本研究以光學顯微鏡、導電度、穿透式電子顯微鏡、電子背向散射繞射、機械性質等量測，來評估微量Zr(≤ 0.2)與冷加工(≤ 20%)對Al-8.3Zn-2.3Mg-2.4Cu鍛造鋁合金微結構與淬火敏感性之影響。透過EBSD觀察，不含Zr之合金在低冷加工量下擁有最大之晶粒(~ 4400 μm2)，在高冷加工量下晶粒明顯細化(~ 1200 μm2)，都呈現完全再結晶之等軸晶粒。含Zr合金則不論是低或高冷加工量下，都呈現細長的織狀晶，平均晶粒都不超過830 μm2，且含Zr合金再結晶比率都低於50%，顯現加入Zr能有效抑制再結晶的發生、與抑制晶粒的成長，使得合金具有細小且具明顯方向性之晶粒。由拉伸性質分析可以觀察到，細小的晶粒提升了合金之強度，且當晶粒愈細長，材料延性愈佳。經端面淬火試驗顯示不論冷加工量多寡，不含Zr合金之淬火敏感性都不高，在固溶空冷下，僅在晶界處異質成核，析出較粗大之非強化η (MgZn2)相。而含Zr合金因均質化所析出之Al3Zr細小安定顆粒，在高冷加工下，Al3Zr與鋁基地之介面為具較高能量之非整合界面，此非整合界面極易成為固溶淬火過程中的強化溶質原子之異質成核點，當固溶空冷過程中（慢速冷卻），Al3Zr顆粒周圍將析出η相，因而降低後續時效時的η’強化相之析出，因而提升了合金之淬火敏感性，導致合金強度減損;而當低冷加工下，Al3Zr與鋁基地介面為低能量之整合介面，合金並無明顯淬火敏感性。;This study is aimed at exploring the effects of trace Zr and cold rolling on the microstructures and quench sensitivity of Al-8.3Zn-2.3Mg-2.4Cu alloys. The result showed that adding Zr could effectively inhibit recrystallization and grain growth. Making the microstructures have fine and directional grains. From the analysis of microstructure and tensile properties, it could be observed that the fine grains increase the strength of the alloy. Meanwhile, the materials have a better ductility when the grains are more elongate. The quenching test showed that no matter how much cold rolling ratio was, the quench sensitivity without Zr alloy was not high. The alloys containing Zr with low cold rolling ratio also didn’t have quench sensitivity. However, the alloys containing Zr with high cold rolling ratio had a high quench sensitivity. When Zr containing alloy applied a high cold rolling ratio, the interface between the Al3Zr particles and the matrix was a semi-coherent interface with higher energy. This semi-coherent interface can easily become the heterogeneous nucleation point of solute atoms during quenching process. By the observation of TEM, with a slow cooling rate after solid solution, η phase will be precipitated around Al3Zr particles. The precipitate of η phase will reduce the precipitation of η’ strengthened phase during subsequent aging, leading to the reduction of alloy strength. On the other hand, under low cold working volume, the interface between Al3Zr and the matrix was coherent with low energy, and the alloy had no obvious quench sensitivity.
