In this paper, the effects of melting temperature and the temperature of metal plate on the solidification structure of Al-16Si alloy have been investigated in detail. An ultra-low-temperature copper tube was used to force undercooling of the melt, while metal plates at different temperatures were employed to achieve temperature-controlled solidification. The results show that when the melting temperature is 800 degrees C, the precipitation of primary Si could be completely inhibited by means of forced melt undercooling, and the eutectic structure composed of fine rod and thin sheet shapes could be obtained by solidifying on the metal plate at room temperature. When the forced undercooling alloy melt is poured onto the metal plate at 527 degrees C and solidified on its surface, the pseudo-eutectic solidification microstructure could be obtained.
This study aims to develop eco-friendly, cost-effective, and energy-efficient hybrid aluminium metal matrix composites (HAMMCs) with enhanced performance. Initially, AA6082-T6 reinforced with 2-4 wt% alumina was fabricated under varied casting conditions to produce mono composites. The optimal alumina content was identified using the Taguchi method. Subsequently, hybrid composites were developed by incorporating 3-5 wt% fly ash while maintaining 3 wt% alumina under identical processing conditions. The influence of reinforcements was evaluated through mechanical, physical, and morphological analyses using SEM coupled with EDS. Results indicate that properties improve and stabilise around 3 wt% alumina and 4 wt% fly ash. An integrated optimisation approach combining orthogonal arrays and GRA was employed to handle multiple responses. The grey relational grade was used to identify the optimal combination of process parameters, whereas ANOVA was applied to evaluate significance of each parameter. Confirmation tests validated the effectiveness of the proposed multi-response optimisation strategy.
This study explores whether bonding can form between the two layers of a bifilm defect in commercially pure Zn melt. The defect was simulated by keeping two ZnO layers in contact with each other and the trapped atmosphere between them in the liquid alloy for 1-100 minutes. Changes in the layers' composition and structure were analysed. Findings indicate that the bifilm layers can gradually bond or 'heal'. The process begins with the growth of ZnO, followed by its transformation into ZnAl2O4, which consumes the oxygen in the trapped atmosphere. Subsequently, the formation of AlN consumes nitrogen. During this phase, bonding between the oxides occurs at some points. Ultimately, the formation of Al2O3 from ZnAl2O4 results in extensive bonding between the two oxide layers. A straightforward mass balance calculation confirmed that even a low Al concentration in the Zn melt - less than 0.004 wt%-is sufficient for these reactions to occur.
The M174 alloy is a high-strength, heat-resistant aluminium alloy. However, due to its high hydrogen solubility during the melting process, porosity defects easily form in the solidified ingot, significantly impacting its properties. This study focuses on investigating the degassing of M174 heat-resistant aluminium alloy using a combined ultrasonic field of degasser and refiner. The degassing effect is evaluated by measuring ingot density under normal pressure and through a reduced pressure test (RPT), with observations made on the presence of pores in RPT sections. Results indicate that treatment temperature, UST power, UST duration and other factors have significant influences on experimental outcomes, the combination of degassing agent, refining agent and ultrasonic field can make melt degassing more effective. This experiment provides a reference for the subsequent work of melt degassing.
Aluminium composites having applications extensively in all sectors owing to their excellent strength-to-weight ratio, high thermal conductivity and inherent corrosion resistance. Nevertheless, incorporating reinforcements to improve mechanical properties can significantly influence the corrosion characteristics of the base metal. The electrochemical studies focus on evaluating the corrosion behaviour of different aluminium matrix composites (AMCs) synthesised with varying beryl compositions (6%, 8%, 10%, 12%) in 0.1 M NaCl at different temperatures. Potentiodynamic polarisation (PDP) results indicate that an increase in the concentration of beryl decreased the corrosion rate till 8%. Morphological studies supported the above results showing minimum roughness for 8% beryl with respect to 0% beryl composite, supporting the EIS and PDP studies. The Monte Carlo (MC) results show that higher adsorption energies (more negative values) indicate that beryl is better able to create a stable, protective layer on the AlBeCe composite surface, which improves corrosion resistance.
Direct rolling for high-silicon ingots simplifies the forming process, but quality control limits their weight. This paper presents the casing of Fe-6.5 wt.% Si alloy ingot with a weight of 200 kg. The air-cooling casting experiment revealed coarse grains and transgranular and surface cracks. A weak cooling method after demoulding is proposed to address these issues. A physical model was established and validated. The evolution of thermal, solidification structure and stress distribution are simulated under air cooling and weak cooling condition. Comparative studies show that applying weak cooling reduces the temperature gradient from the centre to the one-sixteen length position from 1.54 K/mm to 0.3 K/mm, achieving an equiaxed crystal ratio of 81.73%. The maximum stress during solidification decreased from 132.35 MPa to 33.81 MPa. Then, weak cooling casting and rolling experiment produces defect-free ingots and plates, confirming the feasibility of the optimisation.
