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Rapidly Solidified Powder Metallurgy Mg-Zn-RE Alloys with Long Period Order Structure
Kawamura Yoshihito 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Mg-Zn-RE alloys had a novel lond period stacking ordered (LPO) structure. Their rapidly solidified powder metallurgy (RS P/M) alloys exhibited a combination of high strength and god ductility (tensile yield strength above 550 MPa and elongation above 5%). The LPO Mg-Zn-RE RS P/M alloys had high elevated temperature strength (tensile yield strength above 380 MPa at 473 K) and exhibited a high-strain-rate superplasticity at higher temperatures. In Japan, a national project for developing high strength LPO Mg-Zn-RE RS P/M alloys has started at 2003 for 5 years, which is founded by the Ministry of Economy, Trade and Industry (METI) of Japan. In the national project, project targets in materials performances have been achieved. The developed LPO Mg-Zn-RE RS P/M alloys exhibited higher tensile yield strength, fatigue strength and corrosion resistance than high strength aluminum alloys of extra-super-duralumin (7075-T6).
Sakamoto Yoshihito,Yamasaki Michiaki,Kawamura Yoshihito 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Fabrication of bulk alloy has been performed through the consolidation of rapidly solidified ribbons. The bulk alloy exhibited excellent mechanical properties, high tensile yield strength of 530 MPa, and large elongation of 3 %. Microstructure of the alloy was characterized by equiaxed fine grains that consist of -Mg, long period ordered (LPO) structure phase, and -type cubic compound. The strengthening of the alloys may be due to fine grains with LPO structure phase and -type compound.
Changes in the Surface Characteristics of Gas-atomized Pure Aluminum Powder during Vacuum Degassing
Yamasaki Michiaki,Kawamura Yoshihito 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Vacuum degassing is essential in the preparation of RS P/M aluminum alloys to remove adsorbates and for the decomposition of hydrated- on the powder surface. Changes in the surface characteristics during vacuum degassing were investigated by X-ray photoelectron spectroscopy and temperature-programmed desorption measurement. Hydrated- decomposition to crystalline- and hydrogen desorption on the surface of argon gas-atomized aluminum powder occurred at 623 K and 725 K, respectively. This temperature difference suggests that the reaction converting hydrated- to crystalline- during vacuum degassing should be divided into the two reactions .
Ochiai, Satoru,Nomoto, Yoshihito,Kobayashi, Shigeki,Yamashita, Yasufumi,Watanabe, Yui,Toyomasu, Yutaka,Kawamura, Tomoko,Takada, Akinori,II, Noriko,Sakuma, Hajime Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.4
Prostate cancer is the secondary most frequently diagnosed cancer in the world. Although numerous prospective randomized trial have been conducted to guide the management of patients with localized or locally advanced prostate cancer, few clinical trials targeting node-positive prostate cancer have been reported. Therefore, there are still controversies in the optimal management of node-positive prostate cancer. Recently, efficacy of multimodality treatment, including radiation therapy (RT), for such patients has been reported in several articles. The results indicate potential benefit of RT both in adjuvant therapy after prostatectomy and in definitive therapy for node-positive prostate cancer. The aim in this article was to summarize the current evidence for RT and evaluate the role in multimodality treatment for patients with node-positive prostate cancer.
High‑Strength AZ91 Alloy Fabricated by Rapidly Solidified Flaky Powder Metallurgy and Hot Extrusion
이태경,Michiaki Yamasaki,Yoshihito Kawamura,Jongbin Go,Sung Hyuk Park 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
A high-strength AZ91 alloy is produced via hot extrusion using flakes fabricated through the rapidly solidified flaky powdermetallurgy. The AZ91 alloy flakes have an extremely fine dendritic structure without any second-phase particles owing tothe fast cooling rate during solidification; these microstructural features considerably promote dynamic recrystallization andprecipitation behaviors during extrusion process. As a result, the AZ91 alloy extruded using the flakes exhibits an almostfully recrystallized microstructure with a very small average grain size of 1.2 μm owing to an increase in the number ofnucleation sites for recrystallization, and it shows a high microstructural homogeneity owing to the numerous Mg17Al12precipitates uniformly distributed throughout the material. This extruded AZ91 alloy has a tensile yield strength of 345 MPa,ultimate tensile strength of 417 MPa, and total elongation of 5.6%. These superior tensile strengths are mainly attributed tothe combined effects of precipitation hardening caused by abundant fine precipitates and grain boundary hardening causedby fine recrystallized grains.
