The alumina dispersed nickel alloy was chosen to study the effect of dispersoid content and thickness reduction ratio by coldrolling on the strength of oxide dispersion strengthening material.
The alloy was produced from nickel and aluminium chlorides with selective reduction method followed by sintering and hotrolling. Then it was coldrolled to total 40% thickness reduction by repeating 8% thickness reduction and annealing at 1200℃, 30min. The ultimate tensile strength of Ni-$Al_2O_3$ alloy at 700℃ was increased continuously with the increased coldrolling. On the other hand, the room temperature strength was increased rapidly at first, but slowly after 20% thickness reduction. It was believed that the increase in U.T.S. at high temperature was due to the well-developed fiberous microstructure and at R.T. the dislocation subcell size which become smaller to a limited size with increased cold-rolling reduction.
The result also indicated that the Ni-8% $Al_2O_3$ alloy had higher strength especially at high temperature than the Ni-4% $Al_2O_3$ alloy. The cause of this phenomena seemed to be the non-ideal distribution of $Al_2O_3$, so more than 4v/0 of $Al_2O_3$ was needed to improve the strengthening effect. The production process variables for obtaining suitable Ni-$Al_2O_3$ powder and consolidated body were also discussed.
산화물 분산강화 금속에서의 분산재의 합량과 압하율이 기계적 성질에 미치는 영향을 조사하기 위하여 Ni-Al2O3 합금을 선택 하였다. Ni-Al2O3 합금을 Ni 과 Al의 염화물을 공침과 하소 및 선별적인 환원을 한 후 소결과 열간압연을 함으로써 제조하였다. 그리고 이 합금을 8%의 압하율로 냉간압연을 하고 1200℃에서 소둔시키는 과정을 하여 최종 40%의 입하율을 얻도록 하였다. 고온강도는 압하율이 증가함에 따라 계속적으로 증가 되었다. 상온강도는 초기에는 많은 증가가 있었으나, 20%압하율 이상에서 완만하였다. 이러한 결과는 냉간가공이 증가함에 따라 섬유상 조직이 계속 발달하며, 전위의 sub coll 크기가 일정한 값으로 작아지기 때문인 것으로 생각된다. 또한 Ni-8v/o Al2O3는 순수 Ni보다 700℃에서의 60%의 UST값의 향상이 있었고 Ni-4v/o Al2O3보다 큰 강도를 보였다.
