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Volume 50, Issue 9
Displaying 1-7 of 7 articles from this issue
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RESEARCH REPORT
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Susumu ARAKAWA, Tomei HATAYAMA, Kazuhiro MATSUGI, Osamu YANAGISAWA2000 Volume 50 Issue 9 Pages 430-434
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSAge-hardening behaviors of Al2O3 particle dispersed Al–4 mass%Cu composites produced by mechanical alloying were investigated by Vickers microhardness test, X-ray diffraction analysis, scanning and transmission electron microscopy. In the MA composites, the Al7Cu2Fe compound was observed in the matrix after solution treatment, because of contamination of Fe atoms during MA. A lot of stable θ phases precipitated on grain boundaries in the early stage of aging, since MA treatment remarkably refined the grain size. The amount of age-hardening of the MA composites significantly decreased compared with that of Al–4%Cu alloy produced by ingot metallurgy. This decrease in the age-hardenability was attributed to the decrease in Cu content of the matrix due to the formation of Al7Cu2Fe and the precipitation of θ on grain boundaries in the early stage of aging. The time to the peak hardness during aging of the MA composites was shortened with increasing the volume fraction of Al2O3 particle.View full abstractDownload PDF (481K) -
Masahiko IKEDA, Shin-ya KOMATSU, Takashi SUGIMOTO2000 Volume 50 Issue 9 Pages 435-440
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSInfluence of Al content on electrical resistivity, hardness and phase transformation behavior of Ti–11 mass%Mo–(0∼7)mass%Al alloys quenched form 1323 K was investigated by means of resistivity and hardness measurements, X-ray diffraction analysis, and optical and electron microscopy. α″ martensite was observed between 1 and 5%A1 and its volume fraction in Ti–11Mo–2Al alloy was the largest, which was estimated from the intensity of X-ray diffraction. On the other hand, no acicular microstructure or reflection of the α″ martensite was observed in 0Al and 7Al alloys. Vickers hardness decreased with increasing Al content up to 2%, reaching a minimum, abruptly increased up to 3 mass% Al, and gradually increased above 3%. Resistivity maximum on temperature-resistivity curve of 0Al alloy appeared at about 210 K. Negative temperature dependence was observed in 1Al, 3Al, 5Al and 7Al alloys, while 2Al alloy in which the volume fraction of α″ martensite was the largest had positive temperature dependence. From these results, it is considered that Ms, starting temperature of α″ martensitic transformation, was elevated with increasing Al content up to 2% and then lowered. Though temperature of β transus is slightly increased by Al content, the increase in Ms of alloys containing Al up to 2% will be attributable to decrease in resistance to lattice deformation, i.e. decrease in the degree of supercooling for martensitic transforming with increasing Al content up to 2%Al because of a hardness decrease due to decrease in the volume fraction of athermal ω that is larger than a hardness increase due to solution hardening of β phase with Al addition. Above 3%Al, it is considered that the decrease of Ms will be attributable to increase in the degree of supercooling because of the smaller effect of athermal ω than that of solution hardening.View full abstractDownload PDF (513K) -
Yoichi TAKAGI, Kazuo MIYAHARA, Risho HAGINAKA, Seiichi MASA2000 Volume 50 Issue 9 Pages 441-445
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSSurface defects that appear as configurations of white dots (hereafter: streak) often occur after surface treatment in 6063 aluminum alloy extruded section. The cause of streak occurrence is thought to be in the welding seam of billet-to-billet extrusion since streak occurrence is concentrated in the beginning part of extrusion. This study surveyed the streak occurrence in detail and examined the influence of the welding conditions of billet-to-billet extrusion upon streak occurrence. In conclusion, this study showed that defective welding occurs partially at seam of billet-to-billet extrusion due to oxide and air enclosure, and that the welding seam remains in extrusion section. Then it was inferred, in the case where the welding seam is near the surface of the extruded section, that pits are formed during pretreatment, and that streak occurs in those locations after pigmentation.View full abstractDownload PDF (534K) -
Ichinori SHIGEMATSU, Naobumi SAITO, Masaru NAKANISHI, Mamoru MABUCHI, ...2000 Volume 50 Issue 9 Pages 446-450
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSMagnesium and magnesium alloys are being increasingly used in various areas of industries due to their low densities and high specific strength. In this research, extruded sheets of AZ31 magnesium alloy were machined by a carbon dioxide laser. Without surface coatings to raise an absorption of laser beam, sheets of 1 mm thickness were able to cut successfully at the condition of beam power 400 W and feeding speed 25 mm/s. Average height of drosses was about 300 μm when feeding speed was larger than 12 mm/s. Furthermore, by using argon as assist gas, processing damages like cracks and pores were inhibited. However, oxidation of the laser-cut surfaces was not depressed perfectly, some oxides were observed in drosses and at the top edge of cut surface. The thickness of melted and re-solidified layer was 7 μm at the upper part of cut surface and 24 μm at the lower part. The re-solidified layer consisted of 2 thin layers at the lower part of cut surface. Refined pores less than 1 μm were observed at the interface of these 2 layers.View full abstractDownload PDF (619K) -
Tetsuro OHWUE, Ken TAKATA, Makoto SAGA, Masao KIKUCHI2000 Volume 50 Issue 9 Pages 451-455
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSUniaxial tensile tests, cylindrical and square shell deep drawing tests of aluminum alloy sheets from RT to 250°C temperatures were carried out in order to investigate temperature dependence of mechanical properties and deep drawability. In these warm working temperatures, tensile strength (TS) decreases and elongation (El) is nearly same from RT to 100°C, but it increases largely with the increase of temperature from 150 to 250°C. This change of El mainly depends on local elongation (L.El) . Cylindrical shell deep drawability increases with ambient temperatures. Square shell deep drawability increases largely from 200°C to 250°C, but it is nearly same from RT to 150°C. ΔLDR (limiting drawing ratio) shows the effect of working temperature from the LDR of RT. The effecive experimental equation between ΔLDR and mechanical properties (TS, El, L.El) is developped.View full abstractDownload PDF (390K) -
Shuhei AIDA, Hiroshi TANABE, Hiroyuki SUGAI, Itaru TAKANO, Hideki OHNU ...2000 Volume 50 Issue 9 Pages 456-461
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSRecently, magnesium alloys are often applied in the auto industries and electric appliances. Most of them are manufactured by using some casting methods. But, from the viewpoints of productivity and quality of product, it is easily expected that the development of press forming technology is strongly required along with other metals and alloys. It is therefore important to grasp the plasticity of magnesium alloys. The purpose of this work is to investigate the possibility of press forming on AZ31 magnesium alloy plate. So, the tensile tests were performed to understand its basic material characteristics, and press forming tests were strived to improve its deep-drawability. The results of this study are summarized as follows. From the tensile test, the elongation of AZ31 was about 10% at room temperature, but the elongation increases in increasing temperature and amounts to 80∼90% at 473 K. It was also found that the limit of drawing ratio of AZ31 plate resulted in 3.2 by heating the die at 473 K or above and by cooling the punch at room temperature or below.View full abstractDownload PDF (552K)
REVIEW
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Yo TOMOTA, Takahisa OHNUKI2000 Volume 50 Issue 9 Pages 462-467
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSDownload PDF (626K)
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