Ochiai, Satoru,Nomoto, Yoshihito,Yamashita, Yasufumi,Watanabe, Yui,Toyomasu, Yutaka,Kawamura, Tomoko,Takada, Akinori,Ii, Noriko,Kobayashi, Shigeki,Sakuma, Hajime Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.2
Glioblastoma (GBM) is the most common and aggressive type of primary brain neoplasm. The current standard therapy for GBM consists of maximal surgical resection within safe limits, followed by radiation therapy (RT) and chemotherapy with temozolomide. Despite advances in treatment, the prognosis of GBM remains poor. Epileptic seizure is one of the most common symptoms in patients with GBM. Valproic acid (VPA), a histone deacetylase inhibitor, is often used as an anti-epileptic drug in patients with brain neoplasms due to its effectiveness and low toxicity profile. Several in vivo and in vitro studies have indicated that VPA has radiosensitizing effects for gliomas and radioprotective influence on normal brain tissue or hippocampal neurons. The results of several retrospective studies have also indicated potential benefit to improve survival of patients with GBM. Moreover, the promising treatment results of a phase 2 trial of concurrent radiation therapy, temozolomide, and VPA for patients with GBM have been recently reported. The use of VPA in patients with GBM has thus recently receiving more attention. In this article, we review the role of VPA in radiation therapy for GBM, focusing on the clinical evidence.
Microstructure and Mechanical Properties of Rapidly Solidified Powder Metallurgy Al-Fe-V-Si-X Alloys
Genkawa Takuya,Yamasaki Michiaki,Kawamura Yoshihito 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
High heat-resistant Al-Fe-V-Si and Al-Fe-V-Si-X rapidly solidified powder metallurgy (RS P/M) alloys have been developed under well-controlled high purity argon gas atmosphere. The (at. %) RS P/M alloy exhibited high elevated-temperature strength exceeding 300 MPa and good ductility with elongation of 6 % at 573 K. Reduction of partical pressure in P/M processing atmosphere led to improvement in mechanical properties of the powder-consolidated alloys under elevated-temperature service conditions. Ti addition to the Al-Fe-V-Si conduced to enhancement of the strength at room temperature. The tensile yeild strength and ultimate strenght were 545 MPa and 722 MPa, respectively.
Vacuum degassing behavior of Zr-, Ni- and Cu-based metallic glass powders
Yamasaki, Michiaki,Iwamoto, Kotaro,Tamagawa, Hirokazu,Kawamura, Yoshihito,Lee, Jin-Kyu,Kim, Hwi-Jun,Bae, Jung-Chan Elsevier 2007 Materials science & engineering. properties, micro Vol.449 No.-
<P><B>Abstract</B></P><P>The vacuum degassing behavior of Zr<SUB>55</SUB>Al<SUB>10</SUB>Ni<SUB>5</SUB>Cu<SUB>30</SUB>, Ni<SUB>59</SUB>Zr<SUB>15</SUB>Ti<SUB>13</SUB>Si<SUB>3</SUB>Sn<SUB>2</SUB>Nb<SUB>7</SUB>Al<SUB>1</SUB>, and Cu<SUB>54</SUB>Ni<SUB>6</SUB>Zr<SUB>22</SUB>Ti<SUB>18</SUB> (numbers indicate at.