Experimental Study On Microstructure And Fatigue Behavior Of 6082 Aluminium Alloys

6082 aluminum alloy has high strength,good corrosion resistance,weldability and formability,so it is widely used in transportation,shipping and construction,especially in high-speed rail applications.Because this type of aluminum alloy is established by the United States and applied in China in recent years.Therefore,the study on the microstructure evolution,fatigue properties and fatigue crack propagation rate of 6082 aluminum alloys in different heat treatment conditions is not yet in-depth.At the same time,little attention has been paid to the evolution of alloy textures during the heat treatment process.In this paper,the hot-rolled,solid-solution and aging 6082 aluminum alloys were given to solve the above problems,and they were made using XRD,SEM,EBSD and mechanical property testing machines.The evolution of alloy structure and the change of mechanical properties under three states were studied,and the evolution of alloy texture in the heat treatment process was explored.At the same time,the fatigue testing machine was used to study the fatigue performance and fatigue crack growth rate of aged 6082 aluminum alloy.And we get the following main conclusions:1)In 6082 aluminum alloy the strengthening phase is Mg₂Si,and the inclusion phase are AlMnFeSi phase and AlFeSi phase.The hot-rolled alloy has less Mg₂Si and large in size.The inclusions AlMnFeSi and AlFeSi have more and larger sizes.In the solid-solution alloy,the strengthening phase Mg₂Si and the inclusion phases AlMnFeSi,AlFeSi are solidly dissolved in the matrix,the size is obviously reduced and solid solution strengthening occurs.There are a large number of Mg₂Si strengthening phases precipitated in the aging alloy,dispersed in the matrix.The content and size of the inclusions AlMnFeSi,AlFeSi slightly reduced.So the comprehensive mechanical properties of the 6082 aluminum alloy are best.2)The small-angle grain boundaries and textures of the hot-rolled,solid-solution,and aging 6082 aluminum alloys are significantly different.The proportion of low angle grain boundaries in hot-rolled 6082 aluminum alloy is 62%.The textures is{112}<111>and{112}<101>,with typical copper-type texture features.The proportion of low angle grain boundaries in solid-solution 6082 aluminum alloy is 9%.The texture is{124}<211>R-type texture and{112}<111>copper-type texture.And R-type texture is called recrystallized texture.The proportion of low angle grain boundaries in aging 6082 aluminum alloy is51%.And the textures changes to brass texture{101}<211>.3)Fatigue strength of aging 6082 aluminum alloy plate is about 80MPa.And the fracture of the coarse second phase particles in the alloy develops into microcracks,which leads to fatigue fracture of the material.4)The fatigue fracture characteristics of the 6082 aluminum alloy sheet in the aging state vary with the stress level.At the low stress level?140MPa?,the distance of the crack source from the surface is about 50?m,the fatigue crack propagation area accounts for about 50%of the entire fracture,and the fatigue zone spacing in the extended area gradually increases from322.3nm to 435.5nm,with the fatigue crack propagation.The quasi-cleavage zone and dimple hybrid morphology are present in the short-break zone,and the dimples are small;At a high stress level?175MPa?,the distance from the crack source to the surface is approximately20?m,the fatigue crack propagation area accounts for approximately 30%of the entire fracture,and the fatigue zone spacing in the extended zone gradually increases from 527.4nm to 878.7nm.The quasi-cleavage and dimple hybrid morphology are also presented,but the dimples are larger.5)The fatigue crack propagation rate life reversed by the Paris formula is:?1?R=0.1,N_p=3.003×10⁶?2?R=0.3,N_p=2.393×10⁶?3?R=0.5,N_p=6.381×10⁵6)The fracture morphology of fatigue crack growth of aging 6082 aluminum alloy plate varies with the stress ratio.When the stress ratio R=0.1,the fatigue crack propagation area accounts for about 1/2 of the whole area,and the fatigue stripe width is 703.1nm.When the stress ratio R=0.3,the fatigue crack propagation area accounts for about 2/5 of the whole area.The fatigue strip width is 849.6nm;When the stress ratio R=0.5,the fatigue crack propagation area accounts for about 1/3 of the entire area,and the fatigue strip width is 937.5nm.