Understanding the wear behavior of Cu-based brake pads, which are used in high-speed railway trains and aircraft, is essential for improving their design and safety. Therefore, the wear mechanism of these pads has been studied extensively. However, most studies have focused on the changes in their composition and not the effects of their manufacturing conditions. In this study, we fabricated commercial Cu-based brake pads containing Fe, graphite, Al2O3, and SiO2 using spark plasma sintering under different conditions. The microstructures and mechanical properties of the pads were investigated. The pads were tribo-evaluated using the ball-on-disc test under various load conditions. Their worn surfaces were analyzed using X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and confocal microscopy in order to elucidate their wear mechanism. In addition, the dynamometer test was performed to confirm whether their wear behavior would be similar under actual conditions. Finally, a comparative analysis was performed using the ball-on-disc test. The results indicated that the brake pads with the same composition but fabricated under different sintering conditions exhibited different wear characteristics. We believe that this research is of great significance for understanding the wear mechanism of Cu-based brake pads and improving their design and hence their performance.

No abstract

Active brazing of zirconia with metallic alloys is a promising method for enhancing the mechanical property of zirconia. However, the brazing process of zirconia and metallic alloys has not been studied in detail because of a limitation in selection of materials and processing conditions. Here, we successfully brazed zirconia with Ti-3Al-2.5V alloy using amorphous Zr54Ti22Ni16Cu8 active filler alloy. By manipulating the brazing temperature from 800 °C to 860 °C, a highest strength of ~186 MPa was achieved at 860 °C. Reduced brittle (Zr,Ti)2(Ni,Cu) intermetallic phases from formation of island-type (Zr,Ti) matrix, ZrO2-X, TiO, and TiO2 interlayer play a key role in increasing the joint strength. Our findings will be helpful in developing brazing processes for zirconia and metallic alloys.

The effects of equal channel angular extrusion (ECAE) process parameters on microstructure and thermoelectric properties of the p-type Bi 0:5 Sb 1:5 Te 3 compound have been investigated. ECAE was carried out under various temperatures (653 K, 693 K, 733 K) and ram speeds (0.5 mm/s, 1 mm/s, 2 mm/s). Fraction of recrystallized grains and grain size was found to be increase with lower ram speed and higher deformation temperature. As a result, Seebeck coefficient increased, and electrical resistivity and thermal conductivity decreased. The decrease in thermal conductivity was attributed to the decrease of lattice thermal conductivity ( ph ) which is independent of electrical properties. Maximum figure-of-merit (2:87 Â 10 À3 K À1 ) was achieved in as-ECAE'ed specimen at 733 K and at ram speed of 0.5 mm/s. This value was found to be 6% higher than that of as-sintered specimen.