INTERFACIAL REACTIONS IN THE LIQUID/SOLID AND LIQUID/VAPOR INTERFACES OF Al-Si-Mg ALLOYS AND B_12 (BC_2) SUBSTRATES

摘要

Interfacial reactions between the Al-6 Si-14 Mg alloy and B_(12) (BC_2) substrates were studied in wettability tests by the sessile drop technique using an L_8 Taguchi experimental design. Specimens of the alloy in the form of cubes were placed on boron carbide substrates prepared by the uniaxial compaction of B_(12) (BC_2) powders. Sessile drop tests were conducted varying the following parameters: temperature (1000 and 1200 °C), time (90 and 120 min), atmosphere (N_2 and Ar→N_2), and substrates prepared with uncoated and coated powders with colloidal SiO_2. The contact angles were measured from photographs, the interfaces were characterized by XRD and SEM, and the thermodynamic feasibility of possible reactions in the system was determined using the HSC™ software and data bases. The nonwetting contact angles observed and the detachment of the metal drop from the substrate can be attributed to the formation of MgO and Al_2O_3 on the meniscus surface.