scholarly journals Dislocation-Controlled Low-Temperature Superplastic Deformation of Ti-6Al-4V Alloy

2021 ◽  
Vol 7 ◽  
Author(s):  
Chao Liu ◽  
Xin Wang ◽  
Ge Zhou ◽  
Feng Li ◽  
Siqian Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Strain Rate ◽  
Deformation Mechanism ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Stress Index ◽  
Sensitivity Index ◽  
Dislocation Glide ◽  
Superplastic Properties ◽  
Superplastic Tension

The superplastic tension and deformation mechanism of Ti-6Al-4V alloy at 923 K and a tensile speed of 10−3, 5 × 10−3, or 5 × 10−2 s−1 was studied on an AG 250KNE electronic tension tester. Through theoretical modeling, the unit dislocation count of this alloy during superplastic deformation was introduced into the Ruano–Wadsworth–Sherby (R-W-S) deformation mechanism map, and a new deformation mechanism map involving dislocation count was plotted. Thereby, the mechanism underling the low-temperature superplastic deformation of this alloy was predicted. It was found the superplastic tension of Ti-6Al-4V at the tested temperature was controlled by dislocation movement, and with an increase in strain rate, the deformation transited from the dislocation-controlled mechanism with a stress index of 4 to the dislocation glide mechanism with a stress index of 5 or 7. At the strain rate of 10−3 s−1, this alloy reached the largest tension rate of 790% and strain rate sensitivity index of 0.52 and had excellent low-temperature superplastic properties.

scholarly journals Rheological Law and Mechanism for Superplastic Deformation of Ti–6Al–4V

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3520
Author(s):  
Chao Liu ◽  
Ge Zhou ◽  
Xin Wang ◽  
Jiajing Liu ◽  
Jianlin Li ◽  
...  
Keyword(s):  
Low Temperature ◽  
Deformation Mechanism ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Material Model ◽  
Sensitivity Index ◽  
Compression Tests ◽  
Dynamic Material Model ◽  
Strain Rate Sensitivity Index ◽  
Evolution Laws

The behaviors of and mechanisms acting in Ti–6Al–4V alloy during low-temperature superplastic deformation were systematically studied by using a Gleeble-3800 thermocompression simulation machine. Focusing on the mechanical behaviors and microstructure evolution laws during low-temperature superplastic compression tests, we clarified the changing laws of the strain rate sensitivity index, activation energy of deformation, and grain index at varying strain rates and temperatures. Hot working images based on the dynamic material model and the deformation mechanism maps involving dislocation quantity were plotted on the basis of PRASAD instability criteria. The low-temperature superplastic compression-forming technique zone and the rheological instability zone of Ti–6Al–4V were analyzed by using hot processing theories. The dislocation evolution laws and deformation mechanisms of the grain size with Burgers vector compensation and the rheological stress with modulus compensation during the low-temperature superplastic compression of Ti–6Al–4V were predicted by using deformation mechanism maps.

Low-Temperature Superplasticity in an Al–Mg–Mn Alloy Subjected to ECAP and Subsequent Isothermal Rolling

2012 ◽  
Vol 735 ◽  
pp. 347-352
Author(s):  
Ilya Nikulin ◽  
Alla Kipelova ◽  
Rustam Kaibyshev
Keyword(s):  
Low Temperature ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Initial Strain Rate ◽  
Sensitivity Coefficient ◽  
Angular Pressing ◽  
Elongation To Failure ◽  
Fine Grained Structure ◽  
Superplastic Properties ◽  
Average Size

An ultra-fine grained structure with an average size of ~ 1 μm was produced in a commercial Al–5.4%Mg–0.5%Mn–0.1%Zr–0.12%Si–0.014%Fe alloy by hot equal-channel angular pressing (ECAP) followed by isothermal rolling (IR). It was found that in the strain rate interval from 5.6×10-4to 2.8×10-2s-1the alloy exhibits a low-temperature superplasticity with elongation-to-failure exceeding 400% and the strain rate sensitivity coefficient of ~0.3. The highest elongation-to-failure of ~ 620% appeared at a temperature of ~ 275°C and an initial strain rate of ~ 5.6×10-3s-1. The relationship between superplastic properties and microstructural evolution of the examined alloy is discussed.

