Accommodation of Grain Boundary Sliding in AZ31 Alloy

2007 ◽  
Vol 345-346 ◽  
pp. 581-584
Author(s):  
Yong Nam Kwon ◽  
Young Seon Lee ◽  
S.W. Kim ◽  
Jung Hwan Lee
Keyword(s):  
Grain Boundary ◽  
Tensile Deformation ◽  
Texture Evolution ◽  
Grain Morphology ◽  
Superplastic Forming ◽  
Az31 Alloy ◽  
Grain Boundary Sliding ◽  
Processing Technique ◽  
Mg Alloys ◽  
Boundary Sliding

Mg alloys could be the lightest alloys among the industrially applicable engineering alloys. Since wrought Mg alloy has limited applications due to the poor formability, casting is currently the main processing technique to fabricate Mg components even though wrought alloys are superior in terms of mechanical properties and reliability. While a lot of research and development has been focused on warm forming under the temperature condition of around 250°C where more formability could be expected, superplastic forming could be another way to get over the low formability of Mg alloys. Like other superplastic materials grain boundary sliding is the main deformation mechanism of Mg superplasticity. Accommodation of stress concentration around triple point of grain boundary should be done favorably if grain boundary sliding continues without any fracture. In the present study, superplastic behavior of AZ31 alloys with several grain sizes was examined firstly. Accommodation of grain boundary sliding of AZ31 alloy would be discussed on the basis of grain morphology and texture evolution after tensile deformation.

Role of Grain Boundary Sliding in Texture Evolution for Nanoplasticity

2017 ◽  
Vol 20 (4) ◽  
pp. 1700212 ◽  
Author(s):  
Yajun Zhao ◽  
Laszlo S. Toth ◽  
Roxane Massion ◽  
Werner Skrotzki
Keyword(s):  
Grain Boundary ◽  
Texture Evolution ◽  
Grain Boundary Sliding ◽  
Boundary Sliding

Direct Observation of Two-Dimensional Grain Boundary Sliding and Switching in ODS Ferritic Steel

2016 ◽  
Vol 838-839 ◽  
pp. 43-50
Author(s):  
Eiichi Sato ◽  
Hiroshi Masuda ◽  
Yoshito Sugino ◽  
Shigeharu Ukai
Keyword(s):  
Grain Boundary ◽  
Ferritic Steel ◽  
Tensile Deformation ◽  
Grain Boundary Sliding ◽  
Grain Structure ◽  
Two Dimensional ◽  
Kernel Average Misorientation ◽  
Boundary Sliding ◽  
High Temperature Tensile ◽  
Region Ii

High-temperature tensile deformation was performed using an oxide-dispersionstrengthened (ODS) ferritic steel,, which has grain structure largely elongated and aligned in one direction, in the perpendicular direction. In the superplastic region II, two-dimensional grain boundary sliding (GBS) was achieved, in which the material did not shrink in the grain-axis direction and grain-boundary steps appeared only in the surface perpendicular to the grain axis. In this condition, a classical grain switching event was observed. Using kernel average misorientation maps drawn with SEM/EBSD, dominant deformation mechanisms and accommodation processes for GBS were examined in the different regions. Cooperative grain boundary sliding, in which only some of grain boundaries slide, was also observed.

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.

Deformation Behavior of Fine Grained Al-Mg Alloy under Biaxial Stress

2006 ◽  
Vol 503-504 ◽  
pp. 475-480 ◽  
Author(s):  
Masafumi Noda ◽  
Kunio Funami
Keyword(s):  
Grain Boundary ◽  
Tensile Deformation ◽  
Grain Boundary Sliding ◽  
Biaxial Stress ◽  
Mg Alloy ◽  
Strain Rates ◽  
Fine Grained ◽  
Biaxial Tensile ◽  
Wide Range ◽  
Boundary Sliding

The grain boundary sliding and the formation of slipped bands and cavitations during biaxial tensile deformation were examined in fine grained Al-Mg alloy. Biaxial tensile testing was conducted with cruciform specimens at initial strain rates of 10-4 to 101s-1. It was found that at the same equivalent strain conditions, the number of cavities under biaxial tension is significantly greater than that under uniaxial tension. A greater prevalence of slipped bands and grain separations were clearly observed under biaxial stress than under uniaxial stress. It was suggested that development of slipped bands resulted from the formation of elongated cavities and multiple deformed bands under biaxial stress. Additionally, the m-value under biaxial stress remained at about 0.3 over a wide range of strain rates. The effects of grain separation and formation of cavities were related to the motion of grain boundary sliding, grain size and loading conditions.

Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys

2004 ◽  
Vol 449-452 ◽  
pp. 665-668 ◽  
Author(s):  
Junichi Koike
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Deformation Mechanism ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Mg Alloys ◽  
Deformation Mechanisms ◽  
Slip Systems ◽  
Dislocation Plasticity ◽  
Boundary Sliding

Deformation mechanisms of Mg-Al-Zn (AZ31) alloys were investigated by performing tensile test at room temperature. In fine grain Mg alloys deformed at room temperature, nonbasal slip systems were found to be active as well as basal slip systems because of grain-boundary compatibility effect. Slip-induced grain-boundary sliding occurred as a complementary deformation mechanism to give rise to c-axis component of strain. With increasing grain size, the activation of the nonbasal slip systems was limited near grain boundaries. Instead of grain-boundary sliding, twinning occurred as a complementary deformation mechanism in large grained samples. Orientation analysis of twins indicated that twinning is induced by stress concentration due to the pile up of basal dislocations. The grain-size dependence on deformation mechanism was found to affect yielding behavior both microscopically and macroscopically which can influence various mechanical properties such as fatigue and creep.

Tungsten wire for incandescent lamps

1990 ◽  
Vol 5 (9) ◽  
pp. 2004-2022 ◽  
Author(s):  
John L. Walter ◽  
Clyde L. Briant
Keyword(s):  
Grain Boundary ◽  
Hot Rolling ◽  
Tungsten Wire ◽  
Grain Morphology ◽  
Grain Boundary Sliding ◽  
Mechanical Processing ◽  
Boundary Sliding ◽  
The Wire ◽  
Incandescent Lamps ◽  
The Relationship

Tungsten wire for incandescent lamp filaments must operate at high temperatures and for long times. To meet these requirements, the grain morphology of the wire must be controlled to reduce the propensity for grain boundary sliding. The morphology is a function of the distribution of very small pockets of potassium in the wire and the mechanical processing from ingot to wire. The behavior of the filament is directly related to the grain morphology. This paper describes the mechanism by which the potassium is incorporated into and distributed in the ingot. The elongation and spheroidization of the bubbles during hot rolling and swaging are also examined and related to the grain morphology of wire. Some indications of the relationship between grain morphology and filament behavior are also given.

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