| 摘要: | 含Zr之Al-Zn-Mg-Cu合金藉由二段式均質化處理，可析出細小且緻密、與鋁基地呈整合介面之Al3Zr顆粒，此散佈相顆粒可有效提升抑制再結晶與晶粒成長的效果，且經高溫固溶後，於淬火過程下，較不易於整合之Al3Zr散佈相上析出η(MgZn2)相，保留了鋁基地中的固溶強化原子，因此於時效處理後，可維持合金良好的機械性質及較低之淬火敏感性；而塑性變形可將儲存能導入合金內部，使合金之再結晶比例隨著加工量上升而增加，另外，二段式均質化合金經塑性變形後，整合且細小的Al3Zr顆粒將會轉變為具較高能量之非整合界面，此時雖仍具良好抑制再結晶與晶粒成長的效果，但卻會提高固溶淬火時於Al3Zr散佈相上析出η(MgZn2)相之機會，導致合金具有較嚴重之淬火敏感性，且隨加工量愈大，淬火敏感性愈明顯。
傳統之一段式均質化，於基地中析出較為粗大且稀疏之非整合Al3Zr顆粒，導致其抑制再結晶與晶粒成長之效果不如二段式均質化，且冷加工並不會改變Al3Zr顆粒與介面的非整合性，故冷加工量並不會造成合金之淬火敏感性之差異。非整合介面之Al3Zr顆粒雖會提高固溶淬火時於散佈相上析出η(MgZn2)相之機會，但其數量較二段式均質化合金少，即代表著η(MgZn2)平衡相可異質成核的位置較少，因此有效地限制了合金機械性質的下降，故其淬火敏感性較經加工之二段式均質化合金為佳。
由研究結果顯示，二段式均質化雖可提高合金之機械性質，但經高加工量之合金其淬火敏感性會明顯提升，故二段式均質化合金在實務製作上適合應用於容易快速淬火之薄板材；而一段式均質化析出稀疏且非整合之Al3Zr顆粒，固溶冷卻時較容易析出平衡相，但卻可維持合金之機械性質與淬火敏感性，故相較於二段式均質化合金，更適合應用於厚材之製作；於合金製作時，藉均質化處理改變晶粒大小、提高機械性質外，亦需注意散佈相與鋁基地之介面關係，以達到降低淬火敏感性之目的。
;After two-stage homogenization, the Al-Zn-Mg-Cu alloy containing Zr will precipitate fine and dense Al3Zr particles that coherence with the aluminum base. The dispersed phase can inhibition of recrystallization and grain growth effectively. After the solid solution treatment, the η(MgZn2) phase is not easily to precipitated on the coherence Al3Zr during the quenching process. And the solid solution atoms are retained in the aluminum base, so after the aging treatment, the alloy can maintain high mechanical properties and low quenching sensitivity. The deformation can introduce the stored energy into the alloy so that the recrystallization ratio of the alloy will increase with the increase of the amount of cold rolling. In addition, the coherence and fine Al3Zr particles in the two-stage homogenized alloy will be transformed into incoherence with higher energy after deformation treatment. Although it still can inhibit recrystallization and grain growth effectively, it will increase the chance of precipitation of the η(MgZn2) phase on the Al3Zr particles during the quenching process. It will result in the alloy having a serious of quenching sensitivity, and with the increase of the deformation amount, the quenching sensitivity is more obvious.
The one-stage homogenization alloy precipitates coarser and sparser incoherence Al3Zr particles, which leads to its effect of inhibiting recrystallization and grain growth is not as good as the two-stage homogenization. The cold working does not change the incoherence between Al3Zr particles and the interface, so the amount of cold working does not cause a difference in the quenching sensitivity of the alloy. Although the incoherence Al3Zr particles will increase the chance of precipitation of the η(MgZn2) phase on the dispersed phase during the quenching process. However, its number is less than that of the two-stage homogenized alloy, which means that the η(MgZn2) phase has fewer sites for heterogeneous nucleation. Therefore, the decline of the mechanical properties of the alloy is effectively limited, so its quenching sensitivity is better than that of the processed two-stage homogenized alloy.
The results show that the two-stage homogenization can improve the mechanical properties of the alloy, but the quenching sensitivity of the alloy will be significantly increased with a high amount of cold deformation. Therefore, the two-stage homogenized alloy is suitable for thin plates which can easy to quickly quench; while the one-stage homogenization precipitates sparse and incoherence Al3Zr particles, it is easier to precipitate the equilibrium phase during the quenching process, but it can maintain the mechanical properties and quenching sensitivity of the alloy, so it is more suitable for the production of thick materials than the two-stage homogenized alloy. In summary, in the production of alloys, in addition to homogenization treatment to change the grain size and improve the mechanical properties, it is still necessary to pay attention to the interfacial relationship between the dispersed phase and the aluminum base to achieve the purpose of reducing the quenching sensitivity. |
