Surface Review and Letters

The current scenario focuses on lightweight and better energy-absorbing structural materials for critical engineering applications in aerospace, automobiles, marine, electronic, and implant materials for biomedical industries. The magnesium-based syntactic foams are the preferred choice of material in the same category due to their lightweight, higher plateau strength, better damping characteristics, and excellent energy absorption behavior. Many works were reported based on the polymer and aluminum-based syntactic foams and their developments. However, the rapidly increasing interest in magnesium-based syntactic foams and the adoption of the applications are still at a nascent stage. This proposed review work comprehensively insights the magnesium-based syntactic foam; various hollow filler material usages and summarizes the influence of physical and mechanical behavior on processing routes and future research opportunities for applications.

During the braking process, frictional heat generation between brake strip and brake block can lead to high temperatures, significantly affecting the braking performance. This paper proposes a novel knee impact test method and innovatively investigates the effect of brake friction surface texture shape on braking performance. A comparative evaluation of the braking performance of different surface textures is conducted using the new knee impact test, with a focus on studying the temperature rise during braking to optimize the brake system. Research findings indicate that the best braking performance was achieved when friction surface texture of the brake block was rhombus-shaped with a diagonal ratio of 5:5. By implementing this improved brake design, the maximum temperature during braking was reduced from 184.44^∘C to 75.963^∘C, resulting in a significant reduction in thermal stress from 155.22 MPa to 64.40 MPa. Moreover, the acceleration and brake distance are extracted and compared with the target values of Euro NCAP. The improved brake acceleration exhibits stability and a deviation from target value within 10%. Additionally, the deviation between our brake distance and target distance is −3.63%. These results provide a valuable reference for improving the braking performance of braking systems in the new knee impact test.

Wire cut electric discharge machining (WCEDM) is a flexible and more essential for the precise machining of hard materials like composites and super alloys. In order to improve the surface texture as the main focus of the WCEDM process, the expansion of the fundamental procedural perceptive is very important. This paper mainly focuses on the prediction of surface quality of Al-Fe-Si alloy (AA8011) matrix composites during the WCEDM process. For the fabrication of composites, the varying proportions (0, 5, 10 and 15 wt.%) of ZrO₂ ceramic particle were incorporated with AA8011 matrix alloy by using stir casting method. In the machining studies, to investigate the effects of reinforcement (wt. %) and the WCEDM process parameters, namely pulse current (amps), pulse-on time ($\mu$s) and pulse-off time ($\mu$s) on machining performance like surface roughness (SR) of the proposed composites. Based on the selection of parameters and their levels, an L16 (4⁴) orthogonal array was most suitable for conducting the WCEDM experiments. A Taguchi technique was employed in this study to determine the optimal conditions of machining parameters through the signal-to-noise (S/N) ratio analysis. The result shows that the minimum SR is achieved at 5 wt.% of reinforcement, 6 amps of pulse current, 110 $\mu$s of pulse-on time and 50 $\mu$s of pulse-off time, respectively. Analysis of variance (ANOVA) results revealed that the reinforcement wt.% has the primary significant factor on SR, trailed by pulse-on time and pulse current, respectively. Furthermore, the regression equation was also developed to predict the SR and that values well agree with the experimental SR.

