Avaliação do efeito da adição de b4c nas propriedades estruturais, microdureza e comportamento a corrosão da liga Cu–11,8Al–0,58Be

Abstract

Shape memory alloys (SMAs) based on the Cu–Al–Be system exhibit promising functional properties; however, they are highly sensitive to grain growth, which promotes intergranular fracture and limits their applicability. This study investigated the influence of boron carbide (B₄C) addition as an inoculant in the Cu–11.8Al–0.58Be alloy, focusing on its effects on microstructure, mechanical properties, and corrosion behavior. Thermodynamic simulations performed using the Pandat software indicated that B₄C promotes the formation of boron- and carbon-rich phases (graphite, B₄C, and AlB₁₂), reducing the fraction of the Bcc matrix phase and increasing microstructural complexity under non-equilibrium solidification conditions. Experimentally, the addition of 0.05 wt.% B₄C acted as an effective grain refiner, producing a more homogeneous equiaxed structure. However, higher additions (≥0.15 wt.%) led to columnar grain growth and reduced structural uniformity. Microhardness measurements showed a decreasing trend with increasing B₄C content, consistent with the Hall–Petch relationship due to grain coarsening. Conversely, electrochemical tests revealed that the addition of 0.10 wt.% B₄C provided the best corrosion resistance, with higher polarization resistance, lower corrosion current density, and a more stable passive film formation. Electrochemical impedance spectroscopy (EIS) analyses confirmed that the ceramic reinforcement significantly affects the capacitive behavior of the metal/electrolyte interface, with the constant phase element (CPE) circuit best fitting the experimental data. In conclusion, controlled addition of small amounts of B₄C improves both the microstructural and corrosion properties of Cu–Al–Be alloys, provided its content remains within moderate levels. These results contribute to the development and optimization of copper-based shape memory alloys with enhanced structural and functional performance for technological applications.