scholarly journals Superplastic Flow and Deformation Mechanism of the Rolled Al-Mg-Li-Sc-Zr Alloy with Banded Microstructure

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 404
Author(s):  
Chengzhi Zhang ◽  
Yang Xiao ◽  
Kaijie Ma ◽  
Yuhan Wang ◽  
Zhipeng Liu ◽  
...  
Keyword(s):  
Superplastic Deformation ◽  
Dominant Role ◽  
Strain Range ◽  
Superplastic Forming ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
High Ratio ◽  
Alloy Sheet ◽  
Superplastic Flow ◽  
Hot Rolled

A hot rolled Al-5Mg-2Li-0.2Sc-0.12Zr alloy sheet with an initial banded microstructure was subjected to high-temperature tensile tests in the temperature range of 450–550 °C, at strain rates ranging from 3 × 10−4 to 1 × 10−2 s−1. The microstructural evolution of the present non-ideal superplastic microstructure (banded morphology) was characterized by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the hot rolled non-ideal superplastic microstructure exhibited excellent superplasticity. The optimal superplastic forming temperature appeared at 500 °C and the largest elongation of 1180% was achieved at 500 °C and 1 × 10−3 s−1. As far as we know, this is the largest elongation for Al-Mg-Li-Sc-Zr alloys. The superplastic deformation of the present hot rolled banded microstructure can be divided into two stages: (i) dynamic globularization due to the dislocation movement and continuous dynamic recrystallization (CDRX), which is responsible for the plastic deformation in the low strain range; (ii) superplastic flow of the spheroidized equiaxed grains with a high ratio of high-angle grain boundaries (HAGBs) and random grain orientation in the high strain range, during which grain boundary sliding (GBS) plays the dominant role in influencing the superplastic deformation.

Damage Development During Superplasticity of Light Alloys

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
R. Boissière ◽  
J. J. Blandin ◽  
L. Salvo
Keyword(s):  
Superplastic Deformation ◽  
Superplastic Forming ◽  
Grain Boundary Sliding ◽  
Mg Alloys ◽  
Damage Development ◽  
Light Alloys ◽  
Irregular Shapes ◽  
Complex Shapes ◽  
Boundary Sliding ◽  
Damage Processes

Superplastic forming (SPF) of metallic alloys allows the production of components with particularly complex shapes since in this regime, due to the predominance of grain boundary sliding (GBS), the material exhibits a high plastic stability. However, in many light alloys (i.e., Al or Mg alloys), superplastic deformation induces damage leading to premature fracture. Despite extensive work in the past, the mechanisms of damage induced by superplastic deformation remain under debate. In particular, due to the important contribution of GBS, voids with very irregular shapes frequently develop, resulting in a difficulty to obtain reliable experimental data from conventional quantitative metallography. It is the reason why the use of X-ray microtomography, providing 3D images of material bulk, is a particularly fruitful technique to investigate damage processes in superplastic materials. Thanks to this technique, damage development during superplastic deformation of Al and Mg alloys is investigated and the three main steps of damage development (nucleation, growth, and coalescence) are discussed.

Superplastic Deformation of Twin Roll Cast AZ31 Magnesium Alloy

2008 ◽  
Vol 604-605 ◽  
pp. 267-277 ◽  
Author(s):  
Lorella Ceschini ◽  
Mohamad El Mehtedi ◽  
Alessandro Morri ◽  
Giuliano Sambogna ◽  
S. Spigarelli
Keyword(s):  
Magnesium Alloy ◽  
Superplastic Deformation ◽  
Large Fraction ◽  
Tensile Tests ◽  
Testing Temperature ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
Molten Metals ◽  
Superplastic Behaviour ◽  
Twin Roll

The aim of the present work was to evaluate the potential for superplastic deformation of the AZ31 magnesium alloy produced by Twin Roll Casting (TRC), a continuous casting technology able to convert molten metals directly into a coiled strip. In order to develop a superplastic microstructure, the TRC sheets were heated at 400 °C for 2 h, then rolled by multiple passes with re-heating between them, with a total thickness reduction of about 60%. The superplastic behaviour of the alloy was studied by tensile tests, carried out at in the temperature range from 400 °C to 500 °C and with initial strain rates of 1•10-3 s-1 and 5•10-4 s-1. The microstructural and fractographic characterization of the alloy was carried out by means of optical (OM) and scanning electron microscopy (SEM). The tensile tests evidenced a superplastic behaviour of the processed AZ31 Mg alloy, with a maximum elongation to failure of about 500% at 460 °C, with a strain rate of 5•10-4 s-1. The microstructure of the alloy after superplastic deformation showed fine and equiaxed grains, with a large fraction of high angle boundaries. Analyses of the fracture surfaces evidenced flow localization around the grains, suggesting that grain boundary sliding (GBS) was the main deformation mechanism. Failure occurred by cavitation, mainly at the higher testing temperature, due to the prevailing effect of grain growth.

