Microstructural Development Due to Laser Treatment and Its Effect on Machinability of Ti6Al4V Alloy
- PDF / 10,950,170 Bytes
- 18 Pages / 593.972 x 792 pts Page_size
- 85 Downloads / 228 Views
ION
TITANIUM and its alloys have grown as technologically important materials because of their increasing range of applications in various sectors. Ti6Al4V is one of the popularly known a+b titanium alloys and is extensively used in biomedical and aerospace applications. These alloys exhibit poor machinability due to their high strength, low elastic modulus and low thermal conductivity. The bulk microstructure of the material
SAGAR V. TELRANDHE and BHAGYARAJ JAYABALAN are with the Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India and also with the National Centre for Aerospace Innovation and Research, Indian Institute of Technology Bombay, Mumbai 400076, India. CHRIST P. PAUL is with the Raja Ramanna Centre for Advanced Technology, Indore 452013, India. SUSHIL K. MISHRA is with the Department of Mechanical Engineering, Indian Institute of Technology Bombay. Contact e-mail: [email protected] Manscript submitted January 3, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
also significantly affects its machinability.[1] The desired microstructure for the required application may not always be favorable for machining. Therefore, the surface and sub-surface microstructure can be altered from its base microstructure to improve the machinability. To achieve an optimum modified microstructure at the surface and sub-surface, it is important to know the effect of the microstructure on machining. Studies were performed to assess the impact of microstructural features such as the phase fraction, crystallographic texture, grain size and morphology on machining of titanium alloys.[2,3] Ti6Al4V alloy can be heat treated to achieve the desired microstructure with enhanced mechanical properties. The literature suggests that the heat treatment significantly influences the machinability of Ti alloys.[4–9] Armendia et al.[4] reported that the tool life decreases considerably when machining b-annealed titanium alloys. According to the findings of Joshi et al.,[5] an increase in the b-fraction leads to an increment in the fracture along the shear bands. This leads to an increase in the segment strain and develops a higher variation in cutting force because of the increase
in the fracture toughness of the material.[6] The rapid cooling after heat treatment often leads to the formation of a martensite phase and also hardens the materials. The needle-like structure developed during quenching makes the material harder than the equiaxed structure.[7] The surface modification through laser heat treatment also contributes to an increase in hardness due to the formation of a martensitic microstructure.[8] The rise in the hardness could result in an increase of the average cutting forces during machining.[9] Several other factors affect the machinability of the Ti alloys. For instance, residual stress resulting from a prior machining process can change the machinability of the material.[6] Processes such as extrusion and prior machining impose compressive stress, and while machining, the shearing
Data Loading...
