Room Temperature Superplasticity in Fine/Ultrafine-Grained Zn-Al Alloys with Different Phase Compositions

2018 ◽  
Vol 385 ◽  
pp. 72-77
Author(s):  
Muhammet Demirtas ◽  
Harun Yanar ◽  
Onur Saray ◽  
Gençağa Pürçek
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Al Alloys ◽  
Phase Boundaries ◽  
Superplastic Behavior ◽  
Al Content ◽  
Α Phase ◽  
Ultrafine Grained ◽  
Superplastic Elongation

Three Zn-Al alloys, namely Zn-22Al, Zn-5Al and Zn-0.3Al, were subjected to equal-channel angular pressing (ECAP), and the effect of ECAP on their microstructure and room temperature (RT) superplastic behavior were investigated in detail referring to previous studies reported by the authors of the current study. ECAP remarkably refined the microstructures of three alloys as compared to their pre-processed conditions. While the lowest grain size was achieved in Zn-22Al alloy as 200 nm, the grain sizes of Zn-5Al and Zn-0.3Al alloys were ~540 nm and 2 µm, respectively, after ECAP. After the formation of fine/ultrafine-grained (F/UFG) microstructures, all Zn-Al alloys exhibited superplastic behavior at RT and high strain rates. The maximum superplastic elongations were 400%, 520% and 1000% for Zn-22Al, Zn-5Al and Zn-0.3Al alloys, respectively. It is interesting to point out that the highest RT superplastic elongation was obtained in Zn-0.3Al alloy with the largest grain size, while Zn-22Al alloy having the lowest grain size showed the minimum superplastic elongation. This paradox was attributed to the different phase compositions of these alloys. The formation of Al-rich α/α phase boundaries, where grain boundary sliding is minimum comparing to Zn-rich η/η and η/α phase boundaries of Zn-Al alloys, is the lowest level in Zn-0.3Al alloy among all the alloys. Therefore, it can be concluded that if it is desired to achieve high superplastic elongation in Zn-Al alloys at RT, keeping Al content at a possibly minimum level seems to be the most suitable way.

scholarly journals Is Superplasticity in the Future of Nanophase Materials?

1990 ◽  
Vol 196 ◽  
Author(s):  
R. W. Siegel
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Atomic Clusters ◽  
Diffusional Creep ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Nanophase Materials ◽  
Boundary Sliding

ABSTRACTThe ultrafine grain sizes and high diffusivities in nanophase materials assembled from atomic clusters suggest that these materials may have a strong tendency toward superplastic mechanical behavior. Both small grain size and enhanced diffusivity can be expected to lead to increased diffusional creep rates as well as to a significantly greater propensity for grain boundary sliding. Recent mechanical properties measurements at room temperature on nanophase Cu, Pd, and TiO2, however, give no indications of superplasticity. Nonetheless, significant ductility has been clearly demonstrated in these studies of both nanophase ceramics and metals. The synthesis of cluster-assembled nanophase materials is described and the salient features of what is known of their structure and mechanical properties is reviewed. Finally, the answer to the question posed in the title is addressed.

Influence of Isothermal Forging Temperature on Microstructure and Tensile Properties of Ti-5.8Al-4.0Sn-4.0Zr-0.7Nb-0.4Si-1.5Ta Near-α Titanium Alloy

2010 ◽  
Vol 97-101 ◽  
pp. 153-157
Author(s):  
Tao Wang ◽  
Hong Zhen Guo ◽  
Jian Hua Zhang ◽  
Ze Kun Yao
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Titanium Alloy ◽  
Tensile Properties ◽  
Room Temperature ◽  
Volume Fraction ◽  
Constant Strain Rate ◽  
Isothermal Forging ◽  
Α Phase ◽  
Transus Temperature

The microstructures and room temperature and 600°C tensile properties of Ti-5.8Al-4.0Sn-4.0Zr-0.7Nb -0.4Si-1.5Ta alloy after isothermal forging have been studied. The forging temperature range was from 850°C to 1075°C, and the constant strain rate of 8×10-3/S-1 was adopted. With the increase of forging temperature, the volume fraction of primary α phase decreased and the lamellar α phase became thicker when the temperatures were in range of 850°C -1040°C; The grain size became uneven and the α phase had different forms when the forging temperature was 1040°C and 1075°C respectively; The tensile strength was not sensitive to the temperature and the most difference was within 20MPa. Tensile strength and yield strength attained to the maximum when temperature was 1020°C; the ductility decreased with the increase of forging temperature, and this trend became more obvious if forging temperature was above the β-transus temperature.

