简介:Semi-solidAl2Y/AZ91magnesiummatrixcompositesslurrywaspreparedbyultrasonicvibration,effectofultrasonicvibrationtemperatureandtimeonmicrostructureofsemi-solidslurrywasinvestigated.Theresultsshowedthatwiththeultrasonicvibrationtemperaturedecreasingthesolidvolumefractionofsemi-solidslurryincreased.Thebestultrasonicvibrationtemperaturewas600oC.Withtheincreaseofultrasonicvibrationtime,theaveragegraindiameterofprimaryа-Mgparticlesdecreasedfirstly,thenincreased,theaverageshapefactorincreasedgraduallyanddecreasedslightlyafter90s,andafewrosettedendriteswereobservedafter120s.Thebestsemi-solidslurrywithaveragegraindiameterof75μmandshapefactorof0.7weregainedafterthemeltwastreatedbyultrasonicvibrationforabout60satnearliquidustemperature(600oC).Atlast,themicrostructureevolutionmechanismofsemi-solidmagnesiummatrixcompositesslurrywasanalyzedbythetheoriesofthermodynamicsandkinetics.
简介:秉着高职公共英语课程的教学宗旨,本研究注重培养学生实际运用语言综合技能的目标,提升学生职业可将持续发展能力,将《新编剑桥商务英语(初级)》系列教材作为高职公共英语教材进行试点教学,通过调研发现,此举符合高职公共英语教学理念及目标,试点班全国高等学校英语应用能力考试(简称PET-3)通过率显著优于普通班。然而,该系列教材若作为公共英语教材还有待完善。