Experimental Investigation of Cavitation Behavior in AZ61 Magnesium Alloy
20 Mar 2005-Materials Transactions (The Japan Institute of Metals and Materials)-Vol. 46, Iss: 3, pp 626-630
TL;DR: In this paper, the authors investigated the rate of cavitation with superplastic strain for a super-plastic AZ61 magnesium alloy at a strain rate of 2 × 10 - 4 s - 1 and temperature of 648 K, under the conditions of which an elongation of more than 250% has been found.
Abstract: The rate of cavitation with superplastic strain was investigated for a superplastic AZ61 magnesium alloy at a strain rate of 2 × 10 - 4 s - 1 and temperature of 648 K, under the conditions of which an elongation of more than 250% has been found. Cavities initiated at grain boundaries. The cavitation showed a growth perpendicular to the applied stress direction after the initial strains. The subsequent growth and coalescence of cavities invariably leads to failure of the material. The experimental growth rates are in good agreement with the rate predicted by the plasticity-controlled growth mechanism.
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25 Mar 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the room temperature tensile properties of a superplastic AZ31 magnesium alloy prior to and following high temperature deformation at 673 and 723 K were examined.
Abstract: Room temperature tensile properties of a superplastic AZ31 magnesium alloy prior to and following high temperature deformation at 673 and 723 K were examined. The material behaved in a superplastic manner at low strain rates, and dislocation creep dominated deformation at high strain rates. The specimens after high temperature deformation exhibited higher ductility and lower strength as the strain rate during high temperature deformation decreased. Pre-existing basal texture changed gradually toward random during high temperature deformation at low strain rates, whereas it was strengthened at high strain rates. Both the basal texture weakening and lower cavity volume fraction brought about the higher ductility following superplastic deformation at lower strain rates.
51 citations
15 Sep 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the texture and tensile properties of a fine-grained Mg-Al-Zn alloy rod processed by extrusion were examined before and after superplastic deformation.
Abstract: The texture and tensile properties at room temperature of a fine-grained Mg–Al–Zn alloy rod processed by extrusion were examined before and after superplastic deformation. The tensile properties at room temperature were influenced by the high-temperature deformation conditions. The specimen after being exposed to superplastic deformation under tension tend to show higher ductility and lower strength at room temperature as the strain rate during high-temperature deformation decreased or as deformation temperature increased. The pre-existing basal texture of the rod slightly weakened after superplastic deformation. However, the texture weakening in the rod was not significant compared with that observed in the counterpart alloy in sheet-form probably because the initial distribution of basal planes differs between them. It is suggested that the rotation of crystallographic orientation induced by slip accommodation for grain boundary sliding plays an important role in texture randomization in superplastic magnesium alloys.
21 citations
15 Dec 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a relatively coarse-grained AZ61 alloy deformed under two conditions for which grain-boundary sliding (GBS) creep controlled plastic flow and which produced the same flow stress of 10MPa.
Abstract: Cavitation behavior has been investigated in a relatively coarse-grained AZ61 alloy deformed under two conditions for which grain-boundary sliding (GBS) creep controls plastic flow and which produce the same flow stress of 10 MPa. At a strain rate of 10−5 s−1 and a temperature of 573 K, GBS creep is rate controlled by grain-boundary diffusion, DGB. At a strain rate of 2 × 10−4 s−1 and a temperature of 648 K, GBS creep is rate controlled by lattice diffusion, DL. Tensile elongation is slightly greater when DGB accommodates GBS deformation. Despite accommodation of GBS by different diffusion mechanisms, cavity evolution under both deformation conditions is quite similar. Cavity volume percent increases similarly with strain under both conditions, as does the radius of the largest cavities. Cavity areal number density distributions are similar between the different deformation conditions when strain is a constant. All the features observed for cavitation indicate that cavity growth is plasticity controlled under both deformation conditions. The theory of plasticity-controlled cavity growth is in very good agreement with experimental data produced for this investigation.
20 citations
TL;DR: In this article, cavities were formed in the random boundaries of superplastic magnesium alloys due to higher boundary energy, and the cavity growth rate of the fine-grained alloy (dominant diffusion process: grain boundary diffusion) was lower than that of the coarse-grain alloy (lattice diffusion) during super-plastic flow.
19 citations
TL;DR: In this paper , the effect of grain size and the type and amount of secondary phase particles on the superplasticity of Mg alloys was systematically examined and reviewed, and the critical conditions for achieving LTS, HSRS and simultaneous achievement of LTS and HSRS were calculated and proposed, and their importance was discussed.
14 citations
References
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TL;DR: In this article, the effect of temperature and grain size on superplastic flow was investigated using a relatively coarse-grained (∼20μm) Mg-Al-Zn alloy for the inclusive understanding of the dominant diffusion process.
175 citations
TL;DR: In this article, the authors conducted constant strain rate tensile tests for fine grained Mg-Al-Zn (AZ91) and MgZn-Zr (ZK60 and ZK61) alloys processed by powder metallurgy (PM) and ingot metallomics (IM) routes.
Abstract: Constant strain rate tensile tests have been conductedfor fine grained Mg-Al-Zn (AZ91) and Mg-Zn-Zr (ZK60 and ZK61) alloys processed by powder metallurgy (PM) and ingot metallurgy (IM) routes. The experimental results revealed that the strain rate was inversely proportional to the cube of the grain size and that the activation energy for superplastic flow was higher than that for grain boundary diffusion. The PM Mg alloys showed superplastic behaviour at higher strain rates than the IM Mg alloys. This is because of smaller grain sizes of the PM Mg alloys. The origin of the high strain rate superplasticity for the PM Mg alloys is unlikely to be associated with the presence of a liquid phase.
124 citations
TL;DR: In this article, the authors examined cavitation during superplastic flow in three aluminium alloys (Supral 220, Al-7475E and Al-CuLi alloy) strained in uni-axial and biaxial tension with varying superimposed hydrostatic pressures and found that the rate of increase of the volume fraction of cavities with strain can be decreased by increasing the superimposed pressure.
124 citations
TL;DR: In this paper, a model for the diffusion growth of cavities in superplastic materials was developed, and it was shown that the rate of change of cavity radius with strain due to super-plastic diffusion growth is given by drdϵ ∼- 45ΩδDgbd2kT(σe) where r is the cavity radius, e is the total strain, Ω is the atomic volume, Dgb is the coefficient for grain boundary diffusion, d is the spatial grain size, T is the absolute temperature, σ is the applied
120 citations