International Journal of Lightweight Materials and Manufacture最新文献

In recent year, Al–Mg₂Si composite becomes a topic to be discussed whether there is a potential to replace common automotive material, Al–Si in applications like piston and brake disk. However, the course with a sharp corner of primary Mg₂Si act as the stress concentration promote the initiation of crack to propagate, resulting in low mechanical and tribological performance. Hence, modification of Mg₂Si particles in Al–Mg₂Si composite is a prime concern. In the current work, the impact of cooling rates on the modification primary Mg₂Si crystal shape in 0.2 wt% Ba modified Al–20%Mg₂Si composite was evaluated. With mould preheating in different temperatures, the cooling rate was controlled. When the mould temperature is lowered, the cooling rate is increased which causes primary Mg₂Si crystal formation with different structures due to Ba atoms adsorption on {100} facets of Mg₂Si crystal which can be considered as external factors strengthening. Once the temperature of mould reduced from 600 °C to 400 °C, 200 °C and lastly to 25 °C, the primary Mg₂Si morphology changed from octahedral to truncated octahedral, truncated cube and finally to a cube respectively. Tensile results showed that Al–20%Mg₂Si-0.2%Ba composite solidified in the mould with temperature of 600 °C, the values of UTS and El% are higher than other composites solidified in other mould temperatures. Furthermore, the tensile fracture surface of Al–20%Mg₂Si-0.2%Ba composite solidified in the mould with temperature of 600 °C depicted less decohesion and debonding of the primary Mg₂Si particles in the aluminium matrix together with fine dimples on the fracture surface which elucidate the ductile fracture mechanism. The size and structure of the primary Mg₂Si in the Al–Mg₂Si composite can be regulated by using this practical, affordable approach, leading to the use of this composite in industrial products.

Biodegradable magnesium (Mg) alloys hold great potential for revolutionizing the field of biomedical engineering by offering temporary support during tissue healing and degrading without leaving permanent residues. However, their clinical applications have been limited due to their relatively high degradation rate. This study focuses on evaluating the in-vitro degradation, fatigue resistance, and fracture toughness properties of Mg alloys under cyclic loading conditions, mimicking real-life scenarios. Wire Electrical Discharge Machining (WEDM) was used to prepare spark-processed Mg samples with complex surface texture, and fine-polished Mg samples were used for comparison. The structural characterization, electrochemical corrosion behavior, degradation assessment, and mechanical integrity of the samples were comprehensively analysed. The results show that the Electrical Discharge processed (EDed) Mg sample exhibited uniformly distributed overlapped craters on the surface, which led to a lower charge transfer resistance and higher corrosion potential compared to the Pristine Mg sample. The rough surface topography and alkaline pH microenvironment of the EDed Mg sample facilitated rapid apatite mineralization, but the resulting Ca-deficient apatite compromised its structural stability. Both EDed and Pristine Mg samples exhibited a significant reduction in fatigue life and lower fracture toughness with prolonged immersion. These findings provide valuable insights into the performance of Mg alloys and their potential applications in biodegradable implants, guiding the design of robust implant materials for enhanced patient outcomes.

This work investigates the influence of parameters of initial ultrafine-grained (UFG) structure in commercially pure (CP) Al on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects. UFG structures were formed via processing CP Al by various methods of severe plastic deformation (high pressure torsion (HPT), equal channel angular pressing (ECAP) and combination of ECAP and cold rolling (CR)). AIH and DIS effects are observed in all the studied UFG structures. However, HPT Al demonstrates large increase of strength due to annealing and drastic gain of ductility after subsequent additional deformation whereas in ECAP Al and ECAP + CR Al both effects are much less pronounced. Microstructure characterization by X-ray diffraction (XRD) analysis, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) was performed for HPT Al and ECAP + CR Al in the three studied states: before and after annealing and after annealing and subsequent additional deformation. Analysis of microstructure evolution during annealing and subsequent additional deformation shows that the key microstructure parameter which is responsible for AIH and DIS effect is the change of dislocation density in grain interior in ECAP + CR Al, whereas in HPT Al the effects are related to the change of dislocation density at/near grain boundaries. In addition, outstanding combination of high strength (∼210 MPa), high electrical conductivity (∼62 %IACS) with sufficiently good ductility (7–10 %) and thermal stability (up to 150°С, at least) was achieved for ECAP + CR Al after annealing at 150 °C, 1h.

This study introduces a new rotary draw bending method that utilizes a variable curvature bending die. Unlike traditional methods that bend tubes with a fixed radius, this method gradually deforms the tube from a large to a small radius. The curvature of the bending die is determined by using an involute curve as the equation for the geometric location of the variable curvature. Hydroforming technology, utilizing fluid under pressure, replaces the mandrel in the rotational tensile bending process. The research was conducted using a thin-walled AA6063 tube with a 13.88 diameter-to-thickness ratio. The bending process was examined at critical bending ratios of 1 and 1.6 times the diameter, with a 90° bending angle. The maximum pressure that can be applied in any bend radius ratio was predicted using the necking criterion. The simulation and experimental tests analyzed the effects of internal fluid pressure and bend die curvature on defects such as wall thinning in the outer curvature of the bend, thickening of the wall in the inner curvature of the bend, and cross-section non-roundness. The results indicate that, at constant pressure, the amount of thinning and thickening of the bent tube is significantly improved when using the variable radius bending die compared to the fixed radius die.

The main objective of this investigation is to study the effect of post weld heat treatments (PWHTs) on tensile properties, hardness, and microstructure of pulsed CMT–MIG (cold metal transfer arc–metal inert gas) welded AA20214-T6 aluminum alloy joints. The welded joints were subjected to PWHT of artificial aging (AA), solution annealing treatment (ST) and ST + aging (STA). The tensile properties and microhardness of joints were evaluated. The microstructure of joints was studied using optical microscope (OM) and transmission electron microscope (TEM). The fractured surface of tensile specimens was analyzed using scanning electron microscope (SEM). Results showed that the tensile properties and hardness of as welded and PWHT joints are inferior compared to base metal (BM). This mainly refers to the microstructural heterogeneity in different regions of joints and softening of heat affected zone (HAZ) induced by the weld thermal cycle. The PWHTs of AA and ST did not show significant effect on tensile strength and hardness of AW joints. However, the slight reduction in elongation was observed in AA and ST joints. The STA joints showed higher joint efficiency of 71.6%, than other joints by compromising on the elongation. This refers to the greater precipitation of hardening precipitates in STA joints compared to AA and ST joints. It exhibited the higher tensile and yield strength of 326 MPa and 266 MPa and the lowest elongation of 3.8%. The STA joints showed 28.35%, 38.28% and 57.77% reduction in tensile strength, yield strength and elongation compared to BM respectively. All the tensile specimens of joints failed in HAZ owing to the lower hardness. This refers to dissolution of precipitates in HAZ. However, the HAZ softening is less severe in STA joints than AW, AA, and ST joints.

The effectiveness of local laser heat treatment technology to enhance the in situ formability of steels and aluminum alloys has already been widely acknowledged for the one-step forming of components with simple shape geometries. The present study demonstrates that this technology is also able to significantly improve the formability of a complex shaped multi-forming industrial part. An industrial grade advanced-high strength Dual-Phase DP1000 steel is used to analyze the multi-forming of a complex part to determine the most appropriate local laser heat treatment parameters and optimize in situ softening by correlating yield strength, ultimate tensile strength, elongation at fracture, strain hardening exponent and instantaneous strain hardening with local temperature dynamics during the laser treatment. Additionally, numerical simulation analysis using Autoform software is carried out to validate the selected heat affected zone and the in situ softening, ensuring that they are appropriate for improving the formability of the industrial part. These findings are then expanded to study the experimental forming of five in situ laser heat treated models, followed by comparative analysis with a benchmark. This study provides an insight and fundamental guidelines to perform in situ laser heat treatment on complex industrial parts leading to the production of the industrial multi-formed component with optimized formability.

Titanium alloys are widely used in various industrial applications due to their excellent properties. Due to its excellent heat conductivity and stability, graphene (Gn) can help Ti components last longer and experience less wear. In the current study, Ti6Al6V2Sn (Ti662) with various wt.% Gn was produced. The composite samples were subjected to metallurgical characterization to analyze the influence of Gn addition in the microstructure and phases formed. The properties such as microhardness and wear resistance were analyzed for all the samples. Variations in the load, sliding velocity, and distance were made during the wear test, and the effects of these factors on the wear rate and morphology of the worn surface were examined. Mechanical property analysis revealed that Ti662 + 0.5Gn exhibited the highest microhardness of 514.32HV, which was 1.45 times that of the matrix material. The sample with 0.5Gn exhibited increased wear resistance, the order of wear resistance observed was Ti662 + 0.5Gn > Ti662 + 0.75Gn > Ti662+1Gn > Ti662 + 0.25Gn > Ti662. The wear rate was reduced by 44.15 % at 40 N, 42.07 % and 52.02 % at 1.5 m/s and 2000 m for Ti662 + 0.5Gn composite. Worn surface morphology revealed that at elevated loads, abrasive and delamination wear was observed while at elevated velocity and distance, the formation of mechanically mixed layer (MML) was observed.

