Relation of Structure, Composition and Glass Forming Ability in Zr-Cu Binary Amorphous Alloys

Molecular dynamics simulation was used to simulate Zr-Cu binary system, in which the relationship between structure, composition and glass forming ability was study. Atomic local structures were analyzed from view of chemical and topological short range order. Reduction fraction of full icosahedra (Bc) was developed to establish the relation of structure-composition and glass forming ability(GFA) in Zr-Cu binary system. Obviously peaks were observed at some certain compositions which own the good GFA. As a structure factor, Bc could be a indicator of GFA of Zr-Cu alloys. Our works contributed to further understanding the effect of atomic structures on glass forming

Relation of Structure, Composition and Glass Forming Ability in Zr-Cu Binary Amorphous Alloys

Molecular dynamics simulation was used to simulate Zr-Cu binary system, in which the relationship between structure, composition and glass forming ability was study. Atomic local structures were analyzed from view of chemical and topological short range order. Reduction fraction of full icosahedra (Bc) was developed to establish the relation of structure-composition and glass forming ability(GFA) in Zr-Cu binary system. Obviously peaks were observed at some certain compositions which own the good GFA. As a structure factor, Bc could be a indicator of GFA of Zr-Cu alloys. Our works contributed to further understanding the effect of atomic structures on glass forming

Influence of Hot Rolling and Heat Treatment on the Microstructural Evolution of β20C Titanium Alloy

The microstructural evolution and underlying mechanism of a new high strength, high toughness near β titanium alloy, β20C, during hot deformation, and heat treatment were studied qualitatively and quantitatively. It was found that dynamic recovery occurs mainly in β phase, while α phase undergoes both a dynamic recovery and continuous incomplete dynamic recrystallization with a fraction of high-angle grain boundaries (≥15°) of 21.1% under hot-rolling. Subsequently, α phase undergoes static recrystallization with an increasing fraction of high-angle grain boundaries (21.1%→60.7%) under annealing, while the grains are equiaxed with refined grain sizes of 1.63 µm observed from the rolling direction (RD) and 1.66 µm observed from the transverse direction (TD). Moreover, the average aspect ratio of the lamellar α phase was 2.44 observed from the RD and 3.12 observed from the TD after hot rolling, but decreased to 2.20 observed from the RD, and 2.53 observed from the TD after annealing. Furthermore, the strict Burgers’ relationship between α and β phases changed after hot-rolling and remains the distortion, even after the static recrystallization process of α phase during annealing

Crystal Plasticity Finite Element Method for Slip Systems Evolution Analysis of α/β Duplex Titanium Alloys during Quasi-Static Tensile Testing

The crystal plasticity finite element method, modeled on a realistic microstructure image, was developed to investigate the evolution of slip systems in grains of α/β titanium alloys during quasi-static tensile testing. By analyzing the data of slip evolution of simulation during the overall plastic deformation process, it was found that the prismatic slip systems in the α phase and the {112} <111> slip systems in the β phase played a leading role. By calculating the Schmid factors, it was found that the values calculated from the local stress, which was represented by major principal stress, were larger than the values calculated from the primary uniaxial tensile direction, which was due to the deviation of the local stress direction from the primary uniaxial tensile direction. Furthermore, the deviation of local stress of α phase was different from that of β phase, which was related to the deformation mechanism. During the deformation, the stress and strain were concentrated in the grains of the α phase, producing a driving effect on the neighboring grains of the β phase. Subsequently, the incompatible deformation produced the concentration of strain at the grain/interphase boundary, thus strengthening the grain interactions and leading to the deviation

Experimental and Numerical Investigation of the Effect of Projectile Nose Shape on the Deformation and Energy Dissipation Mechanisms of the Ultra-High Molecular Weight Polyethylene (UHMWPE) Composite

The effect of projectile nose shape on the ballistic performance of the ultra-high molecular weight polyethylene (UHMWPE) composite was studied through experiments and simulations. Eight projectiles such as conical, flat, hemispherical, and ogival nose projectiles were used in this study. The deformation process, failure mechanisms, and the specific energy absorption (SEA) ability were systematically investigated for analyzing the ballistic responses on the projectile and the UHMWPE composite. The results showed that the projectile nose shape could invoke different penetration mechanisms on the composite. The sharper nose projectile tended to shear through the laminate, causing localized damage zone on the composite. For the blunt nose projectile penetration, the primary deformation features were the combination of shear plugging, tensile deformation, and large area delamination. The maximum value of specific energy absorption (SEA) was 290 J/(kg/m2) for the flat nose projectile penetration, about 3.8 times higher than that for the 30° conical nose projectile. Furthermore, a ballistic resistance analytical model was built based on the cavity expansion theory to predict the energy absorption ability of the UHMWPE composite. The model exhibited a good match between the ballistic resistance curves in simulations with the SEA ability of the UHMWPE composite in experiments

