Papers by Author: Masato Ueda

Abstract: To develop a low-cost β Ti alloy, the influence of Mn in Ti-Al-Fe alloys on solution treatment behavior and mechanical properties was investigated. Although it has been known that Mn is a β stabilizing element in Ti alloys, Mn has not often been used for Ti alloys in spite of its low cost and sustainability so far, since Mn easily evaporates under low-pressure atmosphere, which is a common condition when melting Ti alloys. Therefore, general β Ti alloys include a high amount of expensive elements such as V, Mo and Nb to stabilize the β matrix phase. In this paper, Ti-8 to 10Mn-1Fe-3Al alloys (mass%) were produced by cold crucible levitation melting under atmospheric pressure to inhibit Mn loss by vaporization. As results, it was found that the β transus was lowered with increasing Mn amount, but the full β phase was obtained in solution-treated alloys over 1113 K, even in the 8%Mn alloy. Through tensile and Charpy impact tests of the full beta-phase samples, the ductility and toughness increase monotonically with increasing Mn amount from 8 to 10% in spite of the tensile strength having almost constant value. Ti-10Mn-1Fe-3Al alloy has the best mechanical properties among the alloys used in this study.

Abstract: This paper is a review of results for Ti-Mn [1], Ti-Mn-Al [2] and Ti-Mn-Fe [3] alloys that have been previously published. Titanium alloys, especially beta-type titanium alloys, have high specific strength, excellent corrosion resistance and good biocompatibility. Unfortunately, applications of titanium alloys are limited by their relatively higher cost. One reason is the use of rare and expensive metallic elements, such as vanadium and molybdenum, as a beta stabilizer. In order to reduce the cost, inexpensive and abundantly available metallic elements should be used as beta stabilizers. Manganese was adopted as a beta stabilizer because it is an abundant metallic element in the Earth’s crust and is relatively low in cost. The heat treatment behavior of Ti-Mn, Ti-Mn-Al and Ti-Mn-Fe alloys was investigated through electrical resistivity and Vickers hardness measurements, X-ray diffraction measurements to identify phase constitution, and observations using a light microscope [1], [2] and [3].

Abstract: The combined chemical-hydrothermal synthesis of TiO2 and CaTiO3 films on pure Ti substrates was examined with a focus on film crystallinity and surface morphology. Pure Ti disks were chemically treated with H2O2/ HNO3 aqueous solutions at 353 K for 20 min in order to form a TiO2 gel layer on the surfaces. The samples were then hydrothermally treated in an autoclave at 453 K for 12 h or 24 h. Anatase-type TiO2 and perovskite-type CaTiO3 films with high crystallinity were obtained upon treatment with distilled water or aqueous NH3 and aqueous Ca(OH)2, respectively. Uniform, crack-free films were obtained. The surfaces showed excellent attachment of osteoblast-like MC3T3E1 cells in an incipient stage. Furthermore, the cells showed satisfactory proliferation, though at a slightly lower rate than on Ti. In addition, the samples were immersed in SBF (Simulated Body Fluid), adjusted to 310 K. A light hydroxyapatite (HAp) precipitate was observed on the unmodified Ti surface after 6 days of immersion. In contrast, precipitation was observed only after 2 to 4 days on the present oxide films. Thus, these oxide films are non-toxic and enhance the deposition of HAp.

Abstract: Although titanium is considered to be a ubiquitous element since it has the tenth highest Clarke number of all elements, it is classified as a rare metal because the current refinement process is more environmentally damaging than the processes used to refine iron and aluminum. Furthermore, the beta stabilizing elements of titanium alloys (e.g., V, Mo, Nb, and Ta) are very expensive due to their low crustal abundances. Manganese is also considered to be a ubiquitous element, since it has the 12th highest Clarke number of all elements. Therefore, manganese is a promising alloying element for titanium, especially as a beta-stabilizer. In order to develop beta titanium alloys as ubiquitous metallic materials, it is very important to investigate the properties of Ti-Mn alloys. In this study, the phase constitution of and the effect of heat treatment on Ti-3.3 to 8.7 mass% Mn alloys were investigated by electrical resistivity and Vickers hardness (HV) measurements and by X-ray diffraction (XRD) analysis and optical microscopy. In 3.3, 5.1, and 6.0 mass% Mn alloys quenched from 1173 K, ’ martensite and  phase were identified by XRD, whereas in the 8.7 mass% alloy, only the  phase was detected. The resistivities at both temperatures increased with increasing Mn content up to 6.0 mass% Mn and the positive temperature dependence of resistivity became negative at 6.0 mass% Mn. LN increased gradually with increasing Mn content up to 8.7 mass% Mn, whereasRT decreased considerably at a Mn content of 8.7 mass% Mn. HV increased with increasing Mn content up to 5.1 mass%, after which it began to decrease. In Ti-3.3 mass%Mn and 5.1 mass%Mn alloys, the resistivity and the resistivity ratio decreased with increasing temperature of isochronal heat treatment because of decomposition of ’ martensite. In 6.0Mn and 8.7Mn alloys, the resistivity and the resistivity ratio decreased, while Vickers hardness increased with increasing temperature of isochronal heat treatment because of isothermal  precipitation. Furthermore, the temperature for the onset of precipitation increased with higher Mn content.

Abstract: The effect of Al addition on the elastic modulus and aging behavior in Ti-10 Cr alloys was investigated by means of electrical resistivity, X-ray diffractometry and Vickers hardness measurements. All of the alloys used were formed from solutions treated at 1173 K for 3.6 ks and then quenched into ice water (STQ). Following STQ, all Al-containing specimens exhibited a  phase, with the athermal  appearing only for alloys with zero Al addition. The elastic modulus was found to decrease with addition of Al from approximately 80 to 70 GPa, due to the suppression of the athermal . The specimens following STQ were isothermally aged at 573 K, 673 K and 773 K. The addition of Al was found to retard the onset of precipitation of the isothermal  phase and decrease the upper limit temperature for precipitation of this phase. On the other hand, as the Al content was increased, precipitation of the  phase was accelerated in the presence of an existing isothermal  phase. By contrast, this precipitation was suppressed under single  phase conditions. Surface modification for osteointegration was also performed. When the modified specimens were immersed in simulated body fluid, the surface modification was found to promote the deposition of HAp.