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晶粒尺寸及Taylor因子对过时效态7050铝挤压型材横向力学性能的影响
发布人：上海艾荔艾金属材料有限公司www.shailiai.com
更新时间：2015-11-19
采用常温冲击实验和拉伸实验研究了大断面7050 铝合金型材横向3 个典型位置的力学性能的差异，并通过OM、EBSD 和TEM分析了其显微组织。
晶粒尺寸及Taylor因子对过时效态7050铝挤压型材横向力学性能的影响EFFECT OF GRAIN SIZE AND TAYLOR FACTOR ON THE TRANSVERSE MECHANICAL PROPERTIES OF 7050 ALUMINIUM ALLOY EXTRUSION PROFILE AFTER OVER-AGING
采用常温冲击实验和拉伸实验研究了大断面7050 铝合金型材横向3 个典型位置的力学性能的差异，并通过OM、EBSD 和TEM分析了其显微组织。结果表明：晶粒尺寸约 12μm的型材芯部比晶粒尺寸约 6μm的边部的屈服强度高，其原因是芯部较硬 copper 取向的形变织构组分更强。根据固溶合金元素含量所得的固溶强化项、亚晶粒尺寸所得的晶界强化项和合金的屈服强度可计算 Taylor 因子，芯部为3.925，边部为2.257。晶界强化模型中Hall-Petch 模型比 Nes模型更适用于计算固溶后的晶界强化对合金屈服强度的贡献。此外，还建立了3 种试样过时效态冲击功与亚晶粒尺寸之间的线性关系。
Generally, it is believed that inside the material the smaller grain size is, the higher yield strength is. In addition to this effect, grain refinement method also ensures that the toughness of the material is not reduced. However, it is found that the relationship between the grain size distribution and mechanical properties is contradiction with this law after the properties have been studied in the transverse direction of a large cross-section 7050 aluminum alloy profile. That is the impact energy and yield strength in the center with a large grain size is higher than those at the edge with the smaller grain size in the thickest section of the profile. Besides that, during the establishment of the yield strength model in over-aging 7050 aluminum alloy, there are two models for the grain boundary strengthening which are Nes model and Hall-Petch model, so the choice from these model is bound to affect the final results of the yield strength model. In order to study and understand the reasons for this phenomenon, the difference of mechanic properties distribution in the cross-section of 7050 aluminum extrusion profile has been investigated by impact test and tensile test at normal temperature, meanwhile, the microstructures have been analyzed by optical microscopy, electron back-scatter diffraction and transmission electron microscope. The results show that lots of the harder deformation texture i.e. Copper texture in the core of the profile leads to higher yield strength in the core with grain size of 12 μm than that in the edge with grain size of 6 μm. And the Taylor factor could be calculated after the solution strengthening by alloying elements, grain boundary strengthening by the sub-grain and the yield stress of the alloy. At last, it reaches to 3.925 in the core, while that is just 2.257 in the edge. Compared with Nes model, the Hall-Petch model is much preferable to the calculation of grain boundary strengthening in yield stress of 7050 aluminum alloys after solid solution treatment. It is established that there is a linear relationship between impact toughness and grain size of three over-aging specimens.
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