稀土Y对7085铝合金铸态组织性能影响及热模拟研究

发布时间：2018-06-04 09:50

  本文选题：7085铝合金 + 热模拟　； 参考：《广西大学》2017年硕士论文

【摘要】：本文以7085铝合金为研究对象,通过添加不同量的稀土元素Y,制备RE-7085铝合金。利用OM、SEM、TEM和XRD等手段研究了RE-7085铝合金微观组织变化规律及铸态条件下的力学性能,并对实验结果进行了理论上的分析和讨论。采用等温热压缩模拟实验的方法,研究了该合金在不同温度、不同应变速率下流变行为,建立了高温流变模型,并确定了动态再结晶临界条件。主要研究成果如下:7085铝合金微合金化结果表明:稀土元素Y能够明显细化7085铝合金的铸态组织,二次枝晶间距减小,使原来网状结构的第二相变成细条状和鱼骨状。同时,Y主要是与Al、Cu等在晶界上形成Al2Cu与Al3Y共晶化合物,沿晶界上聚集,沿枝晶分布。随着稀土元素Y的加入,可以明显提高7085铸态下铝合金的显微硬度和室温拉伸性能,却对合金的导电性能有不利影响。RE-7085铝合金的热模拟实验结果表明:在压缩量为50%,变形温度为350℃-450℃,变速率为0.1s-1-5s-1条件下,合金表现出正的应变速率敏感性。其真应力-真应变曲线在应变速率较低而温度较高时(ε=0.1s-1,450°C)时,表现出明显动态再结晶特征;在应变速率较高时(ε=1s-1,ε = 5s-1),表现出动态回复特征。本文RE-7085铝合金的变形激活能为175KJ/mol,根据热变形过程中的微观组织分析,说明稀土 Y能明显抑制7085铝合金在高温变形过程中的动态再结晶过程中晶粒的长大;合金动态再结晶晶粒数目,随变形温度的升高和应变速率的降低而有所增加,但晶粒尺寸变化不大。
[Abstract]:In this paper, 7085 aluminum alloy was studied and RE-7085 aluminum alloy was prepared by adding different amount of rare earth element Y. The changes of microstructure and mechanical properties of RE-7085 aluminum alloy under as-cast condition were studied by means of TEM and XRD. The experimental results were analyzed and discussed theoretically. The rheological behavior of the alloy at different temperature and strain rate was studied by means of isothermal compression simulation. The rheological model at high temperature was established and the critical condition of dynamic recrystallization was determined. The main results are as follows: the results of microalloying show that the rare earth element Y can refine the as-cast structure of 7085 aluminum alloy and decrease the secondary dendrite spacing, which makes the second phase of the original mesh structure become fine and fishbone. At the same time, Al2Cu and Al3Y eutectic compounds were formed at grain boundaries with Albumin and Cu, which aggregate along grain boundaries and distribute along dendrites. With the addition of rare earth element Y, the microhardness and room temperature tensile properties of 7085 as-cast aluminum alloy can be improved obviously. However, the thermal simulation results of RE-7085 aluminum alloy show that the alloy shows positive strain rate sensitivity under the conditions of 50 compression, 350 鈩，

本文编号：1976924