In this study, the effect of pre-aging treatment for inhibition of natural aging of Al-4.8Zn-1.3Mg alloy by extrusion process was investigated. Firstly, the as-cast microstructure of Al-4.8Zn-1.3Mg alloy billet and its evolution during homogenization(460℃, 4h + 510℃, 5h) were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness analysis. The as-cast microstructures of Al-4.8Zn-1.3Mg alloy reveal Mg2Zn, Al5Cu, Al3Cu formed between dendrities. After homogenization, MgZn, Al4Cu, Al13Cu phases precipitated into the matrix. In addition, standard deviation of homogenized billet was improved than as-cast billet from 2.62 to 0.99. According to pre-aging(100℃, 1h) Al-4.8Zn-1.3Mg alloy by extrusion process, yield strength and tensile strength deviation improved more than condition by natural aging.

ABSTRACT
 1. 서 론
 2. 실험내용 및 방법
  2.1 균질화 열처리
  2.2 안정화 열처리
 3. 실험결과 및 고찰
  3.1 주조재 미세조직 특성
  3.2 균질재 미세조직 특성
  3.3 균질 열처리 후 경도 산포
  3.4 안정화 열처리 후 기계적 특성 평가
 4. 결 론
 References

• 이창연(Assistant Manager, DaejooKores Company) | Chang-Yeon Lee Corresponding Author