start-ver=1.4 cd-journal=joma no-vol=89 cd-vols= no-issue=11 article-no= start-page=337 end-page=343 dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=20251101 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Ti-18Nb-xAl‡‹à‚Ì\¬‘Š‚ÆÞ—¿“Á«‚É‹y‚Ú‚·Al“Y‰Á—ʂ̉e‹¿ en-subtitle= kn-subtitle= en-abstract= kn-abstract=The Ti-18mass%Nb alloy with a quenched ƒ¿h martensitic structure exhibited a high damping capacity. However, there are issues such as lower strength than annealed ƒ¿+ƒÀ structure and decreasing damping capacity due to heating until 400 K. Therefore, in this study, to address these issues, we investigated the effect of Al addition on the constituent phases and material properties of Ti-18Nb-xAl alloys. The crystal structure was determined by examining the lattice constant and unit volume using X-ray diffraction, and optical microscopy was also performed. The material properties were investigated by Vickers hardness, Youngfs modulus, internal friction, tensile tests, and DSC measurements. Vickers hardness and tensile strength increased with increasing Al content. This is thought to be due to the combined effects of the refinement of the microstructure and solid-solution strengthening due to Al addition. The Youngfs modulus increased slightly from 0Al to 1Al, but increased significantly to 4Al. Internal friction was highest for 0Al and decreased for 4Al, whereas 7Al showed a higher value than 1Al. In the DSC heating curves, there was a decrease in the exothermic peak starting temperature and an increase in the phase-transformation heat with the addition of Al, except for 1Al. It was suggested that these changes in Ti-18Nb-xAl alloys were influenced by the structure of the quenched ƒ¿h phase, texture, and pseudoelasticity or phase transformation by deformation. en-copyright= kn-copyright= en-aut-name=MantaniYoshikazu en-aut-sei=Mantani en-aut-mei=Yoshikazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoYoshito en-aut-sei=Takemoto en-aut-mei=Yoshito kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Materials Science and Engineering, National Institute of Technology (KOSEN), Suzuka College kn-affil= affil-num=2 en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= en-keyword=ternary titanium alloy kn-keyword=ternary titanium alloy en-keyword=martensite kn-keyword=martensite en-keyword=lattice constant kn-keyword=lattice constant en-keyword=hardness kn-keyword=hardness en-keyword=Youngfs modulus kn-keyword=Youngfs modulus en-keyword=internal friction kn-keyword=internal friction en-keyword=cyclic tensile test kn-keyword=cyclic tensile test en-keyword=texture kn-keyword=texture END start-ver=1.4 cd-journal=joma no-vol=85 cd-vols= no-issue=11 article-no= start-page=405 end-page=412 dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=2021111 dt-online= en-article= kn-article= en-subject= kn-subject= en-title=Formation Mechanism of Tempering-Induced Martensite in Ti-10Mo-7Al Alloy kn-title=Ti?10Mo?7Al‡‹à‚ÌÄ–ß‚µ—U‹Nƒ}ƒ‹ƒeƒ“ƒTƒCƒg‚ÌŒ`¬‹@\ en-subtitle= kn-subtitle= en-abstract= kn-abstract=The formation mechanism of ƒ¿AA?martensite (ƒ¿AAMt) induced by tempering at 450?550Ž for a short time was investigated using Ti?10Mo?7Al alloy. The solution treated and quenched (STQ) sample was composed of ƒÀ phase and a small amount of ƒ¿AAMq, and a large amount of ƒ¿AAMt was generated by rapid tempering at 550Ž?3 s using a salt bath. However, ƒ¿AAMt was completely transformed into a single ƒÀ phase by aging at 200Ž for 3 min. Reversibility was observed between the ƒ¿AAMt transformation and the ƒÀ reverse transformation. In?situ high?temperature X?ray diffraction measurements revealed that ƒ¿AAMq ¨ ƒÀ reverse transformation occurred at 200Ž and that a thermally activated ƒ¿AAiso was generated at 450Ž due to the slow heating rate. In?situ optical microscopic observation of STQ sample with rapid lamp heating revealed that ƒ¿AAMt was formed during heating process. However, ƒ¿AAMt did not generate under following conditions; that is, a slow heating rate, thin sample plate, and a small temperature difference until tempering by preheating. On the other hand, rapid tempering using thick plate from liquid nitrogen (?196Ž) to 250Ž was performed to ensure a sufficient temperature difference, but ƒ¿AAMt was not generated at all. From the cross?sectional observation of the STQ plate, it was found that ƒ¿AAMq was hardly formed on the surface of the sample, but was formed abundantly inside the sample. On the other hand, in the rapidly tempered plate, a large amount of ƒ¿AAMt was distributed in the surface layer than inside sample. These results suggest that the thermal compressive stress induced by rapid heat treatment contributes to the formation of ƒ¿''M. en-copyright= kn-copyright= en-aut-name=TakemotoYoshito en-aut-sei=Takemoto en-aut-mei=Yoshito kn-aut-name=’|Œ³‰Ã—˜ kn-aut-sei=’|Œ³ kn-aut-mei=‰Ã—˜ aut-affil-num=1 ORCID= en-aut-name=YasunoMikiko en-aut-sei=Yasuno en-aut-mei=Mikiko kn-aut-name=ˆÀ–ìŽÀŠóŽq kn-aut-sei=ˆÀ–ì kn-aut-mei=ŽÀŠóŽq aut-affil-num=2 ORCID= en-aut-name=IkemotoMasaki en-aut-sei=Ikemoto en-aut-mei=Masaki kn-aut-name=’r–{‰ëŠî kn-aut-sei=’r–{ kn-aut-mei=‰ëŠî aut-affil-num=3 ORCID= en-aut-name=AndoHiroyuki en-aut-sei=Ando en-aut-mei=Hiroyuki kn-aut-name=ˆÀ“¡Š°K kn-aut-sei=ˆÀ“¡ kn-aut-mei=Š°K aut-affil-num=4 ORCID= en-aut-name=ShimizuIchiro en-aut-sei=Shimizu en-aut-mei=Ichiro kn-aut-name=´…ˆê˜Y kn-aut-sei=´… kn-aut-mei=ˆê˜Y aut-affil-num=5 ORCID= affil-num=1 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil=‰ªŽR‘åŠw‘åŠw‰@Ž©‘R‰ÈŠwŒ¤‹†‰È affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil=‰ªŽR‘åŠw‘åŠw‰@Ž©‘R‰ÈŠwŒ¤‹†‰È affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil=‰ªŽR‘åŠw‘åŠw‰@Ž©‘R‰ÈŠwŒ¤‹†‰È affil-num=4 en-affil=Faculty of Engineering, Okayama University kn-affil=‰ªŽR‘åŠwHŠw•” affil-num=5 en-affil=Faculty of Engineering, Okayama University of Science kn-affil=‰ªŽR—‰È‘åŠwHŠw•” en-keyword=ƒ¿''?martensite kn-keyword=ƒ¿''?martensite en-keyword=thermal stress kn-keyword=thermal stress en-keyword=tempering kn-keyword=tempering en-keyword=in situ observation kn-keyword=in situ observation en-keyword=reverse transformation kn-keyword=reverse transformation END