Microstructure and Corrosion Resistance of 7075 Aluminium Alloy Composite Material Obtained from Chips in the High-Energy Ball Milling Process

• Published in: Materials Vol. 17; no. 21; p. 5331
• Main Authors: Kościelniak, Barbara, Groch, Diana, Nowak, Wojciech J., Drajewicz, Marcin, Kwolek, Przemysław
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-11-2024
• Subjects: Alloys; Aluminum; Aluminum base alloys; Ball milling; Carbon dioxide; Cold pressing; Comminution; Composite materials; Corrosion and anti-corrosives; Corrosion mechanisms; Corrosion potential; Corrosion rate; Corrosion resistance; Corrosion resistant alloys; Developing countries; Electrochemical impedance spectroscopy; Energy; Environmental impact; Fluorides; Global warming; Grinding; Hot pressing; Intermetallic compounds; LDCs; Mechanical properties; Metal scrap; Metals; Microstructure; Porosity; Powder metallurgy; Powders; Raw materials; Recycling; Rotational spectra; Scrap metals; Silicon carbide; Sintering; Sintering (powder metallurgy); Specialty metals industry; Strain hardening; Titanium; Titanium alloys; Titanium dioxide; Waste management; Wear resistance; Poland; Germany
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17215331

The high-energy ball milling process was applied to fabricate a composite material from 7075 aluminium alloy milling chips, silicon carbide, and titanium dioxide powders. Raw materials were ground, and the obtained powders were cold pressed and sintered. It was demonstrated that this method can be used in the recycling of aluminium alloy scrap characterised by a high surface-to-volume ratio, and also that chemical removal of the oxide layer from chips is not necessary. The finest particles, with 50 vol.% of their population below 36 μm, were obtained after grinding for 60 min at a 1000 rpm rotational speed. Such an intensive grinding was necessary to fabricate the compact composite material with a homogeneous microstructure and a low porosity of 0.7%. The corrosion resistance of the composites was studied in 3.5 wt.% NaCl solution using cyclic voltammetry and electrochemical impedance spectroscopy, and corrosion rates in the range of ca. 342 and 3 μA∙cm−2 were obtained. The corrosion mechanism includes aluminium alloy dissolution at the matrix/reinforcement interphase and around intermetallic particles localised within the matrix grains.