Superplasticity of AZ91 Alloy ECAPed with Different Routes

2011 ◽  
Vol 299-300 ◽  
pp. 94-97
Author(s):  
Feng Li ◽  
Sheng Guo ◽  
Xin Che ◽  
Li Jia Chen
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Sensitivity Coefficient ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Az91 Alloy ◽  
Az91 Magnesium Alloy ◽  
Elongation To Failure

Equal channel angular pressing (ECAP) was conducted using the die with a 90° angled channel under routes A, BC and C for hot extruded AZ91 magnesium alloy. Tensile tests were carried out at 300 °C and initial strain rates ranging from 2×10−4 to 5×10−3 s−1. The experimental results show that different routes have obviously effect on elongation to failure. It is found that the highest elongation to failure is 410 % at a strain rate of 2×10−4 s−1 for the ECAPed AZ91 alloy with route BC. At the same strain rate, route BC can bring the greater superplasticitic deformation compared with routes A and C. Moreover, the strain rate sensitivity coefficient m values of about 0.3 to 0.5 are attained for the ECAPed AZ91 alloys with different routes. For the ECAPed AZ91 alloys, the main superplastic deformation mechanism is the grain boundary sliding, while the main accommodation mechanism is the dislocation creep mechanism controlled by the grain boundary diffusion.

A Comparative Study on Superplasticity of Mg-Zn-Y-Zr Processed by ECAE and Hot Rolling

2007 ◽  
Vol 551-552 ◽  
pp. 203-208 ◽  
Author(s):  
Wei Neng Tang ◽  
Hong Yan ◽  
Rong Shi Chen ◽  
En Hou Han
Keyword(s):  
Hot Rolling ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Grain Boundary Sliding ◽  
Diffusional Creep ◽  
Dislocation Creep ◽  
Fine Grained ◽  
Microstructure Observation ◽  
Elongation To Failure

Superplastic deformation (SPD) behaviors of two fine-grained materials produced by ECAE and hot rolling methods have been contrastively studied in this paper. It is found that the optimum superplastic condition in as-ECAEed material was at 350°C and 1.7×10-3s-1 with elongation to failure about 800%; while in as-rolled material, the largest elongation to failure about 1000% was obtained at 480°C and 5.02×10-4s-1. Microstructure observation showed that grain evolution and cavitation behavior were different in these two materials during superplastic deformation. The controlled mechanisms for superplasticity, i.e. grain boundary sliding (GBS), dislocation creep and diffusional creep, at different deformation conditions were discussed in terms of strain rate sensitivity coefficient, stress exponent and activity energy.

Study on the Super-Plastic Property of ECAPed Magmesium Alloy

2011 ◽  
Vol 311-313 ◽  
pp. 640-643
Author(s):  
Ying Jie Li ◽  
Xiu Zhi Zhang ◽  
Feng Li
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Plastic Property ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Flow Activation Energy ◽  
Super Plastic ◽  
Deformation Behaviors ◽  
Lower Temperature

In this paper, the influence of temperature and strain rate on the superplastic deformation behaviors of the Mg-Zn-Nd alloy has been investigated through performing tensile tests at different temperatures and strain rates. After 4 passes of ECAP by route C, the strain-rate sensitivity coefficients reached 0.32 at 300°C, indicating that the ECAPed Mg-Zn-Nd alloy exhibited a good superplasticity at lower temperature. The results of flow activation energy showed that the super-plastic deformation mechanism of magnesium alloys is grain-boundary sliding controlled by grain boundary diffusion.

Superplasticity of an AA2519 Aluminum Alloy

2016 ◽  
Vol 838-839 ◽  
pp. 278-284
Author(s):  
Ivan Zuiko ◽  
Marat Gazizov ◽  
Rustam Kaibyshev
Keyword(s):  
Strain Rate ◽  
Thermomechanical Processing ◽  
Rate Sensitivity ◽  
Initial Strain Rate ◽  
Tensile Tests ◽  
Sensitivity Coefficient ◽  
Initial Strain ◽  
Strain Rates ◽  
Average Grain Size ◽  
Elongation To Failure

A commercial AA2519 alloy with a chemical composition of Al-5.64Cu-0.33Mn-0.23Mg-0.15Zr (in wt. %) was subjected to two-step thermomechanical processing (TMP) providing the formation of fully recrystallized structure with an average grain size of ~7 mm in 3 mm thin sheets. Superplastic tensile tests were performed in the temperature interval 450-535°C and initial strain rates ranging from ~2.8 x 10-4 to ~6.0 x 10-1 s-1. The highest elongation-to-failure of ~750% appears at a temperature of ~525°C and an initial strain rate of ~1.4 × 10-4 s-1 with the corresponding strain rate sensitivity coefficient of ~0.46.

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.

A Model for the Effects of Strain Rate and Temperature on the Deformation Behavior of Ultrafine-Grained Metals

2011 ◽  
Vol 291-294 ◽  
pp. 1173-1177
Author(s):  
Zi Ling Xie ◽  
Lin Zhu Sun ◽  
Fang Yang
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Deformation Response ◽  
Ultrafine Grained ◽  
Boundary Sliding

A theoretical model is developed to account for the effects of strain rate and temperature on the deformation behavior of ultrafine-grained fcc Cu. Three mechanisms, including dislocation slip, grain boundary diffusion, and grain boundary sliding are considered to contribute to the deformation response simultaneously. Numerical simulations show that the strain rate sensitivity increases with decreasing grain size and strain rate, and that the flow stress and tensile ductility increase with either increasing strain rate or decreasing deformation temperature.

