Effect Of Heat Treatment On Structure And Property Of ZM6 Magnesium Alloy By Solid-state Recycling

As the prevalent application of magnesium alloy, it become more and more important for the recycling of magnesium alloy to recycle scraps appropriately and prolong the lifetime. The solid-state recycling method is good for saving resource, reducing cost, and preventing pollution of environment. The problem of liquid-state recycling which is complicated and unsafe since magnesium alloy are readily oxidized can be solved by solid-state recycling. It has a well development potential. The ZM6 magnesium alloy samples are prepared by hot extruding from machined chips. This method is safe without protective covering and fusion, which is based on plastic deformation theory, dynamic recrystallization and dynamic recovery mechanism, dispersion strengthening and diffusion welding mechanism.The study selected a set mould with the extrusion ratio of 25:1, modular angle of 60?, 6mm of working tape, and 2? of rounding at the entrance of mould. It can meet the property test of materials prepared by hot extrusion from recycled machined chips, which is according to the design principle of extrusion mould. The extruded bars were strengthened by different treatment processes, then the microstructure was observed, the mechanical property was tested, and compared with as-cast and the samples prepared by hot extrusion from cast ingot.The result shows that, compared with the as-cast ZM6 magnesium alloy, the grain is refined obviously since dynamic recrystallization have taken place in the process of hot extrusion, after T4 heat treatment, the ultimate strength (UTS) and the plasticity of quenched alloy is lower than that of extruded material without any thermal treatment, one of the prime reasons in that the strength loss due to the recrystallization is greater in magnitude than the increase due to solid solution strengthening. Heat treatment of T5 and T6 strengthen the strength of extruded alloy. After heat treatment of T5, the grain is not grow up almost. But at heat treatment of T6, the grain is grow up evidently and separate second phases particles appear in the microstructure. The prime reason of mechanical property changed is the separated second phases particles composed rare earth element. After quenched, the maximum strength increase is achieved after 16h aging, about 294.50MPa. At this time of day, the strength of alloy has been strengthened 27.00% compare with the hot extruded alloy without any heat treatment. Although the values of ductility played down, but the ductility ofδnear 13.50% is quite accepted. The fracture surface of cast alloy with T6 treatment appeared a particular structure of chasm. The phase of brittleness contained the phase of basic. The strength and the ductility increased at the same time.