Browsing by Subject "Titanium"

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    Deformation and recrystallisation of powder processed commercially pure titanium
    (Maney Publishing, 2012) Knutsen, R D; Petersen, S
    The hot deformation behaviour of powder sintered commercially pure titanium has been compared to the behaviour of equivalent wrought metal under identical test conditions. Deformation was performed by uniaxial compression under vacuum at 900°C at nominal strains of 0·2, 0·4 and 0·65. The deformed microstructures were rapidly cooled to room temperature and subsequently annealed at 870°C. Lower grain growth, higher flow stress and greater incidence of recrystallisation were observed for the sintered metal. This behaviour is mainly attributed to the higher interstitial levels in the sintered metal which results in a lowering of the effective deformation temperature.
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    Open Access
    Extraction of flank wear growth models that correlates cutting edge integrity of ball nose end mills while machining titanium
    (Springer Verlag (Germany), 2011) Ramesh, K; Siong, Lim Beng
    The application of titanium alloys are increasingly seen at aerospace, marine, bio-medical and precision engineering due to its high strength to weight ratio and high temperature properties. However, while machining the titanium alloys using solid carbide tools, even with jet infusion of coolant lower tool life was vividly seen. The high temperatures generated at the tool–work interface causes adhesion of work-material on the cutting edges; hence, shorter tool life was reported. To reduce the high tool–work interface temperature positive rake angle, higher primary relief and higher secondary relief were configured on the ball nose end-mill cutting edges. However, after an initial working period, the growth of flank wear facilitates higher cutting forces followed by work-material adhesion on the cutting edges. Therefore, it is important to blend the strength, sharpness and surface integrity on the cutting edges so that the ball nose end mill would demonstrate an extended tool-life. Presently, validation of tool geometry is very tedious as it requires extensive machining experiments. This paper illustrates a new feature-based ball-noseend-mill–work interface model with correlations to the material removal mechanisms by which the tool geometry optimization becomes easier. The data are further deployed to develop a multi-sensory feature extraction/correlation model to predict the performance using wavelet analysis and Wagner Ville distribution. Conclusively, this method enables to evaluate the different ball nose end mill geometry and reduces the product development cycle time.
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    Open Access
    Microstructure evolution in Ti-6A1-4V alloy during hydrogen dosing at elevated temperature
    (2011) Matthews, L A; Knutsen, R D
    Synopsis: The embrittlement of the Ti-6Al-4V alloy by hydrogen dosing at elevated temperature has been investigated. Metal coupons were subjected to isothermal treatments in a partial hydrogen atmosphere in the temperature range from 650ºC–950ºC and the degree of embrittlement after treatment was determined by dropweight impact testing. Embrittlement was found to be inversely related to reaction temperature as a result of the combined effects of greater hydrogen absorption and titanium hydride precipitation at the lower isothermal temperatures.
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    Open Access
    Microstructure evolution in Ti-6A1-4V alloy during hydrogen dosing at elevated temperature.
    (The Southern African Institute of Mining and Metallurgy, 2011) Matthews, L A; Knutsen, R D
    The embrittlement of the Ti-6Al-4V alloy by hydrogen dosing at elevated temperature has been investigated. Metal coupons were subjected to isothermal treatments in a partial hydrogen atmosphere in the temperature range from 650ºC-950ºC and the degree of embrittlement after treatment was determined by dropweight impact testing. Embrittlement was found to be inversely related to reaction temperature as a result of the combined effects of greater hydrogen absorption and titanium hydride precipitation at the lower isothermal temperatures.