Microstructural development and mechanical properties of wide gap and conventional transient liquid phase bonds between Ti-48Al-2Cr-2Nb substrates

Abstract

An investigation of microstructural development and structure -property relationships in a transient liquid phase bonded Ti -48Al -2Cr -2Nb (at.-%) alloy (abbreviated here to 48 -2 -2) is presented. The use of copper containing interlayers is examined. The primary focus of the paper is wide gap composite interlayers consisting of copper as a liquid former, plus a TiAl alloy (binary TiAl or 48 -2 -2) as a non-melting diffusional sink. However, bonds employing commercial purity copper foils of thickness 5 and 50 mm are also examined. Bond microstructures are characterised by edge-on transmission electron microscopy, plus scanning electron microscopy and light microscopy. Mechanical properties are determined through the use of room temperature shear and bend testing, supplemented by both room and elevated temperature tensile testing. The formation of copper containing intermetallics at the bond line and the formation of c-TiAl by both epitaxial growth and non-epitaxial precipitation are discussed. The microstructure of the bonds is compared with that of the parent 48 -2 -2 material. The influence of both the main bond line microstructure and the fillets on the mechanical properties of transient liquid phase bonded 48 -2 -2 is determined.MST/4938

Modelling the influences of solid-state interdiffusion and dissolution on transient liquid phase sintering kinetics in a binary isomorphous system

“…[11]. The corresponding change in particle size from a Bss to a Bo at T P can be obtained by a Bo ¼ a Bss ½ð1 ÿ W Ao Þ=ð1 ÿ W Ass Þ 1=3 [13] Using these new initial conditions for cases in which T P . T A , the stepwise solution of Figure 7 can then be used to calculate the rate of isothermal solidification for a case involving dissolution.…”

“…This ''variable melting point'' (VMP) behavior is being used in the development of TLPS solder and brazing compounds [4][5][6][7][8][9][10] and in wide-gap transient liquid phase bonding (TLPB). [12,13] The primary disadvantage of TLPS is that it is relatively sensitive to processing conditions. [14,15] This is primarily attributable to the variability in the volume of liquid generated during sintering.…”

Microstructure and mechanical strength of transient liquid phase bonded Ti3SiC2 joints using Al interlayer

“…The joint region is held at this bonding temperature until the joint solidifies isothermally due to interdiffusion. The TLP bonding technique has been used successfully in joining structural metals, 17,18 intermetallics, 19,20 oxide and non-oxide ceramics. [21][22][23][24] In this paper, joining of Ti 3 SiC 2 ceramic via Al interlayer was conducted using TLP bonding method.…”

Transient-liquid-phase and liquid-film-assisted joining of ceramics

“…Transient-Liquid-Phase (TLP) Joining TLP joining has been applied to a range of structural metals [17][18][19][20][21][22], notably nickel-base superalloys, and more recently the method has been extended to intermetallics [23][24][25]. Reviews of this process are available in the literature [21,22].…”