Study On Microstructure And Properties Of Al-Mg Alloy By Continuous Rheo-extrusion

The Al-Mg alloy has high strength,good electrical conductivity,thermal conductivity and weldability and good corrosion resistance which can be processed into kinds of profiles,therefore it is widely used in various fields.However with the increase of Mg content,the strength and toughness of Al-Mg alloy increase gradually.At the same time,the high Mg aluminum alloy will bring difficulties to melting and casting and subsequent mechanical and welding processes.Based on the above,the development of processing method with efficient,high-performance,energy saving is of great significance for the industrialization of Al-Mg alloy production.The continuous reho-extrusion which is combined with casting and forming is a forming method with short process,high efficiency and low energy consumption.Alloying is an important way to improve the performance of A1 alloy.The Sn has unique alloying in A1 alloy which has small solid solubility in A1 alloy and has strong ability to combine with the vacancy.It is one of the most potential alloying elements in Al alloy which can effectively improve the Al alloy of microstructure and properties,but the mechanism is not clear.Fully understand and recognize the mechanism of alloy elementary Sn in Al alloy is of important guiding significance for the development and application of new type Al alloy.Based on the above analysis.In this paper,the Al-xMg(x=3?4?5?6 wt.%)and Al-5Mg-xSn(x=0.2?0.4?0.6 wt.%)were processed by continuous reho-extrusion.The effect of Mg content on microstructure and properties of Al-Mg alloy rod was obtained and the microstructure and mechanical properties of as cast and as extruded Al-5Mg were compared.As well as the effect of Sn content on microstructure and properties of Al-5Mg alloy rod was obtained.Finally the Al-5Mg-1Sn alloy rod was treated by stabilization heat treatment.The following conclusions are obtained:(1)The Al-xMg(x=3?4?5?6 wt.%)with good microstructure and mechanical properties were prepared by continuous reho-extrusion.The microstructure of alloy rod is fine equiaxed crystal,and the average grain size of Al-Mg alloy rod is between 15-27 ?m.With the increase of Mg content,the average grain size decrease and the tensile strength increase,while the elongation will decrease.(2)The continuous reho-extrusion Al-5Mg alloy and the cast Al-5Mg alloy are compared which shows that the mechanical properties of the extruded Al-5Mg alloy is obvious superior to the cast.The coarse dendrite structure is avoided in casting.The tensile strength and elongation of the extruded Al-5Mg alloy rod are respectively 277.5MPa and 15.5%which are 41.3%and 48.1%higher than that of the cast Al-5Mg alloy respectively.(3)The aluminum-magnesium-tin alloys were obtained.With the increase of Sn element content,the elongation is dramatic improved,the elongation is increased by 43%,when the content of Sn is 1,but the tensile strength is decrease.The comprehensively considered and the alloy compared should be Al-5Mg-1Sn.(4)The stabilizing heat treatment process of Al-5Mg-1Sn alloy by continuous reho-extrusion was studied.The result show that the tensile strength of the alloy increases by 8%and the elongation decrease slightly by the treatment of 300 ? 3h and air cooling.The main reason for the above phenomenon is that the second Al3Mg2 phase are precipitated by the stabilization heat treatment.