Fabrication of High Aluminum Content Mg alloys using a Horizontal Twin Roll Caster
This study was aimed for investigating of manufacturing high aluminum content Mg alloys using a horizontal twin roll caster. Recently, weight saving has been key issues for lighter transport equipments as well as electronic componen t parts. As alternative materials to aluminum alloys, developin g magnesium alloy with higher strength has been expected. Normally hi gh Aluminum content Mg alloy has poor ductility and is difficul t to be rolled because of its high strength. However, twin roll casting pr ocess is suitable for manufacturing wrought Mg alloys because materials can be cast directly from molten metal. In this study, manufact uring of high aluminum content magnesium alloy sheet using the roll casting process has been carried out. Effects of manufactur ing parameter, such as roll velocity, pouring temperature and roll gap, on casting was investigated. A microscopic observation of the crys tals of cross section of as cast strip as well as rolled strip was conduc ted. Keywords—AZ91, AZ111, AZ121, Magnesium alloys, Twin roll casting
Development of manufacturing process of wrou- ght magnesium alloy sheets by twin roll casting
AbstrAct Purpose: The purpose of the work is to development of a strip casting technology for manufacturing magnesium alloy sheets. The aim of the work is to establish a manufacturing process and technology to facilitate the economical manufacture of high-strength magnesium sheet alloys. Design/methodology/approach: A horizontal type twin roll caster was used to manufacture magnesium alloy sheets. Pair of copper alloy roll, pure copper roll and steel roll was used for the horizontal type twin roll caster. The diameter of the rolls was 300mm and the width of rolls was 100 and 150mm. Findings: The magnesium alloy sheets could be succcessfully manufactured by the horizontal twin roll caster. The product sheet thickness in the present experiment was 2.0 to 5.0mm. The equiaxed microstrucure was observed in cast magnesium alloys when a pair of copper and cupper aolly rolls were used. The mean grain size of the cast magnesium alloys strip was from 30 to 60 micrometers. After hot rolling process, the grain size was reduced to about 10 micrometers. The obtained magnesium alloy sheet indicated a good plastic formability by a warm-drawing test.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.