Electron irradiation induced vitrification at dislocations in quartz
Recent observations using the ‘weak beam’ electron microscopy technique of split images of dislocations in quartz have been interpreted as arising either from dissociation of the dislocations into partials1, or from a glassy (metamict) phase at the core2, resulting from irradiation damage. In this letter we describe observations of lattice images of near end-on dislocations in quartz, which enable us to distinguish between these two models.
Dislocation images in quartz and the determination of Burgers vectors
Abstract It is demonstrated that the Burgers vectors of dislocations in quartz can be positively identified from the results of conventional diffraction contrast experiments in the electron microscope. Dislocations having an a Burgers vector were found in experimentally-deformed natural and synthetic crystals, and dislocations with a c Burgers vector were also observed in a synthetic crystal. The factors that complicate the successful execution of diffraction contrast experiments on quartz are discussed.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.