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SiCp / Mg-Al 복합재료의 조직에 미치는 용융가공의 영향
윤여창,최정철,남태운,박익민 ( Yeo Chang Yoon,Jeong Cheol Choi,Tae Woon Nam,Ik Min Park ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.4
N/A Mg-9wt.%Al and Mg-9wt.%-1.6wt%Zn/SiCp(particle size 40㎛) metal-matrix-composite specimens were manufactured by rheo-compocasting method, known for its effect of improving the wettability. The ceramic reinforcement particles(SiCp) were dispersed in the semi-solid magnesium alloy matrix slurry being vigorously stirred in a high frequency induction furnace under inert atmosphere. A microstructural study of the dispersed particles in the specimens, prepared under different conditions as regards the time(10min, 20min, 30min) and temperature of the stirring, was made with the aid of optical microscope and SEM. The effect of superheating was also observed. It is revealed that 30 minutes` stirring time of the semi-solid at 40% solid fraction temperature(Mg-9wt.%Al : 590℃, AZ91 : 576℃), as determined by the lever rule, gives a satisfactorily uniform distribution of the particles. The superheating is observed to enhance further the uniformity.
급속응고한 AZ91 합금의 미세조직 및 기계적 특성에 미치는 Y 첨가의 영향
최재영(Jae Young Chol),박훈모(Hoon Mo Park),남태운(Tae Woon Nam) 한국주조공학회 2000 한국주조공학회지 Vol.20 No.6
N/A In the present study, the effect of yttrium addition on the microstructure and mechanical property of rapidly solidified AZ91 alloy by melt spinning process is estimated. As yttrium was added, the microstructure of RS ribbons and extrudates became finer than those of AZ91, and RE related phases (Al₂RE) were formed. In the case of the addition of 3wt%Y, the microstructure of extrude showed the finest grain size. At room temperature, the AZ91 + 3wt%Y alloy showed the highest tensile strength, 352㎫ due to precipitation of β(Mg_(17)Al_(12)) phase and Al₂RE phase. At the elevated temperature, the mechanical property of AZ91 + 3wt%Y alloy was higher than those of other Mg alloys. The reasons were that Al₂Y compound was thermally stable and suppressed the grain growth. In contrast with Al₂Y compounds, β phase was thermally unstable and could not suppress the grain growth at the elevated temperature. Therefore, Al₂Y phase contributed to improve the thermal stability of RS AZ91 alloy.
급속응고한 AZ91 합금의 미세조직 및 기계적 특성에 미치는 Misch metal 첨가의 영향
엄승열 ( Seung Yeul Eum ),박훈모 ( Hoon Mo Park ),남태운 ( Tae Woon Nam ) 한국주조공학회 2000 한국주조공학회지 Vol.20 No.1
The purpose of this study is to investigate the effect of misch metal addition on the microstructure and mechanical property of rapidly solidified AZ91 alloy by melt spinning process. As the contents of misch metal(rare earth element:Ce, La, Nd, Pr) was increased, the microstructure of RS ribbons and extrudates became finer than those of AZ91, and RE related phases (Al11RE3, Al2RE) were formed. At room temperature, the rapidly solidified AZ91 +1 wt%Mm alloy showed the highest tensile strength, 430 MPa due to precipitation strengthening ofβ(Mg17Al12) phase and Al11RE3 phase. At the elevated temperature, the mechanical property of AZ91 +3 wt%Mm alloy was higher than those of other Mg alloys. The reasons were that Al11La3 phase was thermally stable and suppressed the grain growth. In contrast with Al11La3 phase, β phase was thermally unstable and could not suppress the grain growth at the elevated temperature. Therefore, Al11RE3 phase contributed to improve the thermal stability of RS AZ91 alloy.