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.

Experimental Study of Squeeze Casting of ZK60 Magnesium Alloy

2011 ◽  
Vol 284-286 ◽  
pp. 1639-1642
Author(s):  
Zhi Hong Guo ◽  
Shu Wei Qu
Keyword(s):  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Strain Rates ◽  
Premature Failure ◽  
Coarse Grains ◽  
Elongation To Failure ◽  
Boundary Sliding ◽  
Cavity Evolution ◽  
Zk60 Magnesium Alloy

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 10-2 s-1 and 10-3 s-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.

Microstructure Features during High Temperature Tensile Deformation of an AZ31 Alloy with Nd and La Additions

2012 ◽  
Vol 578 ◽  
pp. 158-161
Author(s):  
Jun Qiao ◽  
Min He ◽  
Fu Bo Bian ◽  
Yu Wang ◽  
Qing Feng Zhang ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Tensile Deformation ◽  
Tensile Tests ◽  
Az31 Alloy ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Premature Failure ◽  
Elongation To Failure ◽  
Cavity Evolution ◽  
High Temperature Tensile

Microstructural features and tensile behaviors of an AZ31 alloy with Nd and La additions 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 450 °C, featured by long steady state deformation. Microstructure studies show that annealed coarse grains were remained in the gauge region after the tensile tests, and the dominate deformation mechanism was dislocation creep, other than dynamic recrystallization or grain boundary sliding. Cavity evolution near fracture end caused premature failure of the material, although fine grains developed through dynamic recrystallization.

Superplasticity in Ultrahigh Carbon (1.6 Pct C) Steel

2007 ◽  
Vol 551-552 ◽  
pp. 199-202 ◽  
Author(s):  
Zhan Ling Zhang ◽  
Yong Ning Liu ◽  
Jie Wu Zhu ◽  
G. Yu
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Ultrahigh Carbon Steel ◽  
Elongation To Failure ◽  
Boundary Sliding ◽  
Dynamic Grain Growth ◽  
Microduplex Structure

Ultrahigh carbon steel containing 1.6 wt pct C was processed to create microduplex structure consisting of fine-spheroidized carbides and fine ferrite grains. Elongation-to-failure tests were conducted at strain rates from 10-4s-1 to 15×10-4s-1, and at temperatures from 600 °C to 850 °C. The steel exhibited superplasticity at and above 700 °C when testing at a strain rate of 10-4s-1, and at 800 °C when testing at strain rates of 7×10-4s-1 and slower. The grains retained the equiaxed shape and initial size during deformation; dynamic grain growth was not observed after superplastic deformation, whereas carbide coarsening was observed. It is concluded that the fine ferrite grains or austensite grains are stabilized by the grain boundary carbides, and grain-boundary sliding controlled by grain boundary diffusion is the principal superplastic deformation mechanism at temperatures in the range of 700-850 °C.

Tensile Properties of Hot Extruded Mg-Zn-Nd-Y-Zr Alloy at Elevated Temperatures

2011 ◽  
Vol 415-417 ◽  
pp. 1157-1163
Author(s):  
Xiao Zhou ◽  
Hai Tao Zhou ◽  
Zhen Dong Zhang ◽  
Rui Rui Liu ◽  
Li Bin Liu
Keyword(s):  
Strain Rate ◽  
Elevated Temperatures ◽  
Peak Stress ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Zk60 Alloy ◽  
Boundary Sliding ◽  
Increasing Temperature ◽  
Zr Alloy

Mechanical properties of extruded Mg-Zn-Nd-Y-Zr alloy are investigated by tensile tests at various temperatures range from room temperature to 350°C with strain rates of 6.0×10-4-6.0×10-1s-1. It is found that the peak decrease with increasing temperature and decreasing strain rate, while the elongation increases with increasing temperature and decreasing strain rate. When deformation temperature is over 250°C, superplasticity occurs. This is ascribed to grain boundary sliding accommodated cavities growth. . At low temperature, the peak stress are a relatively higher than that of ZK60 alloy. This is explained by the grain refining effect and the precipitates of Mg9Nd and Mg6Zn3Y2.

