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Superplastic Deformation and Viscous Flow in an Zr-Based Metallic Glass at 410 Degrees C

Description: The thermal properties of an amorphous alloy (composition in at.%: Zr-l0Al-5Ti-l7.9Cu-14.6Ni), and particularly the glass transition and crystallization temperature as a function of heating rate, were characterized using Differential Scanning Calorimetry (DSC). X-ray diffraction analyses and Transmission Electron Microscopy were also conducted on samples heat-treated at different temperatures for comparison with the DSC results. Superplasticity in the alloy was studied at 410 degrees C, a temperature within the supercooled liquid region. Both single strain rate and strain rate cycling tests in tension were carried out to investigate the deformation behavior of the alloy in the supercooled liquid region. The experimental results indicated that the alloy did not behave like a Newtonian fluid.
Date: December 1, 1998
Creator: Liu, C.T.; Mukai, T.; Nieh, T.G.; Wadsworth, J. & Wang, J.G.
Partner: UNT Libraries Government Documents Department

An investigation of cavitation in a mechanically alloyed 15 vol % SiCp/IN9021 aluminum composite

Description: A mechanically alloyed 15 vol % SiCp/IN9021 aluminum composite exhibited a maximum elongation of 610 % at a very high strain of 5 s{sup {minus}1} at 823 K. Nonetheless, the maximum elongation was obtained at a lower strain rate than that where the maximum m value (about 0.5) was obtained. This discrepancy between the optimum superplastic strain rate for the largest elongation and the strain rate for the maximum m value was believed to be associated with the cavitation behavior. Cavitation behavior of the SiCp/IN9021 aluminum composite was, therefore, carried out. It was found that cavities initiated at ends of particulate reinforcements and parallel to the applied stress direction within initial small strains, and their subsequent growth and coalescence invariably leads to premature failure. Experimental results indicated that cavity growth is plasticity controlled and can be described by a model proposed by Stowell.
Date: July 1, 1993
Creator: Higashi, K.; Okada, T.; Mukai, T.; Tanimura, S.; Nieh, T. G. & Wadsworth, J.
Partner: UNT Libraries Government Documents Department

Compressive Properties of a Closed-Cell Aluminum Foam as a Function of Strain-Rate and Temperature.

Description: The compressive deformation behavior of a closed-cell Aluminum foam (ALPORAS) manufactured by Shinko Wire. Co. in Japan was evaluated under static and dynamic loading conditions as a function of temperature. High strain rate tests (1000 - 2000/s) were conducted using a split-Hopkinson pressure bar(SHPB). Quasi-static and intermediate strain rate tests were conducted on a hydraulic load frame. Little change in the flow stress behavior as a function of strain rate was measured. The deformation behavior of the Al-foam was however found to be strongly temperature dependent under both quasistatic and dynamic loading. Localized deformation and stress state instability during testing of metal foams will be discussed in detail since the behavior over the entire range of strain rates indicates nonuniform deformation.
Date: January 1, 2001
Creator: Gray, G. T. (George T.), III; Liu, C. (Cheng); Trujillo, C. P. (Carl P.); Jacquez, B. (Benito); Mukai, T. & Cady, C. M. (Carl McElhinney)
Partner: UNT Libraries Government Documents Department