Journal of Materials Engineering and Performance最新文献

This study investigated the effect of the strain path followed during the unidirectional and two-step cross-rolling on the microstructure, texture, and mechanical properties of Nb-10Hf-1Ti refractory alloy (1 mm thick sheet). It has been demonstrated for the first time that the refractory alloy Nb-10Hf-1Ti can be smoothly cross-rolled like unidirectional rolling. The cross-rolling results in a stronger texture as compared to the unidirectional rolling. The development of a strong texture during cross-rolling as a result of a change in strain path is due to a partial texture transition from the γ-fiber to the α-fiber and strengthening of the texture components (left{001right}langle 110rangle). The grains are observed to be significantly finer after unidirectional rolling as compared to cross-rolling. A mixture of fine and coarse grains is observed after cross-rolling. The finer grains are related to the γ-fiber (〈111〉IIND)) while the coarser grains are associated with α-fiber (〈110〉IIRD). The visco-plastic self-consistent (VPSC) model establishes that the average number of active slip systems is significantly higher for cross-rolled samples than the unidirectional rolled. The presence of a higher number of active slip systems in cross-rolled relaxes the deformation constraints, resists grain fragmentation, and results in coarse as well as fine grains. The unidirectional rolling shows less deformation constraint and a higher extent of grain fragmentation which results in overall finer grains. The higher dislocation density, higher number of slip systems, and formation of cellular dislocation network results in higher work hardening of the cross-rolled sample. The highly work-hardened cross-rolled sample displays early attainment of saturation stress and results in moderately higher tensile strength compared to the unidirectional rolled sample.

In this paper, closed-cell aluminum foam sandwich structures with metallurgically bonded interfaces were fabricated utilizing a compression-powder metallurgical foaming technique. The aluminum foam sandwich structure was subjected to low-velocity impact tests with single and repetitive impact energy using a drop hammer testing machine. The mechanical responses, impact damage processes, and energy absorption characteristics with different impact energies and sandwich structure thicknesses were investigated through experimental testing. Based on the energy absorption index, the influence of specimen thickness on the energy absorption performance of the aluminum foam sandwich structure was quantitatively assessed. The results of the study can provide an important reference for the design of collision-resistant and energy-absorbing aluminum foam sandwich structures under low-velocity impact. To provide a theoretical basis for developing new lightweight aluminum foam sandwich structures with high impact resistance.

Grinding remains a critical finishing process in manufacturing, yet it is often constrained by excessive friction, thermal damage, and inefficient coolant delivery—especially when machining hard-to-grind materials like MO40 steel. This study explores the design and evaluation of five innovative grinding tools, fabricated using vat photopolymerization-based 3D printing, each featuring distinct geometric modifications to enhance grinding performance. The tested designs included: a Standard Tool (ST), a Cylindrical Cooling Channel Tool (CCT), a Venturi Cooling Tool (VCT), and two V-grooved tools (T100 and T200) tailored for improved chip evacuation and thermal regulation. Experimental assessments revealed that structured geometries significantly influence tool behavior. Among them, the T100 tool exhibited the highest grinding ratio, lowest wear rate, and finest surface finish, attributed to enhanced coolant flow and reduced thermal load. These findings demonstrate the potential of geometrically engineered, 3D-printed tools to overcome conventional grinding limitations, paving the way for more efficient and sustainable machining of advanced alloys.

