Sc元素对Al-Cu-Li合金微观组织、力学性能及疲劳裂纹扩展行为的影响

Effect of Sc Element on Microstructure,Mechanical Properties and Fatigue Crack Propagation Behavior of Al-Cu-Li Alloys

【目的】对含Sc元素的Al-Cu-Li合金的微观组织、力学性能及疲劳裂纹扩展进行分析,总结Sc元素添加对晶粒组织、析出行为、力学行为及疲劳裂纹扩展的影响因素,为设计高综合性能的Al-Cu-Li合金提供参考。【方法】采用硬度、室温拉伸和疲劳裂纹扩展试验,结合SEM/EDS、EBSD和TEM表征,分析Sc元素对Al-Cu-Li合金的影响。【结果】无Sc合金的晶粒尺寸比含Sc合金的大。无Sc合金的硬度为182±2 HV3,明显高于含Sc合金的171±2 HV3。室温拉伸性能也表明,无Sc合金的强度明显高于含Sc合金,但含Sc合金的断后伸长率更高。循环加载次数相同时,含Sc合金的裂纹长度明显低于不含Sc的合金,无Sc合金的FCP速率高于含Sc合金。【结论】含Sc合金中形成Al3(Sc,Zr)相,提高高温下的稳定性,增加对晶界的钉扎作用,抑制晶粒的长大。AlCuFeMn和AlCuSc(W)相均消耗Cu元素,减少时效过程中T1相的析出,降低合金强度。与不含Sc合金相比,裂纹迂回绕过含Sc合金形成的W相,导致裂纹在传播路径上发生偏转,含Sc合金的位错密度更高,在高应力强度因子下,能够更好地阻挡裂纹扩展。

[Purposes]The microstructure,mechanical properties and fatigue crack propagation of Al-Cu-Li alloy containing Sc element were analyzed.The influence factors of Sc element addition on grain structure,precipitation behavior,mechanical behavior and fatigue crack propagation were summarized,which provided reference for the design of Al-Cu-Li alloy with high comprehensive performance.[Meth-ods]Hardness,room temperature tensile and fatigue crack propagation tests,combined with SEM/EDS,EBSD and TEM characterization,were used to analyze the effect of Sc elements on the microstructure,mechanical properties and fatigue crack propagation behavior of Al-Cu-Li alloys.[Findings]The grain size of Sc-free alloys was larger than that of Sc-containing alloys.The hardness of the Sc-free alloy was 182±2 HV3,which was significantly higher than that of the Sc-containing alloy of 171±2 HV3.The room temperature tensile properties also showed that the strength of the Sc-free alloy was significantly higher than that of the Sc-containing alloy,but the elongation at break of the Sc-containing alloy was higher.At the same number of cyclic loading,the crack length of the Sc-containing alloy was significantly lower than that of the Sc-free alloy,and the FCP rate of the Sc-free alloy was higher than that of the Sc-containing alloy.[Conclusions]The formation of Al3(Sc,Zr)phase in Sc-containing alloys improves sta-bility at high temperatures,increases pinning to grain boundaries,and inhibits grain growth.Both AlCu-FeMn and AlCuSc(W)phases consume Cu elements,which reduces the precipitation of the T1 phase dur-ing the aging process and lowers the strength of the alloys.Compared with Sc-free alloys,cracks mean-der around the W phase formed by Sc-containing alloys,leading to crack deflection in the propagation path,and Sc-containing alloys have a higher dislocation density,which provides a better blockage of crack propagation at high stress-strength factors.