Diffusion Bonding of γ(TiAl) Alloys: Influence of Composition, Microstructure, and Mechanical Properties

The metallurgical factors governing the solid-state diffusion bonding of TiAl alloys have been characterized using scanning electron microscopy together with energy-dispersive X-ray (EDX) spectroscopy and electron backscattered diffraction (EBSD) analysis. The investigations were performed on TiAl alloys with various compositions and microstructures, which had been thoroughly mechanically characterized. The process zone of the bonds typically consists of a fine-grained layer of α2(Ti3Al) phase at the former contact plane, followed by relatively large, defect-free γ(TiAl) grains and a region of deformed parent material. The evolution of the process zone involves phase transformation and recrystallization processes, which are triggered by asperity deformation at the contact plane and the unavoidable contamination of the diffusion couple with oxygen and nitrogen. The structural details depend on the alloy composition and the bonding conditions. In the final section of the article, technical aspects, including the tensile strength of diffusion bonds, will be discussed.

[1]  U. Kattner,et al.  Thermodynamic Assessment and Calculation of the Ti-Al System , 1992, Metallurgical and Materials Transactions A.

[2]  R. Hayes,et al.  Tension creep of wrought single phase γ TiAl , 1995 .

[3]  M. Yoo,et al.  Physical constants, deformation twinning, and microcracking of titanium aluminides , 1998 .

[4]  A. Elschner,et al.  The oxidation behaviour of niobium containing γ-TiAl based intermetallics in air and argon/oxygen , 1995 .

[5]  R. Wagner,et al.  Novel design concepts for gamma-base titanium aluminide alloys , 2000 .

[6]  Young-Won Kim,et al.  Gamma titanium aluminides , 1995 .

[7]  F. J. Humphreys,et al.  Recrystallization and Related Annealing Phenomena , 1995 .

[8]  A. Evans,et al.  The Thermally Activated Deformation of Crystalline Materials , 1969 .

[9]  N. Hansen,et al.  Subgrain coalescence and the nucleation of recrystallization at grain boundaries in aluminium , 1979, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[10]  K. Ishida,et al.  Phase equilibria among α (hcp), β (bcc) and γ (L10) phases in Ti–Al base ternary alloys , 2000 .

[11]  H. Clemens,et al.  Diffusion bonding of intermetallic Ti-47Al-2Cr-0.2Si sheet material and mechanical properties of joints at room temperature and elevated temperatures , 1997 .

[12]  H. Inui,et al.  Low-temperature deformation of single crystals of a DO19 compound with an off-stoichiometric composition (Ti-36·5 at.% Al) , 1994 .

[13]  T. Nakano,et al.  The effect of orientation and lamellar structure on the plastic behavior of TiAl crystals , 1992 .

[14]  H. Clemens,et al.  Diffusion bonding of ?-TiAl sheets , 1999 .

[15]  R. Schafrik.  Dynamic elastic moduli of the titanium aluminides , 1977 .

[16]  Y. Mishin,et al.  Diffusion in the Ti–Al system , 2000 .

[17]  R. Wagner,et al.  The compression behaviour of niobium alloyed γ-titanium alumindies , 1998 .

[18]  M. Holmquist,et al.  Hot isostatic diffusion bonding of titanium alloy Ti-6Al-4V to gamma titanium aluminide IHI alloy 01A , 1998 .

[19]  H. Clemens,et al.  Compressive deformation of lamellar microstructures – a short review , 2007 .

[20]  F. Appel.  An electron microscope study of mechanical twinning and fracture in TiAl alloys , 2005 .

[21]  K. Shinozaki,et al.  Diffusion Bonding of Intermetallic Compound TiAl. , 1991 .

[22]  R. Hayes,et al.  A first report on the creep deformation and damage behavior of a fine grained fully transformed lamellar gamma TiAl alloy , 1994 .

[23]  M. Palm,et al.  Phase equilibria in the AlNbTi system at high temperatures , 1998 .

[24]  E. Wallach,et al.  Diffusion-bonding of TiAl , 1993 .

[25]  F. Appel.  Diffusion assisted dislocation climb in intermetallic gamma TiAl , 2001 .

[26]  H. Inui,et al.  Temperature dependence of yield stress, deformation mode and deformation structure in single crystals of TiAl (Ti−56 at.% Al) , 1997 .

[27]  P. Hazzledine.  Coherency and loss of coherency in lamellar TiAl , 1998 .

[28]  G. Schoeck.  The Activation Energy of Dislocation Movement , 1965, February 1.

[29]  Jens Lothe John Price Hirth,et al.  Theory of Dislocations , 1968 .

[30]  V. Paidar.  Channelling of Plastic Deformation by Interfaces in TiAl Intermetallics , 2002 .

[31]  M. Hosomi,et al.  Deformation of polysynthetically twinned crystals of TiAl with a nearly stoichiometric composition , 1990 .

[32]  A. Menand,et al.  Interstitial solubility in γ and α2 phases of TiAl-based alloys , 1996 .

[33]  F. Appel,et al.  Strain ageing in γ(TiAl)-based titanium aluminides due to antisite atoms , 2002 .

[34]  Annick Loiseau,et al.  Weak-beam observation of a dissociation transition in TiAl , 1988 .

[35]  L. Zhao,et al.  Creep properties of near γ-TiAl+W with a lamellar microstructure , 1994 .

[36]  L. Zhao,et al.  Current understanding of creep behaviour of near γ-titanium aluminides , 1995 .

[37]  R. Wagner,et al.  Thermally activated deformation mechanisms in micro-alloyed two-phase titanium amminide alloys , 1997 .

[38]  E. Nes,et al.  Subgrain growth during annealing of heavily deformed metals , 1989 .

[39]  M. Aindow,et al.  A high-resolution electron microscopy study of steps on lamellar γ-α2 interfaces in a low-misfit TiAl-based alloy , 1999 .

[40]  R. Wagner,et al.  Dislocation dynamics in carbon-doped titanium aluminide alloys , 1997 .

[41]  R. Wagner,et al.  Microstructure and deformation of two-phase γ-titanium aluminides , 1998 .