As a common structure in the material medium, the heterogeneous interfacial structure redistributes the stress field after the explosion stress wave acts on the material, which is easy to cause damage or even fracture of the material. In order to study the evolution process and distribution characteristics of strain field in media with heterogeneous interfaces under different initiation modes, an ultra-high-speed digital image correlation experimental system was established. Chloroform bonded polycarbonate (PC) board and polymethylmethacrylate (PMMA) board were used to construct heterogeneous interface structure. By changing the position of initiation point in PC board, the initiation point near the interface end was defined as hole bottom initiation. When the interface is far away from the end of the hole, the dynamic response characteristics of the explosion stress wave through the heterogeneous interface media are studied. The experimental results show that the interface has different hindering ability to stress waves under different initiation modes. The cracking phenomenon of the interface is macroscopic when only the opening is used, which is mainly due to the stress concentration area formed at the interface due to the action of reflected transverse tension waves. The contribution of detonation mode to the tensile and compressive strain field of PMMA medium is different. The influence on the transverse compressive strain field is mainly reflected in the strain field strength, while the influence on the longitudinal tensile strain field is mainly reflected in the strain field strength and strain zone morphology distribution. Under different initiation modes, the absolute value of the attenuation index in PC medium is greater than that of PMMA when it is close to the end of the gun hole, and the PMMA is larger when it is far away from the end. The difference is shown in the distribution of strain attenuation index in different media.

Material degradation due to slurry erosive wear affects components exposed to particle-entrained slurries. This study investigates the slurry erosion behavior of AZ31 Magnesium alloy processed through friction stir processing. The base and processed materials were subjected to slurry jet erosion test under various impingement angles. Alumina abrasive particles of 700 µm nominal size were used as the erodent. Experimental results indicated that the base and processed materials exhibit ductile erosion behavior, with maximum mass loss occurring at an oblique angle of 30°. With increase in impact angle, mass loss is found to be decreased. Compared to the unprocessed alloy, material processed through friction stir processing at 1500 rpm tool rotation speed and 60 mm/min traverse speed showed minor mass loss at all impingement angles. Surface profile analysis revealed a ‘U’-shaped scar profile, regardless of the impingement angle. Furthermore, surface roughness decreased with increasing impact angle. Scanning electron microscopy confirmed that micro-cutting and ploughing mechanisms dominated at shallow angles, while indentation and plastic deformation were more prevalent at higher impingement angles.

Due to the transient nature of the blasting process and the complexity of the blasting effect, the number and spatial distribution of detonation points significantly affect the intensity and damage distribution of the strain field in the medium. Based on this, this paper studies the time-varying effect of the spatial position of the detonation point on the strain field and the damage distribution using the digital image correlation method and LS-DYNA numerical simulation. The results indicate that the influence of the number of initiation points along the gun hole on the strain field primarily manifests in the characteristics of strain history and the intensity distribution of the strain field. The axial strain and radial strain exhibit a single peak distribution pattern at a single-point initiation, with the strain intensity gradually increasing in the direction of detonation. In contrast, the strain intensity at two-point initiation exhibits a double peak distribution pattern and presents a symmetrical distribution along the center of the gun hole, significantly enhancing the strain field intensity at the center of the two initiation points. The experimental results of the two-point initiation model are corroborated through the numerical simulation. In general, the damage length can be divided into four expansion stages based on the distance between initiation points. When the distance between the initiation points reaches a certain extent, the damage length at the central position peaks and is no longer influenced by the distance between the initiation points. The damage degree in the center area of the gun hole accurately represents the total energy of the area, and the two physical quantities demonstrate a positive correlation.

NiTi thin coatings are increasingly explored to enhance the performance of bearing steel (AISI 52100) components in engineering applications due to their superior mechanical and tribological properties. In this research, NiTi thin coatings were deposited on bearing steel substrates using radio frequency magnetron sputtering. The deposition process was conducted with power densities of 1.72 W/cm² for Ni and 2.96 W/cm² for Ti, at a working pressure of 0.4 Pa. The microstructure, mechanical, and tribological properties of the coating were characterized using a range of techniques, including GI-XRD, FESEM, EDS, nanoindentation, scratch testing, 3D surface analysis, and ball-on-disk tribological testing. The composite interlayer developed columnar dendrites extending toward the NiTi coating layer, with a gradient distribution of Ni and Ti elements observed in the elemental spectra. The NiTi coating demonstrated a hardness of 7.57 GPa, marking a 33.9% improvement compared to the AISI 52100 substrate. The tribological performance of the coating was evaluated against a Si₃N₄ ball using a reciprocating ball-on-disk tribometer under varying loads. The NiTi-coated specimens exhibited superior wear resistance compared to the uncoated AISI 52100 substrate under identical conditions. The NiTi coating achieved the lowest coefficient of friction (0.036) at a 1.5 N sliding load and the minimum wear rate (3.39 × 10⁻⁶ mm³/N m) at a 1.25 N sliding load.

