磁场频率对AZ91合金焊接接头直接时效的组织和性能的影响

Effect of magnetic frequency on microstructure and properties of AZ91 magnesium alloy welded joint after direct aging

对AZ91镁合金板进行钨极氩弧焊(TIG),并在焊接过程中施加了不同频率纵向交流磁场,焊后对焊接接头直接进行了时效处理,并和焊后固溶时效处理方式进行了对比。结果表明,随着磁场频率的增加,AZ91镁合金焊接接头经直接时效处理后,焊缝中的β-Mg_(17)Al_(12)相由连续状析出形态变成非连续状析出,其组织形态与焊后固溶时效相比,β-Mg_(17)Al_(12)相较粗大且数量减少;并随着磁场频率增加,直接时效后的焊接接头析出β-Mg_(17)Al_(12)相先变得均匀细小后又变得粗大,其接头的力学性能先变好后变差,而焊接接头的抗电化学腐蚀性先减小后增大。与固溶时效相比,直接时效后接头的力学性能较差,但耐腐蚀性能更好。

Different frequency AC longitudinal magnetic field was employed in welding AZ91 magnesium alloy plate with TIG, and the microstructure and properties of the welded joint were analyzed after direct aging treatment, and compared with that after solid solution and aging treatment. The results show that with the increase of magnetic frequency, the β-Al12Mg17 phase in the welded joint separated out in continuous precipitation then become discontinuous precipitation during direct aging, and compared with the solid solutioned and aged one, the grain size of β-Al12Mg17 phase increases and the number of 13-Al12Mg17 phase decreases. With the increase of magnetic frequency, the grain size of β-Al12 Mg17 phase in the welded joints after direct aging decreases first and then increases, and the micro-hardness, tensile strength and plasticity of the welded joints first increase and then decrease, the corrosion resistance first decreases and then increases. Compared with the solid solution and aging, the mechanical properties of the joints after direct aging are decreased, but the corrosion resistance is more preferable.