【摘要】 研究复合添加稀土元素Yb和过渡元素Zr,Cr对Al-Zn-Mg-Cu超高强合金组织、强韧性和局部腐蚀(晶间腐蚀和剥落腐蚀)性能的影响。结果表明:单独添加Zr和复合添加Cr,Yb的合金均发生了再结晶现象,合金的强度、韧性和腐蚀抗力均较低。而在Al-Zn-Mg-Cu合金中复合添加Zr,Yb,Cr形成大量10~20 nm、共格的固溶部分Zn,Mg,Cu的(Al,Cr)3(Zr,Yb)弥散相,这些均匀分布于基体的细小共格弥散相能强烈钉扎位错和亚晶界,抑制基体再结晶,使合金亚晶界上的析出相与晶内近似,晶界无沉淀析出带(PFZs,precipitate-free zones)不明显。复合添加Zr,Yb,Cr的Al-Zn-Mg-Cu合金在保持高强度和塑性的同时,沿晶断裂抗力和局部腐蚀抗力显著提高。T6态Al-Zn-Mg-Cu-Zr-Yb-Cr合金的断裂机制主要为韧窝型断裂,剥落腐蚀等级降至EA。再结晶晶界成为超高强Al-Zn-Mg-Cu合金腐蚀和断裂的优先扩展路径。更多还原

【Abstract】 The effect of Zr,Yb and Cr additions on microstructures,mechanical properties and localized corrosion( intergranular corrosion and exfoliation corrosion) behaviors of ultra-high strength Al-Zn-Mg-Cu alloy was investigated. The results showed that Al-ZnMg-Cu-Zr alloy was partially recrystallized and Al-Zn-Mg-Cu-Cr-Yb alloy was fully recrystallized,strength,fracture toughness and corrosion resistance of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Cr-Yb alloys were relatively low. Meanwhile,10 ~ 20 nm spherical coherent dispersoids identified as Zn,Mg,Cu-containing( Al,Cr)3( Zr,Yb) formed in Al matrix by adding Zr,Yb and Cr in combination to Al-Zn-Mg-Cu alloy. The uniform distribution of fine,coherent dispersoids remarkably inhibited the recrystallization of Al matrix by strongly pinning dislocations and subgrain boundaries. The precipitation states in the grain and at the grain boundary were similar and precipitate-free zones( PFZs) were not clear. Composited additions of Zr,Yb and Cr to Al-Zn-Mg-Cu alloy remarkably enhanced resistance to intergranular fracture and localized corrosion with strength,fracture toughness and ductility being improved. The fracture mechanism was mainly dimple-type transgranular cracking with minor intergranular cracking and the exfoliation corrosion decreased to EA in T6-tempered Al-Zn-Mg-Cu-Zr-Yb-Cr alloy. Corrosion and fracture cracking propagated along recrystallized grain boundaries in ultra-high strength Al-Zn-Mg-Cu alloys.更多还原