Superplastic Forming Limit and Instability of AZ31B Sheet

2011 ◽  
Vol 686 ◽  
pp. 343-347
Author(s):  
Mei Juan Song ◽  
Ling Yun Wang ◽  
Rao Chuan Liu
Keyword(s):  
Superplastic Deformation ◽  
Tensile Deformation ◽  
Forming Limit Diagram ◽  
Superplastic Forming ◽  
Alloy Sheet ◽  
Forming Limit ◽  
Local Necking ◽  
Bulging Test ◽  
First Time ◽  
Az31b Magnesium Alloy Sheet

The superplastic bulging test of AZ31B magnesium alloy sheet of 0.6mm thick was carried out on Alliance RT/50 tensile machine at 573K and 3.3×10-4S-1. It is found that either in tensile-compressive deformation or in bi-axis tensile deformation, the judgment criterion for local necking of superplastic deformation is dε2=0. The superplastic forming limit diagram(FLD) at 573K and 3.3×10-4S-1 was established for the first time.

scholarly journals Cavity Behavior of Fine-Grained 5A70 Aluminum Alloy during Superplastic Formation

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1065 ◽  
Author(s):  
Sheng Li ◽  
Shunyao Jin ◽  
Zhongguo Huang
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Initial Strain Rate ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Internal Damage ◽  
Cavity Nucleation ◽  
Diffusion Growth ◽  
Fine Grained ◽  
Pinning Effect

The study of the exact physical mechanism of cavity nucleation and growth is significant in terms of predicting the extent of internal damage following superplastic deformation. The 5A70 alloy was processed by cold rolling for 14 passes with a total reduction deformation of 90% (20–2 mm) and the heat treatment was inserted at a thickness of 10 and 5 mm at 340 °C for 30 min. The superplastic tensile tests were performed at 400, 450, 500, 550 °C and the initial strain rate was 1 10−3 s−1. Cavities were observed at the head of the particle and the interface of the grain boundaries. It is suggested that the cavity was nucleated during the sliding/climbing of the dislocations, due to the precipitate pinning effect and the impeding grain boundary during grain boundary sliding (GBS). In this study, the results demonstrated a clear transition from diffusion growth to superplastic diffusion growth and plastic-controlled growth at a cavity radius larger than 1.52 and 13.90 μm. The cavity nucleation, growth, interlinkage and coalescence under the applied stress during the superplastic deformation, as well as the crack formation and expansion during the deformation, ultimately led to the superplastic fracture.

Improvement of Plastic Workability of Rolled AZ31 Alloy Sheet by Surface Thermo-Mechanical Treatment

2005 ◽  
Vol 488-489 ◽  
pp. 449-452
Author(s):  
Yu Yoshida ◽  
Keita Arai ◽  
Shigeharu Kamado ◽  
Yo Kojima
Keyword(s):  
Grain Refinement ◽  
Crystallographic Orientation ◽  
Rolling Texture ◽  
Tensile Tests ◽  
Az31 Alloy ◽  
Alloy Sheet ◽  
Subsequent Annealing ◽  
Stretch Formability ◽  
Hot Rolled ◽  
Equiaxed Grains

Ingots of AZ31 alloys were prepared for the present study. The ingots were hot rolled to 0.5 mm thickness. In order to develop rolled magnesium alloy sheet having excellent plastic formability, the authors attempted the grain refinement and randomization of the rolling texture of the alloy by means of surface modification utilizing wet-type shot blast (wet blast) and subsequent annealing. Then the microstructural observations including texture analysis and tensile tests were carried out. Furthermore, the bendability and stretch formability were investigated. After wet blast and subsequent annealing at 573K for 1h, the region of 50 µm depth from the sheet surface that experienced deformation by wet blast is recrystallized, and fine and equiaxed grains are generated. Although rolling texture remained in the central part of the sheet, the recrystallized grains near the surface of such specimens have random crystallographic orientation. The tensile strengths of both rolled and wet-blasted specimens are almost the same but the elongation of the latter increases due to grain refinement and randomization of crystallographic orientation. Such a microstructural feature realizes bending with the radius of 1 mm without cracks and wrinkles and leads to an increase in limiting stretching depth by 1.5~2 mm.

