加压方式对铝夹层AZ31B/Cu扩散钎焊接头组织和性能的影响

Effects of loading methods on microstructure and properties of diffusion welded joint of AZ31B/Cu with Al interlayer

为了实现镁铜之间的可靠连接,以铝为中间夹层,在加热温度为500℃、保温时间20 min条件下,分别采用不同的加压方式对AZ31B和Cu进行扩散焊接。利用SEM、EDS、XRD、显微硬度计、万能拉伸实验机分析焊接接头的显微组织和性能。结果表明:扩散钎焊接头包括钎缝区和镁基体渗透区两部分。间歇性梯度加压时,钎缝区厚度最大,达到0.56 mm,显微组织依次为铜侧条状A_(l2)CuMg化合物、均匀连续的层片状(α-Mg+Al_(12)Mg_(17))_(共晶)和(Mg_2Cu+α-Mg)_(共晶)、镁侧Mg_2Cu化合物,接头平均剪切强度达到71.67 MPa;梯度加压时的钎缝区厚度减小,显微组织中的条状化合物增多,共晶组织为菊花状(α-Mg+Al12Mg17);恒压时的钎缝区厚度最小,约为0.3 mm,组织以粗大的Al-Cu二元化合物和Al-Cu-Mg三元化合物为主,接头硬度最大,平均剪切强度降低至60.33 MPa。加压方式对钎缝区的厚度、共晶组织分布形态和接头的力学性能均有较大影响,间歇性梯度加压下接头的硬度最低,剪切强度最高。

In order to achieve realiable connection between magnesium, a experiment of diffusion brazing of AZ31 B/Cu with Al interlayer under different loading methods was carried out at 500 ℃ for 20 min. The microstructure and mechanical properties of the welded joint were analyzed by SEM, EDS analysis, micro-hardness test and tensile testing machine. The results show that the diffusion welded joints consist of brazing seam zone and the grain boundary penetration zone of magnesium substrate. At intermittent gradient pressure, the thickness of the brazing seam zone is 0. 56 mm, and the microstructure of brazing seam zone is composed of a small amount of fine strips Al2CuMg compounds and tiny homogeneous lamellar eutectic structure that concluded （α-Mg ＋ Al12Mg17 ） eutectic structure and （Mg2Cu ＋α-Mg） eutectic structure, the highest shear strength of the welded joint can reach 71.67 MPa. Under gradient pressure, the thickness of brazing seam zone reduces, and the content of fine strips compounds increases, eutectic structure is （ α-Mg ＋ Al12 Mg17 ） that presents chrysanthemum shape. When using constant pressure, the thickness of brazing seam zone is only 0. 3 ram, the microstructure is mainly dominated by massive AI-Cu binary compound and Al-Cu-Mg ternary compound, so the welded joint achieves biggest hardness, however the shear strength reduces to 60.33 MPa. The pressure mode has great influence on the thickness of brazing seam zone, the distribution of the euteetie structure and the mechanical performance of the joint, and the maximum shear strength and the minimum hardness appear at intermittent gradient compression.