CALCULATION OF MECHANICAL AND FOUNDRY CHARACTERISTICS OF Al-Si ALLOYS USING REGRESSION ANALYSIS

Al-Si alloys alloyed with Mn and Mg are widely used in industry, especially as cast alloys. The presence of Mg allows subsequent heat treatment, which will improve mechanical properties. Al-Si alloys generally contain Fe; its content between 0.3 and 0.5 wt% increases strength and fluidity. But the content higher than 1 wt % causes the formation long, hard, and brittle needles of β – phase (FeSiAl 5 ) which act as notches. Mn improves strength and mechanical properties at high temperature. Excessive Fe segregate with Mn in coarse “chinese script” particles (Fe,Mn) 3 Si 2 Al 15 which are less harmful than β – phase. Alloys containing 3.8-11.20 wt% Si, 0.12-1.76 wt% Fe, 0-2.25 wt% Mn and 0-0.73 wt% Mg, modified with 0.02 wt% Sr were analysed. The samples were cast in the form of a "harp" for calculating the fluidity by the vertical method and in samples for tensile tests – ultimate tensile strength ( R m ), total elongation ( A 5 ), the reduction of the area (contraction Z ), and hardness HV 10 were determined. In addition, the microstructure was evaluated. From these sources, the equations that define the relationship between the composition of the alloy and its properties were determined by linear regression analysis. There is a strong correlation ( r 2 = 0.73-0.81) between the properties calculated with obtained equations and the actual values. The content of Mn (0.3 wt%) and Mg (0.25 wt%) was determined by optimization using DoE (design of experiments), which will ensure optimal values of the analysed properties.