Contact-reactive brazing mechanism of Al_0.3CoCrFeNi high-entropy alloys using a niobium interlayer

The contact-reactive brazing of Al_0.3CoCrFeNi high-entropy alloys with a Nb interlayer was researched. The effects of Nb thickness and brazing temperature on the interfacial microstructure and mechanical properties of Al_0.3CoCrFeNi joints were investigated. The results show that with Nb thickness increasing from 10 to 100 μm, the average width of Al_0.3CoCrFeNi joints is increased from 127 to 492 μm and the erosion volume of Al_0.3CoCrFeNi base metals (BMs) by face-centered cubic-Nb eutectic liquid is enlarged accordingly. With increasing brazing temperature from 1280 to 1360 °C, the intergranular penetration of eutectic liquid into Al_0.3CoCrFeNi BMs becomes more severe and lamellar Laves phase is broken-up and spherized. The shear strength of joint is increased gradually from 374 to 486 MPa and then decreased to 475 MPa. The maximum shear strength value of 486 MPa is obtained when brazing at 1340 °C for 10 min, reaching about 78% of the shear strength of Al_0.3CoCrFeNi BMs. Besides, the brazing mechanism was analyzed in details.