Research On Transient Supercooled Liquid Phase Bonding With Amorphous Alloy Interlayer

Diffusion bonding technology is a sophisticated method of connection, with higher strength, less deformation, could welding dissimilar materials, such as ceramics and metals, iron and copper, is hot materials science research. This paper presents a new method of diffusion welding--transient subcooled liquid phase diffusion bonding. This method takes bulk amorphous alloy as middle tier, uses its superplasticity in supercooled liquid region to connect materials under, then raises temperature to achieve metallurgical bonding.In this paper, we use Cr18Mn18N nitrogen steel and TiAl-Ni(GH4049) as research subjects, analyses the morphology、composition and mechanical properties of the bonding joints by a variety of analytical methods, such as XRD、EDS、DSC、SEM、tensile strength, we can get these conclusions:1) We propose a new method-transient subcooled liquid phase diffusion bonding, and discuss the principles and characteristics, then compare with other welding methods, analyse the welding process and parameters. The experimental results show that this new method can implemente effectively connecting of high nitrogen steel and TiAl-Ni dissimilar metal under the phase transition temperature.2) We establish the Pilling model to simulate transient subcooled liquid phase diffusion bonding of amorphous alloy experimental theories, mainly divide into two stage:plastic deformation and shrinkage phase, the shrinkage phase mainly rely on plastic deformation and Atomic diffusion to shrinkage. At the beginning of the second phase contact area mainly through plastic deformation to increase, at last Atomic diffusion occupies a major role.And we build formulas to calculate relationship of the holding time、pressure and temperature:we need 3.86ks to take high quality connection under 5MPa/773～1113K conditions for TiAl-Ni with Zr-based amorphous alloys3) Paper use mechanical alloy method to prepare bulk amorphous alloy, through DSC to analyse supercooled liquid region:Fe60Cr15Mn10N15 bulk amorphous alloy has glass transition temperature Tg=437℃, Crystal temperature Tx=519℃, supercooled liquid phase district width Δ Tx=82℃.Then we use Fe60Cr15Mn10N15 amorphous alloy as a middle layer to bonding high nitrogen steel. With the improvement of temperature and holding time, interface metallurgical bonds better and mechanical properties improve. When spreading temperature is 950℃, holding time is 90min, pressure is 5MPa, obtained high mechanical properties joint and the tensile strength reached 432MPa.4) Paper use Zr50Al15Ni10Cu25 amorphous alloy as middle-tier, through transient subcooled liquid phase diffusion bonding mothod to connect TiAl-Ni dissimilar materials, the bonding joint has good interface without holes、cracks and other defects, the mechanical properties improved when the connection temperature rised and diffsion time rised. When the proliferation temperature is 880 ℃, holding time is 90min, pressure is 5MPa, we obtained high mechanical properties joint and the tensile strength reached 412MPa.