Euler multiphase model was used to predict the macrosegregation and grain size in the direct chill casted ingots. The simulation results reveal the formation mechanisms of the macrosegregation pattern and the grain size distribution, and demonstrate the effect of adjusting Mg/Si ratio, increasing Cu content and adding Ce/Ag. The sedimentation of equiaxed grains dominates the melt flow in the melt pool of the direct chill casting process, and thus the segregation pattern and grain size distribution. Macrosegregation, as well as grain size distribution, shows alternating positive/negative pattern in the radial direction, which is determined by the sedimentation of negatively segregated equiaxed grains, the melt flow along the melt pool and the thermal buoyancy-driven descent flow. Compared with the alloy with Ce/Ag addition, the increase in Cu or Mg content enhances the formation of solute segregation in the ingot.
Metal Matrix Composites (MMCs) are now recognised as the most efficient and effective materials for achieving sustainable development in Industries. Additionally, it fulfils the design requirements across various applications, including aerospace, renewable energy and biomedical devices. Stir casting is a highly suitable method for manufacturing MMCs owing to its inherent capabilities, such as lower cost in mass production and proven process. This paper aims to present a comprehensive overview of the diverse manufacturing approaches adopted in the fabrication of MMCs with consideration of organic and inorganic volume reinforcements. As per our observations, the stir-casting process helps us in bulk production and reduces the cost of fabrication. The utilisation of variable processing techniques for energy and time management has been identified as a factor that significantly impacts the quality and quantity of the produced items. Furthermore, this critical review extensively addresses pertinent recommendations concerning process variables, existing challenges, and casting methods.
In this work, the metallurgical and mechanical properties of AA6082 aluminium alloy reinforced with different weight percentages of SiC and TiO2 (2%, 4%, 6%, and 8%) was analysed. AA6082 (6 vol.% SiC + 4 vol. % TiO2) composite exhibited increases in the maximum UTS of 19.98%, and hardness of 19.21%, while maximum hardness increases of 28.71% for MMC_S4 (8 vol.% SiC + 2 vol. % TiO2). Microhardness measurements revealed a linear improvement with rising TiO2 content, peaking at 125.5 hV in the AA6082/8 wt% SiC/2 wt% TiO2 composite - a 28.71% increase compared to the base alloy. This increase was attributed to the hardness of nanoparticles and grain refinement. Microstructural analysis showed significant grain refinement as the SiC and TiO2 content increased, with the 6% SiC and 4% TiO2 composite displaying the finest grain size. However, higher TiO2 concentrations presented difficulties in achieving uniform nanoparticle dispersion, leading to clustering and porosity.
Aluminium alloys are used as replacements for heavier materials due to their strength and density. The regulations to reduce CO2 emissions have promoted the development of higher-power output engines, and heat-treated aluminium-copper is designed for such engines. In addition, these alloys can be used as toolings for plastics. Hence, there is a need to evaluate the effect that the microstructure exerts on the mechanical properties of Al-Cu alloys over a wide temperature range. Al-Cu alloys were cast, varying their composition, and tested in tension at room temperature and within the 150 to 300 degrees C range after maintaining them for up to 200 h at the testing temperature. It was found that the yield strength of some alloys was above 200 MPa after 200 h at 200 degrees C. Therefore, it would be possible to use such alloys for toolings and combustion engines with adequate processing.
This work developed a self-curing investment casting slurry with a short cure time to mitigate the prolonged drying regime of conventional investment slurry. Powdered charcoal served as microporous phase in the slurry, for sequestering entrapped gases. Other slurry components include silica sand, bentonite, sodium silicate and ammonium hydrogen bicarbonate which serve as refractory base, binder, hardener and curing agents, respectively. Their optimal mixing proportion was determined to be 48 wt. % silica sand, 40.4 wt. % bentonite, 5.6 wt. % ammonium hydrogen bicarbonate and 6 wt. % charcoal. They were mixed into a slurry with acidified water and sodium silicate solution. Casting surface areal parameters Sa, Sq and Sz of 1.40, 1.74 and 12.30 mu m, respectively, were obtained, indicating a smooth surface. The optimal composition was trialled to cast a replica OEM automobile component and was able to accurately reproduce the features of the wax pattern, with minimal superficial defects.
