FTMT (Final Thermomechanical Treatment)에 의한 Al-6.94%Zn-2.69%Mg 합금의 材質强化 現象을 一段 및 二段時效 경우와 서로 비교하여 조사 분석한 결과, FTMT에 의하여 Al-6.94%Zn-2.69%Mg 합금의 强度는 일반적인 時效處理에 의한 경우보다 높았다. 이와같이 FTMT에 의한 超强化效果는 轉位와 析出物과의 상호작용에 의한 것으로 설명될 수 있었다. 30%보다 낮은 deformation을 가하고, GPzone의 溶解溫度보다 낮은 온도에서 最終時效處理를 하는 것이 FTMT에 의해 기계적 성질을 향상시키는데 보다 효과적이었다. Al-6.94%Zn-2.69Mg 합금의 FTMT에 의한 强化效果가 最終時效溫度가 T_GP (GPzone의 溶解溫度)보다 높을 때에는 一段 및 二段時效보다도 적었었다. 一段時效에 의한 0.2% 耐力은 41㎏/㎟ 인데 비하여 FTMT에 의한 0.2% 耐力은 그보다 30∼40% 증가된 57㎏/㎟ 이었다.

An investigation has been carried out to clarify the effects of final thermomechanical treatments(FTMT) on strengthening phenomena in comparison with isothermal and two-step ageing in Al-6.94%Zn-2.69%Mg alloy. Al-6.94%Zn-2.69%Mg alloy processed by FTMT exhibits higher strength than that of conventionally processed. From these results, the super-hardening effects obtained by final thermomechanical treatment may be explained by the interactions between dislocations induced by deformation and precipitates formed by ageing. Deformation less than 30% and final ageing at lower temperature than the solvus temperature of G.P.zones are desirable in obtaining remarkable improvement in mechanical properties by FTMT. The mechanical properties of Al-6.94%Zn-2.69%Mg alloy processed by FTMT exhibit lower strength than those of isothermal and two-step ageing when the temperature of final ageing is higher than the solvus temperature of G.P.zones. Maximum value of 0.2% proof stress resulted by FTMT is 57㎏/㎟, while that resulted by isothermal ageing is 41㎏/㎟.