Vol.:(0123456789) 1 3 Metals and Materials International https://doi.org/10.1007/s12540-019-00550-6 Efect of Semi‑Solid Heat Treatment on the Microstructure and Dry Sliding Wear Behavior of Al–20Si Alloy at Optimized Parametric Conditions Mihira Acharya 1  · Animesh Mandal 1 Received: 22 October 2019 / Accepted: 15 November 2019 © The Korean Institute of Metals and Materials 2019 Abstract Hypereutectic Al–20Si alloy needs optimization of diferent process parameters in order to obtain maximum wear resist- ance for tribological applications aerospace and automobile industries. The present study attempts to fnd the best possible combination of the process parameters for the semi-solid heat treatment of the alloy in Taguchi Method. The efects of three diferent control variables i.e. sliding velocity, sliding distance, and load on the wear characteristics were investigated. The optimal values of control factors were determined on the basis of ‘smaller-is-better’ approach from Taguchi optimization technique. The optimized conditions for wear tests were then applied to the isothermally heat-treated samples (10–30 min) at 600 °C. The quantitative analysis shows the signifcant change in the size, morphology, and distribution of primary Si and eutectic Si with heat treatment. Moreover, the worn surfaces were analyzed from the microstructures obtained in Field Emission Scanning Electron Microscopy (FESEM). The improved wear resistance observed in the case of 20 min of hold- ing time can be attributed to the combined efect of refnement of primary Si, modifcation of eutectic Si and equiaxed α-Al during semi-solid heat treatment. Keywords Al–20Si · Primary Si · Eutectic Si · Wear · Taguchi · ANOVA 1 Introduction Al–Si alloys have been preferred as potential candidate materials for applications in the aerospace and automo- tive industry due to its high strength to weight ratio, good corrosion resistance and wear resistance [1–5]. The wear properties can be improved by dictating the shape, size, and distribution of diferent phases present in it. It is well known that the typical as-cast microstructure of hypereutectic alloy contains primary Si, eutectic Si and α-Al phase [6]. The presence of primary and eutectic Si is responsible for better wear resistance of the alloy [7–9]. Extensive studies have been carried out over the years to observe the efect of sili- con on dry sliding wear behavior of Al–Si alloys [10–12]. Wang investigated the efect of diferent wt% of silicon contents in Al–Si alloy synthesized through spray casting [13]. However, it has been observed that the coarse primary Si and acicular eutectic Si obtained in conventional cast- ing leads to poor wear resistance. The recent studies have focused on controlling the microstructure in order to achieve better wear resistance [14]. Thus, diferent routes have been adopted to cast Al–20Si alloy. Among rapid solidifcation techniques, spray casting was used to reduce the size of Si particles by providing a large cooling rate. [13]. Teng et al. [15] incorporated 15 vol% of SiC to enhance the wear resistance in spray casting process. Similarly, Kang and El [16] studied the wear behavior of hypereutectic Al–Si alloy synthesized with selective laser melting route. However, compared to these processes, addition of trace elements for modifcation in the conventional casting route is rela- tively economic. Thus, considerable eforts have been made to change the morphology and distribution of the Si parti- cles in Al–Si alloys with the addition of diferent elements [17–22]. It was found that the refnement of primary Si and modifcation of eutectic Si from acicular to nearly spherical morphology enhances the wear resistance [23–25]. This can be attributed to better bonding between Si particles and Al * Mihira Acharya ma10@iitbbs.ac.in 1 Indian Institute of Technology Bhubaneswar, School of Minerals, Metallurgical and Materials Engineering, Argul, Odisha 752050, India