MICROSTRUCTURAL CHARACTERIZATION OF SPRAY DEPOSITED Al-Y-Ni-Co-Zr ALLOY AND Al-Y-Ni-Co-Zr + SiC_p METAL MATRIX COMPOSITE

摘要

The aim of this work is the microstructural characterization of the Al_(84)Y_3Ni_8Co_4Zr_1 alloy and the metal matrix composite (MMC) Al_(84)Y_3Ni_8Co_4Zr_1 + SiC obtained through spray deposition process. Both materials were processed through an Osprey~(TM) equipment. The ratio between the gas volumetric flow rate (m~3/min) and the metal mass flow rate (kg/min) used was G/M = 8.7m~3/kg for the alloy and 8.1m~3/kg for the MMC, the flow rate of SiC being 0.2kg/min. The characterization of the deposit and overspray were done through X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with the microanalysis (EDS) and differential scanning calorimetry (DSC). In the granulometric range of 5-20 μm, the alloy and of the MMC powders presented amorphous phases (volumetric fraction of 46 and 65%, respectively), Al-fcc, Al_3Zr, Al_9Co_2 and "Al_(16)Ni_3Y". The MMC also presented SiC . The alloy and the MMC (with 3%vol SiC) deposit presented a volumetric porosity of 1.4 and 4.0%, respectively, and have showed a totally crystalline: microstructure presenting the following phases: Al-fcc, Al_9Co_2, Al_3Zr, "Al_(16)Ni_3Y". The MMC also presented SiC phase. The formation of amorphous phase in the overspray and the absence of such phase in the deposit for the alloy and MMC, together with the low values of porosity, are evidences that the deposit was formed by a high volume fraction of still fully liquid droplets, providing temperature and time enough to the complete crystallization of the deposit.