Contributions of Grain Boundary Sliding and Solute Drag Creep to High-Temperature Ductility in Fine-Grained Polycrystalline 5083 Alloys

2014 ◽  
Vol 922 ◽  
pp. 360-365 ◽  
Author(s):  
Takashi Mizuguchi ◽  
Tsutomu Ito ◽  
Kota Kimura ◽  
Yasuhiro Tanaka
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Solute Drag ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Solid Solution Alloy ◽  
Friction Stir ◽  
Fine Grained ◽  
Elongation To Failure ◽  
Boundary Sliding

In this study, the high-temperature ductility of a fine-grained, polycrystalline 5083 solid solution alloy was investigated. The composition of the alloy in mass% was Al–4.5 Mg–0.68 Mn–0.19 Fe–0.13 Si–0.11 Cr. Grain refinement was effectively achieved in the stir zone by a friction stir process, and the grain size could be reduced to 3.7 μm. Tensile tests were performed at temperatures ranging from 643 to 743 K and strain rates ranging from 0.001 to 0.1 /s. The stress–strain curves showed that the flow stress continuously decreased until it reached a maximum value of stress and fractured after the initial strain hardening occurred. The value of elongation-to-failure was more than 100% when temperatures were greater than 693 K. The high ductility observed at this point can be referred to as superplastic-like elongation. This phenomenon has been reported in some Al–Mg alloys. The experimentally determined stress exponent (n value) and activation energy for deformation were about 2.5 and 123 kJ/mol, respectively. These results suggest that the grain boundary sliding, accompanied by solute drag motion of dislocations, was a rate controlling process for deformation.

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.

scholarly journals The role of grain size evolution in the rheology of ice: implications for reconciling laboratory creep data and the Glen flow law

2021 ◽  
Vol 15 (9) ◽  
pp. 4589-4605
Author(s):  
Mark D. Behn ◽  
David L. Goldsby ◽  
Greg Hirth
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Stress Exponent ◽  
Ice Sheets ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Ice Flow ◽  
Size Evolution ◽  
Boundary Sliding ◽  
Flow Law

Abstract. Viscous flow in ice is often described by the Glen flow law – a non-Newtonian, power-law relationship between stress and strain rate with a stress exponent n ∼ 3. The Glen law is attributed to grain-size-insensitive dislocation creep; however, laboratory and field studies demonstrate that deformation in ice can be strongly dependent on grain size. This has led to the hypothesis that at sufficiently low stresses, ice flow is controlled by grain boundary sliding, which explicitly incorporates the grain size dependence of ice rheology. Experimental studies find that neither dislocation creep (n ∼ 4) nor grain boundary sliding (n ∼ 1.8) have stress exponents that match the value of n ∼ 3 in the Glen law. Thus, although the Glen law provides an approximate description of ice flow in glaciers and ice sheets, its functional form is not explained by a single deformation mechanism. Here we seek to understand the origin of the n ∼ 3 dependence of the Glen law by using the “wattmeter” to model grain size evolution in ice. The wattmeter posits that grain size is controlled by a balance between the mechanical work required for grain growth and dynamic grain size reduction. Using the wattmeter, we calculate grain size evolution in two end-member cases: (1) a 1-D shear zone and (2) as a function of depth within an ice sheet. Calculated grain sizes match both laboratory data and ice core observations for the interior of ice sheets. Finally, we show that variations in grain size with deformation conditions result in an effective stress exponent intermediate between grain boundary sliding and dislocation creep, which is consistent with a value of n = 3 ± 0.5 over the range of strain rates found in most natural systems.

Superplasticity of Mg-Zn-Y Alloy Prepared by Extrusion of Machined Chip

2012 ◽  
Vol 735 ◽  
pp. 259-264
Author(s):  
Takaomi Itoi ◽  
Syuichi Fudetani ◽  
Mitsuji Hirohashi
Keyword(s):  
Grain Size ◽  
Hot Extrusion ◽  
Initial Strain Rate ◽  
Grain Boundary Sliding ◽  
Initial Strain ◽  
Strain Rates ◽  
Long Period ◽  
Dominant Deformation Mechanism ◽  
Mean Grain Size ◽  
Boundary Sliding

Mg96Zn2Y2 (at.%) extruded alloy was fabricated by hot-extrusion of the Mg96Zn2Y2 machined chip. The Mg96Zn2Y2 extruded alloy consisted of a long period stacking ordered (LPSO)-, Mg3Zn3Y2- and Mg- phases. The Mg phase with mean grain size of 450 nm was confirmed by TEM. However, the LPSO- and Mg3Zn3Y2- phases had relatively large grain size compared with Mg phase. The Mg96Zn2Y2 extruded alloy also showed superplasticity at temperatures of 623 K and 723 K with initial strain rates from 2×10−1 s−1 to 2×10−3 s−1. The maximum elongation of 450 % was achieved at 723 K with an initial strain rate of 2×10−3 s−1. From TEM observation, it is considered that grain boundary sliding of Mg grains was dominant deformation mechanism of the Mg96Zn2Y2 extruded alloy at high temperature range.

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