Abstract
Aluminium casting alloy LM4 (EN 1706 AC-45200) composites with TiB2 (1, 2, and 3 wt.%) as reinforcements were produced using the two-stage stir casting method. OM and SEM study shows uniform and homogeneous reinforcement distribution in LM4 + TiB2 composites. As-cast composites were subjected to single-stage solution treatment at 520°C for 2 h and multistage solution treatment at 495 and 520°C for 2 and 4 h, followed by hot water quenching at 60°C and aging at 100 and 200°C for different time intervals. The hardness of as-cast and artificially aged composites were compared in both conditions. Compared to as-cast LM4 alloy, 20-45% improvement in hardness was observed for LM4 + TiB2 as-cast composites. 60-150% improvement in hardness was observed in artificially aged LM4 + 3 wt.% TiB2 composites when aged at 100 and 200°C during peak aged conditions. TEM images confirmed the presence of primary strengthening solute-rich phases after age hardening treatment such as θ’-Al2Cu and θ”-Al3Cu, which are responsible for hardness increment. An artificial neural network (ANN) model was created to predict the hardness trend of these composite samples using MATLAB R2021b, and results proved that the ANN model developed can be utilized as an effective tool to predict the hardness of treated composite samples.
Highlights
Compared to as-cast LM4 alloy, 80-150% increase in hardness was observed when aged at 100°C and 65-120% increase in hardness was observed at 200°C during stage solution heat treatment (SSHT) and multistage heat treatment (MSHT), respectively
In preparation of composites, two-stage stir casting is proved to be the best one as all the composites with 1, 2, and 3 wt.% TiB2 exhibited uniform distribution of reinforcement particles, which is clear from the optical microscope images
The hardness results show that with an increase in wt.% of TiB2, the hardness has increased, and MSHT samples aged at 100°C with 3 wt.% TiB2 exhibited the highest hardness values when compared to other samples
Summary
Castings made of aluminum-based alloys have played a significant part in the expansion of the aluminium industry. Because of their unique qualities, aluminium alloys have been utilized in the aircraft industry with a substantial substitution of steel components[1,2]. LM4 alloy (hypoeutectic alloy) offers a remarkable blend of strength, low coefficient of thermal expansion at increased temperatures, and great wear resistance[5] and can be used in clutches, tool handles etc[3]. In comparison to other aluminium alloys, LM4 aluminium alloy has higher mechanical strength and greater wear resistance[6]. The type, vol.%, and size of precipitate from supersaturated solid solution during ageing treatments determine the strength of aluminium alloys[12]. Solutionizing time is a critical variable that contributes to the dissolution of Cu phases and improves precipitation of θ” and θ’-Al2Cu during aging13. θ” and θ’ precipitates are considered to be responsible for strengthening of the A319 alloy during aging treatment[12,14,15,16]
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