Structure Evolution and Deformation Mechanisms in Ultrafine-Grained Aluminum under Tension at Room Temperature

2010 ◽  
Vol 667-669 ◽  
pp. 915-920
Author(s):  
Konstantin Ivanov ◽  
Evgeny V. Naydenkin
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Structure Evolution ◽  
Dislocation Slip ◽  
Polished Surface ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Boundary Sliding

Deformation mechanisms occurring by tension of ultrafine-grained aluminum processed by equal-channel angular pressing at room temperature are investigated using comparative study of the microstructure before and after tensile testing as well as deformation relief on the pre-polished surface of the sample tested. Deformation behavior and structure evolution during tension suggest development of grain boundary sliding in addition to intragrain dislocation slip. Contribution grain boundary sliding to the overall deformation calculated using the magnitude of shift of grains relative to each other is found to be ~40%.

Effects of Temperature, Strain Rate and Grain Size on Superplastic Behavior of Magnesium

2012 ◽  
Vol 488-489 ◽  
pp. 27-34 ◽  
Author(s):  
Muhammad Waseem Soomro ◽  
Thomas Rainer Neitzert
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Magnesium Alloys ◽  
Room Temperature ◽  
Superplastic Forming ◽  
Experimental Results ◽  
Superplastic Behavior ◽  
Influence Of Temperature ◽  
Effects Of Temperature ◽  
Temperature Strain

The influence of temperature, grain size and strain rate on superplasticity of magnesium is investigated. Different approaches are compared along with their experimental results to show the variation in the amount of superplasticity by varying above mentioned parameters. At room temperature magnesium alloys usually have poor formability but recent studies of some alloys such as ZE10, AZ31, AZ61 AZ60, AZ80 and AZ91 are pointing that by varying the temperature along with grain size and strain rate improved formability is possible or even superplastic forming of these alloys can be achieved to meet the demands of automotive, aircraft and other weight conscious industries.

scholarly journals Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size

2017 ◽  
Author(s):  
Jiangjiang Hu ◽  
Weiming Sun ◽  
Taihua Zhang ◽  
Yusheng Zhang
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Room Temperature ◽  
Indentation Depth ◽  
Dislocation Motion ◽  
Coarse Grained ◽  
Ultrafine Grained ◽  
Pile Up ◽  
Different Grain Size ◽  
Multiple Slips

At room temperature, the indentation morphologies of crystalline copper with different grain size including nanocrystalline (NC), ultrafine-grained (UFG) and coarse-grained (CG) copper were studied by nanoindentation at the strain rate of 0.04/s without holding time at indentation depth of 2000 nm. As the grain size increasing, the height of the pile-up around the residual indentation increases and then has a slightly decrease in the CG Cu, While the area of the pile-up increases constantly. Our analysis has revealed that the dislocation motion and GB activities in the NC Cu, some cross- and multiple-slips dislocation insides the larger grain in the UFG Cu, and forest dislocations from the intragranular Frank-Read sources in the CG Cu, would directly induce these distinct pile-up effect.

scholarly journals Recent Development of Superplasticity in Aluminum Alloys: A Review

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 77 ◽  
Author(s):  
Laxman Bhatta ◽  
Alexander Pesin ◽  
Alexander P. Zhilyaev ◽  
Puneet Tandon ◽  
Charlie Kong ◽  
...  
Keyword(s):  
Grain Size ◽  
Aluminum Alloys ◽  
Grain Boundary ◽  
Solute Drag ◽  
Grain Boundary Sliding ◽  
Dislocation Motion ◽  
Vital Role ◽  
Superplastic Behavior ◽  
Wide Range ◽  
Commercial Applications

