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Fujita Masashi,Kimura Hisamichi,Inoue Akihisa 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
New Al-based alloys with very high ultimate tensile strength were developed in high Al concentration range of 91-95 at.% for Al-Fe-Cr-Ti-M (M: Co and Mo) systems and Al-Fe-Cr-Mo-Ti-Co system by the dispersion of nanoscale quasicrystalline particles in Al phase. The effect of adding elements, M was discussed in the viewpoint of stability of super-cooled liquid state and formation ability of quasicrystalline phase. The P/M Al-Fe-Cr-Ti-M alloys with dispersed nanoscale quasicrystalline particles exhibited ultimate tensile strength of 350MPa at 573K and 200MPa at 673K.
Inoue, Akihisa,Kimura, Hisamichi,Yamaura, Shin-ichi 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.6
By the dispersion of nanoscale quasicrystalline and amorphous particles in Al phase, new Al-based alloys with good mechanical properties were developed in a high Al concentration range of 93-95 at.% for Al- Cr-Ce-Co, Al-V-Fe, Al-Ti-M and Al-Fe-Cr-Ti alloy systems. The Vickers hardness of a melt-quenched (MQ) Al_(84.6)Cr_(15.4) alloy with almost a single icosahedral quasicrystalline phase (QC) was 710. The addition of Ce and Co in the Al-Cr binary alloys was effective for the extension of the concentration range of the QC to a lower solute concentration range. The fracture strength (σ_(f)) increased to 1340 MPa for the MQ Al_(94.5)Cr₃Ce₁Co_(1.5) alloy in which the particle size and volume fraction were approximately 40 nm and 70 %, respectively. The σ_(f) of the MQ Al_(94)V₄Fe₂ alloy was 1390 MPa and the particle size and volume fraction were about 10 nm and 50 %, respectively. Similarly, σ_(f) of the MQ Al_(93)Ti₄Fe₃ alloy was 1320 MPa and the particle size and volume fraction were about 11 nm and 30 %, respectively. Powder metallurgy (P/M) Al_(93)Fe₃Cr₂Fe₂ alloy with dispersed nanoscale QC exhibited ultimate tensile strength (σ_(UTS)) of 660 MPa, 0.2 % proof stress (σ_(0.2)) of 550 MPa, plastic elongation (ε_(P)) of 4.5 %, Young's modulus (E) of 85 GPa, Vickers hardness (Hv) of 192 and specific strength (σ_(UTS)/ρ) of 2.20x10^(5) Nm/kg at room temperature and sUTS of 350 MPa, σ_(0.2) of 330 MPa and ε_(P) of 1.5 % at 573 K. The QC structure in the P/M Al_(93)Fe₃Cr₂Ti₂ alloy remained almost unchanged even after annealing for 720 ks at 573 K and good wear resistance against S50C steel was also maintained for the extruded alloy tested at sliding velocity of 0.5 to 2 m/sec. These mechanical properties are promising for the future extension of the new Al-based alloys to practical materials.
The Effect of Cerium on Microstructures and Mechanical Properties of Mg-4Al-2Sn-1Ca Alloy
Kim, Byeong Ho,Kimura, Hisamichi,Park, Yong Ho,Park, Ik Min The Japan Institute of Metals 2010 Materials transactions Vol.51 No.7
<P>The development of new creep resistant magnesium alloys has become a major research focus. This study examined the microstructure and creep properties of Mg-4.0 mass%Al-2.0 mass% Sn-1.0 mass%Ca alloys containing Ce. The results showed that Ce could improve dramatically the tensile strength and ductility of the alloy at room temperature and increase the creep resistance at elevated temperatures significantly. With a trace amount of Ce, the morphology changed from a coarse CaMgSn phase to a refined shape and the microstructure of the alloy was remarkably refined.</P>
Influence of Addition of Ge on the Microstructure and Corrosion Properties of Magnesium
Kim, Byeongho,Park, Kyungchul,Kimura, Hisamichi,Park, Yongho,Park, Ikmin The Japan Institute of Metals 2012 Materials transactions Vol.53 No.1
<P>The corrosion properties of Mg–<I>x</I>Ge (<I>x</I> = 0, 0.5, 1.0, 1.5 and 2.0 mass%) alloys were investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy tests were carried out in a 3.5% NaCl solution at pH 7.2 to measure the corrosion properties of Mg–<I>x</I>Ge (<I>x</I> = 0, 0.5, 1.0, 1.5 and 2.0 mass%) alloys. Microstructural analysis showed that a Mg<SUB>2</SUB>Ge phase formed mainly in the interdendritic areas. The volume fraction of the Mg<SUB>2</SUB>Ge phase was increased with increasing Ge content. The corrosion resistance of the Mg–<I>x</I>Ge alloys was improved by Ge addition. In particular, the Mg–1.5 mass%Ge alloy showed the superior corrosion resistance of the alloys examined.</P>
