EFFECT OF HEAT TREATMENT ON THE CORROSION RESISTANCE OF AL-SI-MG ALLOY FABRICATED BY SELECTIVE LASER MELTING AND CASTING IN A KOH ENVIRONMENT

• Main Author: Firmansyah, Charles
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83309
• Institution: Institut Teknologi Bandung

Selective laser melting (SLM) is an additive manufacturing method that produces near-net-shape functional components by selectively melting metal powder in two-dimensional layers using a high-powered laser as a heat source. The SLM method results in fine microstructures and high hardness due to rapid cooling, compared to alloys processed using casting techniques. Heat treatment is commonly used to modify the mechanical properties of Al-Si-Mg alloys fabricated by SLM, also affecting their microstructure and corrosion resistance. However, aging heat treatment can increase susceptibility to micro-galvanic corrosion. This study focuses on heat treatment to modify the microstructure, revealing that stress relief from SLM is crucial for enhancing both mechanical properties and corrosion resistance. Specimens measuring 10 × 10 × 5 mm were prepared from SLM-produced samples in the XZ plane (building direction) and cast ingots. The corrosion behavior of these two alloys was analyzed using open circuit potential, Tafel polarization, and immersion in a 1 M KOH solution, considering aluminum's function in aluminum-air batteries. The microstructure and phases formed before and after heat treatment were investigated using optical microscopy and X-ray diffraction (XRD). Corrosion products were also studied using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and XRD. The results indicated that solution treatment heat treatment improved corrosion resistance by reducing the corrosion rate obtained from Tafel polarization ~90,48% and ~91,92% for SLM and cast samples, respectively. Based on immersion corrosion tests, solution treatment heat treatment enhanced corrosion resistance by inhibiting mass loss ~46,06% and ~11,13% for SLM and cast Al-Si-Mg alloys, respectively. Precipitate strengthening tended to decrease corrosion resistance. Heat treatment effectively increased the hardness of cast alloys ~24,32% during 2-hour aging but reduced the hardness of SLM-fabricated Al-Si-Mg alloys ~36,71% after solution treatment.