Aluminum alloys can be used in the fabrication of intricate geometry and curved parts for a wide range of uses in aerospace and automotive sectors, where high stiffness and low weight are necessitated. This paper outlines a review of various research investigations on the superplastic behavior of aluminum alloys that have taken place mainly over the past two decades. The influencing factors on aluminum alloys superplasticity, such as initial grain size, deformation temperature, strain rate, microstructure refinement techniques, and addition of trace elements in aluminum alloys, are analyzed here. Since grain boundary sliding is one of the dominant features of aluminum alloys superplasticity, its deformation mechanism and the corresponding value of activation energy are included as a part of discussion. Dislocation motion, diffusion in grains, and near-grain boundary regions being major features of superplasticity, are discussed as important issues. Moreover, the paper also discusses the corresponding values of grain size exponent, stress exponent, solute drag creep and power law creep. Constitutive equations, which are essential for commercial applications and play a vital role in predicting and analyzing the superplastic behavior, are also reviewed here.

scholarly journals INVESTIGATION OF SUPERPLASTIC BEHAVIOR OF CERTAIN (Zn – Al) ALLOYS

2019 ◽  
Vol 18 (4) ◽  
pp. 604-615
Author(s):  
Sora H Abed ◽  
Abdul Wahid K Rajih ◽  
Ahmed O Al-Roubaiy
Keyword(s):  
Mechanical Properties ◽  
Cold Rolling ◽  
Room Temperature ◽  
Al Alloys ◽  
Al Alloy ◽  
Test Results ◽  
Superplastic Behavior ◽  
Partial Remelting ◽  
Hot Rolled ◽  
Hot Test

Super plasticity behavior finds applications in so many fields, for example the aerospacemanufacturing that is the main bazaar for super plasticity, but automotive, medical, sports,cookware and architectural applications have their share too. "In this work a study of thesuperplastic behavior of a new Zn-Al alloy was conducted. In addition to the investigation ofthe possible superplastic behavior of Zn-0.5Al alloy. These alloys were prepared by usinggravity and chill casting techniques. Zn-0.5Al alloy was subjected to hot rolling at 250 ºCand cold rolling at room temperature, while Zn-48Al alloy was also hot rolled at 250 ºC to20% reduction in the thickness of sample followed by partial remelting at 500 ºC. Severaltests were carried out such as physical, mechanical and chemical which include (XRF, XRD,OP, SEM, Microhardness (HV) and Tensile (cold, hot) test). Results showed that the"Zn-0.5Al alloy has poor mechanical properties and may not be regarded as a superplastic alloycompared with Zn-48Al alloy. The Zn-48Al alloy generally enhanced all properties. Themaximum elongation of (450%) was obtained in Zn-48Al alloy after thermomechanicalcontrolling process and partial remelting.

Strain Rate Sensitivity of Ultrafine Grained FCC- and BCC-Type Metals

2006 ◽  
Vol 503-504 ◽  
pp. 781-786 ◽  
Author(s):  
Johannes May ◽  
Heinz Werner Höppel ◽  
Matthias Göken
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Testing Temperature ◽  
Ultrafine Grain ◽  
Ultrafine Grain Size ◽  
Ultrafine Grained

The dependence of the strain rate sensitivity (SRS) of α-Fe and Al 99.5, as typical representatives of fcc- and bcc-type metals, on the testing temperature and with respect to the microstructure is investigated. In particular, the differences between conventional grain size (CG) and ultrafine grain size (UFG) are pointed out. UFG Al 99.5 generally shows an elevated SRS compared to CG Al 99.5. In case of α-Fe the SRS of the UFG state is decreased at room temperature, but increased at 200 °C, compared to the CG state. It is shown that the SRS also influences the ductility of UFG-metals in tensile tests.

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