Theoretical Deduction of Constitutive Equations with Variational Parameters during Superplastic Tension

2014 ◽  
Vol 941-944 ◽  
pp. 1509-1512
Author(s):  
Zhi Ping Guan ◽  
Xiao Fang Guan ◽  
Yu Quan Song
Keyword(s):  
Strain Rate ◽  
Test Data ◽  
Constitutive Equations ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
State Equation ◽  
Sensitivity Index ◽  
Tensile Tester ◽  
Strain Rate Sensitivity Index ◽  
Superplastic Tension

In this article, firstly, the strain hardening index and the strain rate sensitivity index were deducted from the general state equation and the mechanical meaning of the two indexes were correspondingly depicted, and then constitutive equations, where both/either of the two indexes appear as constants, were theoretically deducted from the same state equation. Secondly, constitutive equations where both/either of the two indexes present as variables were put forward by numerical simulation. Next, constitutive equations were built, where mechanical variables are replaced by test data obtained on an electronic universal tensile tester with the capacity to carry out a true constant strain rate path. Finally, based on the test data of Zn-5%Al during superplastic tension, it is proved that the theoretical results in this article are valid.

SUPERPLASTIC BEHAVIOR OF COARSE-GRAINED Al-Mg ALLOY

2012 ◽  
Vol 06 ◽  
pp. 401-406 ◽  
Author(s):  
HAOYAN DIAO ◽  
REHAN QAYYUME ◽  
TINGTING WANG ◽  
SHASHA ZHAO ◽  
CHAOLI MA
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Sensitivity Index ◽  
Maximum Elongation ◽  
Dislocation Glide ◽  
Elongation To Failure

This paper concentrates on the study of the superplastic response of coarse-grained Al - Mg alloys under uniaxial tension at different temperatures (ranging from 400°C to 525°C) and strain rates (10-2 S-1, 10-3 S-1 & 10-4 S-1). The microstructures have been analyzed using optical (OM) and transmission electron microscopy (TEM). It has been observed that continuous re-crystallization occurs during hot deformation of the alloy at the temperature of 425°C and strain rate of 10-2S-1. At the temperature of 425°C and strain rate of 3.78×10-3S-1, this Al - Mg alloy has the maximum elongation to failure of 181%, which is sufficient for manufacturing of extremely complex shapes using superplastic forming technology. The constant strain rate sensitivity index m and TEM observations show that in this case deformation mechanism involved is dislocation glide. Recrystallization during the hot tension greatly enhanced the plasticity of the coarse-grained material at a strain rate of about 10-2S-1 and the maximum elongation changes as a function of the strain rate.

scholarly journals Superplastic Behavior of Al-Mg-Mn Alloy: An Experimental & Numerical Investigation

2018 ◽  
Vol 778 ◽  
pp. 45-52
Author(s):  
Tayyaba Zaman ◽  
Rehan Qayyume ◽  
Amjad Ali ◽  
Shaheed Khan ◽  
Chaoli Maa
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Deformation Mechanism ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
Deformation Response ◽  
Surface Optical ◽  
Dominant Deformation Mechanism

Deformation response of Al-4.46Mg-0.48Mn alloy under uniaxial tensile loading was investigated at temperatures ranging from 400°C - 525°C and at strain rates of 3x10-3s-1, 1x 10-3s-1& 10-4s-1. The alloy exhibited a maximum elongation >480% at a strain rate of 10-3s-1and 525°C. At all conditions, the dominant deformation mechanism governing the superplastic deformation was investigated as a function of strain rate and temperature. The contributions of strain-rate sensitivity and strain hardening were analyzed in relation to the observed tensile ductility. The strain rate sensitivity index (m) and average activation energy (Q) values revealed that the dominant deformation mechanism is grain boundary sliding (GBS). The GBS phenomenon was further confirmed through high magnification examination of deformed surface. Optical microscopy (OM) and Scanning Electron Microscopy (SEM) showed that dynamic re-crystallization occurs during hot deformation of the alloy which causes reasonable enhancement of plasticity.

