Optical microstructures and mechanical properties of Na gas atomized Al-20Si-5Fe alloying powder and its hot extrudates were studied on 3 different types of powder size distribution. This powder showed the size distribution of 10~210㎛. Also the microstructures of α-Al, primary and eutectic Si and needle shaped intermetallic compounds were observed by optical microscope. These needle shaped intermetallic compounds were identified as δ-AI₄FeSi₂ by XRD and EDX analysis. The ultimate tensile strength(UTS) of these alloy extrudates was increased from 324 to 390 MPa with decreasing powder size range from 120~210㎛ to 10~64㎛. A value of Micro-vic-kers hardness was simillar to the result of UTS. These extrudates showed better wear resistance than those of Al-20Si-2X(X : Ni, Cr, Zr), although they are insensitive to the size distribution. These results indicate that the presentation of δ-AI₄FeSi₂ intermetallic compounds contributed to the wear resistance improvement.

In this study, cathodic protection experiment was carried out by Al-alloy sacrificial anode in marine environments which have specific resistance(σ) if 25~7000Ω.cm and investigated protection potential, current density and loss rate of Al-alloy sacrificial anode. The main results resistance(σ) of 400Ω.cm, the cathodic protection potential appears high about-720 mV(SCE). But below specific resistance(σ) of 300Ω.cm, the cathodic protection potential appears low about-770 mV(SCE) and simultaneously, cathode is protected sufficiently. 2) The loss rate of Al-Alloy sacrificial anode became large with decreasing specific resistance and increasing the ratio(A sub(c)/A sub(a) of bared surface area of anode and cathode. 3) The loss rate of Al-alloy sacrificial anode(w) to the mean current density of anode(i) is as follows. w=ai+b (a, b : experimental constants)

Recently with the rapid development in marine and shipbuilding industries such as marine structures, ships and chemical plants, it takes much interest in the study of corrosion fatigue characteristics that was close up an important role in mechanical design. In this study, characteristics of corner crack propagation on the base metal and heat affected zone of 5086 Al-Alloy was tested by using of a rotary bending fatigue tester and was investigated under the environments of specific resistance, σ=25Ω cm and air. The corrosion fatigue crack initiation and corrosion fatigue life sensitivity were quantitatively inspected for 5086 Al-Alloy in the specific resistance, σ=25Ω cm. Main results obtained are as follows: (1) The corrosion sensitivity of heat affected zone under specific resistance, σ=25Ωcm shows approximately 1.69~2.22 and corrosion sensitivity of base metal is more susceptible than that of heat affected zone. (2) The corrosion fatigue life sensitivity on heat affected zone decreases eminently than that of initial corrosion fatigue crack. (3) The characteristics of quarter elliptical corner crack propagation shows that depth crack is more grown than surface crack at crack initiation, but the surface crack is more propagated than depth crack as the crack propagation is increased. (4) The surface crack and depth crack growth on heat affected zone by softness show delayed phenomenon than that of base metal.

평면 굽힘부식피로 시험기를 사용하여 선박용 알루미늄합금재의 부식피로파양에 관한 연구를 한 결과 다음과 같은 결론을 얻었다. 1. 비저항이 증가함에 따라서 초기 부식피로균열발생까지의 반복회수는 지연되고, 그 부식감수성은 감소하는 양상을 나타낸다. 2. 비저항이 감소할수록 Paris rule의 실험상수 m 값은 작아지면서 응력강도 계수값에 비해 부식에 의한 영향이 더욱 민감해 진다. 3. 알루미늄 5086 합금의 부식피로균열은 입계균열파양의 양상을 보이고 있다. 4. 응력강도계수값이 증가함에 따라 부식감수성은 감소되어지고 응력강도계수값이 40kg.mm super(-3/2) 이상일 때 부식감수성은 거의 균일하게 된다.

고역알루미늄합금의 파괴특성에 미치는 시효열처리의 영향에 대하여 검토한 결과는 다음과 같다. 1. 현미경 조직의 관찰결과 190℃, 12hr로 시효열처리한 것이 시효강화된 양호한 조직과 미세한 석출분포를 나타내고 있음을 알 수 있었다. 2. 계단식시효열처리에 의하여 정상시효열처리보다 시효시간을 반정도로 단축시킬 수 있었고, 이들 조직도 유사하였다. 3. 인장파단면의 SEM 전자현미경 사진관찰결과는 190℃, 12hr으로 시효열처리한 것은 딤플형 입계 및 입내연성파괴를 나타내나, 이를 제외한 대부분은 시효열처리 시간과 온도에는 관계없이 입계연성파괴인 것이 관찰되었다.

분극전위변화에 따른 고역 내식성 알미늄합금(5083)의 SCC 거동을 연구 검토한 결과를 요약하면 다음과 같다. 1. 5083 알미늄합금의 K 하(IC)은 134.81~148.38kg/mm 상(3/2)이며, 전위변화에 따라 K 하(Ii)은 75.92~145.78kg/mm 하(3/2)이다. 2. K 하(I)-V의 거동은 양분극시 Region I 과 II가 나타나고, K 하(Ii)/K 하(IC)의 비가 작을수록 crack성장속도도 빠르게 나타난다. 3. 분극전위 -987mV SCE에서 crack성장속도가 가장 지연되므로 122mV SCE을 음분극하면 SCC 방지효과를 얻을 수 있을 것으로 생각된다. 4. 입계의 β상의 석출은 분극전위가 클수록 크게 나타난다.

In this study, corrosion potentials were evaluated according to the composition ratio of Zn-Al alloy. Alloys were fabricated according to the composition ratio of Zn-Al. The corrosion potential was measured according to ASTM B 627-84. As a result of the study, the measured value of corrosion potential tended to increase with increasing composition ratio of Al.

In this study, corrosion potentials were evaluated according to the composition ratio of Zn-Al alloy. Alloys were fabricated according to the composition ratio of Zn-Al. The corrosion potential was measured according to ASTM B 627-84. As a result of the study, the measured value of corrosion potential tended to increase with increasing composition ratio of Al.