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High-entropy alloys (HEAs) have received considerable interest over the past decade due to their intriguing structural, chemical, and physical properties. Additive manufacturing (AM), also termed three-dimensional (3D) printing, generates parts with complex geometries and internal features layer-upon-layer from a computer-aided design (CAD) 3D file. In recent years, explosive research on AM of HEAs has been inspired. This paper performs a comprehensive and critical review on the recent progress in additively manufactured (AM-ed) HEAs, with a special focus placed on the similarities and differences in the microstructure and mechanical behavior between the AM-ed HEAs and the as-cast or thermo-mechanically processed (TMP-ed) counterparts. To gain a better understanding of the formation of the AM microstructure, the working principles, rapid solidification effects, and subsequent thermal cycling effects of various metal AM techniques, e.g., directed energy deposition (DED), selective laser melting (SLM), and electron beam melting (EBM), are also introduced. In the end, several future research directions are suggested towards the design of advanced HEAs with the superior strength-ductility synergy via 3D printing.

Additive manufacturing (AM) is a novel materials processing approach to create parts with three-dimensional (3D) geometries...

Introducing ductile crystalline dendrites into glassy matrix to produce in situ bulk metallic glass composites (BMGCs) is an effective strategy to enhance the ductility of bulk metallic glasses (BMGs). However, the microstructural control of the crystalline dendrites is a challenge, and potent toughening of BMGs often requires a high volume fraction of the crystalline phase that impairs the strength and causes the strength-ductility tradeoff. Moreover, existing processing techniques of BMGCs mostly rely on liquid metal casting, which imposes an inherent size limitation due to the required rapid cooling for glass formation. Here we fabricate a multi-layered Zr-based BMGC with a well-controlled gradient in volume fraction of the crystalline dendrites via laser additive manufacturing (LAM) that allows site-specific control of the cooling rate and the resultant microstructure. The gradient BMGC shows an exceptional combination of yield strength (>1.3 GPa) and tensile ductility (~13%). Such enhanced strength-ductility synergy is attributed to the synergetic strengthening from the interaction of the adjacent layers and the asynchronous deformation mode associated with the heterogeneous microstructure. The gradient or functionally-graded structure design motif, enabled by the versatile LAM technology, opens a new window to the development of high-performance BMGCs on a large scale for structural applications.

This paper focuses on aircraft engine ignition system. Fault characteristic database containing fault waveforms of different fault types are obtained by many experiments. The outputting ignition waveform is made waveform image matching with all the typical fault waveforms of fault characteristic database by waveform image matching algorithm, then fault type of ignition system can be determined.