Experimental characterization of LM13 aluminum piston alloy: composition, mechanical properties, microstructure, and preliminary heat-treatment response

Abstract

LM13 is a near-eutectic Al–Si–Cu–Ni–Mg casting alloy used for pistons and other thermally loaded components. This study provides an integrated preliminary characterization of an industrially relevant LM13 casting by combining optical emission spectrometry, Brinell hardness, tensile and Charpy V-notch testing, optical microscopy, and a duration-based heat-treatment dataset. The measured concentrations of the principal alloying elements were 12.965% Si, 1.468% Cu, 1.044% Mg, and 1.068% Ni, which were within the stated BS 1490 limits used for comparison. The mean as-cast hardness was 91.7 ± 2.9 HBW (n = 3). The recorded tensile strength and elongation were 138.63 MPa and 0.72%, respectively, while the Charpy absorbed energy was 1.3 ± 1.2 J (n = 3) at 25 °C. In a separate dataset, all ten specimens exhibited increased hardness after heat treatment; the mean increase was 17.2%, and the highest recorded post-treatment hardness was 84 HBW for the specimen associated with 17 h. Optical micrographs showed an aluminum-rich matrix containing constituents that were morphologically consistent with silicon-rich phases and with apparent casting discontinuities. The results establish a consolidated baseline dataset for the LM13 casting under investigation. Because the complete thermal cycle was unavailable and a single specimen represented each treatment duration, the duration-dependent response is interpreted as preliminary. It does not establish an optimal heat-treatment condition