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Volume 45, Issue 10
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Hiromitsu KANEDA, Takao CHOH1995 Volume 45 Issue 10 Pages 537-542
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe fabrication of magnesium matrix composites using spontaneous infiltration phenomenon becomes possible by adding SiO2 powder (infiltration agent) to SiCp powder (reinforcement), even at relatively low holding temperature and under argon atmosphere. It is probably because the wettability between Mg melt at the infiltration front and reinforcement is improved by Mg/SiO2 thermit reaction heating. In this paper, the infiltration velocity is measured. Especially the effects of SiCp diameter from 2 to 8μm and SiO2 content are discussed. The results show that the infiltration velocity is in the range from 0.01 to 0.7mm•s-1, and it depends both on SiCp diameter and on SiO2 content. The effect of SiO2 content on infiltration velocity is complex, i. e. the velocity increases with increasing SiO2 content up to 15mass%, and then decreases steeply. This decrease is probably caused by the increased infiltration resistance with MgO and Mg2Si, products of Mg/SiO2 reaction. Up to 15mass%SiO2, the increasing of infiltration front temperature by increasing SiO2 content is efficient, resulting in faster infiltration velocity. Above this content, the effect of infiltration resistance by the reaction products becomes more significant than that of the temperature increase, resulting in slower velocity.View full abstractDownload PDF (993K) -
Yasuo SUZUKI, Biing Hwa YAN, Hwa Ou HSU1995 Volume 45 Issue 10 Pages 543-548
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSIn order to investigate the electrical discharge machining characteristics and the improvement on the work surface of 7075 aluminum alloy, a series of EDM tests by using both normal dielectric and cooling dielectric were carried out. Summarizing the data given by EDM experiments, it is verified that the electrical discharge machining characteristics closely related to the discharge energy. The cooling dielectric has a significant influence on the electrical discharge machining characteristics of 7075 aluminum alloy. The main results indicate that the material removal rate of normal EDM is larger than that with cooling dielectric, but it seems certain that material removal mechanism has no difference between both normal EDM and EDM with cooling dielectric. Although, comparing with the normal dielectric, the cooling dielectric seems to has not much effect to restrict the discharge points growth, there is a better work surface finish obtained due to the surrounding recasting rise of melt cavities restricted by using cooling dielectric. It is also found that a thinner recasting layer can be obtained when machining with cooling dielectric.View full abstractDownload PDF (2011K) -
Takeshi MURAKAMI, Yoshihiro MIYOSHI, Tsuneo TAKAHASHI1995 Volume 45 Issue 10 Pages 549-553
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSTexture measurements were made of upsetting forged disk to 50 and 70% reduction from semi-continuously cast rod and extruded rod of ZK60A alloy having weak [1120] and strong [1010] fiber texture parallel to rod axes respectively. The method of Harris for inverse pole figures of fiber textures was used. To verify if the method is appropriate for measurement of forging texture in magnesium, texture in extruded plate of AZ31 alloy was also measured. Initial textures changed during upsetting gradually to [0001] orientation parallel to upsetting direction, sharpness of these fiber texture being more shape at surface layer on disk than inner layer and at higher reduction. Textures in various location in disk from cast bar were uniform in comparison with that from extruded rod in which upsetting direction are parallel to extrusion direction.View full abstractDownload PDF (801K) -
Yoshihiro NAKAYAMA, Tetsuya TAKAAI1995 Volume 45 Issue 10 Pages 554-559
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSEffects of cold rolling conditions on the generation of the surface residual stress in the 5083 aluminum alloy plates were experimentally investigated. The generation behavior of the residual stress was examined in view of plate thickness, working roll diameter and one pass reduction in area. The obtained results were summarized as follows. Thicker specimens exhibited relatively higher surface residual stress in tensile manner than thinner ones. Surface residual stresses decreased with increasing the total reduction in area. The specimen rolled by large working rolls showed higher compressive stress than the specimen rolled by small rolls. The parameters of ωf and (t/l)2 which represent the geometrical conditions in the final rolling process significantly affected the generation behavior of the surface residual stress.View full abstractDownload PDF (760K) -
Kazutoshi SEKIHARA, Satoshi OHNISHI, Shigeharu KAMADO, Yo KOJIMA1995 Volume 45 Issue 10 Pages 560-565
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSStrain-induced AZ91D magnesium alloy bulk was semi-solid press-formed. Microstructure and mechanical properties of the formed specimen were investigated. By using strain-induced bulk, a microstructure is able to be obtained in which fine and nearly spherical magnesium solid solution distributes uniformly. Furthermore, the eutectic phase becomes finer by rapid cooling. The tensile properties of the press-formed specimen are sufficiently superior to those specified in JIS. Particularly, 0.2% proof strength of the formed specimen remarkably surpasses that of JIS specification due to the formation of fine eutectic phase. Since the eutectic phase is the initiation of fracture, however, the mechanical properties are greatly influenced by the quantity and distribution of eutectic phase. For instanse, ductility of formed specimen is considerably small because of the existence of continuous eutectic phase at grain boundaries. Nevertheless tensile properties could possibly be improved (better than JIS specification) owing to disappearance of the eutectic phase by T4 or T6 treatment.View full abstractDownload PDF (2252K) -
Makoto TSUTSUI, Naoya MURAKAMI, Hiroaki OHSAWA1995 Volume 45 Issue 10 Pages 566-571
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSIn order to examine the possibility of combined application of SuperPlastic Forming and Diffusion Bonding (SPF/DB) to superplastic aluminum alloy sheet, relationships between bonding conditions and bonding strength were investigated experimentally. Superplastic A7475 sheet was diffusion-bonded in scarf joint configuration with various scarf angles at 788K in the air atomosphere, then bonding strength of the joint was measured by tensile test at room temperature. The stress state on the interface of the joint was taken into consideration to evaluate the strength of the bonding area. Estimation of bond strength reveals that sufficient high strength could be obtained if the bonding conditions are ordered properly.View full abstractDownload PDF (910K) -
Hiroyuki UCHIDA, Toshihiko SHINYA1995 Volume 45 Issue 10 Pages 572-577
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe creep deformation behavior of magnesium and Mg-Al alloys was analyzed by using the θ projection concept based on the following equation:
ε=θ1{1-exp(-θ2t)}+θ3{exp(θ4t)-1}
where ε is creep strain, t time and θ1-θ4 the parameters determined by curve fitting. The equation was able to reproduce the creep curves even in the tertiary creep stage. In solid solution hardened alloys containing up to 6 mass% Al parameters θ1 and θ3 were independent of temperature, but temperature dependent in the precipitation hardened alloy containing 9 mass%Al. The activation energy for θ1 and θ3 in Mg-9 mass%Al alloy was 30kJ/mol, and this value was equal to that of discontinuous grain boundary precipitation of Mg17Al12 during aging. The activation energy for θ2 related to strain hardening rate was 100kJ/mol, and that for θ4 related to recovery or weakening rate was 134kJ/mol. The activation energy of θ4 was almost same as that of self-diffusion in pure Mg, indicating that the recovery or weakening rate is controlled by climbing of dislocations.View full abstractDownload PDF (1205K) -
Kazuhiro NAKATA, Shogo TOMIDA1995 Volume 45 Issue 10 Pages 578-584
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (1362K) -
Kenji MATSUDA1995 Volume 45 Issue 10 Pages 585-586
Published: October 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (457K) -
1995 Volume 45 Issue 10 Pages vi
Published: 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (95K)
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