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Volume 42, Issue 11
Displaying 1-13 of 13 articles from this issue
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Mitsuo NIINOMI, Toshiro KOBAYASHI, Igor Alexeevich AKMOULIN1992 Volume 42 Issue 11 Pages 605-613
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
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Masahiko MORINAGA, Jun-ichi SAITO, Masao MORISHITA1992 Volume 42 Issue 11 Pages 614-621
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
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Masahiko IKEDA, Shin-ya KOMATSU, Takashi SUGIMOTO, Kiyoshi KAMEI1992 Volume 42 Issue 11 Pages 622-626
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSElectrical resistivity anomalies in β type Ti alloys including negative temperature dependence were previously interpreted by fully reversible formation and disappearance of athermal ω phase with cooling and heating. In the present work, influence of Al addition up to 10mass% on some properties of Ti-20%V alloy in as quenched state from β region were investigated. Resistivity increases with concentration of solute Al. Addition of 3%Al changes the temperature-resistivity curve of Ti-20%V alloy, which had a resistivity maximum between 77K and room temperature, to the curve having negative temperature coefficient in whole of the above temperature range. In alloys below 5%Al, hardness decreases slightly with Al addition, namely no solid solution hardening by Al can be observed. However, the hardening appears above 8%Al clearly. These results suggest that the starting, perhaps also finishing, temperature of athermal ω phase formation is lowered and that the amount of athermal ω phase at room temperature is decreased by the Al addition. This interpretation is qualitatively confirmed by electron diffraction.View full abstractDownload PDF (1530K) -
Masakazu OKAZAKI, Takayuki SUGANUMA, Yoshiharu MUTOH, Kuninori MINAKAW ...1992 Volume 42 Issue 11 Pages 627-632
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe fatigue strength was investigated in Ti-6Al-4V alloy with several kinds of microstructures. It is significantly affected by several kinds of factors relating to microstructures, especially by size of equiaxial primary α grain and volume fraction of α phase. The effects of microstructures are discussed, based on observation of the crack initiation sites. The small fatigue crack growth behavior is also investigated, by employing a replication technique. The rates of small crack growth in all materials, in which the microstructure also plays an important role, are notably higher than those of long crack. It is also found that the information on the microstructure dependence in large crack growth is not always applicable to that in small crack growth.View full abstractDownload PDF (1066K) -
Keizo SAKURAI, Katsushige ADACHI, Koichi OGAWA1992 Volume 42 Issue 11 Pages 633-637
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSMajor problems in drilling titanium like chip welding which leads to frictional heating and consequently to high cutting temperature are attributed to properties of titanium. Severe chip adhesion and easy chipping are problems also encountered in drilling titanium. On the other hand, low frequency vibratory drilling is known to have an inhibitory effect on the plastic deformation zone as well as to curb the increase in cutting temperature. This drilling method is thought to be effective in combating the aforementioned problems in drilling titanium, thus low frequency vibratory drilling is employed in the investigation of the cutting characteristics of Ti-6Al-4V alloy. From this study, low frequency vibratory drilling is found to be effective in accelerating the cutting fluid cooling effect and reducing drill point friction heat as a result of the much improved cutting fluid permeability.View full abstractDownload PDF (962K) -
Bo GONG, Mitsuo NIINOMI, Toshirou KOBAYASHI, Yukitoshi OHYABU1992 Volume 42 Issue 11 Pages 638-643
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSHydrogen absorption behavior and microstructual change by thermochemical processing (TCP) with hydrogen in Ti-6Al-4V (Ti-6.4) alloy were investigated. Mechanical properties and fracture toughness of Ti-6•4 and Ti-5Al-2.5Fe(Ti-5•2.5) alloys subjected to various TCP were, then, investigated.
