Support structure, a critical component in the design for additive manufacturing (DfAM), has been largely overlooked by additive manufacturing (AM) communities. The support structure stabilises overhanging sections, aids in heat dissipation, and reduces the risk of thermal warping, residual stress, and distortion, particularly in the fabrication of complex geometries that challenge traditional manufacturing methods. Despite the importance of support structures in AM, a systematic review covering all aspects of the design, optimisation, and removal of support structures remains lacking. This review provides an overview of various support structure types—contact and non-contact, as well as identical and dissimilar material configurations—and outlines optimisation methods, including geometric, topology, simulation-driven, data-driven, and multi-objective approaches. Additionally, the mechanisms of support removal, such as mechanical milling and chemical dissolution, and innovations like dissolvable supports and sensitised interfaces, are discussed. Future research directions are outlined, emphasising artificial intelligence (AI)-driven intelligent design, multi-material supports, sustainable support materials, support-free AM techniques, and innovative support removal methods, all of which are essential for advancing AM technology. Overall, this review aims to serve as a foundational reference for the design and optimisation of the support structure in AM.

Titanium (Ti) alloys are widely used in high-tech fields like aerospace and biomedical engineering. Laser additive manufacturing (LAM), as an innovative technology, is the key driver for the development of Ti alloys. Despite the significant advancements in LAM of Ti alloys, there remain challenges that need further research and development efforts. To recap the potential of LAM high-performance Ti alloy, this article systematically reviews LAM Ti alloys with up-to-date information on process, materials, and properties. Several feasible solutions to advance LAM Ti alloys are reviewed, including intelligent process parameters optimization, LAM process innovation with auxiliary fields and novel Ti alloys customization for LAM. The auxiliary energy fields (e.g. thermal, acoustic, mechanical deformation and magnetic fields) can affect the melt pool dynamics and solidification behaviour during LAM of Ti alloys, altering microstructures and mechanical performances. Different kinds of novel Ti alloys customized for LAM, like peritectic α-Ti, eutectoid (α + β)-Ti, hybrid (α + β)-Ti, isomorphous β-Ti and eutectic β-Ti alloys are reviewed in detail. Furthermore, machine learning in accelerating the LAM process optimization and new materials development is also outlooked. This review summarizes the material properties and performance envelops and benchmarks the research achievements in LAM of Ti alloys. In addition, the perspectives and further trends in LAM of Ti alloys are also highlighted.

Despite the industrial significance of grain size for enhancing mechanical properties and formability, the in-depth deformation mechanisms at elevated temperature are still unclear. To investigate the functions of grain size on hot workability and deformation mechanisms, three groups of Mg-1.2Zn-0.2Y alloy specimens with different grain sizes were hot compressed and then studied by combining constitutive model, processing map and microstructural observations. The results showed that the enhanced hot workability accompanying low deformation activation energy and small instability regime was obtained with refined grain size. During hot deformation, the decreased grain size in Mg-1.2Zn-0.2Y alloy mainly improved the plastic deformation homogeneity, especially for the weakened local straining around grain boundaries. As a result, the dynamic recrystallization nucleation and texture development at lower strain level were influenced by the initial grain size. At higher strain magnitude, the growth and coarsening of dynamic recrystallized grains would further release strain localization and improve hot workability, while the texture was less impacted. Further, unlike the primary basal slip and deformation twinning in the specimen with coarse grain at low temperature, non-basal slips of dislocations were initiated with less deformation twins in the specimens with refined grain size.