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Researchers: 
Dr. Ibrahim Karaman and Dr. Raymundo Arroyave

Background: 
Additive manufacturing (AM), or 3D Printing, has achieved significant advancements since its inception in 1980s, and led to a revolution in the manufacture of parts in traditional 3D space. Now it is witnessing further evolution through the introduction of 4D printing. The fourth “D” refers to the dimension of time, where the 3D printed part undergoes a controlled change in shape or properties in response to an external stimulus over time such as heat, stress, light, and moisture, among others9-11. This approach is used most often in polymers, while 4-D printing of metallic materials is lagging behind. Now a few recent works, mostly from the PI’s group12-13, have begun to explore 4-D printing of active metallic systems, shape memory alloys (SMAs). In this project, we take advantage of the fact that the physical and functional responses of SMAs depend greatly on the processing schemes employed during AM (such as selection of energy source power and scan speed, layer density, and scan line spacing). By controlling the processing parameters, AM-fabricated SMAs can be tailored to achieve spatial and time-dependent functional responses through the control of the local composition and microstructure.

Research Plan: 
The REU students will participate in the various stages of the research, including systematic studies of the effects of laser power, scan speed, and scan line spacing on the local composition and microstructure of various nickel-titanium SMAs and new NiCoMnIn magnetic SMAs using two different AM techniques: laser powder bed fusion and direct laser energy deposition. The REU students will also be involved in conducting parametric post-AM heat treatment studies, determining magnetic and mechanical properties using various characterization instruments, determining local compositions using simple spectroscopy techniques, and identification of microstructures using optical and electron microscopy with the help of graduate students. Students will have the opportunity to conduct magneto-thermo-mechanical characterization of samples that another REU student fabricated to analyze the effect of AM parameters on the physical and mechanical properties under multiple fields (mechanical load, magnetic field, and temperature) using the state-of-the-art experimental systems available at Texas A&M.