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

1990 ◽  
Vol 196 ◽  
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.

Dynamic Grain and Particle Growth in a Non-Superplastic Al-4Cu Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 797-802 ◽  
Author(s):  
Oleg V. Rofman ◽  
Pete S. Bate
Keyword(s):  
Boundary Migration ◽  
Rate Sensitivity ◽  
Particle Growth ◽  
Tensile Tests ◽  
Sensitivity Index ◽  
Particle Coarsening ◽  
Cu Alloy ◽  
Strain Rate Sensitivity Index ◽  
The Matrix ◽  
Static Annealing

The effect of deformation on the microstructure of a Al-4wt.%Cu alloy has been investigated. Evaluation of the microstructural changes was made by comparing results after both static annealing and tensile testing (deformed and non-deformed regions) at 450 °C. Uniaxial perturbed-rate tests showed that the Al-4wt.%Cu has a low value of the strain rate sensitivity index (m ~ 0.22) and cannot be considered as a superplastic material. It was found that in the deformed regions, specimens showed a significant increase in the grain and particle size. These changes were accompanied by an increase in the aspect ratio of the matrix grains. Tensile tests carried out at constant strain rates and stopped at intermediate strains helped to estimate the rate of the grain and particle growth and the contribution of deformation to it. To examine in detail the mechanism of the particle coarsening during deformation, additional tensile tests were made using the Al-4wt.%Cu alloy annealed at temperature conditions leading to abnormal grain size. Results of these tests also showed strain-induced particle coarsening, so that dynamic particle coarsening was not simply caused by boundary migration effects.

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.

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.

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.

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

2016 ◽  
Vol 838-839 ◽  
pp. 459-467 ◽  
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.

Cavity of Al-Cu-Mg Alloy during Superplastic Deformation

2007 ◽  
Vol 551-552 ◽  
pp. 645-650
Author(s):  
Min Wang ◽  
Hong Zhen Guo ◽  
Y.J. Liu
Keyword(s):  
Strain Rate ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Room Temperature ◽  
Mg Alloy ◽  
Deformation Condition ◽  
Second Phase ◽  
Rate Condition ◽  
Second Phase Particles ◽  
Strain Rate Condition

According to the characteristic of appearing cavitation in the metals during superplastic deformation, the influence of strain rate on cavity evolvement, the influence of cavity on superplastic deformation capability, and the formation, development process of cavity were investigated for Al-Cu-Mg alloy (i.e. coarse–grained LY12). The results show that: ①The pore nucleation occurs not only at triangle grain boundaries, but also along nearby the second phase particles, and even within grains. The cavities at the triangle grain boundaries are present in V-shape, others near the second phase particles and within grains are present in O-shape. These cavities may result from disharmony slippage of grain boundaries. ②The tendency of cavity development decreases with increasing of strain-rate. In lower strain-rate condition, though Al-Cu-Mg alloy has better superplasticity, many big cavities in the specimen may reduce the room temperature properties of the alloy. In higher strain-rate condition, Al-Cu-Mg alloy has certain superplasticity and room temperature properties as well as few cavities forming. By analyzing, viscous layer on grain boundaries is very thin and grain sizes can be refined during their extruding and rotating each other in higher strain-rate superplastic deformation condition. ③Growth and coalescence of cavity are the main reason of the superplastic fracture of Al-Cu-Mg alloy. And small and a certain amount of cavities with dispersion and independence state are very useful to crystal boundary slippage.

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