The microstructural characterization along the solidification process of metallic alloys is fundamental, since once understood the correlation between steps of the manufacturing process and characteristics of the final component, the attainment of appropriate properties can be previously planned. In this sense, functional relations permitting microstructural parameters and mechanical and wear resistances to be correlated, would be fundamental for the pre-programming of final properties. Binary Al-Bi alloys have been studied in the literature with focus on tribological applications, i.e. specifically for bearing and internal parts of combustion engines. However, the design of new engines, which will be subjected to higher loads and velocities, will demand better properties to support the operation at higher temperatures, and Al-Bi binary alloys will need to be replaced with new alternative Al-Bi-X alloys. The objective of the present study is to contribute to the understanding of modifications caused by a third alloying addition, in particular Si and Ni, on the microstructural evolution and the corresponding mechanical and tribological properties. The role of Si and Ni on the strengthening of the Al-rich matrix, and of Bi as a solid lubricant are well-known characteristics. However, the literature is scarce on detailed studies relating microstructure evolution, phases characterization and application properties of alloys of the ternary systems Al-Bi-Si e Al-Bi-Ni. In the present work a wide experimental study is envisaged, focusing on the microstructural evolution of such alloys, identifying phases, morphologies and characteristics length scales along solidification. These alloys will be solidified under transient heat flow conditions for a wide range of cooling rates during unidirectional solidification. Solidification thermal parameters such as the growth rate (V), the thermal gradient (G), and the cooling rate (T ) will be experimentally determined. Experimental growth laws relating microstructural and thermal parameters and functional relations between mechanical and wear resistances as a function of representative microstructural length scales will be developed. To complement the comprehension on the microstructure evolution of these alloys, Bridgman growth of samples of some alloys compositions will be filmed in situ using X-ray techniques, in the Institut Matériaux Microélectronique Nanosciences de Provence (IM2NP) - Aix Marseille Université (AMU), France, through a research internship (BEPE-FAPESP).
News published in Agência FAPESP Newsletter about the scholarship: