Journal of Materials Engineering and Performance最新文献

In this study, the vertical centrifugal casting was used to produce a bimetallic ring blank with an outer layer of 40Cr and an inner layer of Q345B. The effects of the pouring temperature of the outer layer, rotational speed of the casting mold, pouring temperature of the inner layer and pouring intervals of the inner and outer layers on the interface bonding behavior of the bimetallic ring blank were studied. The axial maximum temperature difference in the inner surface of the outer layer first decreased and then, increased with increasing pouring temperature of the inner layer, and first, increased and then, decreased with increasing rotational speed. The pouring temperature of 1570 °C in the outer layer and rotational speed of 800 r/min were recommended as the optimum parameters for the outer layer, which contributed to minimum temperature difference in the axial direction of the inner surface of the outer layer. Increasing the pouring temperature of the inner layer effectively reduced the defects of porosity caused by interfacial shrinkage, but the effective stress at the bonding interface was enhanced. As the pouring intervals increased, metallurgical bonding at the interface became more difficult, which led to poor quality at the bonding interface. A pouring temperature of 1600 °C in the inner layer and a pouring interval of 221 s were recommended as the optimum parameters for the inner layer, and they contributed to sound interface bonding. Under the optimum centrifugal casting parameters, the transition area was characterized by a serrated/canine-shaped interface and obvious diffusion of elements. The shear strengths measured along different directions met the required properties for the materials. A tight metallurgical bonding interface in the bimetallic ring blank was achieved.

In the friction stir welding (FSW) process, it becomes challenging to utilize conventional FSW for welding unequal-thickness sheets due to the shoulder's difficulty in simultaneously acting on two plates with different thicknesses. This study proposed an enhanced FSW technique for achieving unequal-thickness welding by employing a 1 + 2 butt joint structure. By doing so, the direct force exertion of the shoulder on the thinner plate is prevented, thereby eliminating plate thinning. Orthogonal experiments were conducted to determine the optimized parameter: 1800 rpm-30 mm/min-0.3 mm, with tensile strength reaching 86.56% of the base material (BM). The microhardness profile exhibits an asymmetric “w” shape in the cross-section of the weld joint. The weld nugget zone (WNZ) shows the highest hardness value at 73 HV, whereas the heat-affected zone (HAZ) demonstrates the lowest hardness value at 39.7 HV. The average grain size of the BM measures 12 µm. Recrystallization occurred in the WNZ, forming a fine equiaxed grain structure with an average grain size of 4.7 µm. The average grain sizes in the two HAZ are 23 µm (thicker sheet) and (thinner sheet) 20 µm, respectively. The peak temperature of the thicker plate, located at an equal distance from the weld's centerline, exceeds the temperature of the thinner plate by 20-35 °C. Consequently, the softening degree of the HAZ in thinner sheets decreased.

Titanium alloy is the most promising superalloy widely used in avionics systems, because of its high strength and great corrosion resistance. Machining efficiency of this alloy can be enhanced with modeling and optimization approaches. In the present work, modeling of response surface methodology is used for milling of Ti-6Al-4V using no-coolant (dry), minimum amount coolant (MAC), and use of liquid carbon dioxide as cryogen with spray of nitrogen gas besides minimum amount of biodegradable mixture (Hybrid). Cutting speed (v), feed rate (f), and depth of cut (d) are input parameters, whereas temperature, tool wear, surface finish, and material removal rate are responses. GA, JAYA, and Rao1, 2, and 3 algorithms were used to solve a multi-objective function (Z). For hybrid condition compared to no-coolant and MAC, 35 and 17% reduction in T, 32 and 21% reduction in V_f, 45 and 33% reduction in R_a, and 45 and 15% improvement in MRR, respectively, was observed. JAYA performed 91, 64, 62, and 57% better than GA, Rao-1, Rao-2, and Rao-3 algorithms, respectively, for MAC condition. It has been observed that JAYA algorithm is better at achieving steady state and requires less generations, whereas Rao algorithms run faster. From the computational tests, it is observed that the performance of the Rao algorithm is superior to the other optimization algorithms. In terms of execution time, Rao-1 performed 49, 74, and 42% better than Rao-3, whereas 60, 77, and 41% better when compared to Rao-2 for three milling conditions, respectively.

Graphical Abstract

In this paper, the effect of heat treatment on the anisotropic mechanical properties of AlSi10Mg formed by selective laser melting (SLM) was studied. AlSil0Mg alloy samples were formed by SLM horizontal and vertical orientation, and T6 heat treatment was performed on the samples. The phase composition, metallographic structure and fracture morphology of the samples were characterized, and the hardness and tensile properties were tested. Results show that the microstructure is obviously homogenized after heat treatment. The morphology of eutectic Si phase changes from the original network structure to irregular block and granular. For AlSi10Mg alloy formed by SLM with different orientations, the anisotropy of strength is quite different (>10%). The anisotropy of hardness is not obvious, and the strength and plasticity of the horizontal orientation forming sample are better. The strength of the samples formed in different orientations decreases and the plasticity increases after heat treatment. The strength anisotropy of different orientations is significantly reduced (<10%). Before heat treatment, the tensile fracture of AlSi10Mg alloy with different orientations is brittle fracture. The fracture morphology is mainly characterized by step and tear distribution. After heat treatment, the tensile fracture is ductile fracture. The fracture morphologies of vertical orientation and horizontal orientation are equiaxed dimples and shear dimples, respectively.

SiC_f/SiC composites are replacing superalloy components in hot sections of gas turbines. The high-velocity combustion gases in gas turbine hot sections contain water vapor. The mechanism of oxidative water vapor attack on SiC is vastly different from that of oxidation in static dry air. Therefore, it is of paramount importance to study the oxidation of these composites in high-velocity combustion environments. This study focuses on the high-temperature oxidation behavior of SiC_f/SiC composites with a BN interfacial coating in both static air and combustion environments. The composite was prepared by the chemical vapor infiltration process (CVI). To elucidate the impact of water vapor in a combustion environment, an oxyacetylene flame apparatus was used. Oxidation of the SiC_f/SiC composite was investigated at 1200, 1300 and 1400 °C, for up to 100 h in static dry air, and for up to 24 h in a combustion environment. The microstructure evolution and recession of the composite under combustion environment were investigated by scanning electron microscopy. The oxidation kinetics of the SiC_f/SiC composite showed a parabolic nature in static air; however, in the combustion environment the composite showed accelerated mass loss owing to the concurrent effects of oxidation and recession.

Advanced ceramics are widely used in various industries like medical, automotive, and aerospace. Production of ceramic components has been constrained due to challenging machining procedures and the difficulty of forming complicated parts. Powder injection molding is one of the suitable methods to produce complex ceramics and overcome the difficulties of producing these parts. This paper investigates the effect of micro and nano powder addition on the rheological properties, segregation, and imbalance filling. For this purpose, different amounts of nano and micro SiC powder (5 wt%, 10 wt%, 15 wt%, and 20 wt% of micro SiC and 1-3 wt% of nano alumina) were added to alumina powder and the prepared feedstocks were injected at various flow rates. Rheological properties of feedstocks and segregation phenomenon in the green parts were investigated by rotational rheometer and thermogravimetric analyzer, respectively. As well as, mold filing, segregation and distribution of temperature during filling were simulated using Moldflow Synergy (Autodesk) 2019 software and compared to the experimental results. It was found that feedstocks containing 15 wt% micro SiC and 2 wt% nano SiC showed the best rheological behavior. The segregation phenomenon was observed in samples injected at flow rate of 15 cm3/s. No imbalance filling was observed in none of the samples, but by increasing the flow rate the segregation was intensified.

Ball burnishing has been an effective surface finishing process that generally requires pressing hardened steel rolls/balls, during feed motion, into the surface of the metallic workpiece. The purpose of this study is to examine the improvement of the burnished surface quality by optimizing several burnishing factors, including ball diameter (d), depth of penetration (p), number of passes (N) and type of lubricants (L) for improving surface quality of AISI 1010 steel plates. A second-order mathematical model is developed to predict the surface quality as functions of ball burnishing parameters. The optimal burnishing parameters were determined by conducting central rotatable design matrix experiments and predicting the response models for the surface roughness and hardness. The optimal burnishing conditions for the steel plates were found by using a ball diameter of 12 mm, a burnishing depth of 0.25 mm, a number of passes of 5 and 15W-40 (L3) for the type of lubricant. With these optimal parameters, the mean surface roughness is reduced from R_a = 2.48 to R_a = 0.37 µm, while Brinell hardness increases from 59 to 70.88 HRB. The results show that all lubricants used in this study had negligible effect on the surface hardness.

Nb₂O₅/TiO₂ composite coatings were prepared in sodium silicate electrolyte, and the high-temperature oxidation properties of the coatings were improved. SEM showed that the number of micro-pores on the surface of the coatings decreased, and the content of Nb₂O₅ increased from 0 to 9.45% with the increase in Nb₂O₅ concentration. The coatings comprised O, Na, Al, Si, P, K, Ti, and Nb. Nb entered and was uniformly distributed in the coatings, and its content increased from 0 to 13.76%. Meanwhile, the thickness of the coatings increased from 29.57 to 43.27 µm. The coatings comprised anatase-TiO₂, rutile-TiO₂, Nb₂O₅, and Al₂TiO₅. The valence of Nb was assigned to Nb₂O₅ and Nb_xO_y. The average oxidation rate decreased from 2.4333 × 10⁻⁵ to 2.8056 × 10⁻⁶ mg cm⁻² s⁻¹. Nb₂O₅ in the coatings hindered the high-temperature oxidation process and improved the high-temperature properties of the coatings.

Numerous studies have been reported in the past on the fabrication of short-range gun silencers by 3D printing of virgin acrylonitrile butadiene styrene (ABS)-based composite matrix. But hitherto little has been reported on enhancing the performance of such silencers (in terms of enhanced mechanical and thermal properties) for a long service life of the functional parts. Also, limited work has been reported on the use of secondary recycled ABS composite in such applications. Melamine formaldehyde (MF) is one of the thermosetting having acceptable flame-retardant capabilities (available as waste from kitchenware product manufacturing). In this study, the MF was reinforced in an ABS matrix based on acceptable rheological properties followed by a twin screw extrusion process for the fabrication of feedstock filament for the fused filament fabrication (FFF) in line with the concept of circular economy. The functional prototypes of secondary recycled ABS-MF composite (87.5-12.5% by wt.) were prepared with FFF, and the mechanical properties (tensile, compression, and flexural) were optimized. The study reveals that infill density (ID) is the most significant factor for the best mechanical properties of functional prototypes as ultimate tensile strength of 31.68 MPa, ultimate compressive strength of 52.09 MPa, and ultimate flexural strength of 91.85 MPa (supported by optical photomicrographs based on scanning electron microscopy analysis). For multi-factor optimization of FFF (for ABS-MF composite) in silencer application, zig-zag infill pattern (IP) with 100% ID, 0.15 mm layer height, 0.9 mm top and bottom layer thicknesses, and wall line count of 2, at a print speed of 50 mm/s was observed as the best combination.