Structural and mechanical properties of Al–Si alloys obtained by fast cooling of a levitated melt

Data on the structure and mechanical properties of cast Al–Si alloys in a wide compositional range from hypo-to high hyper-eutectic composition are scares. These properties depend on many factors during solidification of the alloys. In the present work, samples were obtained by rapid cooling of levitated melts of various compositions from 11.5 to 35 wt.% Si. The measurements revealed linear concentration dependences of density and Youngʹs modulus. The average temperature coefficient of Youngʹs modulus in the range from room temperature to 500 °C and the yield point for bending both had maxima at about 20 wt.% Si. The hysteresis of the temperature dependence of Youngʹs modulus had a minimum at about 20 wt.% Si as well. Changing Youngʹs modulus temperature coefficient and Youngʹs modulus hysteresis as a function of the Si content are connected with the creation of the Guinier–Preston zones. Values of the yield point are explained by the plasticity of components of the eutectic structure, primary crystals and grain boundaries. The extrema of the concentration dependences of the mechanical properties occurred for the fine-grained structure arisen from coupled eutectic-like growth. Solidification at other conditions led to formation of primary crystals of α solid solution or primary Si crystals.