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

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.

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

Frontiers in Materials ◽

10.3389/fmats.2020.606092 ◽

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.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.551-552.463 ◽

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.

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Superplastic Deformation and Mechanisms of the Commercial Aluminium Alloy Al-4Cu-I.6Mg-0. 8Mn

MRS Proceedings ◽

10.1557/proc-196-391 ◽

1990 ◽

Vol 196 ◽

Cited By ~ 1

Author(s):

Yuwen Liu ◽

Guang Yang ◽

Jianshe Lian ◽

Xianwen Zeng

Keyword(s):

Superplastic Deformation ◽

Early Stage ◽

Microstructural Analysis ◽

Rate Sensitivity ◽

Tensile Tests ◽

Sensitivity Index ◽

Second Phase ◽

Strain Rate Sensitivity Index ◽

Second Phase Particles ◽

Commercial Aluminium

ABSTRACTThe superplastic deformation behavior and mechanisms of commercial Al-4cu-1.6 Mg-0.0Mn have been studied, using tensile tests with microstructuraL observations being carried out by optical and transmission etectronmicroscopy. The results of tensile tests show that considerable superplasticflow can be obtained without any pretreatment to this atloy.The maximum elongaton achieved is 42096 and the strain rate sensitivity index, m, is 0.49. Microstructural analysis reveals that the dominant mechanism in the early stage of deformation is diffusion. As strain increases, grain-borundary sliding and grain rearrangment take the dominant part in thedeformation process, and diffusion becomes an accommodation mechanism. Second phase particles effectively restrict grain growth during deformation. Cavity initiation and growth during deformation are the direct cause of specimen failure.

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

Materials ◽

10.3390/ma11071212 ◽

2018 ◽

Vol 11 (7) ◽

pp. 1212 ◽

Cited By ~ 7

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.

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Common Mechanism for Superplastic Deformation in Different Classes of Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.735.26 ◽

2012 ◽

Vol 735 ◽

pp. 26-30 ◽

Cited By ~ 1

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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Heat Assisted Dieless Drawing Process of Superplastic Metal Microtubes - From Zn22Al to β Titanium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.838-839.459 ◽

2016 ◽

Vol 838-839 ◽

pp. 459-467 ◽

Cited By ~ 1

Author(s):

Tsuyoshi Furushima ◽

Ken-Ichi Manabe

Keyword(s):

Cross Sections ◽

Rate Sensitivity ◽

Sensitivity Index ◽

Outer Diameter ◽

Drawing Process ◽

Initial Shape ◽

Dieless Drawing ◽

Superplastic Alloy ◽

Strain Rate Sensitivity Index ◽

Contact Situation

A heat assisted superplastic dieless drawing process that requires no dies or tools is applied to the drawing of a Zn-22Al and β titanium superplastic alloy for not only circular but also noncircular microtubes such as square, rectangular and noncircular multi core tubes having square inner and rectangular outer cross sections. As a result, the tendency has been to increase the limiting reduction in area with increasing strain rate sensitivity index m value. We successfully fabricate Zn-22Al alloy, AZ31 magnesium, β titanium circular microtubes with outer diameter of 191μm, 890μm and 180μm, respectively. Furthermore, a noncircular micro tube, which has inner square tubes with a 335μm side, and an outer rectangular tube of 533×923μm were fabricated successfully. During the dieless drawing process, the geometrical similarity law in cross section which the tube is drawn while maintaining its initial shape can be satisfied. The smooth surface can be obtained in case of superplastic dieless drawing process without contact situation with dies and tools. Consequently, it is found that the superplastic dieless drawing is effective for the fabrication of circular and noncircular multicore microtubes.

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