Peritectic melting of Ti–Ag has been shown experimentally to form bicontinuous structures, but the mechanism remains unclear. Here we use phase-field simulations to show that these structures arise from a morphological instability of liquid film migration in three dimensions: a Ti-rich solid growing through an Ag-rich liquid film develops a branched seaweed or dendritic structure whose side branches coalesce to form handles, generating a high-genus bicontinuous topology. A sharp-interface theory predicts a dealloying-front velocity and an initial ligament width that are constant in time, in contrast to liquid metal dealloying; subsequent [Formula: see text] coarsening reproduces the experimentally observed final ligament width.
Titanium matrix composites (TMCs) fabricated with conventional carbon sources suffer from TiC coarsening, agglomeration, and limited mechanical performance. Here, 4 nm carbon polymer dots (CPDs) were employed as a novel carbon source to prepare TMCs reinforced with sub-20 nm TiC particles. Ultrahigh-density coherent TiC-Ti interfaces serve as both dislocation sources and obstacles, inducing a self-hardening effect to a sustain high strain-hardening rate. Moreover, nano-TiC particles altered traditional strain-bearing paradigm dominated by grain boundaries, enhancing intragranular strain accommodation. Consequently, the nano-TiC/Ti(CPDs) composite achieves a high tensile strength of 1285 MPa and elongation of 19.1%, significantly outperforming the conventional micron-TiC/Ti(CB) composite.
A novel leaf-like multiscale structured discontinuously reinforced titanium matrix composite (DRTMCs) for room and high-temperature service was fabricated via field-assisted sintering technology (FAST) and heat treatment. The heat-treated DRTMCs comprised equiaxed primary α (αp), acicular secondary α (αs), lamellar β, TiB whiskers, nano-La2O3 and silicides. It exhibited an exceptional room-temperature ultimate tensile strength (UTS) of 1508 MPa with 9.1% elongation (EI), while retaining outstanding strength at 750°C. In situ tensile tests, TEM, and EBSD were utilized to reveal the intrinsic strengthening mechanisms, offering critical guidance for developing advanced high-performance DRTMCs.
The martensitic 100Cr6 bearing steel suffers from severe strength-toughness trade-off, restricting its service reliability. Herein, ultrafine martensite/bainite heterostructure was fabricated via rolling-induced grain refinement and austempering-enabled heterostructure. Microstructure, mechanical performance, strengthening contributions and heterogeneous deformation-induced toughening behaviors were systematically investigated via multi-scale characterization and crystal plasticity simulation. Ultrafine martensite/bainite heterostructure was obtained to achieve synergistic strength of 2150 MPa and toughness of 14.5 J/cm2. Strain mismatch at M/B interfaces induces dispersed microcracks, interfacial back stress reduces crack-tip stress intensity and induces crack deflection, while tortuous and bifurcated crack propagation paths dissipate additional fracture energy, realizing prominent strength-toughness synergy. This work provides a facile strategy for high-performance bearing steel design.
Suppressing recrystallization in Ni-based single-crystal superalloys is critical to maintaining single-crystal integrity and high-temperature performance. Here, electro-pulsing treatment with a negligible temperature rise was introduced as a preconditioning strategy and was found to suppress recrystallization during subsequent solution heat treatment. Compositional analysis shows no detectable long-range solute redistribution occurred during electro-pulsing treatment. While microstructural and residual stress characterizations revealed reduced geometrically necessary dislocation density, weakened dislocation entanglement, and remarkedly relieved residual stress. These findings demonstrate electro-pulsing as a promising route for recrystallization control in Ni-based single-crystal superalloys, and identify residual stress and dislocation structures as key factors governing recrystallization susceptibility.IMPACT STATEMENTThis work identifies electro-pulsing as a new approach to suppress recrystallization in as-cast Ni-based single-crystal superalloys, and reveals residual stress and dislocation structures as key drivers of recrystallization.
