ABSTRACT Multifunctional materials (MFMs) exhibit multiple useful functions without complex joint mechanisms. Compared with soft MFMs, metallic MFMs are desired due to their superior mechanical properties and durability. However, the design and fabrication of MFMs are daunting tasks, requiring the organic integration of multiple metals and alloys during manufacturing processes. Additive manufacturing, especially directed energy deposition (DED), has the potential in this regard due to its capability to deposit multimaterials site‐specifically. Through carefully programmed printing paths, novel applications arise and achieve functionalities unseen before. Here, we showcase the versatility of such techniques by four case studies of metallic MFMs: (i) tuning magnetic lifting force, (ii) securely and durably embedding information as material fingerprints, (iii) improving conventional ferrofluidic seals, and (iv) possessing programmable mechanical properties. This work demonstrates the possibilities of using DED to achieve multifunctionalities in metallic materials and provides enlightenment to a wide range of engineering applications.

ABSTRACT Metal matrix composites (MMCs) are attracting increasing attention owing to their high strength, thermal stability, and wear resistance, making them essential in industries such as aerospace, automotive, and energy. However, traditional manufacturing methods often face limitations in achieving the complex geometries and uniform reinforcement dispersion necessary to optimize the performance and reliability of the final product. To address these challenges, additive manufacturing (AM) has emerged as a promising approach offering enhanced design flexibility, precise microstructural control, and improved material efficiency. This study discusses the advantages of AM in MMC research and classifies AM‐based MMC fabrication methods into three categories: (1) using reinforcement‐dispersed metal powders, (2) co‐feeding metal and reinforcement powders during AM, and (3) in situ formation of MMCs through reactive processes during AM. This review compares the characteristics and microstructural differences between these methods and highlights the mechanical and structural advantages of AM. Despite their potential, challenges, such as microstructural uniformity and process optimization, necessitate further research. Finally, future research directions for advancing AM‐based MMC fabrication technologies are discussed.

ABSTRACT Growing demand for secure, sustainable, and affordable magnetic materials has drawn significant attention to rare‐earth‐free Fe‐based permanent magnets. This review integrates recent advances from atomic‐scale theory to bulk processing. We first outline the fundamental parameters that govern permanent‐magnet performance, such as saturation magnetization ( M s ), magnetocrystalline anisotropy, Curie temperature ( T c ), and microstructural factors. We then survey four principal material families. The first is Fe–Co alloys whose anisotropy is enhanced through lattice strain and light‐element doping. The second is chemically ordered Fe–Ni, tetrataenite, originally discovered in meteorites. The third is nitrogen‐rich iron phases typified by α″‐Fe 16 N 2 . The fourth is iron phosphides and borides such as Fe 2 P and Fe–B. Although calculations predict outstanding magnetic strength, experimental results remain limited by phase instability, grain‐size effects, and processing constraints. To bridge this gap, we highlight four complementary research directions: strain engineering, heteroatom doping, deliberate microstructure control, and data‐driven ab initio calculations. Coordinated progress in these areas could yield Fe‐based magnets with high coercivity and robust magnetization, enabling practical devices for electrified transport, renewable‐energy conversion, and compact electronics without costly rare‐earth elements.

ABSTRACTThermochemical treatments performed at low temperatures (< ∼500°C) have received increasing interest for the surface modification of austenitic stainless steels. In fact, when treatment media rich in nitrogen and/or carbon are used at these temperatures, the formation of chromium compounds is inhibited and the interstitial atoms are retained in the face‐centered cubic lattice of austenite beyond the solubility limit. The obtained supersaturated solid solution, known as expanded austenite or S‐phase, has high hardness and can maintain or even increase the corrosion resistance in many environments. In the international literature, many studies are present that highlight the effects of the formation of this phase on tribological properties, fatigue resistance, corrosion behavior, wettability, biocompatibility, and magnetic properties of austenitic stainless steels. However, using analogous treatment conditions, expanded austenite can be obtained in many other alloys having a matrix with a face‐centered cubic lattice, such as austenitic steels, nickel and cobalt alloys, and the more recent medium‐ and high‐entropy alloys, but the studies on this topic are mostly at their very beginning. In this review, the characteristics and properties of expanded austenite and of the modified surface layers in which it is present are analyzed and discussed, considering all the different alloys in which this supersaturated phase can be produced. The role of alloy elements in promoting or hindering the formation of expanded austenite and the competing compound precipitates is taken into account. The opportunities and challenges of the low‐temperature treatments are highlighted, and possible future directions for the investigation are suggested.

ABSTRACTSolid‐state magnetocaloric cooling attracts increasing attention as a novel technique for its high efficiency in energy conversion and its sustainability. Several high‐quality magnetocaloric materials (MCMs) have been found, but among these MCMs, (Mn,Fe)2(P,Si)‐based materials are one of the most promising candidates for its giant magnetocaloric effect (GMCE), noncritical components, and tuneable Curie temperature (TC) around room temperature. To further accelerate its practical market applications, a lot of studies have been made to enhance the GMCE, tune TC, and reduce the thermal hysteresis (ΔThys). This review mainly focuses on introducing the latest efforts to optimize the GMCE performance of this material family, including doping with different elements, microstructural improvements, and practical manufacturing techniques. Besides that, we further suggest possible approaches to boost the material engineering and highlight promising efforts of applying machine learning in the search for the optimal composition and structure of (Mn,Fe)2(P,Si)‐based MCMs. This bridges the gap between fundamental research and engineering to advance the magnetocaloric energy conversion technology closer to real applications.

Abstract Spintronics is an innovative field that exploits the intrinsic spin property of electrons instead of their charge, holding the promise of revolutionizing conventional electronic devices. Over the past decade, researchers have been actively exploring new materials as potential replacements for traditional spintronic materials. This endeavor is driven by the aspiration to create spintronic devices with ultralow power consumption, ultrahigh storage density, and remarkable stability. In recent years, topological quantum materials (TQMs) have attracted considerable interest due to their unique band structure and exceptional properties. These materials carry the potential to pave the way for breakthroughs in the design of spintronic devices, offering promising solutions to solve challenges currently faced in the field of spintronics. In this review, we first introduce the properties of various TQMs, including band structure and crucial transport properties. Subsequently, we focus on the diverse applications of TQMs in spintronics. Delving further, we discuss the current challenges and the potential directions for advancing and exploring TQMs.

Abstract Lithium metal is a promising electrode material for next‐generation high‐energy‐density rechargeable batteries with its high theoretical capacity (3860 mAh g−1) and low standard electrode potential (−3.04 V vs. SHE). However, the special physicochemical properties of lithium metal, including low tensile strength, viscoplastic creep, and high reactivity hinder the processing and preparation of lithium strips toward ultrathin thickness (≤20 μm). Developing new matrixes, interfaces, and processing methods can be promising for overcoming these problems. This review summarizes the physicochemical properties of lithium metal and the design principles for preparing the ultrathin Li metal, and concludes the recent development in this field from the perspective of processing design, and proposes to provide in‐depth understanding of reliable fabrication of ultrathin lithium metal strips, and prospects the challenges and opportunities of ultrathin‐scale preparation and processing of lithium metal.