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LD11铝合金热处理工艺的研究
Study on the Heat Treatment Process of the LD11 Aluminum Alloy
【作者】 李艳春；
【导师】 王丽萍；
【作者基本信息】 哈尔滨理工大学 ， 材料加工工程， 2009， 硕士
【摘要】 本文对LD11铝合金的热处理工艺做了系统的研究,借助于力学性能的测定以及光学金相显微镜、扫描电镜进行组织观察和断口扫描等分析手段,优化了该合金热处理工艺的参数,确定了LD11铝合金的最佳热处理工艺,并对合金的强化机理进行了探讨。研究结果表明:固溶处理过程中,固溶温度低时,强化相在合金中溶解的浓度低,固溶温度高时Si颗粒缓慢粗化,削弱了时效强化的效果;固溶时间较短时,强化相析出较少,合金的性能较差,固溶时间过长,Si相的过大生长对合金起到了割裂作用,使其塑性降低;单级时效热处理制度中,采用分别改变热处理制度的各个参数的方法进行试验,时效时间短时,强化相析出不充分,使其强度较低,时效时间过长,发生了过时效;时效温度较低时,强化相不能充分析出,时效温度过高时,小颗粒的溶解大颗粒的长大使其形成无析出区,使其延伸率下降。得出最佳的热处理工艺为:固溶温度520℃,固溶时间3.5h,时效温度165℃,时效时间8h。双极时效采用了正交设计试验优化合金的热处理工艺,得出最佳的热处理工艺为固溶温度520℃,固溶时间3.5h,一级时效温度140℃,一级时效时间3h,二级时效温度165℃,二级时效时间3.5h;在低温的一级时效区,强化相不溶解而是缓慢生长,而残留的过饱和固溶体则继续分解析出少量的亚稳定相,合金中的的Cu、Mg和其它原子不断的从固溶体中析出并扩散到亚稳相中;在随后的二级高温时效过程中,晶内析出相粗化速度减慢,使合金具有很好的延伸率。
【Abstract】 The heat treatment of LD11 alouminum alloy was researched in this paper. The mechanical properties of the alloy after different heat-treatments. The fractograph and microstructure of the alloy after heat treatments were observed by SEM and optical microscope. The strengthening mechanism of the alloy was analyzed and the parameters of the heat-treatments were modified.The results show that during solution treatment, the solubility of strengthen phase is proportional to solution temperature. and silicon phase particles coarsen slowly at high solution temperature, which decreases the strengthening effect. There is a small number of precipitates in the alloy solution for short time. while silicon phase will grow when the alloy soluted for a long time. Both of these will decrease the properties of the alloy. for one-step aging treatment, short treatment time will result in incomplete precipitation, which decreases the strength of the alloy. over aging will carry out when aging for a long time. The strengthening particles precipitate completely when aging at lower temperatures. The strengthening particles will re-solute into matrix and forming non-precipitates zone, which decreases the elongation of the alloy. The optimized one-step aging treatment is: solution at 520 for 3.5h, and one-step aging at 165 for 8h.The two-step aging treatment is analyzed by using orthogonal examination. The optimum heat treatment process is: solution at 520 for 3.5h, first aging at 140 for 3h, and then aging at 165 for 3.5h. During the first aging process, strengthening particles grow slowly and do not solute.Some meta-stable phases precipitate from supersaturated aluminum solution. precipitates coarsening speed is low during the second aging process. As a result, the alloy has good extensibility.