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3D printing leads to the formation of an alloy with shape memory with increased super-elasticity – ScienceDaily

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The technique of 3D printing using laser powder melting offers potential in the manufacturing industry, especially in the production of nickel-titanium alloys with memory shape with complex geometry. Although this manufacturing technology is attractive for use in the biomedical and aerospace fields, it has rarely demonstrated the super-elasticity required for specific applications using shape-memory nickel-titanium alloys. Defects and changes made to the material during the 3D printing process prevented the appearance of super-elasticity in the 3D-printed nickel-titanium.

Researchers at the University of Texas at A&M recently demonstrated excellent tensile super-elasticity by producing a memory memory alloy by laser powder melting, almost doubling the maximum super-elasticity reported in the 3D printing literature.

Nickel-titanium alloys with shape memory have different applications due to their ability to return to their original shape when heated or relieved applied stress. Thus, they can be used in the biomedical and aerospace fields for stents, implants, surgical devices and aircraft wings. However, the development and proper fabrication of these materials requires extensive research to characterize the functional properties and study the microstructure.

“Shape memory alloys are intelligent materials that can memorize their shape at high temperatures,” said Dr. Lei Xue, a former doctoral student in the Department of Materials Science and Technology and the first author of the publication. “Although they can be used in a variety of ways, making memory alloys into complex shapes requires fine-tuning to ensure that the material exhibits the desired properties.”

Laser powder fusion is an additive manufacturing technology that represents a method of efficient and effective production of nickel-titanium alloys with shape memory, which offers a way to quickly fabricate or prototype. This technique, similar to polymer 3D printing, uses a laser to melt metal or alloy powders layer by layer. The layer-by-layer process is advantageous because it can create parts with complex geometry that would be impossible in traditional manufacturing.

“Using a 3D printer, we scatter the alloy powder on a substrate and then use a laser to melt the powder, forming one complete layer,” Xue said. “We repeat this layering, scanning the same or different samples until the desired structure is formed.”

Unfortunately, most nickel-titanium materials do not withstand the current process of melting the laser powder layer, which often leads to printing defects such as porosity, deformation or delamination caused by a large thermal gradient and brittleness from oxidation. In addition, the laser can change the composition of the material by evaporation during printing.

To combat this problem, the researchers used the optimization framework they created in a previous study that can determine the optimal process parameters to achieve a flawless structure and specific material properties.

Using this structure, as well as changes in the composition and refined process parameters, the researchers produced nickel-titanium parts that exhibited constant tensile elasticity at room temperature of 6% in the printed state (without heat treatment after fabrication). This level of super-elasticity is almost twice the level previously seen in the literature for 3D printing.

The ability to produce alloys with shape memory using 3D printing with increased super-elasticity means that the materials are more able to withstand the applied deformation. The use of 3D printing to develop these wonderful materials will reduce the cost and time of the production process.

In the future, researchers hope that their discoveries will lead to the wider use of printed nickel-titanium alloys with shape memory in biomedical and aerospace applications.

“This study can serve as a guide on how to print nickel-titanium alloys with shape memory with the desired mechanical and functional characteristics,” Xue said. “If we can adjust the crystallographic texture and microstructure, there will be many more applications in which these alloys with shape memory can be used.”

This study was funded by the U.S. Army Research Laboratory, a grant from the National Research Priorities Program, the National Research Foundation of Qatar, and a grant from the U.S. National Science Foundation.

Among other participants of the publication – the head of the Department of Materials Science and Technology, Dr. Ibrahim Karaman; professors of materials science and technology, Dr. Kadri Kan Atli and Dr. Raimundo Arroyo; former student of materials science and engineering, Dr. Abkhinov Shrivastova and current student Nathan Height; Wm Michael Barnes ’64, Professor, Department of Industrial Systems and Engineering, Dr. Alaa Elvani; student of industrial systems and engineering Chen Zhang; and U.S. Army Research Laboratory researchers Dr. Usher S. Leff, Dr. Adam A. Wilson, and Dr. Darin J. Sharar.

Source of history:

Materials provided University of Texas A&M. The original was written by Michelle Revels. Note: Content can be edited by style and length.

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