Data on the effect of high-pressure torsion processing on secondary cast Al–10%Si– Cu piston alloy: Methods, microstructure and mechanical characterizations

The dataset presented here shows the microstructure and mechanical properties of secondary (recycled) cast aluminum-silicon (Al–Si) piston alloys processed through severe plastic deformation technique, known as high-pressure torsion (HPT). The HPT processing was undertaken for 1/4, 1/2, 1 and 10 turns of the lower anvil (rotating at constant speed of 1rpm) while the upper anvil maintained at a normal pressure of 3.0 GPa. The data on microstructural evolution obtained at the central region and edge of the circular (disk) HPT sample were obtained using optical and scanning electron microscopy and these data are presented here. The data on the analysis of the particle shape, sizes and distribution from the micrographs using ImageJ software are also presented. Data on mechanical properties characterized using Vickers microhardness measurement across the surface of HPT sample are also shown. Pictures depicting the microhardness measurement scheme, high-pressure torsion facility and sample nomenclature are presented.


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The dataset presented here shows the microstructure and mechanical properties of secondary (recycled) cast aluminum-silicon (AleSi) piston alloys processed through severe plastic deformation technique, known as high-pressure torsion (HPT). The HPT processing was undertaken for 1/4, 1/2, 1 and 10 turns of the lower anvil (rotating at constant speed of 1rpm) while the upper anvil maintained at a normal pressure of 3.0 GPa. The data on microstructural evolution obtained at the central region and edge of the circular (disk) HPT sample were obtained using optical and scanning electron microscopy and these data are presented here. The data on the analysis of the particle shape, sizes and distribution from the micrographs using ImageJ software are also presented. Data on mechanical properties characterized using Vickers microhardness measurement across the surface of HPT sample are also shown. Pictures depicting the microhardness measurement

Data
The data presented here is on the evolution of the properties of secondary aluminum-silicon. Piston alloy severely deformed through high-pressure torsion (HPT). The picture of the HPT facility used is shown in Fig. 1. Fig. 2 represent the optical and SEM micrographs of the unprocessed secondary AleSi piston alloy showing the dominant phases identified via EDS technique. The SEM image showing the breakdown of phases at the edge of the alloy after 1/4 turn is represented in Fig. 3. Fig. 4 shows the various microstructural transformations at the central and periphery of the samples after 1/2 turn. Figs. 5 and 6 represent the microstructure changes at the center and edge of the samples processed at 1 and 10 turns respectively. The data of circularity analyses determined through the ImageJ software for the microstructure of the samples at different number of turns of the HPT process are presented in Table S1 and plotted in Fig. 7. Microhardness data and corresponding profiles along the radial surface are shown For high-pressure processing, microscopy and microhardness measurements, the samples were ground to SiC grade #1200, washed in acetone, polished to 1/4 m diamond paste and oxide polish suspension finish (0.05 m) and sonicated in ultra-sound bath in distilled water and dried.

Data source location
University of Southampton, UK and Department of Mechanical and Manufacturing Engineering, University of Nairobi, Kenya Data accessibility Data is with this article

Value of the data
The data can be used as a basis for understanding the evolution of microstructure and mechanical properties of recycled (secondary) cast Ale10%SieCu piston alloys processed through high-pressure torsion (HPT) at different number of turns. The data can be used as a reference study for improvement of behavior of recycled aluminum alloys through HPT and evolution of homogeneity across the surface of the processed samples. The data will be beneficial to researchers, scientists and industrialists interested in understanding, interpreting and utilizing high pressure torsion in processing of recycled aluminum alloys.
The new method of evaluation of microhardness and the corresponding hardness data presented here will be beneficial to researchers to analyze the homogeneity evolution with the strains. This will further enhance development of HPT processes for effective and uniform straining of alloys for industrial applications.  Table 1 and Fig. 9. The dataset on variation of the hardness with equivalent strains are also shown in Table 2 and Fig. 10.

Experimental design, materials, and methods
The recycled AleSi piston alloy used in this research had the following composition: 10.6%Si, 1.36% Cu, 1.08%Ni, 0.78%Mg, 1.06%Fe, 0.08%Mn, 0.03%Cr, 0.06%Ti, 0.02%Sn, 0.09%Zn and 0.04%K. The alloy was produced through sand casting. Specimens of the recycled cast AleSi piston alloys were sliced from the as-received ingots with a diameter of 10 mm and ground with abrasive papers to a thickness of 0.8e0.85 mm. The HPT processing was conducted at room temperature at 1rpm rotation of the lower anvil and under a pressure of 3.0 GPa of the upper anvil on an HPT facility shown in Fig. 1. Briefly, the  HPT facility consists of high-strength tool steel lower and upper anvils with circular cavities of 10 mm diameter and 0.25 mm thickness. The specimens were processed for 1/4, 1/2 1 and 10 turns of highpressure torsion processing.
Samples from the as-received alloy and the HPT-processed specimens were mounted and ground using silicon carbide papers up to #1200. They were then polished up to 1/4 mm mirror-like finish using diamond pastes. Finally, the specimens were polished to oxide polish suspension finish (0.05 m). The  microstructural observations were undertaken using optical and scanning electron microscopy. Identification of the intermetallic phases in the alloy was carried out using the Electron diffraction Spectrometer (EDS) incorporated into the SEM equipment. The micrographs are presented in Figs. 2e6. The images were also analyzed using ImageJ software to quantify the microstructural refinement during the HPT process. From the analysis, the area (A) and circularity of particles were obtained.   Table 1 Microhardness data and their corresponding error bars for unprocessed samples and samples processed at 1/4, 1/2, 1 and 10 high-pressure turns (Plots in Fig. 9 9. The average Vickers microhardness (Hv) against the distance from the center of the disk for 1/4, 1/2, 1 and 10 turns of HPT processing at a pressure of 3 GPa on the upper die and at a rotational speed of 1rpm of lower die. The microhardness line profile for the as received sample is also shown for comparison. The error bars computed using 95% confidence level are also shown.