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文中对高韧性铝合金7150及7475之间的拉伸性能、断裂韧性、疲劳裂纹扩展速度、淬火敏感性及抗应力腐蚀裂纹性进行了比较。还研究了杂质(铁及硅)含量对这些性能的影响,讨论了添加微量元素(7175合金中的锆及7475合金中的铬)的一些作用。研究的结果表明,7150厚的板抗拉强度及屈服强度比7475厚的板高,前者的伸长率及断裂韧性比后者的低。即使减少铁和硅的含量,7150合金T651状态厚板的晶粒及断裂韧性仍然没有得到改善。在7475厚板的断口面上出现许多细韧窝(0.1～0.5微米间隔)。一方面,在7150厚板断口上有少量的韧窝。从而认为,断口表面的差别是由于添加的微量元素的作用。锆在7150合金中以亚稳定相Al_3Zr形式析出,它是L1_2有序结构,与基体共格。另一方面,7475合金中的铬以亚稳定相形式析出,与基体非共格。因此在含铬的化合物周围要比含锆的比合物周围容易产生塑性变形,因为平衡相粒子(MgZ_2)在含铬化合物的晶界上析出,并且与含锆化合物相比,在含铬化合物附近更容易形成无析出区。于是7175合金的这种塑性比7150合金的更好。
The tensile properties, fracture toughness, fatigue crack growth rate, quench sensitivity and stress corrosion cracking resistance of high ductility aluminum alloy 7150 and 7475 were compared in this paper. The effect of impurity (iron and silicon) content on these properties was also studied and some of the effects of adding trace elements (zirconium in 7175 alloy and chromium in 7475 alloy) were discussed. The results show that the 7150 thick plate tensile strength and yield strength than the 7475 thick plate height, the former elongation and fracture toughness than the latter. Even if the content of iron and silicon is reduced, the grain and fracture toughness of the 7150 alloy T651 plate are still not improved. A number of fine dimples (0.1 to 0.5 micron spacing) appear on the fracture surface of the 7475 slab. On the one hand, there are a small number of dimples on the fracture of the 7150 slab. Thus, the difference in the fracture surface is due to the effect of added trace elements. Zirconium precipitates in the form of metastable phase Al_3Zr in 7150 alloy, which is an L1_2 ordered structure which is in agreement with the matrix. On the other hand, the chromium in the 7475 alloy is precipitated as a metastable phase and is non-coherent with the matrix. Therefore, plastic deformation around the chromium-containing compound is more likely to occur than that of the zirconium-containing compound because the equilibrium phase particles (MgZ 2) are precipitated at the grain boundary of the chromium-containing compound, and in comparison with the zirconium-containing compound Near the formation of more precipitation-free zone. Thus the 7175 alloy is more plastic than the 7150 alloy.