Three-layer aluminum/polymer/aluminum composite sheets are among the new materials developed to reduce the weight and fuel consumption of vehicles. Using the conventional methods for joining these materials to other materials is challenging. In this paper, the joinability of the three-layer aluminum/polymer/aluminum to a single-layer 1 mm-thickness aluminum sheet, in the clinching process is investigated. Three-layer sheets of AA5754/polyethylene/AA5754 with thicknesses of 0.5/0.6/0.5 mm were produced under laboratory conditions using two different methods; with and without a local reinforcement piece in the polymer core. The prepared specimens are joined using various geometric parameters of the clinching tools. The joint sections and their geometric parameters including interlock and neck thickness are evaluated in different joint conditions. Also, the strengths of the joints are examined by shear and peel tests. Studies show that it is possible to use the clinching process to join aluminum/polymer/aluminum sheets. Also, with a proper design of tools, the joint strength can be in the same order as the strength of the clinching of single-layer sheets. The maximum shear and peel test strengths, obtained in this study are 1288 N and 540 N, respectively. Increasing the pin penetration depth increases the interlock up to an optimal value. However, further increases in the pin penetration depth will decrease the neck thickness and joint strength. The conical angle of the pin, increasing the die cavity depth, and using a local reinforcement piece reduces the strength of the clinched joint and interlock in these materials. In all the test conditions, the most suitable joint conditions were when the failure mode was combined bottom separation and neck fracture mode.

The article presents the results of research that make it possible to solve a significant scientific problem associated with the creation of new technologies for processing hard-to-deform aluminum-silicon alloys. For this purpose, tasks were set and solved for the development of technological schemes for obtaining longish products from AlSi12 and AlSi5 alloys using the methods of electromagnetic crystallization ingots of a small cross-section and the manufacture of deformed semi-finished products in the form of rods and wire using the method of combined rolling-extrusion (CRE) and drawing. To solve these problems, the modeling of the CRE process, theoretical and experimental studies were carried out, the results of which made it possible to obtain pilot batches of welding wire from the AlSi12 alloy, the level of properties of which meets the requirements of current standards. To analyze the combined rolling-extrusion, modeling was carried out using the DEFORM 3D software package. Regularities were established for changing the temperature-rate and force parameters of this process along the deformation zone. Since the use of the proposed technological scheme for the combined processing of aluminum-silicon alloys leads to a decrease in labor intensity and production costs, it can be recommended for use in industry to obtain longish products from them.

Three polymeric materials; polystyrene (amorphous), low-density polyethylene (semi-crystalline), and poly(methyl methacrylate) (amorphous) were used to explore their behavior and properties during processing using a co-rotating twin-screw extruder. Injection molding and compression molding were used for preparing the test specimens. Screw speed and barrel set temperatures were considered as the main processing variables while observing the process energy consumption of the extruder. The tensile, thermal, and rheological properties of the extruded materials under different processing conditions were evaluated. Test results confirmed that the motor power of the extruder for processing polystyrene and low-density polyethylene increased with increasing screw speed and decreased with increasing barrel set temperatures. Motor power for processing poly(methyl methacrylate) increased significantly with increasing screw speed. The total power consumption of the barrel heaters for processing polystyrene and low-density polyethylene slightly increased with the barrel set temperatures. The tensile modulus of polystyrene decreased with increasing screw speed at higher barrel set temperatures, while low-density polyethylene showed no significant variation. The tensile modulus of poly(methyl methacrylate) did not exhibit a clear trend with the extruder process settings. The effect of process settings on the glass transition temperature and melting temperature of the polymers was not significant, and no evidence was found of any molecular degradation during processing. Rheological properties of poly(methyl methacrylate) showed a significant variation with increasing screw speed and barrel set temperatures, while those of polystyrene and low-density polyethylene did not exhibit a consistent variation.