The aim of this work is to investigate microstructure,corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution.There are lot...The aim of this work is to investigate microstructure,corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution.There are lots of closed pores that are filled with another oxide compound compared with the typical surface morphology with pore coated until 350 V of coating voltage.The thickness of oxide layer increases with increasing coating voltage.The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium permanganate consists of MgO and Mn2O3.Corrosion potential of the oxide layer on AZ91 Mg alloy obtained at different plasma electrolytic oxidation(PEO) reaction stages increases with increasing coating voltage.The corrosion resistance of AZ91 Mg alloy depends on the existence of the manganese oxide in the oxide layer.The inner barrier layer composed of the MgO and Mn2O3 may serve as diffusion barrier to enhance the corrosion resistance and may partially explain the excellent anti-corrosion performance in corrosion test.Nanohardness values increase with increasing coating voltage.The increase in the nanohardness may be due to the effect of manganese oxide in the oxide layer on AZ91 Mg alloy coated from electrolyte containing KMnO4.展开更多
Recently, a semi-solid metal processing has been acknowledged as a cost-effective technique to be able to manufacture high quality product for the transportation industry. In this study a hypo-eutectic Al alloy was fa...Recently, a semi-solid metal processing has been acknowledged as a cost-effective technique to be able to manufacture high quality product for the transportation industry. In this study a hypo-eutectic Al alloy was fabricated by means of an electromagnetic stirrer in continuous casting process and the microstructural change during solidification due to a fluid flow by electromagnetic stirring was examined. Due to the forced fluid flow during solidification a dendritic phase of primary α phase of Al alloy was turned into a globular phase, which can make the Al alloy get a thixotropic behavior in the semi-solid region. In order to establish the quantitative relationship between microstructure and the process parameters, the morphology shape, a silicon distribution and a size of primary α phase were observed according to casting speed in continuous casting machine. The primary α phase was turned into the degenerate dendrites approaching a spherical configuration with increasing casting speed. The fine-grained and equiaxed microstructure appeared at higher casting speed. A segregation behavior of Si element was declined with increasing casting speed and a very uniform distribution of Si element was observed on the billet at a casting speed of 600 mm·min-1. A thickness of the solidifying shell of the billet was shortened with increasing the casting speed.展开更多
基金supported by a grant from the Center of Advanced Materials Processing(CAMP) of the 21st Centry Froniter R&D Program Funded by the Ministry of Knowledge Economy(MKE),Koreasupported by the Korea Science and Engineering Foundation (No.2009-0079807)
文摘The aim of this work is to investigate microstructure,corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution.There are lots of closed pores that are filled with another oxide compound compared with the typical surface morphology with pore coated until 350 V of coating voltage.The thickness of oxide layer increases with increasing coating voltage.The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium permanganate consists of MgO and Mn2O3.Corrosion potential of the oxide layer on AZ91 Mg alloy obtained at different plasma electrolytic oxidation(PEO) reaction stages increases with increasing coating voltage.The corrosion resistance of AZ91 Mg alloy depends on the existence of the manganese oxide in the oxide layer.The inner barrier layer composed of the MgO and Mn2O3 may serve as diffusion barrier to enhance the corrosion resistance and may partially explain the excellent anti-corrosion performance in corrosion test.Nanohardness values increase with increasing coating voltage.The increase in the nanohardness may be due to the effect of manganese oxide in the oxide layer on AZ91 Mg alloy coated from electrolyte containing KMnO4.
基金This work was financiallysupported bythe KISTProgram(No.2E19470)and by the Components&Materials Technology Development Program of Ministry of Commerce,Industry and Energy of Korea.
文摘Recently, a semi-solid metal processing has been acknowledged as a cost-effective technique to be able to manufacture high quality product for the transportation industry. In this study a hypo-eutectic Al alloy was fabricated by means of an electromagnetic stirrer in continuous casting process and the microstructural change during solidification due to a fluid flow by electromagnetic stirring was examined. Due to the forced fluid flow during solidification a dendritic phase of primary α phase of Al alloy was turned into a globular phase, which can make the Al alloy get a thixotropic behavior in the semi-solid region. In order to establish the quantitative relationship between microstructure and the process parameters, the morphology shape, a silicon distribution and a size of primary α phase were observed according to casting speed in continuous casting machine. The primary α phase was turned into the degenerate dendrites approaching a spherical configuration with increasing casting speed. The fine-grained and equiaxed microstructure appeared at higher casting speed. A segregation behavior of Si element was declined with increasing casting speed and a very uniform distribution of Si element was observed on the billet at a casting speed of 600 mm·min-1. A thickness of the solidifying shell of the billet was shortened with increasing the casting speed.
