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Z. Zúberová L. Kunz T.T. Lamark Y. Estrin M. Janeček 《Metallurgical and Materials Transactions A》2007,38(9):1934-1940
The work focuses on experimental examination of the fatigue behavior of magnesium alloy AZ31 produced by three different procedures:
squeeze casting (SC), hot rolling (HR), and equal-channel angular pressing (ECAP). The microstructures produced were studied
by light and transmission electron microscopy (TEM). Squeeze-cast AZ31 had low porosity and coarse grains, while hot-rolled
material showed microstructure with grain size of 3 to 20 μm. The finest grain structure with the average grain size of about 1 to 2 μm was found in the material pressed 4 times at 200 °C using the ECAP technique, route B
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. It was shown that low- and high-cycle fatigue behavior under symmetric loading at room temperature and with loading frequency
of 20 Hz is strongly dependent on the technique employed in producing the alloy. The ECAP was shown to improve the fatigue
life of the material in the low-cycle region over that of the squeeze-cast material. However, the fatigue life of AZ31 after
ECAP was slightly lower than that of the hot-rolled material. In the high-cycle region, the hot-rolled material and the material
that underwent ECAP exhibit the same fatigue strength, which is superior to that of the squeeze-cast alloy. Fatigue crack
initiation and the character of fracture were examined by means of scanning electron microscopy.
This article is based on a presentation made in the symposium entitled “Ultrafine-Grained Materials: from Basics to Application,”
which occurred September 25–27, 2006 in Kloster Irsee, Germany.
相似文献
Z. Zúberová (Cand. Scient. Phys.)Email: |
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P. Wesseling B.C. Ko L.O. Vatamanu G.J. Shiflet J.J. Lewandowski 《Metallurgical and Materials Transactions A》2008,39(8):1935-1941
Annealing studies at different temperatures, as well as those conducted with 940 MPa hydrostatic pressure, were conducted
on amorphous ribbons of Al87Ni7Gd6. The studies were performed to investigate the evolution of structure under different conditions and to particularly examine
the effects of superimposed hydrostatic pressure during annealing. This amorphous alloy devitrifies at low temperatures via the precipitation of nano-crystalline α-Al particles. The effects of these various exposures on the amount of devitrification have been quantified using a variety
of analytical techniques (i.e., X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM)). In addition,
the effects of devitrification on the mechanical properties have been quantified using microhardness indentation and uniaxial
tension tests.
This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February
25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of
Materials Committee.
相似文献
J.J. Lewandowski (Leonard Case, Jr., Professor of Engineering)Email: |
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T. Furuhara H. Kawata S. Morito G. Miyamoto T. Maki 《Metallurgical and Materials Transactions A》2008,39(5):1003-1013
The crystallography of bainitic ferrite nucleated at austenite grain boundaries was studied in an Fe-9Ni-0.15C (mass pct)
alloy. The relationship between bainitic ferrite orientations (variants) and grain boundary characters, i.e., misorientation and boundary orientation, was examined by electron backscatter diffraction analysis in scanning electron
microscopy and serial sectioning observation. Bainitic ferrite holds nearly the Kurdjumov–Sachs (K-S) orientation relationship
with respect to the austenite grain into which it grows. At the beginning of transformation, the variants of bainitic ferrite
are severely restricted by the following two rules, both advantageous in terms of interfacial energy: (1) smaller misorientation
from the K-S relationship with respect to the opposite austenite grain and (2) elimination of the larger grain boundary area
by the nucleation of bainitic ferrite. As the transformation proceeds, variant selection establishing plastic accommodation
of transformation strain to a larger extent becomes important. Those kinds of variant selection result in formation of coarse
blocks for small undercooling.
This article is based on a presentation given in the symposium entitled “Solid-State Nucleation and Critical Nuclei during
First Order Diffusional Phase Transformations,” which occurred October 15–19, 2006 during the MS&T meeting in Cincinnati,
Ohio under the auspices of the TMS/ASMI Phase Transformations Committee.
相似文献
T. Furuhara (Professor)Email: |
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P. Sahu A.S. Hamada R.N. Ghosh L.P. Karjalainen 《Metallurgical and Materials Transactions A》2007,38(9):1991-2000
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