3D printing creates high strength and high plasticity titanium alloy

November 03, 2021

Liu Jinchuan, a foreign academician of the Chinese Academy of Engineering and professor of The City University of Hong Kong, and his team creatively proposed a 3D printing strategy to develop a titanium alloy with high strength and high plasticity by adjusting the mixing degree of different powders in the molten pool, according to the Chinese Academy of Sciences. The study was published in Science.

In general, the inhomogeneity of composition in metallic materials is often seen as a major defect, and one that researchers strive to avoid. On the one hand, people are not aware of the positive effects of component inhomogeneity. On the other hand, the traditional methods usually can not effectively control the composition fluctuation within the material.

Using earlier computational simulations, the researchers found that a certain degree of composition inhomogeneity contributes to the creation of unique heterogeneous microstructures that improve the mechanical properties of materials. Therefore, they believe that the material composition inhomogeneity can be actively exploited and become an effective alloy design method.

To regulate the composition fluctuations inside the alloy, the researchers used 3D printing technology. This is a pure direct molding technique, but few people have thought of applying it to alloy design. In the 3D printing process, metal powders melt and solidify rapidly. Due to the super fast cooling rate, the compositional gradient generated in the molten pool is successfully preserved.

Based on this new idea, the researchers tried to mix two common alloy powders, including stainless steel powder, in the 3D printing process. Through carefully selected powder types and special printing parameters, they achieved a controllable composition gradient at the micron level.

This micron-scale composition gradient not only brings phase stability and spatial modulation of microstructure, but also improves the mechanical properties of titanium alloys, making it one of the smallest grain sizes that can be achieved in titanium alloys for 3D printing, Liu said.

Liu also said it was a metastable titanium alloy with a lava-like microstructure. "This unique microstructure gives the alloy excellent mechanical properties and fine grain structure, allowing the alloy to have extremely high uniform deformation ability while maintaining high strength and low density of titanium alloy."

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