Abstract
Laser penetration welding of magnesium alloys and pure titanium TA2 with unequal thickness was performed. Mg base metal with different Al content (AZ31B, AZ61A, AZ91D) was used to investigate the influence of Al element in microstructure and mechanical properties of Mg/Ti dissimilar joints. The results revealed that the change of Mg base metal did not influence the weld appearance of the joints. Three kinds of joint all presented the best mechanical property when the laser power was 3500 W. With the increase content of Al elements in Mg base metal, a reaction layer was observed which was identified as Ti3Al. The highest enrichment of Al element was obtained and its fraction reached 19.31 at% at the AZ91/TA2 interface. The chemical potential gradient of Al from AZ91 to Ti alloy was higher than that from the other two base metals based on thermodynamic calculation. The maximum fracture load reached 3597 N when AZ61 was employed as the base metal and the fracture position was the Ti base metal. AZ31/TA2 joints failed at the weld seam without necking due to the rapid propagation of cracks at the Mg/Ti interface. The AZ91/TA2 joint failed inside the Mg fusion zone with necking at the middle area of the weld, which resulted from the precipitation of brittle phases such as Mg–Al, Ti–Al phases in the fusion zone of Mg alloys.
Highlights
Nowadays, hybrid components of lightweight materials have been receiving extensive attention to achieve reduction of emissions and green development, which increases the demand for weight reduction in advanced manufacturing industry [1,2,3,4]
In response to the above problems, investigations have been carried out and the results suggested that metallurgical reaction could be achieved by adding alloying elements such as Al, Cu, Ni [12,13,14,15] which can react with or possess obvious solid solubility in Mg and Ti alloy
The purpose of this work was to establish the relationship between Al content and interfacial microstructure and thermodynamics, which lay a good foundation for the selection of the suitable base metal in the actual applications of Mg/Ti laser penetration welding with unequal thickness
Summary
Hybrid components of lightweight materials have been receiving extensive attention to achieve reduction of emissions and green development, which increases the demand for weight reduction in advanced manufacturing industry [1,2,3,4]. Magnesium (Mg), as one of the lightest engineering structural materials, has attracted wide attention due to its advantages of high strength, excellent formability and recyclability [5,6,7]. The application of Mg/Ti dissimilar metal in spacecraft, such as the tail cabin and engine bracket, is of particular interest since the hybrid component would further reduce overall weight. It is urgent to achieve reliable joining of Mg/Ti dissimilar metals [10,11].
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