Investigation and validation of mass change mechanisms during the sintering process of aluminum-based hybrid composites using thermogravimetric analysis

Powder metallurgy is a metal manufacturing method that has been evolving since the 19th century, encompassing the stages of powder production, mixing, compaction, and sintering, and it continues to advance steadily. Powders produced by various techniques are homogenously mixed and compressed within a metal mold. They are then sintered at high temperatures in a controlled atmosphere to enhance the strength of the parts. The correct execution of the sintering process is crucial for the material's mechanical and physical properties. Therefore, the proper selection of sintering parameters is of great importance. Although the approach of using 0.7-0.8 times the melting temperature of the material is generally accurate and widely used in the literature for the sintering process, this temperature can vary when producing different composite materials. In this context, thermogravimetric analyses offer a more precise and accurate approach for determining sintering temperatures in composite material production. Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) are used to determine mass losses/gains and melting temperatures. TGA measures mass loss due to degradation, while DTA shows temperature changes. These analyses are crucial for evaluating the thermal stability of materials. The primary objective of this research is to investigate the detailed mass changes that occur during the sintering process of aluminum matrix hybrid composite materials, which are not well-documented in the literature, using TGA/DTA analysis. The goal is to identify the sources of mass loss and gain resulting from temperature changes during sintering. In this study, eight different powder mixtures were prepared using 99.9% pure aluminum powder as the matrix, reinforced with Cu, Mg, Zn, graphene, SiC, B₄C, and WC. The mixtures were homogenized, and their mass change behavior was examined through Thermogravimetric Analysis/Differential Thermal Analysis (TGA/DTA). Based on the temperatures corresponding to mass gain and loss observed in the TGA/DTA results, the samples pressed under 110 MPa were subjected to sintering at the determined temperatures. The mechanical properties of the produced hybrid composite materials were evaluated through density and hardness tests. Microstructural characterization and possible phase transformations were investigated using Optical Microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Energy Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD) analyses.