Materials Science Forum Vols. 539-543

Abstract: In this work, the comprehensive study of an interesting Pd/AlGaAs pseudomorphic high electron mobility transistor (pHEMT) based hydrogen sensor is implemented. The theoretical analysis and simulation are made by using a two-dimensional simulator Medici. In addition, a practical device is fabricated successfully. Based on the variations of the catalytic metal work function, the DC characteristics of experimental and simulated results are compared and studied.

Abstract: Dynamic compressive tests were conducted on Zr-based amorphous alloys and amorphous matrix composite containing dendritic β phases. Dynamic compressive tests were conducted using a compressive Kolsky bar and then the test data were analyzed in relation to microstructure and fracture mode. Under dynamic loading, the maximum shear stress and ductility of the amorphous alloy and composite were considerably lower than those under quasi-static loading because of the decreased resistance to fracture. Deformation under dynamic loading lowered strain and compressive strength because of reduced fracture resistance, and the alloy containing dendritic β phases showed better compressive strength and ductility than the monolithic alloy.

Abstract: Twin- roll casting of magnesium alloys is a rapidly solidifying process, which can directly produce thin strips from molten metal. In this paper, based on a pilot vertical type twin-roll caster, 3D models of twin-roll casting process were used for simulation of thermal flow and solidification on depending of casting speed, molten pool level and pouring temperature. The effect of side dams on thermal flow behavior was also considered. Based on the analyzed results, a proper concave slot nozzle was designed to compensate temperature variation across the width of strip. Comparing with parallel type slot nozzle, it can adjust temperature distribution along the roll width continuously by adopting proper concave curves, which is more flexible than rectification boards delivery system. Strips of magnesium alloy AZ31 were produced in the pilot caster with the concave slot nozzle. The experiments show that surface quality of as cast strip was improved by using the new type of nozzle.