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Using area detectors for stress determination by diffraction methods in a single exposure greatly simplifies the measurement process and permits the design of portable systems without complex sample cradles or moving parts. An additional advantage is the ability to see the entire or a large fraction of the Debye ring and thus determine texture and grain size effects before analysis. The two methods most commonly used to obtain stress from a single Debye ring are the so-called $$\cos \alpha $$ and full-ring fitting methods, which employ least-squares procedures to determine the stress from the distortion of a Debye ring by probing a set of scattering vector simultaneously. The widely applied $$\sin ^2\psi $$ method, in contrast, requires sample rotations to probe a different subset of scattering vector orientations. In this paper, we first present a description of the different methods under the same formalism and using a unified set of coordinates that are suited to area detectors normal to the incident beam, highlighting the similarities and differences between them. We further characterize these methods by means of in situ measurements in carbon steel tube samples, using a portable detector in reflection geometry. We show that, in the absence of plastic flow, the different methods yield basically the same results and are equivalent. An analysis of possible sources of errors and their impact in the final stress values is also presented. [ABSTRACT FROM AUTHOR]

This paper reports on damage morphology created in low-cycle high-load spherical indentations of feldspar porcelain and leucite glass ceramic to mimic teeth clenching or grinding. Maximum contact stresses were evaluated as functions of cycle numbers and applied loads using a Hertz model. The surface damage of the two materials after low-cycle high-load indentation testing was viewed using scanning electron microscopy to understand the relations between crack propagation and microstructures. The results indicate that the maximum contact stresses for both materials reduced significantly with the cycles (ANOVA, p < 0.05) but did not show a significant change with the applied loads (ANOVA, p > 0.05). Feldspar porcelain can endure much less maximum contact stress than leucite glass ceramic. Low-cycle high-load spherical indentations induced extensive ring cracks, wedging of crack faces by debris, fragmentation, and pulverization on feldspar porcelain surfaces. In contrast, leucite glass ceramic surfaces yielded only minimum microcracks at 500 N load and localized fractures and cracks at the higher loads of 600 and 700 N. This study shows that leucite glass ceramic had much higher resistance to low-cycle high-load fatigue impacts than feldspar porcelain and it can be a better choice for restorations under teeth clenching and grinding conditions. [ABSTRACT FROM AUTHOR]

Sn-Co alloys are promising Pb-free solders, while plating layers and substrates of Ag and Cu are commonly encountered in electronic products. This study examines the interfacial reactions between Sn-0.25 wt% Co/Ag and Sn-0.25 wt% Co/Cu at 180 and 210 °C, with and without current stressing. CoSn3 precipitates are found in the solder matrix in the as-prepared condition. In Sn-0.25 wt% Co/Ag couples, a continuous Ag3Sn reaction phase layer is observed at the interface and Ag3Sn phase particles are dispersed in the matrix, with and without current stressing. When there is a 500 A/cm2 electrical current, the growth rate of the Ag3Sn phase is not affected at either the cathode side or the anode side. However, the passage of an electrical current leads to the formation of needle-like Ag3Sn phase particles in the solder matrix. In Sn-0.25 wt% Co/Cu couples, both Cu6Sn5 and Cu3Sn reaction phases are formed at the interface, with and without current stressing. Cu6Sn5 precipitates, with a higher Co content, are found in the matrix, mostly nucleated on CoSn3 precipitates. When there is a 500 A/cm2 electrical current stressing, all the reaction phase layers are thicker and the anode interfaces are nonplanar. It is observed that there is cracking and that there are discontinuous Cu6Sn5 layers at the interface and that a significant amount of Cu6Sn5 phase in the matrix accompanies 500 A/cm2 electrical current stressing. [ABSTRACT FROM AUTHOR]

Strain-induced abnormal grain growth was observed along the gage length during high-temperature uniaxial tensile testing of rolled Mg-Al-Zn (AZ31) sheet. Effective strain and strain rates in biaxial forming of AZ31 sheets also affected the nature of grain growth in the formed sheet. For the uniaxial testing done at 400 °C and a strain rate of 10-1s-1, abnormal grain growth was prevalent in the gage sections that experienced true strain values between 0.2 and 1.0. Biaxial forming of AZ31 at 5 × 10-1s-1 and 400 °C also exhibited abnormal grain growth at the cross sections which experienced a true strain of 1.7. Uniaxially tested sample at 400 °C and a strain rate of 10-3s-1, however, showed no abnormal grain growth in the gage sections which experienced true local strain values ranging from 1.0 to 2.3. The normalized flow stress versus temperature and grain size compensated strain rate plot showed that the deformation kinetics of the current AZ31 alloy was similar to that reported in the literature for AZ31 alloys. Orientation image microscopy (OIM) was used to study the texture evolution, grain size, and grain boundary misorientation during uniaxial and biaxial forming. Influence of deformation parameters, namely strain rate, strain, and temperature on grain growth and refinement were discussed with the help of OIM results. [ABSTRACT FROM AUTHOR]

This paper presents new data and a summarization of earlier work, especially by the authors, regarding the large strain deformation (generally severe plastic deformation) of pure zirconium, generally at elevated temperatures (300-800 °C range). It appears clear, now, that Zr deforms by classic five-power-law creep. Large strain deformation revealed recovery controlled mechanisms with grain refinement occurring by geometric necessary boundaries and/or the recovery-based mechanism of geometric dynamic recrystallization depending on the amount of grain elongation that occurs. No discontinuous dynamic recrystallization or grain growth was observed in the authors' tension and rolling studies. The refined ultra-fine grained substructure showed dramatically improved tensile properties over conventionally processed Zr. [ABSTRACT FROM AUTHOR]