Diffusion Bonding in Superplastic Super Alpha-2
Superplasticity
The alloy Super Alpha-2,based on atomic% composition Ti-25Al-10Nb-3V-1Mo, manufactured by Timet, was obtained in the form of rolled sheet of 3mm thickness, a grain size of 3 µm. Studies of microduplex Super Alpha-2 sheet have shown that the material has a considerable potential for superplastic deformation at temperatures in the range 940-980°C - Stress Strain Rate Data - but this drops off at 1000,1020°C. Specimens were pulled to failure at a constant velocity equivalent to an initial strain rate of 10%/min (1.66x10-3/s). At 940°C, 960°C and 980°C, tensile elongations to failure were ~ 840%, 1350% and 960%, but only 390% and 230% at 1000 and 1020°C (due to excessive grain growth in the higher volume fractions of b-phase).
Fig. 2 Samples deformed to failure at 10%/min (constant velocity).
Diffusion Bonding
Sound bonds were produced using isostatic pressure for two different surface finishes; P60 (Ra=0.65 µm and l=15.0µm) and P1200 (Ra=0.2 µm and l=10.0 µm), at temperatures of 960°C and 980°C under conditions which were fully consistent with the predictions of the computer model described in the paper and within the limits of reliability of the materials property data available for Super Alpha-2.
Fig.3 Shows the go/no go areas for bonding the P1200 finish TIMET super alpha-2 within 1 hour
Fig.4 Shows the go/no go areas for bonding the P60 finish TIMET super alpha-2 within 2 hours
On the modelling of diffusion bonding in materials - Superplastic super alpha-2, John Pilling, Norman Ridley and Mohammed Islam, Materials Science and Engineering 205, (1996) 72-78.
Related Papers
Solid State Bonding in Superplastic Ti-6Al-4V, J. Pilling, D. W. Livesey, J. B. Hawkyard and N. Ridley, Metal Science 18 (1984) 117-122.
The Kinetics of Isostatic Diffusion Bonding in Superplastic Materials, J. Pilling, Materials Science and Engineering 100 (1988) 137-144.
Isostatic Diffusion Bonding of Superplastic Ti-6Al-4V, M. T. Salehi, J. Pilling, N. Ridley and D. L. Hamilton, Materials Science and Engineering A150 (1992) 1-6.
Superplastic Behaviour and Isostatic Diffusion Bonding of Titanium Auminide Alloy Super Alpha-2. N.Ridley, M.T.Salehi and J. Pilling, Proc. Conf Properties and Applications of Metallic and Ceramic Materials, Ed. M.H.Loretto and C.J.Beevers, Vol II, MCE Publications, Birmingham (1992) 1007- 1012.
Superplasticity and Diffusion Bonding of microsduplex super alpha 2, N.Ridley, M.F.Islam and J.Pilling, in Structural Intermetallics, ed. R.Darolia, J,Lewandowski and C.T.Liu, publ. TMS, Warrendale, PA, (1993) 63-68.
Isostatic Diffusion Bonding of Ti-6Al-4V and Super a2 Intermetallic alloy. N.Ridley, M.F.Islam and J.Pilling, in Proc. 7th Int. Titanium Conf., San Diego July 1992. Ed. F.H.Froes and I Caplan, publ TMS, Warrendale Pa. (1993) 1625-1632.
Isostatic Diffusion Bonding of Microduplex Stainless Steels N. Ridley, M. T. Salehi and J. Pilling, Materials Science and Technology, 8 (1992) 791 - 795.
Solid State Bonding in Superplastic Al-7475, J. Pilling and N. Ridley, Materials Science and Technology 3 (1987) 353-359.
Go to Superplasticity Home Page or return to index.