The $\alpha$-Fe(100)/Cr(100) interface has an important effect on the precipitation of the Cr-rich phase in ferritic stainless steel, and alloying elements affect the stability of the $\alpha$-Fe(100)/Cr(100) interface. However, it is difficult to clearly understand the effect of alloying elements on the $\alpha$-Fe(100)/Cr(100) interface behavior experimentally. Therefore, the first-principles calculation is employed to address this problem in this paper. First of all, the segregation behaviors of alloy elements (Mo, Nb, and Si) on the $\alpha$-Fe(100)/Cr(100) interface were systematically investigated. And then, the effects of these alloying elements on the property of the $\alpha$-Fe(100)/Cr(100) interface were studied. Based on the density functional theory, the work of adhesion (W_ad), interfacial energy (γ_int), doping energy ($E$${}_f$), and electronic properties of the $\alpha$-Fe(100)/Cr(100) interface were analyzed. The results show that the body-centered $\alpha$-Fe(100)/Cr(100) interface is constructed by using seven layers of $\alpha$-Fe(100) and Cr(100) surface models. The W_ad is 6.115 J.m${}^{-2}$, and the γ_int is −0.12 J.m ${}^{-2}$. The doping atoms tend to segregate on the surface of $\alpha$-Fe(100). When the Si atom doped in the interface, the W_ad increases, and the γ_int reduces. The doping of the Si strengthens the bonding strength of the interface and promotes the nucleation of the Cr-rich phase. While the addition of Mo and Nb atoms decreases the W_ad of $\alpha$-Fe(100)/Cr(100) interface, increases the γ_int. The bonding strength of the interface is weakened and the nucleation of the Cr phase is inhibited. Based on this result, it is clearer to understand the effect of Mo, Nb, and Si atoms on the precipitation of the Cr-rich phase in ferritic stainless steel.

Magnesium composites stay relevant for the applications of biodegradable implant as they are harmless and possess characteristics such as density and elastic modulus analogous to the cortical bone in humans. But corrosion is one major issue associated with magnesium when the biomedical applications are contemplated. Moreover, load bearing abilities are also required in case of an orthopedic implant. In this study, to achieve the desired implant characteristics, hybrid nanocomposites (HNCs) of Mg–2.5Zn binary alloys such as metal matrix, hydroxyapatite (HAp), and reduced graphene oxide (rGO) as reinforcements were fabricated via the vacuum-assisted stir casting method. The overall weight percentage of the reinforcements was fixed at 3% and both the reinforcements varied in compositions by weight to prepare the samples S0 (Pure Magnesium), S1 (Mg–2.5Zn–0.5HAp–2.5rGO), S2 (Mg–2.5Zn–1.0HAp–2.0rGO), S3 (Mg–2.5Zn–1.5HAp–1.5rGO), S4 (Mg–2.5Zn–2.0HAp–1.0rGO), and S5 (Mg–2.5Zn–2.5HAp–0.5rGO), respectively. The influence of mechanical characteristics such as tensile strength, compressive strength, and microhardness as well as the corrosion over the surface of the nanocomposite in simulated body fluid (SBF) have been assessed for their suitability as biodegradable orthopedic implants. Results suggest that the fabricated nanocomposites exhibit superior characteristics in comparison to pure magnesium. Increasing the HAp from 0.5 wt.% to 2.5 wt.% enhanced the compressive strength and reduced the corrosion rate. On the other hand, increasing the rGO from 0.5 wt.% to 1.5 wt.% increased the tensile strength. The formation of apatite layer over the composites is observed in the SBF solution. Among all the fabricated hybrid nanocomposite samples, the sample S3 (Mg–2.5Zn–1.5HAp–1.5rGO) with equal wt.% of HAp and rGO exhibited 209.60 MPa of ultimate tensile strength, 300.1 MPa of ultimate compressive strength, and a corrosion rate of 0.91 mm/year thus making it the best suited and a prospective material for biodegradable implant application.

In this study, electrophysical, electromagnetic and mechanical properties, fracture toughness and forming limit diagram (FLD) of Al base composite samples have been studied experimentally. All samples have been fabricated via accumulative roll bonding (ARB) process. To this purpose, AA1060/ Fe₂O₃ composite strips with thickness of 1 mm have been fabricated with up to eight ARB passes at $300^{\circ }$C. In this study, magnetic Al/Fe₂O₃ composites reinforced with 0, 5% and 10 wt.% of Fe₂O₃ particles have been manufactured via ARB. The microstructure was studied by optical microscopy (OM). Also, by decreasing the thickness of layers at higher number of passes (increasing the plastic strain), the bonding quality among the layers was improved. Scanning electron microscopy (SEM) fracture surface morphology of samples after the tensile test showed that by increasing the passes, the fracture style (mode) converted to shear ductile at higher ARB passes. So, deep dimples shrink slowly and their number and depth decreased relative to the annealed sample. As the criterion of formability, the area under the FLDs dropped sharply after the first pass and then improved by increasing the passes. Results of fracture test have shown that the value of fracture toughness has been enhanced continually to the maximum value of 34.3 MPam${}^{1/2}$ at the 8th pass.

