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Al-Si 합금에 Ni, Ce 첨가 효과와 압출온도의 영향
이태행,홍순직 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.1
The effect of extrusion temperature on the microstructure and mechanical properties were studied in He-gas atomized $Al_{81-(x+y)}Si_{19}Ni_xCe_y$ alloy powders and their extruded bars using SEM, tensile testing and thermal expansion testing. The extruded bar of $Al_{73}Si_{19}Ni_7Ce_1$ alloy consists of a mixed structure in which fine Si particles with a particle size below 20∼500nm and very fine $Al_3Ni,\;Al_3Ce$ compounds with a particle size below 200nm are homogeneously dispersed in Al martix with a grain size below 500nm. With increasing extrusion temperature, the microstructural scale was decreased. The ultimate tensile strength of the alloy bars has incresed with decreasing extrusion temperature from 500 to 35$0^{\circ}C$ and $Al_{73}Si_{19}Ni_7Ce_1$ alloy extreded at 35$0^{\circ}C$ shows a highest tensile strength of 810 MPa due to the fine namostructure. The addition of Ni and Ce decreased the coefficients of thermal expansion and the effects of extression temperature on the thermal expansion were not significant.
원심분무법에 의한 고강도 7XXX 알루미늄 합금 분말의 제조
이태행,임승무,조성석 ( Tae Hang Lee,Seong Moo Im,Sung Suk Cho ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.6
N/A 7XXX aluminum alloy powders produced by the self-manufactured rotating disc atomizer were investigated to determine the influence of the atomization parameters on the particle size distributions in air atmosphere. The particle size distributions are almost always bimodal with the dominant mode on the large particle size. Average powder size of 7XXX aluminum alloy is 74/㎛∼125/㎛ when melt is poured with the rate of 9g /sec at 730℃ on a rotating disc of 30㎜ diameter at 6300rad /sec. The mass of finer particle increased when disc diameter, angular velocity, pouring temperature increased and pouring rate decreased. The powder shapes of bimodal change from acicular to tear-drop and from tear-drop to ligament with increasing powder size. Powder shape was determined by the atomization mechanism and oxidation in liquid state. Microstructure of powders appeared to be cell and cellular dendrite. The SDAS of Al-7.9wt%Zn-2.4wt%Mg-1.5wt%Cu-0.9wt%Ni Powders is 0.8㎛∼1.0㎛ for the powders of size+44㎛∼53㎛ and 1.6㎛∼1.8㎛ for the powders of size+105㎛∼125㎛, repectively.
초 미세조직 Al<sub>81</sub>Si<sub>19</sub> 합금분말 압출재의 미세조직과 기계적 성질에 미치는 압출온도의 영향
이태행,홍순직 한국분말야금학회 2003 한국분말재료학회지 (KPMI) Vol.10 No.5
The effect of extrusion temperature on the microstructure and mechanical properties was studied in gas atomized $Al_{81}Si_{19}$ alloy powders and their extruded bars using SEM, tensile testing and wear testing. The Si particle size of He-gas atomized powder was about 200-800 nm. Each microstructure of the extruded bars with extrusion temperature (400, 450 and 50$0^{\circ}C$) showed a homogeneous distribution of primary Si and eutectic Si particles embedded in the Al matrix and the particle size varied from 0.1 to 5.5 ${\mu}m$. With increasing extrusion temperature from 40$0^{\circ}C$ to 50$0^{\circ}C$, the ultimate tensile strength (UTS) decreased from 282 to 236 ㎫ at 300 K and the specific wear increased at all sliding speeds due to the coarse microstructure. The fracture behavior of failure in tension testing and wear testing was also studied. The UTS of extrudate at 40$0^{\circ}C$ higher than that of 50$0^{\circ}C$ because more fine Si particles in Al matrix of extrudate at 40$0^{\circ}C$ prevented crack to propagate.
급속응고된 Al<sub>81-(x+y)</sub>Si<sub>19</sub>Ni<sub>x</sub>Ce<sub>y</sub> 합금의 나노조직과 기계적 특성
이태행,홍순직 한국분말야금학회 2003 한국분말재료학회지 (KPMI) Vol.10 No.6
In order to produce good wear resistance powder metallurgy Al-Si alloys with high strength, addition of glass forming elements of Ni and Ce in $Al_{81}$Si$_{19}$ alloy was examined using SEM, TEM, tensile strength and wear testing. The solubility of Si in aluminum increased with increasing Ni and Ce contents for rapidly solidified powders. These bulk alloys consist of a mixed structure in which fine Si particles with a particle size below 500 nm and very fine A1$_3$Ni, A1$_3$Ce compounds with a particle size below 200 nm are homogeneously dispersed in aluminum matrix with a grain size below 600 nm. The tensile strength at room temperature for $Al_{81}$Si$_{19}$, $Al_{78}$Si$_{19}$Ni$_2$Ce$_{0.5}$, and $Al_{76}$Si$_{19}$Ni$_4$Ce$_1$ bulk alloys extruded at 674 K and ratio of 10 : 1 is 281,521, and 668 ㎫ respectively. Especially, $Al_{73}$Si$_{19}$Ni$_{7}$Ce$_1$ bulk alloy had a high tensile strength of 730 ㎫. These bulk alloys are good wear-resistance bel ter than commercial I/M 390-T6. Specially, attactability for counterpart is very little, about 15 times less than that of the I/M 390-T6. The structural refinement by adding glass forming elements such as Ni and Ce to hyper eutectic $Al_{81}$Si$_{19}$ alloy is concluded to be effective as a structural modification method.d.tion method.
Co, Ni 로 개량되어 급속응고된 P/M 7075 알루미늄 합금의 조직 및 기계적 성질
조성석,이태행,조성길 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.3
The main objective aim of this study is to improve mechanical properties of a 7075 aluminum alloy. The alloy composition of a 7075 alloy was slightly modified. To enhance the precipitate hardening effect the content of zinc was increased by 2wt% also, 1wt% cobalt and 1wt% nickel were added to provide the dispersion hardening effect. These alloys were prepared by rapid soidification and hot extrusion. The experimental results suggest that newly developed P/M aluminum alloys exhibit much higher tensile strength than an I/M 7075 alloy. Especially, the alloys produced from fine powders show higher tensile strength and elongation compared to those from coarse powders. Improvements in tensile strength are attributed to suppression or elimination of coarse secondary phases, refinement of grain size and homogeneous distribution of fine precipitate particles, Co₂Al_9, Al₃Ni and oxide particles.
급속응고된 알루미늄합금 분말의 압출가공시 Cold compact 의 Preheating 에 관한 연구
조성석,이태행 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.3
Preheating processes before the extrusion of rapidly solidified Al-7.9wt%Zn-2.4wt% Mg-1.5wt%Co-0.92wt%Ni alloy powders were studied. Cellular dendrite structures of aluminum alloy powders are found to be decomposed when cold compacted powders are preheated at the temperatures above 490℃. In an aluminum alloy preheated at 490℃ and hot extruded, the density of pores is lower than 0.1% and the maximum diameter of pores is less than 1㎛. The grain size of the aluminum alloy is less than 1㎛ and fine oxide particles are dispersed uniformly within grains and at grain boundaries. After solution (490㎛/1hr) and aging (120㎛/1hr) treatments, the room temperature yield, strength tensile strength and elongation of the aluminum alloy are 71.9㎏/㎟, 76㎏/㎟ and 5.0%, respectively.