Research on Superplasticity of Supplied 5A06 Aluminium Alloy Sheet

2016 ◽  
Vol 838-839 ◽  
pp. 127-131
Author(s):  
Bao Peng Bi ◽  
Yong Wang
Keyword(s):  
Aluminum Alloy ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Strain Rate Range ◽  
Alloy Sheet ◽  
Uniaxial Tensile ◽  
5A06 Aluminum Alloy ◽  
Bulging Test

Superplasticity of supplied 5A06 aluminum alloy is reviewed in this paper. Supplied 5A06 aluminum alloy is researched on superplasticity by the methods of same strain rate high temperature uniaxial tensile tests at temperature range375°C-500°Cand strain rate range 2.5×10-4s-1~1.0×10-2s-1. Microstructure and fracture of tensile samples are analyzed and discussed, deduce that grain boundary sliding (GBS) is the predominant deformation mechanism. Superplastic formability of the alloy is evaluated by gas bulging test at elevated temperatures. Gas bulging test demonstrates the deformation process parameters for the best superplastic formability is 400°Cand 0.005s-1 ,suggesting good application prospect for this aluminum alloy.

Superplasticity and Superplastic Formability of Hot-Rolled AZ31 Magnesium Alloy

2007 ◽  
Vol 551-552 ◽  
pp. 231-235
Author(s):  
D.L. Yin ◽  
C.W. Wang ◽  
Jing Tao Wang ◽  
Yan Dong Yu
Keyword(s):  
Threshold Stress ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Strain Rate Range ◽  
Dome Height ◽  
Uniaxial Tensile ◽  
Az31 Mg Alloy ◽  
Bulging Test ◽  
Hot Rolled

The superplasticity of a hot-rolled AZ31 Mg alloy was investigated by uniaxial tensile tests at temperature range 250-450oC and strain rate range 0.7×10-3-1.4×10-1s-1. Superplastic formability of the alloy was evaluated by gas bulging test at elevated temperatures. The threshold stress for grain boundary sliding (GBS) was calculated and the topography during superplastic deformation was observed by SEM. It is found that, at 400 oC and 0.7×10-3 s-1, the maximum elongation reaches 362.5%. GBS is the predominant deformation mechanism and characterized by a pronounced improvement in homogeneity with increasing temperatures, indicating a transformation of GBS mode from cooperative GBS (CGBS) to individual GBS (IGBS). The improved homogeneity of GBS can be interpreted in terms of decreased threshold stress with increasing temperatures. Gas bulging test demonstrates that the temperature for the best superplastic formability is 400 oC and a hemispherical part with a specific limiting dome height of 0.51 was obtained, suggesting good application prospect for this alloy.

scholarly journals Superplastic Deformation of Al–Cu Alloys after Grain Refinement by Extrusion Combined with Reversible Torsion

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5803
Author(s):  
Kinga Rodak ◽  
Dariusz Kuc ◽  
Tomasz Mikuszewski
Keyword(s):  
Superplastic Deformation ◽  
Intermetallic Phase ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Microstructural Study ◽  
Cu Alloys ◽  
Al2cu Phase ◽  
Phase Size ◽  
Boundary Sliding ◽  
Superplastic Properties

The binary as-cast Al–Cu alloys Al-5%Cu, Al-25%Cu, and Al-33%Cu (in wt %), composed of the intermetallic θ-Al2Cu and α-Al phases, were prepared from pure components and were subsequently severely plastically deformed by extrusion combined with reversible torsion (KoBo) to refinement of α-Al and Al2Cu phases. The extrusion combined with reversible torsion was carried out using extrusion coefficients of λ = 30 and λ = 98. KoBo applied to the Al–Cu alloys with different initial structures (differences in fraction and phase size) allowed us to obtain for alloys (Al-25%Cu and Al-33%Cu), with higher value of intermetallic phase, large elongations in the range of 830–1100% after tensile tests at the temperature of 400 °C with the strain rate of 10−4 s−1. The value of elongation depended on extrusion coefficient and increase, with λ increasing as a result of α-Al and Al2Cu phase refinement to about 200–400 nm. Deformation at the temperature of 300 °C, independently of the extrusion coefficient (λ), did not ensure superplastic properties of the analyzed alloys. A microstructural study showed that the mechanism of grain boundary sliding was responsible for superplastic deformation.

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