Papers by Keyword: Titanium (Ti)

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Authors: Mitsuru Takemoto, Shunsuke Fujibayashi, B. Otsuki, Tomiharu Matsushita, Tadashi Kokubo, Takashi Nakamura
Abstract: Generally, characterizations of pore structures of porous biomaterials are mainly based on 2-dimensional (2-D) analysis using cross sectional micrographs. However, interconnectivity of each pore may be more important factor, when tissue ingrowth into deeper pores is considered. In this paper, using micro-CT imaging with 3-D image processing software, analyses of porous material based on 3-demensional (3-D) geometrical considerations were successfully performed. Plasmasprayed porous titanium implant (PT) and four types of sintered porous titanium implants (ST50- 200, ST50-500, ST70-200, and ST70-500) that possess different porosities (50% and 70%) and pore sizes (200-500+m and 500-1500+m) were analyzed in this study. A micro focus X-ray computed tomography system was employed to acquire microstructural information from the porous implants. Using 3-D image processing software, we performed three types of 3-D analysis including detection of the dead space (% dead pore), analysis of interconnectivity by blocking the narrow pore throat with caliber less than 52 +m (% pore with narrow throat) and analysis of material construct by contracting thin strut with thickness less than 52 +m (% construct with thin strut). ST50S and ST50L possessed interconnected porous structure with thicker strut; however, pore throat was considered to be relatively narrow. On the other hand, PT implant possesses favorable interconnectivity despite its’ low porosity; however, relatively thin strut indicate the structural disadvantage for mechanical property. These results suggest that the 3-D analysis of pore and strut structure using micro focus X-ray computed tomography and 3-D image processing software will provide effective information to develop porous implant.
Authors: Konstantin Vassilevski, Alton B. Horsfall, C. Mark Johnson, Nicolas G. Wright, Anthony G. O'Neill
Authors: Seung Wook Baek, Won Bae Lee, Ja Myeong Koo, Chang Yong Lee, Seung Boo Jung
Abstract: Microstructure and mechanical properties of friction welded and vacuum brazed Ti/AISI 321 stainless steel have been evaluated with various welding conditions. Maximum tensile strength of friction welded joints was approximately 420 MPa with the conditions of 400 MPa of upset pressure (P2) and friction time (t1) within 2.0 s. Maximum tensile strength of brazed joints was acquired under the condition of 900 °C brazing temperature and 5 min. brazing time and showed approximately 275MPa which was about 80% of that of the Ti base metal. Friction welded Ti/AISI 321 joints showed the superior tensile strength than that of brazed Ti/AISI 321 due to thinner intermetallic compound layer.
Authors: Hiroshi Asanuma
Abstract: A new designing concept to realize multifunctional structural material systems is proposed and demonstrated in this paper. The concept can be explained as follow: There exist a couple of competitive structural materials which normally compete with each other because of their similar and high mechanical properties, and they tend to have secondary properties which are different from each other or opposite among them. So if they are combined together to make a composite, the similar properties, normally high mechanical property, can be maintained, and the other dissimilar properties conflict with each other, which will generate functional properties. According to the proposed concept, a CFRP (carbon fiber reinforced plastics)/aluminum laminate was fabricated and its actuation capabilities and multifunctionality were successfully demonstrated. A titanium fiber/aluminum matrix composite was also fabricated, where the fiber was oxidized for electrical insulation and strengthening. This material system is very simple, but it can generate many useful functions such as heating, actuation, temperature sensing, deformation sensing and healing.
Authors: A. El Bouari, A. El Jazouli, J.M. Dance, G. Le Flem, R. Olazcuaga
Authors: I.I. Parfenova, E.I. Yuryeva, Sergey A. Reshanov, V.P. Rastegaev, A.L. Ivanovskii
Authors: Bin Shen, Hong Bao Liu, Xie Min Mao, Chong He Li
Abstract: An hBN-Y2O3 composite investment moulding material was developed for investment casting Ti-6Al-4V alloy. Hexagonal boron nitride (hBN) powders plus a few Y2O3 powders were used as the investment mould material to prepare the shell mould with colloidal yttria as binder. The results show that the hBN-Y2O3 composite investment mould can be used to cast Ti-6Al-4V alloy, and has lower cost compared with the traditional yttria based investment mould, because of chemically inert of hexagonal boron nitride and its lower density. Moreover the interfacial reaction between the Ti and hBN-Y2O3 composite shell mould was investigated with measurement of microhardness and scanning electron microscopy (SEM) with energy dispersive (EDS).
Authors: Xiao Teng Wang, H. Hamasaki, M. Yamamura, R. Yamauchi, Takashi Maeda, Yoshihisa Shirai, Fusahito Yoshida
Abstract: In this paper, the high temperature, deformation behaviour of beta titanium alloy Ti-20V-4Al-1Sn sheet is studied by performing uniaxial tension experiments at three different strain rates at high temperatures of 700°C, 750°C and 800°C. The stress-strain curves for these temperatures show strain rate sensitivity, yield point phenomena and continuous flow, softening patterns. Microstructures of deformed specimens at several representative deformation stages and different strain rates are studied using an optical microscope. Dynamic recovery does not occur at the early stage of deformation including the yield-point and the subsequent yield drop regime, but it is activated at a large deformation stage, where it is affected by both strain rate and strain. A viscoplastic, constitutive model, based on the assumption of rapid dislocation multiplication, is proposed to describe such high temperature, yield-point phenomena. In this modelling, the softening effect due to dynamic recovery is also considered. The stress-strain responses, predicted by the constitutive model, well capture the yield-point phenomena, strain rate sensitivity and subsequent continuous flow, softening behaviour of the beta titanium alloy.
Authors: W.H. Lee, Y.H. Kim, N.H. Oh, Y.W. Cheon, Y.J. Cho, C.M. Lee, K.B. Kim, N.S. Lee
Abstract: Coatings of hydroxyapatite (HA) on the porous-surfaced Ti compact have been conducted by electrostatic spray deposition (EDS). The precursor solution for the HA coating by ESD was prepared by mixing nano-scaled HA powder with ethyl alcohol. As-deposited HA films on the substrate were heat-treated (400 ~ 900 °C) and their physical characteristics were investigated by Scanning Electronic Microscopy (SEM), X-ray Diffractometer (XRD), and X-ray Photoelectronic Spectroscopy (XPS). As-deposited HA films were consisted of HA particles which were uniformly distributed on the Ti substrate, showing a porous structure. By heat treatment, HA particles were agglomerated each other and melted to form a highly dense and homogeneous coating layer consisted of equiaxed nano-scaled grains. HA coatings on the porous-surfaced Ti compact consisted of highly crystalline apatite phase with the Ca/P ratio of about 1.67 were successfully obtained by using ESD.
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