CA-MIG热源处理下钛/铝异质合金界面显微组织特性

采用Al-Si5焊丝进行TC4钛/1060铝异质结构的CA-MIG连接,采用SEM、EDS等显微分析手段对不同热输入下所获接头的Ti/Al界面显微组织特点、界面附近元素分布进行分析,研究Ti/Al界面特性随热源热输入变化的演变规律。结果表明,CA-MIG热源热输入对Ti/Al界面显微组织具有显著影响。当热源热输入低于0.91 kJ/cm时,钛与铝基焊缝之间仅形成了一层界面反应层。当热源热输入处于0.91~1.55 kJ/cm时,钛与焊缝之间形成了两种Ti/Al界面,一种为单层结构的齿状Ti(Al,Si)₃;另一种由α-Ti(Al,Si)均匀层、Ti₅Si₃纳米颗粒+Ti(Al,Si)₃混合层、齿状Ti(Al,Si)₃层3层结构组成。当热源热输入超过1.55 kJ/cm后,除了上述两种Ti/Al界面外,局部微区钛合金发生熔化,与铝基焊缝之间形成了成分复杂的熔合区,熔合区内存在大量的裂纹缺陷。

Microstructure characteristics of Ti/Al interface using CA-MIG heating processing

The aluminum-based Al-Si5 wire was applied in Ti-TC4/1060Al dissimilar thermal joining. The analysis on microstructures and elements distributions of Ti/Al interfaces under different CA-MIG heat inputs was carried out using SEM and EDS to understand the evolvement law of Ti/Al interfacial features with the increasing of CA-MIG heat input. It was found that the Ti/Al interfacial microstructure changed obviously with the change of CA-MIG heat input. A single dentate Ti(Al,Si)₃ interfacial reaction layer was observed between titanium and aluminum base welds with the heat input lower than 0.91 kJ/cm. Two different Ti/Al interfaces were observed between titanium and the weld in a single sample with the heat input in the range of 0.91-1.55 kJ/cm. Except for the interface with a single dentate Ti(Al,Si)₃ layer, a multilayered structure including a thin uniform α-Ti(Al,Si) layer, a Ti(Al,Si)₃ layer dispersed with Ti₅Si₃ nanoparticals and a dentate Ti(Al,Si)₃ layer was observed. Once the heat input surpassed 1.55 kJ/cm, except the above two Ti/Al interfaces, the titanium was partially melted in certain part, and complex fusion zones were formed between titanium and weld metal, and a A large amount of micro cracks were observed in the fusion zone.