Low-Temperature Superplasticity of the Ni-Based EK61 Superalloy and Application of this Effect to Obtain Sound Solid Phase Joints

2018 ◽  
Vol 385 ◽  
pp. 150-154 ◽  
Author(s):  
Elvina Galieva ◽  
Vener Valitov ◽  
Ramil Lutfullin ◽  
Aerika Bikmukhametova
Keyword(s):  
Low Temperature ◽  
Strain Rate ◽  
Solid Phase ◽  
Rate Sensitivity ◽  
Strain Rate Range ◽  
Sensitivity Factor ◽  
Temperature Range ◽  
Ultrafine Grained ◽  
Nickel Based Alloy ◽  
Superplastic Properties

It is shown that formation of ultrafine-grained structure in EK61 superalloy up to grain sizes less than 1 μm provides to realize superplastic properties. The influence of deformation in the temperature range 600-1100 °C and strain rate range 10-4s-1– 10-3s-1on the microstructure and properties of ultrafine-grained nickel-based alloy EK61 is studied. It is established that in temperature range 750-900 °C the alloy demonstrates superplasticity (SP) characteristics: strain rate sensitivity factor “m” correspond to 0.39-0.59, stable structure and low changes in the form and size of grains. The maximum SP is displayed at temperatures of 800 °C, wherein the elongation is 1431 %. It has been experimentally confirmed that the use of low-temperature superplasticity is a promising for processing sound solid phase joints by pressure welding of similar and dissimilar Ni-based superalloys.

A Study on Superplastic Behavior and Microstructural Evolution of an Isothermally Forged TiAl Based Alloy

2007 ◽  
Vol 551-552 ◽  
pp. 463-466
Author(s):  
Hua Ding ◽  
D. Song ◽  
Z.Q. Pan ◽  
C.P. Zhang ◽  
J.Z. Cui
Keyword(s):  
Strain Rate ◽  
Superplastic Deformation ◽  
Boundary Migration ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Sensitivity Index ◽  
Superplastic Behavior ◽  
Strain Rate Sensitivity Index ◽  
Boundary Sliding ◽  
Equiaxed Grains

Superplastic behavior and microstructure evolution of an isothermally forged Ti-47Al-1Cr-1V-1.5Mo-1.5Nb alloy were investigated. The results showed that the strain rate sensitivity index, m, increased with strain during the superplastic deformation, and it kept as a constant when the strain reached a certain value. The maximum value of m was 0.53 at 900°C and strain rate of 5x10-4 s-1. During the superplastic deformation, the as received material with lamellae and subgrains were refined due to dynamic recrystallization, and small and equiaxed grains with high angle boundaries were formed, creating a better condition for superplastic deformation. Grain boundary sliding and boundary migration were the main superplastic deformation mechanisms and slip and twining were also very important during the superplastic deformation of the alloy.

scholarly journals Low-Temperature Superplasticity and Deformation Mechanism of Ti-6Al-4V Alloy

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1212 ◽  
Author(s):  
Ge Zhou ◽  
Lijia Chen ◽  
Lirong Liu ◽  
Haijian Liu ◽  
Heli Peng ◽  
...  
Keyword(s):  
Low Temperature ◽  
Deformation Mechanism ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Deformation Mechanisms ◽  
Temperature Deformation ◽  
Deformation Activation Energy ◽  
Before And After ◽  
Different Temperatures ◽  
Elongation To Failure

The low-temperature superplastic tensile behavior and the deformation mechanisms of Ti-6Al-4V alloy are investigated in this paper. Through the experiments carried out, elongation to failure (δ) is calculated and a set of values are derived that subsequently includes the strain rate sensitivity exponent (m), deformation activation energy (Q) at low-temperature superplastic deformation, and the variation of δ, m and Q at different strain rates and temperatures. Microstructures are observed before and after superplastic deformation. The deformation mechanism maps incorporating the density of dislocations inside grains at temperatures of 973 and 1123 K are drawn respectively. By applying the elevated temperature deformation mechanism maps based on Burgers vector compensated grain size and modulus compensated stress, the dislocation quantities and low-temperature superplastic deformation mechanisms of Ti-6Al-4V alloy at different temperatures within appropriate processing regime are elucidated.

Common Mechanism for Superplastic Deformation in Different Classes of Materials

2012 ◽  
Vol 735 ◽  
pp. 26-30 ◽  
Author(s):  
K. Anantha Padmanabhan ◽  
Herbert Gleiter
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Physical Mechanism ◽  
Rate Sensitivity ◽  
Common Mechanism ◽  
Sensitivity Index ◽  
Strain Rate Sensitivity Index ◽  
Definition Of

An earlier proposal is generalized to explain superplasticity in different classes of materials and grain size ranges. A definition of “superplasticity” as due to a unique physical mechanism, rather than in terms of extreme elongations and/ or strain rate sensitivity index, m, being more than or equal to 0.30 emerges.

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