SYNTHESIS AND CHARACTERIZATION OF ALLOYSAl-10, 30, 50 AND 70% WEIGHT SiOBTAINED BY MECHANICAL ALLOY

Abstract

Al-Si alloys, with concentrations of 10, 30, 50 and 70% Si weight, have been synthesized by mechanical alloy and characterized by DRX, MEB, DSC and Impedance. For alloy powders X-rays detected only diffractions of Al-and Si-relevant to the cubic system, with space group Fm-3m for Al and Fd-3m for Si; The aAland aSinetwork parameters showed different behaviors depending on whether the alloy is hypoeutectic or hypereutectic. The crystallite sizes decrease as the grinding time increases independently of the Si concentration to a final value between 25 to 30 nm at 40 hours of grinding; The relative deformation for hyper eutectic Si concentrations increases with the Si concentration and tends to grow at milling times greater than 40 hours. Microscopy reveals changes in morphology with the Si concentration and EDS analyses show the presence of oxygen, iron, and carbon. Density decreases with increasing Si amount and with increasing grinding time. The impedance techniques are shown as a useful tool in the characterization of alloys, reflecting a different behavior for hypoeutectic and hypereutectic structures. The electrical resistivity values reported in this work are framed between the limit values established for two phase isotropic composites. The calorimetric study reflects a single endothermic reaction around 579 ºC and 567 ºC, for hypo and hyper eutectic alloys, which analyzed by deconvolution and the kinetic method of Sestak-Berggren was mainly associated with the eutectic transformation reported in the phase diagram. The presence of oxygen in the most loaded samples decreases the value of said temperature and its enthalpy.