The main objective of the research is to synthesize the Al-Mg nanocomposite with 5wt% alumina (Al2O3) and 0-9wt% of nano silicon carbide (SiC) particle through semi-solid stir processing. X-ray diffraction and mechanical properties of Al-Mg-SiC nanocomposites are measured and compared with Al-Mg alloy. The Al-Mg/5wt%Al2O3/ 9wt%SiC alloy nanocomposite identified higher microhardness (131HV) and tensile stress (208MPa). It was subjected to a dry drilling process via MTAB vertical type CNC machine using CBN coated tool under the combinations of low spindle speed (300 and 500rpm) and feed rate (5, 10, 15, and 20mm/min). After the drilling operation, the tool wear and surface roughness were measured by each cutting condition. The composite dry drilled with 500rpm at maximum feed rate showed the optimum tool wear of 0.033mm and recorded by 55sec machining time for 20mm depth of cut. Similarly, low surface roughness (1.1 +/- 0.01 mu m) with better surface is noted.
In this study, a centrifugally cast A413/Al3Ni in-situ functionally graded composite was successfully drilled using an Electrical Discharge Machine to understand its machining performance. In addition to the selected process parameters for Electro Discharge Drilling, volume fraction of in-situ Al3Ni trialuminide in three zones (inner, mid, and outer) across the radial thickness of the fabricated cylinder was also considered for drilling operation. The experiments were planned using a Taguchi-based design of experiment, and drilling parameters were optimised using Grey Relational Analysis (GRA) to reduce Surface Roughness (SR) and Tool Wear Rate (TWR) while improving Material Removal Rate (MRR). Multi-response optimisation resulted in using a pulse ON time of 3 mu s, a pulse OFF time of 9 mu s, a volume fraction of 8.3% of Al3Ni trialuminide, and a pulse current of 12 A produces better drilling performance. Further, SEM investigation of drilled surfaces was carried out to identify the impact of machining.
Excellent strong points and robust resistance to abrasion, corrosion, and wear are essential for the aircraft industry. The goal of the current project was to develop a novel, high-performance material for the space sector. Stir casting was used to manufacture MMC AL7075-WC-TiB2, and their tribological properties were examined. Five composites in all, AL/T, AL/W, AL/WT (1:2), AL/WT (1:1), and AL/WT (2:1), were created. The composites underwent microhardness, wear, and tensile testing; the results were compared to those of the AL7075 alloy. Because of the reinforcing effect of the highly hard WC particles, the AL/W composite demonstrated a higher hardness value of 160 hB in the Brittleness hardness test when compared to other materials. Because of the higher dislocation density, tensile testing showed that the AL/W composite had the maximum tensile strength of 507 MPa. Furthermore, because the WC particles supplied a larger resisting force, the wear tests showed that the AL/W composite had the lowest wear rate, at 0.00115 mm3/m. Additionally, there is potential for future study in this field by constructing the composite using a variety of fabrication techniques, including dust metallurgy, vacuum casting, press casting, and so forth, and then assessing its performance.
This research synthesis the aluminium hybrid composite made with 5-15% of nano SiC and 5% of ZrO2 reinforcement via ultrasonic vibration-assisted stir casting techniques. Influences of hybrid reinforcements on tribological behaviour of composites are evaluated by different sliding spans (1000 to 3000m), load (10-20N), and sliding speed (1.5 to 4.5m/s). The hybrid Al5083/5wt% ZrO2/15wt% SiC composite is noted to have a lower wear rate ranging from 0.0008-0.0016 mm3/Nm and enhanced friction coefficient of 12-0.25 at 4.5m/sec for 3000m under 30N applied load. Moreover, the increased sliding speed and distance lead to an increase in the wear rate and limits the friction coefficient. The tribological behaviour of the hybrid composite Al5083/5wt% ZrO2/15wt% SiC was observed to exhibit diverse surface characteristics due to the occurrence of delamination, wear debris, tribo-chemical wear regimes, and two-body and three-body abrasion wear. Furthermore, the presence of pits and oxide layers was also noticed.
This study focuses on the investigation of AA2014-SiC MMNCs and their properties, manufactured through a novel stir-ultrasonic-squeeze casting technique. The combination of these three methods gives better dispersion of the SiC nanoparticles as well as lesser porosity of the casting. The weight percentage of SiC added was varied to study the effect of it on the properties. Microstructural analysis was carried out to understand the dispersion of SiC nanoparticles within the aluminium. The addition of SiC nanoparticles significantly improved the tensile strength, yield strength, and hardness up to 5%wt. At 7% wt. of SiC, these properties deteriorated. The tribological properties of the AA2014-SiC MMNCs were studied using a ball-on-plate linear reciprocation type multi-function tribometer. As the hardness of the composite increased with %wt of SiC, the wear rate and coefficient of friction of the composite decreased significantly up to 5 wt% SiC beyond which both the properties again have increased.
