【作者】 冯菁菁；

【导师】 李润霞； 袁晓光；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2009， 硕士

【摘要】 Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg合金与Al-5.5Fe合金相比具有更加优良的性能。但是合金中仍然存在大量尺寸粗大的针状Al₃Fe相,严重割裂基体。本课题使用半固态成形的方法制备合金,从而细化合金组织,使得合金具有更好的性能。本文以提高半固态Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg合金的力学性能为目的,研究不同的热处理工艺对半固态合金力学性能的影响,从而设计出合理的热处理工艺制度。采用了SEM、TEM、X-射线衍射等手段观察了合金的形貌,分析了合金热处理强化的强化机理及其强化相的析出特征。研究结果表明:Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg合金经过半固态成形后,力学性能从161MPa上升到270MPa。半固态挤压成形Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg合金经过T6热处理后,合金的力学性能下降。分别采用不同的热处理工艺制度对合金进行T6热处理后,合金的力学性能均不如半固态成形合金的力学性能,且随着固溶时间的延长,合金的力学性能越来越低。实验发现,半固态挤压相当于热处理加热升温的作用,导致第二相回溶,以及合金经固溶处理后第二相长大,合金力学性能下降。将半固态成形的Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg合金进行T1热处理,发现合金的力学性能有较大幅度的提高,在160℃时效10h时,合金的抗拉强度达到最高315Mpa,提高了16.7%。合金在160℃时效时经历了典型的三个阶段时效特征,并且随着时效时间的延长,合金的延伸率与抗拉强度有着相同的变化趋势。在合金时效后的TEM照片中发现了弥散析出的G.P区及亚稳相。合金时效初期,G.P区在{001}面上形成并具有片状结构,随着时效时间的增加,亚稳相θ″相和θ′也由G.P区转变而来,并在{100}_α面上生长成为盘片状,θ′相直径约为200nm。它们的析出是导致合金力学性能上升的直接原因。在时效达24h时,θ相析出,它具有正方结构,与基体无共格关系。更多还原

【Abstract】 Although the Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy has better performance compared with Al-5Fe alloy,a large number of needle-like thick Al₃Fe phases which separate matrix still in the alloy.The semi-solid forming technology has been used to prepare alloy in this issue with the purpose is to thin structure and improve performance of the alloy.The effect of different heat treatment technology on properties of semi-solid formation alloy has been studied to improve mechanical properties of the alloy,then, designs reasonable heat treatment technology system.SEM,TEM,X-Ray have been used to observer microstructure of alloy.Heat treatment strengthening mechanism and precipitation feature of strengthening phase have been analyzed.The experimental results indicate that UTS of Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy increase from 161MPa to 270MPa after semi-solid formation.The UTS of semi-solid formation Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy decrease after T6 heat treatment.The mechanical properties of the alloy are lower than that after semi-solid formation when different T6 heat treatment process.Mechanical properties of alloy are lower and lower with the extension of the solution time.Study have shown that semi-solid formation similar to the strong plastic deformation that lead to re-dissolution of second phase and the role of it is equivalent to warming of heat treatment which lead to grow up of the second phase and lead to decrease of mechanical properties of alloy.The UTS of semi-solid formation Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy have a substantial increase after T1 heat treatment. The tensile strength of alloy reach to the highest value 315Mpa after aged at 160℃for 10h. There are three stages of aging process,the change of elongation and tensile strength of alloy have the same trend.Diffusion-precipitation G.P zone which have sheet structure form in {001} and meta-stable phase are found.G.P zone transformed into meta-stable phaseθ″andθ′which growth in {100}αwith the increase of aging time.The diameter ofθ′is about 200nm.The direct reason that leads to the increase of mechanical properties is precipitation ofθ″phase.θphase which formed when aging at 160℃for 24h have square structure and have not coherence with matrix.更多还原