It is usually required that Ti-1300 alloys be able to withstand a greater load under special conditions, such as the controllable collision of a space shuttle and rapid collision of an automobile. Because of a good combination of strength and toughness, Ti-1300 alloys are widely applied in the aerospace industry. However, during the service process, the alloy components inevitably bear extreme loads. This paper uses high-speed tensile technology to systematically study the effects of different strain rates on the deformation of the microstructure and deformation mechanism of Ti-1300 alloys and to clarify a relation between the microstructure and mechanical properties. The results show that no phase transformation occurs during the high-speed tensile process at strain rates of 200 s⁻¹ and 500 s⁻¹. The deformation mechanism is mainly due to dislocation slip. The fracture mode is ductile fracture at the two strain rates, due to the connection between micro-voids promoted by dislocation slip. The ultimate tensile strengths are 1227 MPa and 1368 MPa, the yield strengths are 1050 MPa and 1220 MPa, and the elongations are 11.3% and 10.4%, respectively. The present results provide theoretical guidance for the further application of metastable β titanium alloys in working environments with high strain rates.

Powder Bed Fusion by Laser Beam Melting (PBF-LB/M) has gained significant interests for fabricating magnesium matrix composites (Mg-MMCs). However, particle agglomeration unavoidably leads to a strength-ductility trade-off. To address this issue, a multi-physics multiscale framework, coupling a microscopic Computational Fluid Dynamics-Discrete Phase Model (CFD-DPM) with a sub-microscopic Sharp Interface Model (SIM), is developed. The CFD-DPM results reveal that Marangoni vortices drive reinforced particles to agglomerate at molten-pool periphery in a single track. Then a layer-wise tuned scheme for hatch spacing is defined as the two-fifths of the molten pool width and confirmed by experiments. The SIM simulations reveal that the particles should not be inert. With the consideration of Brownian motion, insufficient free reorientation of particles ahead of solid-liquid interface can explain why the particle pushing mechanism dominates in the experiments instead of the engulfment mechanism from the perspective of interfacial energy. With the optimized hatch spacing of 60 μm, an increase in tensile strength (~349.2 MPa) with decent ductility (~4.3%) is achieved in the as-fabricated TiCN/AZ91D composites. The solute co-segregation of Al/Zn/Mn elements enhances particle/matrix interfacial bonding and may delay microcrack initiation. The activation of dislocations near particle/matrix interface facilitates the release of stress concentration and enhances deformation uniformity. This particle-dispersion optimization strategy can also be applied for fabricating other high-performance Mg-MMCs by PBF-LB/M.