Effect of holding time on microstructure and properties of Ni-Sn composite brazed joint
For Ni/Ni-Sn/Ni composite brazing,it was proposed to use the thickness of the intermetallic compound(IMC)layer and the IMC content(volume fraction)in the weld to characterize the evolution process of the interface and internal microstructure of the weld during the brazing process,and the effect of holding time on the microstructure and properties of the Ni-Sn composite brazing joints was studied.The results show that only one intermetallic compound Ni3 Sn4 is formed in the joint,and mainly distributed at the interface of the base metal and around all Ni particles in the weld.The thickness of the IMC layer at the interface and the content of Ni3 Sn4 inside the brazing joint continuously increase with the increase of holding time.When the holding time is 240 min,the content of intermetallic compounds reaches 83.23%,forming a high-temperature resistant brazing joint composed of Ni3 Sn4 compounds and residual Ni particles.The shear strength of the joint shows a trend of first increasing and then slowly decreasing with the increase of holding time,and the fracture position shifts from the inside of the weld to the interface.When the holding time is 180 min,the shear strength of the joint reaches the maximum value of 28.47 MPa,and the fracture position occurs at the IMC layer of the interface.
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