Characterization of Diffusion Bonding of Stainless Steel AISI 316 and Pure Titanium sheets Using Copper Interlayer

Abstract

The present work is focused on diffusion bonding between pure titanium and austenitic stainless steel( AISI 316) using interlayer of pure copper foil in vacuum atmosphere of ( 1.5 x10-5 mbr.) at different temperatures (850,900,950 and 990) Co for diffusion times of (20,30,40,50 and 60 min.) under different pressures (1.5,2,3 and 4) Mpa. Many tests and inspections: tensile shear and microhardness tests, also SEM EDS and X-ray diffraction techniques were utilized to characterize the bonded joints. Tensile shear test results showed that the maximum shear strength of diffusion bonded joints was (96.34) MPa at 950°C, pressure 3Mpa and 50 min. with an efficiency of joint (75%) and maximum diffusion depth of (88 µm) The maximum micro hardness of (338.6 Hv )was obtained in the copper interlayer metal compared with the base metals(stainless steel and titanium) due to formations of brittle intermetallic compounds. The EDS and XRD analysis results confirmed the formation of different intermetallic compounds [FeTi, ( Cu + Ti37Cu63Fex ), TiCu, Ti2Cu, Ti3Cu4,]. The surface fracture topography showed that fracture is located at the bright brittle intermetallic compound phase(Ti3Cu4) which was 85% of the fractured area and 15% was at the (Ti2Cu)dark region.