2219/5A06异种铝合金焊接裂纹萌生机理（英文）

Mechanism of Crack Initiation of Dissimilar Joints between 2219 Aluminum Alloy and 5A06 Aluminum Alloy

采用OM、SEM、EDS及显微硬度实验,对不同焊丝获得的2219/5A06异种接头的软化微观形貌与裂纹萌生机理进行分析。结果表明:5A06侧HAZ晶粒长大不明显未发生软化现象,2219侧HAZ发生较明显的软化;通过EDS线扫描分析可知,2325-5A06、5B06-2219的熔合线附近发生了明显的Mg、Cu扩散行为,2325-2219、5B06-5A06的熔合线附近元素扩散行为不明显;与5B06焊缝相比,2325焊缝裂纹倾向更大,因为5B06焊缝不存在明最显的低熔点共晶相,而2325焊缝存在大量的低熔点共晶Al_2CuMg和CuAl_2,Al_2CuMg共晶的存在是致使其产生裂纹的根本原因。硬度测试结果表明:2325焊缝的硬度(HV)约为1000 MPa,5B06焊缝的硬度(HV)约为800 MPa。

The crack initiation mechanism of dissimilar aluminum alloy welded joints was studied.The base metals were 2219aluminum alloy and 5A06 aluminum alloy,while the filler wires were 2325 and 5B06.The microstructure was analyzed by optical microscope(OM),scanning electron micrograph(SEM)and energy dispersive spectroscopy(EDS).The results show that the weld hardness(HV)obtained by the 2325 is about 1000 MPa and that by 5B06 is about 800 MPa.Compared with that of the weld obtained by 2219 and 2325,the grain growth of HAZ(heat affected zone)of the weld obtained by 5A06 and 2325is so weak that the joint softening phenomenon doesn’t exist.The diffusion and segregation of Mg element and Cu element can be obviously observed in the welded fusion zone(FZ)obtained by 2325 and 5A06,and that by 5B06 and 2219.Compared with the welded joint obtained by 5B06 filler wire,the great cracking tendency can be found in dissimilar welded joint obtained by2325 filler wire,because there is no obvious low melting eutectics in welded joint by 5B06 filler wire.Many low melting eutectics(Al2CuMg and CuAl2)are present in the welded joint by 2325 filler wire,and the Al2CuMg eutectics are fundamental cause for the crack initiation.