Superplastic Behavior of Friction-Stir Welded Joints of an Al-Mg-Sc Alloy with Ultrafine-Grained Microstructure

2016 ◽  
Vol 838-839 ◽  
pp. 338-343 ◽  
Author(s):  
Sergey Malopheyev ◽  
Sergey Mironov ◽  
Igor Vysotskiy ◽  
Rustam Kaibyshev
Keyword(s):  
Strain Rate ◽  
True Strain ◽  
Rate Sensitivity ◽  
Initial Strain Rate ◽  
Sensitivity Coefficient ◽  
Friction Stir ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Superplastic Properties

The commercial Al-5.4Mg-0.2Sc-0.1Zr alloy was subjected to equal-channel angular pressing at 300°C to a true strain ~12 followed by cold rolling to a total thickness reduction of 80%. The ultrafine-grained sheets were joined by friction stir welding (FSW). To evaluate superplastic properties of the weldments, the tensile samples including all of the characteristic FSW microstructural zones were machined perpendicular to the welding direction and pulled up to failure in the temperature range of 400 to 500°C and at strain rates of 2.8×10-4 s-1 to 5.6×10-1 s-1. The friction-stir welded material exhibited excellent superplastic properties. The highest elongation-to-failure of ~1370% was recorded at a temperature of ~450°C and an initial strain rate of 5.6×10-2 s-1, where the strain rate sensitivity coefficient was about 0.64. The relationship between superplastic ductility and microstructure is discussed.

Enhanced Tensile Ductility of AZ80 Magnesium Alloy

2011 ◽  
Vol 284-286 ◽  
pp. 1635-1638
Author(s):  
Jun Qiao ◽  
Yu Wang ◽  
Guo Dong Shi ◽  
Bao Xin Nie
Keyword(s):  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Strain Rates ◽  
Premature Failure ◽  
Az80 Magnesium Alloy ◽  
Coarse Grains ◽  
Elongation To Failure ◽  
Boundary Sliding ◽  
Cavity Evolution

Tensile behaviors of extruded and rolled AZ80 Mg alloy were investigated with elongation-to-failure tensile tests at constant temperatures of 300 °C, 350 °C, 400 °C, and 450 °C, and constant strain rates of 10-2s-1and 10-3s-1. Experimental data show that the material exhibits tensile ductilities of over 100% at 400 °C and 450 °C, featured by long steady state deformation. Microstructure studies show that annealed coarse grains were remained in the gauge region during the tensile tests, and the enhanced tensile ductilities resulted from dislocation creep, other than dynamic recrystallization or grain boundary sliding. Cavity evolution and recrystallized coarse grains near fracture end caused premature failure of the material.

Slip Induced Strain Rate Sensitivity for Superplastic Material?

2012 ◽  
Vol 735 ◽  
pp. 31-36 ◽  
Author(s):  
Hector Basoalto ◽  
Paul L. Blackwell
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Microstructural Parameters ◽  
Sliding Mechanism ◽  
Physically Based ◽  
Boundary Sliding

The conventional consensus has it that the magnitude of the strain rate sensitivity observed in superplastic materials is linked with grain boundary sliding. The grain boundary sliding mechanism is thought to theoretically produce a strain rate sensitivity exponent of 0.5, which is in good agreement with experimental data. The present paper argues that a rate sensitivity of 0.5 can be generated by dislocation slip under certain temperature and strain rate regimes that overlap with conditions representative of superplasticity. A physically based slip model that links the relevant microstructural parameters to the macroscopic strain rate is proposed.

Superplasticity of an AZ91 Magnesium Alloy

2007 ◽  
Vol 567-568 ◽  
pp. 365-368 ◽  
Author(s):  
Zoltán Száraz ◽  
Zuzanka Trojanová ◽  
Talant Ryspaev ◽  
Volker Wesling
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Hot Extrusion ◽  
Az91 Magnesium Alloy ◽  
Physical Mechanisms ◽  
Heat Treated ◽  
Elongation To Failure ◽  
Az91 Magnesium ◽  
Two Stages

The superplastic deformation characteristics of the AZ91, the mostly used magnesium alloy, were investigated at various strain rates in the interval from 3x10-5 to 1x10-2 s-1 and temperature of 420 °C. To prepare superplastic alloys thermo-mechanical treatment was used. Cast materials were heat-treated in two stages, after homogenization at 415 °C for 10 h were submitted to the precipitation annealing at temperature in the range of 200-380 °C for 10 h, and deformed by hot extrusion. Microstructure of samples was observed by the light microscope Olympus. Strain rate sensitivity parameter m has been estimated by the abrupt strain rate changes method. The strong strain rate dependence of the m-parameter was found. The highest elongation to failure, 584%, was found for the samples aged at 380 °C. Possible physical mechanisms of the superplastic flow are discussed.

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