| Magnesium alloy has great potential and value for research in the field of biodegradable medical materials,but the Mg-Zn-Mn alloy material produced by our team can’t meet the requirements of practical application on various aspects.In order to produce the high-performance materials,the topic for Mg-Zn-Mn alloy preparation process and a variety of organizational performance enhancing process are studied systematically by our team.In this paper,the research content include alloy smelting,casting homogenization heat treatment,extrusion process,equal channel angular pressing process,and the annealing process.Eventually we determine the most reasonable composite experimental technology of material organization performance reinforcement.I adapt the previous smelt process using in our team,Two different diameter molds are used in my research,respective 140 mm and 90 mm.When the casting mould’s diameter is 140 mm,the average grain size of the ingot casting is about 200 microns,When the casting mould’s diameter is 90 mm,the average grain size of the ingot casting is about 100 microns,under these smelting conditions,the ingot casting is solid solution structure.Because the time of thermal insulation and cooling is short,the composition of ingot casting is uneven.Using the bigger ingot casting as the raw materials,I contrast the microstructure and properties of materials after extruding at three different extrusion temperatures,which respectively are 250℃,300℃,330℃,all of them are extruded at 0.5 mm/s.Because of the poor plasticity of 140 mm ingot casting,the specimen crack after extruding in high speed,so I choose the 90 mm ingot casting as the raw material.I contrast four different extrusion speeds,which respectively are 0.5mm/s,1 mm/s,1.5 mm/s,2mm/s,the results show that when the extrusion speed is 0.5mm/s.The specimen on higher speed extrusion has bigger grain size relatively than the specimen on lower speed extrusion.The plasticity is more important than the strength,so 0.5mm/s is the best extrusion speed.This paper systematically study the four basic parameters,they respectively are the path,the extruding speed,extrusion temperature,and extrusion numbers.I have studied their effects on the process of strengthening,the lower temperature the more refined microstructure.There are no difference on organization and properties between different extrusion speed samples,and the higher speed can make the materials crack,so lower extrusion speed is better.Besides I find that the friction would affect the specimen’ organization.Through researching on four paths,I find that the path of BC has the highest organizational refinement efficiency,the samples extruded on path of BC has uniform grain size.With the increase of extrusion numbers,the comprehensive performance like corrosion resistance,hardness,tensile strength and plasticity are greatly improved after multiple numbers extruding.In addition to above reinforcement technology,I also have studied the anneal’effects on the specimen after ECAP.Because the grain grow up after annealing,the strength of all specimens decline at different levels,but higer elongation.When the annealing parameters are 220℃/6h,the specimen has highest elongation about 40%.The material’s plasticity significantly increased. |