%) metallic glass powders has been investigated and compared with that of Al alloy powder. It was found that the alloy composition influenced the gas desorption behavior with heating <I>in vacuo</I>. Zr<SUB>55</SUB>Al<SUB>10</SUB>Ni<SUB>5</SUB>Cu<SUB>30</SUB> and Ni<SUB>59</SUB>Zr<SUB>15</SUB>Ti<SUB>13</SUB>Si<SUB>3</SUB>Sn<SUB>2</SUB>Nb<SUB>7</SUB>Al<SUB>1</SUB> metallic glass powders exhibited little H<SUB>2</SUB> gas desorption from powder surfaces during vacuum degassing. Because Zr in the Zr-based and Ni-based amorphous alloy powders produced a native zirconium oxide layer, the surface of the Zr<SUB>55</SUB>Al<SUB>10</SUB>Ni<SUB>5</SUB>Cu<SUB>30</SUB> and Ni<SUB>59</SUB>Zr<SUB>15</SUB>Ti<SUB>13</SUB>Si<SUB>3</SUB>Sn<SUB>2</SUB>Nb<SUB>7</SUB>Al<SUB>1</SUB> amorphous alloys had no influence on adsorbed H<SUB>2</SUB>O. Cu<SUB>54</SUB>Ni<SUB>6</SUB>Zr<SUB>22</SUB>Ti<SUB>18</SUB> metallic glass powder was the most affected by atmospheric H<SUB>2</SUB>O among the metallic glass powders examined in this study. The adsorbed H<SUB>2</SUB>O and Cu metal may react with each other with the formation of Cu<SUB>2</SUB>O and liberation of H<SUB>2</SUB> during vacuum degassing. In order to obtain sound P/M final products with Cu-based P/M alloys, oxygen-free copper powders should be used in well-controlled atmospheres with low H<SUB>2</SUB>O partial pressures.</P>
Development of High Strength Mg-Zn-Gd Alloys by Rapid Solidification Processing
Kim Min-Chul,Yamasaki Michiaki,Kawamura Yoshihito 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Rapidly solidified ribbon-consolidation processing was applied for preparation of high strength bulk Mg-Zn-Gd alloys. Mg alloys have been used in automotive and aerospace industries. Rapid solidification (RS) process is suitable for the development of high strength Mg alloys, because the process realizes grain-refinement, increase in homogeneity, and so on. Recently, several nanocrystalline Mg-Zn-Y alloys with high specific tensile strength and large elongation have been developed by rapidly solidified powder metallurgy (RS P/M) process. Mg-Zn-Y RS P/M alloys are characterized by long period ordered (LPO) structure and sub-micron fine grains. The both additions of rare earth elements and zinc remarkably improved the mechanical properties of RS Mg alloys. Mg-Zn-Gd alloy also forms LPO structure in -Mg matrix coherently, therefore, it is expected that the RS Mg-Zn-Gd alloys have excellent mechanical properties. In this study, we have developed high strength RS Mg-Zn-Gd alloys with LPO structure and nanometer-scale precipitates by RS ribbon-consolidation processing. and and bulk alloys exhibited high tensile yield strength (470 MPa and 525 MPa and 566 MPa) and large elongation (5.5% and 2.8% and 2.4%).
Corrosion Behavior of Rapidly Solidified Mg-Zn-Y Alloys in NaCl Solution
Izumi Shogo,Yamasaki Michiaki,Sekigawa Takahiro,Kawamura Yoshihito 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Compositional dependence of corrosion behavior of rapidly solidified Mg-rich Mg-Zn-Y alloys in NaCl aqueous solution has been investigated. Mg-Zn-Y ternary alloys containing small amounts of Zn exhibited low corrosion rate, although the (at. %) binary alloy showed severe corrosion with violet evolution of hydrogen. The alloy with highest corrosion-resistance was , its corrosion rate was about 1 mm year-1 in 0.17 M (1.0 wt. %) NaCl solution. alloy exhibited passive region in anodic polarization curves when immersed in NaCl solution. Rapidly solidification and small amount of Zn addition may bring about an increase in electrochemical homogeneity of Mg-Zn-Y alloys, resulting in enhancement of corrosion resistance.