Structure, properties and corrosion resistance of PM composite materials based on EN AW-2124 aluminum alloy reinforced with the Al 2O 3 ceramic particles

Abstract

Investigations of composite materials based on EN AW-2124 aluminum alloy reinforced with the Al 2O 3 particles with various weight ratios of 5, 10, and 15% are presented. Powders of the starting materials were mixed in the laboratory vibratory ball mill to acquire the uniform distribution of reinforcement particles in the matrix material. The components were initially compacted at cold state in a die with the diameter of ∅26 mm in the laboratory vertical unidirectional press with a capacity of 350 kN. The obtained P/M compacts were heated to a temperature of 480–500 °C and finally extruded with the extrusion pressure of 500 kN. Bars with a diameter of 8 mm were obtained as the end product. Based on the microstructural examinations of the obtained composite materials, the uniform distribution of the reinforcing particles in the aluminum matrix was revealed. Hardness tests and the ultimate compressive strength tests made it possible demonstrate that both these properties change along with the reinforcing particles concentration change. As an example, hardness increased from 89.27 HV1 for the material without the reinforcing phase to 123.4 HV1 for 15% Al 2O 3, and the ultimate compressive strength decreases along with the increase of the reinforcing phase fraction from 798 MPa for 5% to 663 MPa for 15% Al 2O 3. Results of the corrosion tests, determined using the potentiodynamic method in the 3% water solution of NaCl indicate that corrosion of the investigated composite materials depends on the volume fraction of the reinforcing particles. It was found out, based on the determined anode polarisation curves that the investigated materials are susceptible to pitting corrosion. Moreover, investigation results indicate that the composite materials reinforced with the ceramic particles with the portions of 5 and 10% are characteristic of a higher corrosion resistance in the selected environment, compared to the matrix material, whereas at the 15% portion this resistance it worse, the anode digestion current grows.