October_2021_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 2 1 1 7 structures achieved by altering the pro- cessing parameters when fabricating MG composites, and hence tailoring the mechanical properties (Fig. 3e) [13] . LDED could be used to selectively clad different regions of parts with MG com- posites for surfaces that require higher wear resistance. LDED and TSAM could also be used to fabricate Fe-based MG systems that have attractive magnetic properties enabled by the amorphous structure. Despite advances in AM of MGs, the infusion into practical applications is an uphill battle. With rapidly advancing technology and business ecosystems around all aspects of AM, MGs have to compete directly with any other materi- al that can be 3D printed. Although MGs possess attractive mechanical proper- ties mentioned above, MGs have low plasticity and poor fatigue limit (ex- acerbated by porosity and other AM defects), are more expensive than con- ventional alloys, and have limited post processing options after printing, i.e., MGs could not be heat treated using hot isostatic pressing (HIP), a common- ly used technique for metal AM parts to relieve stresses and reduce porosity. Re- search efforts are underway in the com- munity to address these issues. As with conventional metal AM, industries with low part count and high-performance requirements such as space, aerospace, defense, and bio- medical devices, would be most suit- able for 3D printing of MGs. Further research is needed to develop alloys specifically for the AM process for both monolithic MGs and MG composites. The main challenge is to identify use cases that leverage the unique proper- ties of MGs and would outperform any other material in a one-to-one compar- ison. ~AM&P For more information: Punnathat Bor- deenithikasem, technologist, NASA Jet Propulsion Laboratory, Califor- nia Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, punna- that.bordeenithikasem@jpl.nasa.gov, scienceandtechnology. jpl.nasa.gov/ punnathat-bordeenithikasem. MGs. Another application that utiliz- es the MG’s elasticity is the expansion sleeve (Fig. 3d). The low stiffness and high elasticity allow the MG expansion sleeve to deformmore easily than a tra- ditional expansion sleeve, therefore of- fering better performance. Moreover, the expansion sleeve is designed such that the part is produced in one piece instead of multiple components that require subsequent assembly. The low stiffness, high elasticity of MGs in addi- tion to ease of design of AM have also inspired researchers to create orthope- dic implants with integrated porosity to facilitate bone growth [20] . LDED was used by researchers to demonstrate the vast range of micro- Fig. 3 — Images of functional components produced by additive manufacturing of metallic glass (MG). (a) MG gears fabricated using LPBF; (b) MG excavation tool bit designed for the excavation of extraterrestrial ice, printed with LPBF; (c) MG guitar bridge made using LPBF; (d) MG expansion sleeve produced with LPBF; (e) LDED system producing multilayer claddings of MG composites. Parts in images (a-d) were manufactured by ©Heraeus AMLOY. Image (e) is reproduced fromBordeenithikasem [13] . (a) (b) (c) (d) (e)