Microcracking is observed at a hydrogen flow rate of over 12.3 ml/s in Ti-6•4 alloy when the starting microstrucure is Widmanstätten α. The microstructures of Ti-6•4 and Ti-5•2.5 alloys are refined by both newly proposed and conventional TCP. Tensile strengths of the both alloys are also improved by various TCP. Newly proposed TCP where hydrogenation and dehydrogenation are conducted below the hydrogenated β transus temperature, that is, BTH (Below Transus Hydrogenation), is found to be effective for achiving a good balance of tensile strength and elongation in both Ti-6•4 and Ti-5•2.5 alloys. Fracture toughness of Ti-6•4 alloy is decreased by TCP while that of Ti-5•2.5 alloy is increased.View full abstractDownload PDF (951K) -
Biing Hwa YAN, Fu Ten SHIEH1992 Volume 42 Issue 11 Pages 644-649
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSIn order to reveal the electrical discharge machining (EDM) of titanium alloy, a series EDM tests on commercial product Ti-6Al-4V with graphite and copper used as the tool electrode materials were carried out at different parameters such as discharge current and pulse duration. The relationships between these factors and material removal rate, surface roughness, enlargement and heat-affected layer were investgated. The following main results were obtained. From the view point of metal removal rate using graphite electrode with negative polarity is remarkably larger than the copper electrode. But from the view point of surface roughness copper electrode is better than graphite electrode. The thickness of heat-affected layer increases with increasing pulse duration and discharge current, especially, when the pulse duration is large enough, the heat-affected layer becomes severely.View full abstractDownload PDF (1761K) -
Takayasu SATO, Kazuo AKASHI1992 Volume 42 Issue 11 Pages 650-656
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSIon nitriding is widely used as an important surface hardening method for various metals. In this method, the sample to be treated is served as a cathode in a d. c. glow diacharge. In our study, what is called "plasma nitriding" was tried in place of ion-nitriding for titanium alloy (Ti-6Al-4V). In this plasma nitriding, the sample generally maintained in an electrically floating state was placed in an r. f. glow plasma generated inductively using pure nitrogen or nitrogen-hydrogen mixture. By addition of hydrogen into nitrogen, the nitriding rate was promoted and δ-TiN phase was preferentially formed at relatively lower temperatures. It is probable that active ions and N-H radicals in the plasma can attribute to such phenomena. According to SEM observation, it was made clear that the change of the nitrided surface morphology became more remarkable with the elapsed time and the increase of hydrogen content in the gas mixture. We also attempted to impose a d. c. bias voltage to the alloy sample in the r. f. plasma. The promotion of nitriding and other interesting phenomena, such as phase transition from ε to δ and increase of surface hardness, were observed in such r. f. plasma nitriding assisted by charged particle bombardment. Thermal nitriding of the same sample without plasma was tried to confirm the characteristics of plasma nitriding.View full abstractDownload PDF (1405K) -
Kouzou KANAYAMA, Kouzi YOSHIOKA, Ichinori SHIGEMATSU, Teruyuki KOZUKA1992 Volume 42 Issue 11 Pages 657-662
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSTo clarify the applicability of a planetary ball die (PBD) to the reducing of welded titanium tubes, simple experiments utilizing the turning lathe are carried out. The surface roughness (Rmax) of reduced tube can be improved to excellent level of 1μm. Values of Vickers micro-hardness, axial strain and angle of twist of reduced tube increase with the increase of reduction rate. When the reduction rate and/or the feeding speed of tube increase, temperature-rise of the tube and the required thrust and torque increase. The increase of revolution speed of die leads to an increase of the temperature-rise and a decrease of the thrust and torque. When the PBD is applied, the thrust can be reduced to a level which is lower than half of that for the ordinary conical die.View full abstractDownload PDF (1134K) -
Naotake NIWA, Shinichi FUJIKAWA, Hideo TAKATORI, Takateru UMEDA1992 Volume 42 Issue 11 Pages 663-667
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe effects of aging after solution-treatment and aging after cold-working on the microstructure and mechanical properties of a commercial beta titanium alloy Ti-13V-11Cr-3Al were investigated. In the aging after solution-treatment, preferential alpha precipitation on beta grain boundaries is remarkable in the aged microstructure and, with increase in aging time, strength increases, however, ductility decreases greatly due to the development of grain boundary cracking. The grain boundary cracking is caused by the preferential precipitation of alpha phase on the beta grain boundaries. In the aging after cold-working, cold-working remarkably promotes aging response and greatly improves strength-ductility balance after aging through suppressing preferential precipitation of alpha phase on grain boundaries and getting more uniform and finer aged microstructure. In this heat-treatment, higher reduction in cold-working and lower temperatures in aging are preferable to the improvement of mechanical properties.View full abstractDownload PDF (1805K) -
Naotake NIWA, Takateru UMEDA, Hideo TAKATORI, Yoshihiko OBATA1992 Volume 42 Issue 11 Pages 668-673
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSEffect of bi-modal microstructure on the fracture toughness of a commercial beta titanium alloy Ti-13V-11Cr-3Al was examined. Bi-modal microstructure is obtained through combination of aging at high temperature and re-aging at low temperature after solution treatment. The bi-modal microstructure is composed of coarse and fine alpha precipitates and beta matrix. The bi-modal microstructure improves fracture toughness-strength balance compared with the microstructure produced by aging at a single temperature after solution treatment. Although the specimens re-aged at 723K for 360ks after aged at 873K or 923K for 10.8ks have almost the same strength of the specimen aged at 723K for 288ks, they have about 40% higher fracture toughness than the specimen aged at a single temperature. The fracture surface ahead of fatigue pre-crack of the CT specimen with bi-modal microstructure has larger and deeper dimples compared with the specimen aged at a single temperature. The fact indicates that larger amount of plastic deformation is necessary for crack propagation from the tip of fatigue pre-crack in the bi-modal microstructure.View full abstractDownload PDF (1070K) -
Bin-Lung OU1992 Volume 42 Issue 11 Pages 674-676
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
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Junichi KANEKO, Yotaro MURAKAMI1992 Volume 42 Issue 11 Pages 677-678
Published: November 30, 1992
Released on J-STAGE: October 30, 2008
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