The present study concentrates on the role and underlying mechanisms of in situ crystallization (employed for nanocrystal formation) in influencing the solidification microstructure and properties of aluminum alloys. By systematically analyzing the effects on α-Al refinement, silicon phase modification, and secondary phase control, as well as exploring the impact on room-temperature mechanical properties, high-temperature deformation behavior, and fatigue performance, this work reveals the potential physical mechanisms of improving mechanical properties by providing nucleation sites and inhibiting grain growth, such as fine-grain strengthening and dispersion strengthening. Moreover, stabilization of the second phase optimizes high-temperature deformation behavior, and a reduction in stress concentration improves fatigue performance. Compared with traditional microstructure control methods, in situ crystallization can achieve deeper grain refinement from micron to nanometer scale, ensuring high uniformity of grain distribution and showing good compatibility with existing processes. By defining the regulation of in situ crystallization on the microstructure and properties of aluminum alloy, the existing research provides a feasible material solution for high stress, high temperature, and high reliability. Its core significance lies in breaking through the performance bottlenecks of traditional modification technology, such as unstable refining effect, element segregation, and so on. The co-promotion of “strength–plasticity–stability” of aluminum alloys and the consideration of process compatibility and cost controllability lay a theoretical and technical foundation for the industrialization of high-performance aluminum alloys.

Additive manufacturing (AM) is revolutionizing the aerospace, transportation, energy, and biomedical fields due to its capacity for rapid production of geometrically complex components. The advancement of alloys for AM is critical to further boost those applications. The first-generation alloys for AM largely rely on conventional commercial alloys that were originally developed under the assumption of near-equilibrium solidification. However, some of these materials are incompatible with the non-equilibrium metallurgical behavior of AM, which may face issues like high crack susceptibility. Thus, the second-generation alloy design for AM builds upon conventional alloy systems by inoculation treatments with alloying elements (e.g., zirconium) or ceramic reinforcements (e.g., titanium carbide) to achieve better material printability and properties. Meanwhile, the limitations of commercial materials underscore the need for developing novel alloys specifically tailored for AM. The third-generation empirical approach for material design adopts a knowledge-driven strategy by leveraging established metallurgical principles and empirical correlations to guide targeted composition optimization. Such trial-and-error strategies for discovering new materials face substantial bottlenecks like long development cycles and high costs. Hence, it has propelled research toward the fourth-generation paradigm—data-driven artificial intelligence (AI) assisted materials design for AM, which is an effective and innovative material solution guided by AM-specific metallurgical features. Advances in AI and robotics will shift the future paradigm of AM-specific alloy design toward an autonomous AI-Lab, which leverages an intelligent AM agent and automated high-throughput AM printing and testing for materials discovery.

Against the backdrop of rapid advancements in lightweighting and integrated die-casting technologies for new energy vehicles, aluminum alloys have emerged as the core lightweight material for automotive structural components due to their excellent specific strength, corrosion resistance, and formability. However, traditional die-cast aluminum alloys generally rely on heat treatment processes to achieve strength and toughness. This not only significantly increases process costs and production lead times, but also leads to critical defects such as blistering and dimensional distortion in large integrated die-castings during heat treatment. Consequently, the development of high-strength and high-toughness die-cast aluminum alloys that meet service requirements in their as-cast state has become an urgent industry need. Although significant progress has been made in recent years in the research on microstructural control and performance enhancement of die-cast aluminum alloys for automotive applications, a systematic, integrated analysis of the strengthening mechanisms for the two mainstream alloy systems—Al-Si-Mg and Al-Mg-Si—remains lacking. This paper systematically reviews the microstructural evolution patterns and intrinsic mechanisms of performance enhancement for these two alloy systems, providing important theoretical references for the composition design and microstructural control of next-generation high-strength, high-toughness aluminum alloys without subsequent heat treatment, as well as supporting the further development of lightweighting technologies for new energy vehicles.