The electrochemical behaviors and coupling behaviors of the Mg2Si and Si phases with α（Al） were investigated, the corrosion morphologies of Al alloys containing Mg2Si and Si particles were observed, and the corrosi...The electrochemical behaviors and coupling behaviors of the Mg2Si and Si phases with α（Al） were investigated, the corrosion morphologies of Al alloys containing Mg2Si and Si particles were observed, and the corrosion mechanism associated with them in Al-Mg-Si alloys was advanced. The results show that Si particle is always cathodic to the alloy base, Mg2Si is anodic to the alloy base and corrosion occurs on its surface at the beginning. However, during its corrosion process, the preferential dissolution of Mg and the enrichment of Si make Mg2Si transform to cathode from anode, leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery at a later stage. As the mole ratio of Mg to Si in an Al-Mg-Si alloy is less than 1.73, it contains Mg2Si and Si particles simultaneously in the grain boundary area, and corrosion initiates on the Mg2Si surface and the precipitate-free zone （PFZ） at the adjacent periphery of Si particle. As corrosion time is extended, Si particle leads to severe anodic dissolution and corrosion of the PFZ at its adjacent periphery, expedites the polarity transformation between Mg2Si and the PFZ and accelerates the corrosion of PFZ at the adjacent periphery of Mg2Si particle.展开更多
A modification of Mg2Si in the hypereutectic Mg-4%Si alloy（mass fraction） with Sr was investigated.Two types of Mg2Si in the alloys were found：polygonal primary Mg2Si and Chinese script type eutectic Mg2Si.Adding A...A modification of Mg2Si in the hypereutectic Mg-4%Si alloy（mass fraction） with Sr was investigated.Two types of Mg2Si in the alloys were found：polygonal primary Mg2Si and Chinese script type eutectic Mg2Si.Adding Al-10% Sr master alloy to the Mg-4%Si alloy clearly reduced the average size of primary Mg2Si and changed the morphology of eutectic Mg2Si from Chinese script type to polyhedral or fine fibre shape.The refinement of primary Mg2Si is mainly attributed to the heterogeneous nucleation mechanism induced by the Sr-rich particles.The modification of eutectic Mg2Si results from the dissolved Sr,which alters the preferred growth manner of the eutectic.展开更多
基金Project (21073162) supported by the National Natural Science Foundation of ChinaProject (2008) supported by the Scientific and Technological Projects of Ningxia, China+1 种基金Project (08JC1421600) supported by the Science and Technology Commission of Shanghai Municipality, ChinaProject (2008AZ2018) supported by the Science and Technology Bureau of Jiaxing City, China
文摘The electrochemical behaviors and coupling behaviors of the Mg2Si and Si phases with α（Al） were investigated, the corrosion morphologies of Al alloys containing Mg2Si and Si particles were observed, and the corrosion mechanism associated with them in Al-Mg-Si alloys was advanced. The results show that Si particle is always cathodic to the alloy base, Mg2Si is anodic to the alloy base and corrosion occurs on its surface at the beginning. However, during its corrosion process, the preferential dissolution of Mg and the enrichment of Si make Mg2Si transform to cathode from anode, leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery at a later stage. As the mole ratio of Mg to Si in an Al-Mg-Si alloy is less than 1.73, it contains Mg2Si and Si particles simultaneously in the grain boundary area, and corrosion initiates on the Mg2Si surface and the precipitate-free zone （PFZ） at the adjacent periphery of Si particle. As corrosion time is extended, Si particle leads to severe anodic dissolution and corrosion of the PFZ at its adjacent periphery, expedites the polarity transformation between Mg2Si and the PFZ and accelerates the corrosion of PFZ at the adjacent periphery of Mg2Si particle.
基金Project(2011BAE22B00) supported by the National Key Technology R&D Program of ChinaProjects(ZR2010EQ021,ZR2010EL013) supported by the Natural Science Foundation of Shandong Province,China
文摘A modification of Mg2Si in the hypereutectic Mg-4%Si alloy（mass fraction） with Sr was investigated.Two types of Mg2Si in the alloys were found：polygonal primary Mg2Si and Chinese script type eutectic Mg2Si.Adding Al-10% Sr master alloy to the Mg-4%Si alloy clearly reduced the average size of primary Mg2Si and changed the morphology of eutectic Mg2Si from Chinese script type to polyhedral or fine fibre shape.The refinement of primary Mg2Si is mainly attributed to the heterogeneous nucleation mechanism induced by the Sr-rich particles.The modification of eutectic Mg2Si results from the dissolved Sr,which alters the preferred growth manner of the eutectic.