This work addressed the effect of CMT-GMAW multi-control welding of Inconel 617 alloy with different wire feed rates (8.9, 9.4, and 9.9 m/min) on the microstructure, hardness, and electrochemical properties. The weld joints are composed of columnar dendritic structure with cellular crystals. Electron backscattered diffraction (EBSD) study showed equiaxed dendrite at the center of weld metal with growth direction perpendicular to the fusion boundary. The weldments showed diffraction peaks at $43.53^{\circ }$, $50.12^{\circ }$, and $74.82^{\circ }$, and these peaks mainly represent gamma ($\gamma$) and gamma prime ($\gamma$’) phases along with the carbide peaks of Ti (C, N), M${}_{23}$C₆ and M₆C. The Base metal (BM) had a lower hardness (232 ± 10 HV${}_{0.2}$) and lower corrosion rate (0.212 mpy) than the weld joints. The increase in wire feed rate (WFR) results in the decrease of microhardness (267 ± 5 − 251 ± 6 HV${}_{0.2}$) and increase in corrosion rate (1.833-28.140 mpy). The base metal exhibited higher potential ($E$${}_{\text{corr}}$) and lower current density ($I$${}_{\text{corr}}$) than the weld joints. As wire feed rate (WFR) increases, heat input increases; solidification time increases, grain boundaries coarsen, resulting in a lower grain boundary (GB) density, and hence increased carbide precipitation and segregation in weld zone leading to higher stable anodic current density, which caused corrosion resistance to deteriorating. The BM was more corrosion resistant than the weld joints. The metallurgical and physical changes caused by the welding process affect the corrosion resistance of the weld joints. This leads to the weld metal corroding faster than the base metal.

The effect of iron content on the structure, morphology and magnetic properties of (Ni${}_{60}$Co${}_{40}$)${}_{100-}$${}_x$Fe${}_x$ powders synthesized by hydrothermal method has been studied. Several samples have been elaborated for different Fe content ($x$= 0, 3, 5, 7, 10 and 13.5). The as- prepared samples have been characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometry (VSM). From XRD spectra and for all Fe content, we have shown the presence of both face centered cubic (FCC) and Hexagonal (HCP) nanosized phases. The lattice parameter increases with increasing Fe content and the grains size varies with Fe content to reach a minimum value of 32 nm for (Co${}_{40}$Ni${}_{60}$)${}_{90}$Fe${}_{10}$. From hysteresis curves, we have extracted the saturation magnetization, Ms, and the coercivity, Hc. We noticed that Ms increases and then decreases as a function of Fe content. The values of Hc vary from 156 Oe to 186 Oe depending on the particles shape.

Vibration is a mechanical phenomenon in which oscillations occur around an equilibrium point. In addition, the used and waste-cutting inserts create a great problem for the industry; therefore, these inserts constitute a problem to be solved in terms of both recycling and waste costs. The aim of this study is to analyze the correlation between vibration process parameters, formed during deep rolling, and surface roughness, micro-hardness with the using of the waste CBN inserts. For this, in total, 27 experiments in total were conducted with the help of a specially designed tool holder after parameters had been selected. The surface roughness, micro-hardness and vibration values of the specimens that were applied deep rolling were measured and the correlation between these values was investigated. When deep rolling was applied to the workpieces with used and waste CBN inserts, it was seen that the waste CBN inserts could be used in deep rolling and that the surface roughness improved and the surface hardness increased. In addition, it was seen that with the increase of the number of passes and rolling forces, the micro-hardness increased, and that feed rate, the number of passes and rolling forces had the biggest effect on vibration, respectively.