Research On Al Alloy And Joining Technology Of 304 Stainless Steeland SiC

Al alloy and joining technology of 304 stainless steel and SiC ceramic are studied in the paper. The results showed that 76.5Al-8.5Ti-5Cu-10 Si alloy was mainly composed of Al-Al2 Cu,Al-Si hypoeutectic low melting point microstructures(493-586℃)and AlTiSi high melting point intermetallic compound(840℃). Except the main solid pahse which can support the substrate, a small amount of liquid phase was found in Al alloy at 500-600℃.The contact angle determined by high temperature wetting experiments was about 50°. The wetting interface was smooth with no obvious defects. The metallurgical bonding of the interface was obtained due to the reaction of Al and Si in alloy and ceramic. The formation ofbrittlephase Al4C3 at the interface was surppressedwith the addition of 10 wt.%Si in the alloy.Using different joining technology,several times joining experiments were conducted to get the effect of different joining technology on the interfacial microstructure. The results indicated that the joining effect got better at 700 ℃for20min.Al3FeSi2, AlFe6 Si and Al3 SiCr intermetallic compounds formed in the interlayer and the reaction layer is about 100μm. The morphology of compounds changed andthe thickness of the reaction layerincreased with the increase of the temperature.The joining effect of the alloy-ceramic interface became worse gradually,even failed at 900℃. While the temperature decreased to 600℃, the reaction layer can not be formed which made the joining of alloy and stainless steel unrealiable.At the same time, the joining of the alloy and ceramic failed. The thickness of the reaction layer was affected directly by the holding time.With the increase of the holding time,the reactionlayer became thicker and the joining rate became lower.All the fracture occurred in the ceramic side of the alloy-ceramic interface in the shear tests.The shear strength value varied with joining effect. It reached the highest at700 ℃ for 20 min,which was 8MPa.The higher the temperature,the larger residual stress in the joints,the more brittle phase, the shear strength became smaller. The carrying capacityof the jointbecame poor with the increase of holding time.Three point bending test showed thatthree point bending strength value of laminar composite increased by 22% than the pure SiC.