Ni/Al/Zn钎料层对AZ31/2024异种金属钎焊接头组织及性能的影响

Influence of Ni/Al/Zn multi-interlayers on microstructure and mechanical performance of AZ31/2024 dissimilar alloy brazing joints

采用Ni/Al/Zn复合钎料层对AZ31和2024合金实现了大气环境下、无钎剂的超声辅助瞬间液相扩散连接(U-TLP),研究采用Ni层、Ni/Zn层、Zn/Ni/Zn层及Al/Zn/Ni/Zn层时钎缝的微观组织及接头的力学性能,分析Ni箔、Al箔及Zn箔在U-TLP过程中的作用。结果表明:通过调整Ni/Al/Zn复合钎料层的组合形式,可以实现对钎缝微观组织的调控及力学性能的改善,采用Al/Zn/Ni/Zn复合钎料层时钎缝剪切强度达到最高值(95.3MPa)。Ni箔起到了"物理屏障"的作用,阻碍了Mg-Al金属间化合物(IMCs)的形成,但是由于铝合金一侧钎缝仅由Al_(3)Ni组成,接头剪切强度仅为21.2 MPa。Zn箔的添加促进铝母材溶解,增加Al_(3)Ni的数量并形成Zn-Al共晶,提高2024合金一侧的连接强度。Al箔的填入降低AZ31合金的溶蚀,并在镁合金侧形成MgZn_(2)、MgZn和含有Mg_(2)Ni、Al_(3)Ni、AlMg_(4)Zn_(11)和NiZn_(8)的混合IMCs层的组织,提高AZ31合金与Ni箔的连接。

By using the Ni/Al/Zn multi-interlayers,the high mechanical performance AZ31/2024 dissimilar alloys joints were made via ultrasonic-assisted transient liquid phase bonding(U-TLP)in air without any fluxes.The microstructure and mechanical performance of the joints were researched by using different set-up of multi-interlayers such as Ni,Ni/Zn,Zn/Ni/Zn and Al/Zn/Ni/Zn.The function of the Ni,Al and Zn foil acted during U-TLP was analyzed.The results show that the phases in the joints can be controlled and mechanical performance of the joints can be improved by adjusting the set-up of the multi-interlayers.The Al/Zn/Ni/Zn interlayers combination significantly increases the shear strength up to 95.3 MPa.The Ni foil,which acts as"physical barrier",prohibits the formation of Mg-Al intermetallic compounds,however,the shear strength is only 21.2 MPa,which is caused by that the joints at 2024 alloys side is only composed of Al_(3)Ni.The Zn foil accelerates the dissolution of Al atom and increases the amount of Al_(3)Ni.In addition,Zn-Al eutectics are formed and improve the joining between the Ni foil and 2024 alloys.The Al foil,whose aim is to slow down the dissolution of AZ31 alloys,helps to form a IMCs layer of mixture that is composed of Mg_(2)Ni,Al_(3)Ni,AlMg_(4)Zn_(11) and NiZn_(8) along the Ni foil and enhance the bonding between Ni foil and AZ31.