A study has been performed on the effect of Thermomechanical treatment of the mechanical properties, especially ductility and toughness, of 7075 Aluminum alloy. In the present work, intermediate thermomechanical treatment (ITMT), thermomechanical treatment-2(TMT-2) and conventional heat treatment have been applied.
The experimental results showed that the ductility and the toughness were increased by ITMT and TMT-2 compared with conventional heat treatment. The both heat treatment of ITMT and TMT-2 were increasing the ductility about 17% compared with conventional heat treatment for the specimen with 40% deformation. The unit propagation energy was increased about 110% on ITMT and about 200% on TMT-2 compared with conventional heat treatment for the specimen with 40% deformation.
It was believed that the increase of ductility by ITMT and TMT-2 was due to grain size refinement, and that the toughness increased by ITMT was due to grain size refinement, retardation of the recrystallization and homogeneous distribution of small Cr-rich particles. It was also believed that the toughness increased by TMT-2 was due to homogeneous distribution of dislocation, reduction of the grain boundary precipitates, retardation of the recrystallization, refinement of grain size and homogeneous distribution of small Cr-rich particles.
본 연구에서는 7075 알미늄 합금을 사용하여 Thermomechanical Treatment가 기계적성질, 특히 연신률과 인성에 미치는 영향을 조사하였다. 본 실험에서는 Intermediate Thermomechanical Treatment(ITMT), Thermomechanical Treatment(TMT-2) 와 Conventional Heat Treatment 로 열처리 하였다.
본 연구결과에 의하면 ITMT와 TMT-2는 재래식 열처리 방법에 비해 연신률과 인성을 증가시키고 있다. 40% 가공처리한 경우, ITMT와 TMT-2 방법은 모두 재래식 열처리에 비하여 연신률은 약 17% 증가하였다. 40% 가공처리한 경우 unit propagation energy는 재래식 열처리에 비해 ITMT에 의해서는 약 110% 증가 하였으며 TMT-2에 의해서는 약 200% 증가하였다.
ITMT와 TMT-2에 의한 연신률의 증가는 미세한 grain size 때문이라고 생각하며 ITMT에 의한 인성의 증가는 grain size 미세화, 재결정억제, 미세한 Cr-rich particle의 균일한 분포 때문 이라고 생각한다. TMT-2에 의한 인성의 증가는 grain size 미세화, 재결정 억제, 미세한 Cr-rich particle의 균일한 분포 이외에도 dislocation의 균일한 분포와 grain boundary precipitate의 억제 때문이라고 생각한다.
