Effect of Pre- and Post-weld Heat Treatments on Linear Friction Welded Ti-5553
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FOR next generation aircraft manufacture, implementation of high strength near-b titanium forgings in fuselage structures and landing gear assemblies is costeffective from the perspective of weight reduction and mechanical performance relative to, for instance, Ti6Al-4V, an a–b grade that has been the standard for the industry for many years.[1] A derivative of the Russian VT-22 alloy, Ti-5Al-5Mo-5V-3Cr, or Ti-5553, is a relatively new metastable b-titanium alloy. Ti-5553 was designed to have a robust forging process, i.e., lower sensitivity to variation in the forming parameters as compared to similar alloys,[2] such as Ti-10V-2Fe-3Al (Ti-10-2-3), and slower kinetics of a precipitation that
PRITI WANJARA, Team Leader, Senior Research Officer, and JAVAD GHOLIPOUR and XINJIN CAO, Senior Research Officers, are with the Structures, Materials and Manufacturing Laboratory, National Research Council Canada - Aerospace, 5145 Decelles Avenue, Montreal, QC H3T 2B2, Canada. Contact e-mail: priti.wanjara@ cnrc-nrc.gc.ca ELVI DALGAARD, formerly Ph.D. Student with the Structures, Materials and Manufacturing Laboratory, National Research Council Canada - Aerospace, and also with McGill University, 3610 University Street, Montreal, QC, H3A 0C5 Canada, is now Senior Analyst with Pratt and Whitney Canada, Longueuil, QC J4G 1A1, Canada. JONATHAN CUDDY, Senior Engineer, is with Standard Aero Limited, 33 Allen Dyne Road, Winnipeg, MB R3H 1A1, Canada. JOHN J. JONAS, Birks Professor of Metallurgy Emeritus, is with McGill University. Manuscript submitted March 5, 2014. Article published online July 29, 2014 5138—VOLUME 45A, OCTOBER 2014
allows air cooling after solution heat treatment.[3] As a result, manufacturability with Ti-5553 offers key advantages as compared to Ti-10-2-3, including a lower level of residual stress, reduced distortion, and deep hardenability over larger gage thicknesses.[4,5] Also, the wider manufacturing processing window of Ti-5553 allows selection of the thermomechanical conditions to tailor the microstructure and impart a wide variety of strength (1160 MPa up to over 1300 MPa), ductility (5 to 13 pct) and fracture toughness values[6,7] to meet a range of loading criteria. Hence, Ti-5553 is an attractive and practical choice for a range of aerospace applications. Overall metastable b-titanium alloys are characterized as having good weldability in the solution annealed condition. However, these alloys are not usually used in the as-welded condition due to the relative softness of the fully b grain structure even in a transformed martensitic condition.[8,9] Post-weld heat treatment of the transformed b grain structure can restore the a phase and increase the strength, but is concomitantly associated with a loss in ductility as compared to the as-welded condition (lower strength but higher ductility).[10,11] However, reported research on weldability and characterizing the post-weld heat treatment response of Ti-5553 remains limited.[12–16] Of the different advanced joining technologies, fusion welding using a lase
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