Ballistic impact response of a heat-treated dual-phase Ti–5.2Mo–4.8Al–2.5Zr–1.7Cr alloy with hierarchical microstructure

In the present study, a dual-phase Ti-5.2Mo-4.8Al-2.5Zr-1.7Cr alloy was hot-rolled at 980 °C with a thickness reduction of 65% and then heat-treated with the strategy of 920 °C/1 h/water quenching +550 °C/6 h/air cooling, and a hierarchical microstructure was prepared, which contained micro-scale equiaxed primary α phase (αp), sub-micro scale rod-like α phase (αr), nano-scale acicular secondary α phase (αs) and β matrix segmented by αs and αr. In addition, the dislocation densities of α phase and β phase were determined as 0.3652 × 1015/m2 and 2.2502 × 1015/m2, respectively. Contributing to αr and αs, the hierarchical microstructure exhibited higher strength (yield strength: 1228 MPa, ultimate tensile strength: 1389 MPa, dynamic compressive strength: 1661 ± 27 MPa). Simultaneously, αp and αr were helpful to the strain transfer, and thus the plasticity was maintained at a considerable level (elongation: 13.4 ± 0.2%, critical fracture strain: 18.9 ± 0.2%). Such hierarchical microstructure overcame the limitation of the strength-ductility trade-off to a certain extent and exhibited a superior combination of strength and ductility. The ballistic impact behavior of the titanium alloy plates with the thickness of 20.3 mm (1#), 19.3 mm (2#) and 18.4 mm (3#) against 7.62 mm armour piercing projectiles illustrated that as the titanium alloy thicknesses decreased from 20.3 mm to 18.4 mm, more ASB-induced cracks were formed near the rear face and connected to form catastrophic cracks in the 2# and the 3# titanium alloy plates, even resulting in the failure for the 3# titanium alloy plate. Ultimately, the 1# and 2# titanium alloy plates exhibited preferable ballistic impact properties

Hot-pressing sintering diffusion bonding of a high-toughness titanium alloy and an ultra-high-strength steel with Ta/Ni dual-interlayer

The powder metallurgy forming of ultra-high-strength steel (UHSS) G33 and its combination with high toughness titanium alloy Ti–7Al–1Mo-0.5V-0.1C were achieved through the application of Ta/Ni dual-interlayer in a hot-press sintering diffusion bonding (HPSDB) process, conducted at 970 °C, 50 MPa, and a duration of 3 h. The resulting bonding strength proved excellent, with a high shear strength of 485.5 MPa. The interface structure, precipitated phases, and element diffusion behavior were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Notably, no intermetallic compounds (IMCs) precipitated in the Ti–Ta diffusion zone or the Ni-G33 diffusion zone, underscoring the effectiveness of the metallurgical bond. Selected area electron diffraction (SAED) and phase diagram calculation were employed to elucidate the mechanisms contributing to the robust bonding strength of the joint with Ta/Ni dual-interlayer. The results revealed that the diffusion zone primarily comprised NiTa2, Ni2Ta, and Ni3Ta with high shear modulus and excellent ductility. Near the bonding interface, Ni3Ta grains exhibited approximate low-angle torsional grain boundaries, effectively impeding dislocation movement. Moreover, the bonding strength was further enhanced by the precipitation of nanoscale tetragonal-Ta dispersed within the Ni2Ta matrix

Preparation of millimeter-scale hard layer on the surface of titanium alloy via self-propagating high temperature synthesis combined with hot pressing sintering process

A hard and thick surface strengthening layer with high interfacial bonding strength was innovatively prepared via self-propagating high temperature synthesis (SHS) combined with hot pressing sintering (HPS) process. The thickness of the surface layer reached 1.1 mm, far exceeding the strengthening layer prepared by the traditional surface modification methods of titanium alloy. The raw materials of the hard layer were carefully designed by mixing powders of Ti, C, B and Ni, and the raw material of the matrix was Ti–6Al–4V powder. During the HPS process (1100 °C, 40 MPa), the Ti–Ni reaction released a large amount of heat, which promoted the Ti–C reaction and Ti–B reaction. The test results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) suggested that a high amount of Ti6C3.75 and TiB were finally generated in the hard layer, and the Vickers hardness value was as high as 1800 HV. Furthermore, the energy dispersive spectrometer (EDS) test results indicated that most Ni atoms diffused to the Ti–6Al–4V side, and NiTi2 phase was mainly distributed at the interface. Obviously, metallurgical bonding was obtained, accounting for the high interfacial bonding strength of 162 MPa. The present work provided significant insights into the design of novel titanium alloy surface modification process