MECHANICAL PROPERTIES OF Si_3N_4/METAL DIFFUSION WELDING TIP

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The mechanical properties of Si 3N 4/metal diffusion welding tip produced by thermal vacuum pressure diffusion welding with pure Al as transition layer were studied. The results show that when temperature, pressure, holding time and cooling rate of diffusion welding are 600 ℃, 80 MPa, 30 min and 2 ℃/min respectively, the maximum of the shear rupture strength of the tip is 112.6 MPa. Fracture takes place very easily 1 mm along the Si 3N 4 side of the welding seam. The thermal residual stress comes from the thermal expansion difference between Si 3N 4 and metal. Metallurgical bond forms between Si 3N 4 and metal by interfacial reaction between Al transition layer and Si 3N 4, metal respectively.