Ti-6Al-4 V titanium alloy thin-walled parts are susceptible to fatigue and plastic deformation due to the distribution of machining residual stresses. To reasonably regulate the distribution of residual stress inside the workpiece, this study investigates the influence of freezing temperature, tool coating, tool path, processing temperature, and feed speed on the distribution of residual stress in Ti-6Al-4 V titanium alloy thin-walled parts by combining an ice-covered milling experiment with low-temperature cutting simulation. The results indicate that ice-covered milling significantly enhances residual compressive stress by a range of 46% to 57.14%, with maximum improvement observed at a processing temperature of −15 °C. The AlTiN tool coating, with low friction and hardness, significantly improves the residual compressive stress of titanium alloy thin-walled parts, reaching −483.3 MPa. Compared with annular feeding, lateral and longitudinal feeding can increase the residual compressive stress value by 18.87 and 23.22%, respectively. The error between simulation and experiment can be minimized to 1.69%. Decreasing processing temperature increases residual compressive stress on the workpiece surface. Increasing the feed rate initially increases and then decreases residual tensile stress on the surface. The low-temperature two-dimensional cutting finite element model accurately predicts residual stress distribution in ice-covered milling and provides an effective practical scheme for thin-walled parts with high quality and precision.

Rack steel is a key material for constructing self-elevating offshore platforms, and as the thickness of steel plates continues to increase, increased requirements are placed on the steel’s hardenability. Boron is a key element in improving the hardenability of steels, but there are currently few reports on its role in rack steels. In this paper the influential mechanism of boron on the hardenability of A514Q Modified rack steel was investigated by conducting end quenching tests, establishing continuous cooling transformation (CCT) curves, and analyzing the grain boundary segregation behavior of boron. The results indicate that the 0.006 wt.% boron addition significantly improves the hardenability, reducing the critical cooling rate for martensitic transformation from 2 to 0.5 °C·s^-1. The boron is mainly enriched in the MA islands, especially those along prior austenite grain boundaries (PAGBs). Besides, the boron atoms are slightly segregated at matrix / MA islands interfaces. The PAGBs segregation of boron can be explained through non-equilibrium segregation mechanism. Analysis suggests that boron addition improves the hardenability of rack steels mainly because the segregation of boron at PAGBs decreases the grain boundary energy.

To improve the bonding strength at the coating/substrate interface and increase the proportion of interfacial metallurgical bonding, plasma spray melting (PSM) technology for coating preparation was proposed. The coatings were prepared using PSM and air plasma spray (APS) on Q235 steel substrates in this paper, respectively. The micro-morphology of the coatings and the morphology of the molten droplet splat and melt pool were characterized by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The mechanical properties of the coatings were also investigated, including bond strength, microhardness, nanoindentation, and residual stress. The coating/substrate metallurgical bonding was analyzed by electron backscatter diffraction (EBSD) and micro-zone x-ray diffraction (XRD). The results showed that the plasma-sprayed coating exhibited distinct continuous metallurgical bonding characteristics with the substrate, and the elemental diffusion depth was approximately 4 μm. Compared to the APS coating, the porosity was reduced to 2.3%. The interfacial region was metallurgically bonded, and the internal bonding strength of the coating reached 53 MPa. Additionally, the coating was less prone to cracking due to the favorable elastic modulus matching between the coating and the substrate.