Relationships between microstructures and properties of chinese ancient bronzes
The typical morphology of alloy lead (Pb) in ancient bronzes made in the Spring-Autumn Warring States Period (770 B.C. -221 B.C.), China, was examined by using electron microscopic techniques. We propose that the main purposes for adding metallic Pb in a large quantity into ancient bronzes, such as arrows and ritual vessel—Ding, were for increasing weight and economical reasons. In order to promote adding efficiency and improve casting quality for getting homogenously distributed Pb particles in the bronzes, a process through inserting Pb rod into the mold is supposed to be used during casting, which provided a process for preventing Pb sinkage. Scanning electron microscope (SEM) observations from the fracture surface of the bronzes revealed that the Pb particle possessed a “hollow-cored bubble” structure, which was formed due to absorbing casting gases during solidification and therefore indirectly eliminated the casting porosity and loosen.
Studies on the Bronzes Excavated from the Tombs in the Xiajiang River Region
129 bronze samples are studied by scanning electron microscopy and metallography.All the samples are made of Cu-Sn alloy and Cu-Sn-Pb alloy,among which 119 samples are of cast structure,and 9 samples show recrystal grain and twin crystal.Maybe these 9 bronzes were first cast and then forged.Only 1 sample shows β'M-quenching.For the samples with identical cultural background,the components are similar.Compared with Chu-style weapons,the content of Pb in the weapons of Ba-Shu style is lower.Proper content of Sn and Pb enables the weapons and tools to have high hardness and tensile strength.After analysis,it can be seen that most of these bronzes were made in the locality,and a small quantity of them were obtained from other places.These samples present a comparatively high bronze technological level of the Ba and Xiajiang River region.The bronze technology in the Xiajiang River region had its own development.
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.