Research On The Preparation Process, Microstructure And Properties Of AZ91 Magnesium Alloy Via Rapid Solidification

The microstructure can be refined obviously by rapid solidification, and the mechanical properties of traditional structural material can be highly improved, so it is possible to supply a feasible way for extensive application of magnesium alloy. It is a current hotspot to rapare high-strength magnesium alloy by rapid solidification technology.In the present study, alloy fluid flow was broken up, the AZ91 magnesium alloy foil was prepared by twin-roll rapid solidification technique, and the effects of the rotate speed, the nozzle aperture, the spurt height, the argon pressure of melt spurt and fluid stream crushing on external pattern were analyzed, a set of processing parameter was obtained, magnesium alloy foil which has fine structure property can be obtained. The stability of microstructure and mechanical property of foil at different technological conditions of heat treatment were studied, and the effect of extrusion process on structure property of rapid solidification extrusion bar was analyzed too, rapid solidification extrusion bar was gained, its structure property was better than traditional cast ingot extrusion bar.The experiment results showed that all of the process parameters have some effects on macro-demension of ribbon chip, microstructure and performance in the process of preparing AZ91 foil by rapid solidification method, and the effects of wheel speed and argon pressure of fluid stream crushing were more obvious. The thickness, length, width and grain size decrease and the microhardness of the ribbon chip increased with the increase of wheel speed and argon pressure of fluid stream crushing. The results showed that, when the wheel speed was 25.12m/s, the nozzle aperture wasφ1mm, The spurt height was 100mm, the argon pressure of melt spurt was 0.1MPa, the argon pressure of fluid stream crushing was 0.3MPa, the ribbon chip was comminution, it was about 8mm in length and 0.15mm in thickness and its grain size was 1~3μm, and the average microhardness was 98.05Hv, it was higher than that of the traditional cast alloy.Heat treatment of AZ91 rapid solidification foil under different processing parameter was studied, then the microstructure and properties were analyzed, the results showed that significant precipitates Mg17Al12 present along the grain boundaries after heating at 200℃for 4 hours, visible as"necklace"type structure, and the grain size was as small as the ribbon chip which did not heat treated, the microhardness was increased to 113.74Hv. The grain size became larger when heating at 250℃, 300℃. It indicated...