  
pp. 56-60
Author(s):  
Guo Hui Quan ◽  
Xu Yong Zhao
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Forging ◽  
Ti Alloy ◽  
Analysis Software ◽  
Time And Space ◽  
Element Analysis ◽  
Β Phase ◽  
Α Phase ◽  
Hot Forging Process ◽  
Deform 3D

In the hot forging process of TC4 Ti-alloy large die forging two beam, the dynamic recrystallization of α phase and recovery of β phase were happened. Using Deform-3D finite element analysis software, the evolution model of grain and phase is constructed and coupled simulation is carried out, on the foundation of simulation results, the evolution law of α phase dynamic recrystallization and β phase transformation in time and space was obtained, so the optimal control of grain and phase was realized. Thus the performances of TC4 Ti-alloy will be improved and optimized, and all this will provide theoretical basis for the forging of large Ti-alloy components.

Microstructure Prediction in Aluminium Extrusion by Means of FEM Simulation

2007 ◽  
Vol 23 ◽  
pp. 157-160
Author(s):  
Lorenzo Donati ◽  
Luca Tomesani ◽  
Lorella Ceschini ◽  
Iuri Boromei
Keyword(s):  
Plastic Deformation ◽  
Fem Simulation ◽  
Fem Analysis ◽  
Extrusion Process ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Microstructure Prediction ◽  
History Of ◽  
Simulation Results ◽  
Aluminium Extrusion

An original inverse extrusion test was developed in order to study the microstructural evolution in the plastic deformation of 6060 and 6082 aluminium alloys. Sample billets were extracted from commercial logs and subjected to plastic deformation in an inverse extrusion process, particularly aimed at producing different strain and strain rate conditions at representative positions within the billet section. Different experiments were performed at various temperatures and strain rates. The particular thermo-mechanical history of each point in different experiments was then reconstructed by FEM analysis. The cups were sectioned and the microstructure was analysed at some representative locations, to relate it to the FEM simulation results.

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