Park, Kyung Chul,Kim, Byeong Ho,Kimura, Hisamichi,Park, Yong Ho,Park, Ik Min The Japan Institute of Metals 2010 MATERIALS TRANSACTIONS Vol.51 No.3
<P>In the present work, the corrosion properties of Mg-<I>x</I>Sn-5Al-1Zn (<I>x</I>=0, 1, 5 and 9 mass%) alloys have been investigated. Potentiodynamic polarization and immersion tests were carried out in 3.5% NaCl solution of pH 7.2 at room temperature to measure the corrosion properties of Mg-<I>x</I>Sn-5Al-1Zn (<I>x</I>=0, 1, 5, and 9 mass%) alloys. Microstrucral analysis shows the Mg<SUB>17</SUB>Al<SUB>12</SUB> and Mg<SUB>2</SUB>Sn phase were mainly precipitated along grain boundaries. With increase of the Sn contents, the volume fraction of the secondary phases, i.e. Mg<SUB>17</SUB>Al<SUB>12</SUB> and Mg<SUB>2</SUB>Sn phase, was increased. The corrosion resistance of Mg-<I>x</I>Sn-5Al-1Zn alloys was improved by the Sn addition. Especially, the AZ51-5 mass%Sn alloy characterized the superior corrosion resistance in the studied alloys. It seems that the presence of Sn stabilized the Mg(OH)<SUB>2</SUB> layers on the surface of Mg alloys and the secondary phases effectively formed semi-continuous structures, resulting in a drastic improvement of corrosion resistance of the Mg alloys.</P>
Investigation on the Microstructure and Mechanical Properties of Mg-Al-Yb Alloys
Jo, Su Mi,Park, Kyung Chul,Kim, Byeong Ho,Kimura, Hisamichi,Park, Sung Kyun,Park, Yong Ho The Japan Institute of Metals 2011 Materials transactions Vol.52 No.6
<P>The effects of Yb addition on the microstructure and mechanical properties of Mg-5Al alloy are investigated. The results indicate that the addition of Yb to the Mg-5Al alloy facilitates the formation of a thermally stable Al<SUB>2</SUB>Yb phase, the refinement of the microstructure and the suppression of the volume fraction of Mg<SUB>17</SUB>Al<SUB>12</SUB> phase in Mg-5Al alloy. Yb addition has little effect on the mechanical properties of the experimental alloys tested at room temperature. At elevated temperatures, however, the ultimate tensile strength (UTS) is significantly increased by Yb addition and Mg-5Al-1Yb has the highest UTS value than other experimental alloys. On the other hand, the yield strength (YS) increases at all tested temperatures due to the grain refinement and dispersion strengthening of the secondary phase. Meanwhile, the elongation (ε) of the experimental alloys decreases at all tested temperatures. Tensile fractographic analysis indicates that cleavage fracture is the dominant mechanism of the Mg-5Al and Mg-5Al-<I>x</I>Yb alloys at room temperature. At elevated temperatures, however, the fracture mechanism of experimental alloys mainly changes from cleavage to quasi-cleavage fracture.</P>
Lee, Wook Jin,Son, Jae Hyoung,Park, Ik Min,Oak, Jeong-Jung,Kimura, Hisamichi,Park, Yong Ho The Japan Institute of Metals 2010 MATERIALS TRANSACTIONS Vol.51 No.6
<P>In order to understand the deformation behavior of randomly orientated ceramic whisker reinforced composite materials, three dimensional (3D) finite element models were developed. The actual distributions of the whiskers in the composite materials were reconstructed for the representative volume element of the composite, using a random sequential adsorption algorithm. The samples were random Al<SUB>18</SUB>B<SUB>4</SUB>O<SUB>33</SUB> whisker reinforced magnesium matrix composites with a volume fraction of 15%. After modeling, the role of the random ceramic whisker in the deformation behavior of the magnesium matrix composite was investigated by the finite element method (FEM). The elastic modulus and stress-strain behaviors of the composite predicted by the microstructure-based model correlated well with the experimental results.</P>