az91镁合金电火花沉积涂层及腐蚀行为分析.docx

ABSTRACT
Magnesium alloy is one kind of structural materials which has high specific strength and ratio of strength, and has been widely applied in many industries including the aerospace, automotive, military, electronic instead of steel, aluminum alloy and other materials. However, due to the structure of its surface is soft and corrosion easy in the presence of chloride or humid environment. These greatly limit the popularization and application of magnesium alloy. In this paper, the elector-spark deposition is used to prepare alloy strengthening coatings on surface of AZ91 magnesium alloy. The influence of the electro-spark deposition voltage, frequency and duty ratio process parameters on cross- section morphology, thickness, surface roughness of deposited coating is analyzed by the means of scanning electron microscopy and energy spectrum
analysis (EDS). In addition , immersion corrosion test of different time and
electrochemical-polarization curve test of AZ81-La alloy coating, aluminum alloy coating and tungsten-remelting modified layer are studied. Also, corrosion resistance, corrosion mechanism, elements distribution and phase structure of AZ81-La alloy coating and tungsten-remelting modified layer were discussed. The results showed that:
①With the deposition voltage increased from 25V to 45V, the amount of melting of
electrode wire and base metal increased with pulse energy increases. The coating thickness increases, internal defects, cracks and holes are obviously,uniformity improved then gradually deterioration trend. At the same time, the coating roughness value is the lowest when the deposition voltage is 30V.
②Electro spark deposition frequency increases from 150Hz to 350Hz,the thickness
of the coating posed of 190um reduces to 120um; The decrease of melting rate and deposition rate resulted in outside air involved in the internal coating. It was got a increase in hole, defect and roughness, and got a loose deposit coating. the droplet fusion