Results 1 - 10 of 1850
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[en] Creep tests are commonly performed by applying constant stress or load to uniaxial specimens, and creep data is obtained in the form of creep strain versus test time. This creep data is further used to determine creep related parameters, such as primary creep extension, the secondary creep rate, time to 1 % creep strain or stress to fracture at a given time. Compressive creep tests have been carried out on two commercial zinc-rich alloys No3 (Zn-4% Al-0.05% Mg). These tests were performed on a standard weighted lever arm constant load compressive creep machine using hollow cylindrical test pieces. The nominal stress range for these tests was 20 to 100 MPa. at temperatures from 70 to 160 degree centigrade. Generally, the primary creep extension was found to increase with copper content and was therefore higher in alloy No5. It was concluded from these tests that alloys No5 had a total creep deformation significantly lower than No3 under all testing condition due to its lower secondary creep rates and thus had better compressive creep strength than alloy No3. (author)
[en] The mechanical test for as room temperature-pressed specimens of PM-Zinalco (Zn-21al-2Cu) were carried out in compression at a room temperature with the initial strain rate ranging from 10/sup -4/ to 10/sup -1/sec/sup -1/. The microstructural changes accompanied by deformation were observed using scanning electron microscopy. The un sintered specimens showed superplastic behavior in contrast, those sintered for 20 h at 200 deg. C not. X-rays studies show that the xi phase (CuZn/sub 4/) present in the powders of the as extruded alloy, transform to the T'phase after a refinement of the powder in a vibratory mill. (author) 4 figs
[en] Dilute Zn solutions in the Zn--Pb--Cd system were investigated by an emf method with concentration cells to show the influence of variation in Pb and Cd concentrations on the Zn activity coefficients. Zinc concentrations were held in the mole fraction range 0.03 less than or equal to /sub Zn/ less than or equal to 0.1 with measurements in the temperature range 714 less than T less than 8770K. The limiting values of Zn activity coefficients for other ternary systems previously investigated were analyzed using Krupkowski's method and the random solution model of Alcock and Richardson. Experimental data for epsilon12 and epsilon13 (here 1 = Zn and 2, 3 are components of investigated ternaries) are compared also with the values obtained from limiting activity coefficients of the particular binary systems
[en] Laser-induced breakdown spectroscopy (LIBS) has been used to provide a rapid analysis of material compositions. A focused Nd: Glass laser beam is used to generated the plasma on the standard sample whose compositions are already known. The measurements of spatial and temporal distribution of target materials have been performed for optimization. The identification of the main elements of five metals (Zn, Al, Pb, Cu, and Fe) using the lines over a 250 A spectral range was demonstrated by the use of single laser pulse to record each spectrum. Optimum conditions of a detector are found as delayed time 620 μsec, slit which 28 μm and gate pulse width 5 μsec in the spectral range of 2900 A - 3300 A. The accuracy of the measurement is 5% for aluminum contents in the composition range of 0.1 - 5% in Zn-based alloy.
[en] In all recent studies on Zn-22 wt% Al, a low strain-rate Region I with n approx. = 3 has been observed. Correcting for concurrent grain growth will change n approx. = 4.1, as reported by Mohamed et al., to n approx. = 3.4, consistent with other work. Possible premature measurement of strain rate in the work of Vaidya et al. does not invalidate their n = 1 findings, since n approx. = 3 has been observed in other studies at the same strain levels. Recent reports of n = 1 in Zn-22 wt% Al at constant torsional velocity must be questioned because of the extremely small loads involved
[en] Highlights: • Increase the strength due to precipitation hardening of T-Mg32(AlZn)49 phase in the Zn modified Al-Mg alloy. • Both high corrosion resistance and high strength are achieved by retrogression and re-aging treatment in Al-5Mg-3Zn alloy. • Large Mg and Zn content difference between GBP and PFZ results in relatively high IGC susceptibility. • The intergranular corrosion mechanism of Zn modified Al-Mg alloy during retrogression and re-aging treatment is clarified. - Abstract: The effects of retrogression and re-aging treatment on the intergranular corrosion behavior of Al-5.0Mg-3.0Zn alloys are systematically studied. The alloy's strength increases when retrogression temperature increases from 390 °C to 420 °C. Samples retrogressed at 390 °C then re-aged are very susceptible to intergranular corrosion and those retrogressed at 405 °C and 420 °C express good corrosion resistance. Then the alloy's corrosion susceptibility rises with increasing retrogression temperature. Grain boundary precipitates are coarsened and distributed discontinuously with decreasing retrogression temperature. Higher retrogression temperature results in higher Mg and Zn content difference and intergranular corrosion susceptibility.