扫描速度对激光熔覆ni基涂层组织性能的影响,稀有金属材料.docx

为了适应公司新战略的发展，保障停车场安保新项目的正常、顺利开展，特制定安保从业人员的业务技能及个人素质的培训计划扫描速度对激光熔覆ni基涂层组织性能的影响,稀有金属材料　　摘要　　摘要　　镁合金因其密度小、比强度与比刚度高、良好的导热性与导电性而被誉为21世纪理想的工程材料但镁合金低的耐蚀性和力学性能制约了其性能优势的发挥.因此采用表面改性技术以增强镁合金表面化学和力学性能具有重要的现实意义，为此本文以AZ91HP镁合金为研究对象，采用激光熔凝技术提高镁合金表面性能较为系统地研究了熔凝层，性能特征及其随激光工艺参数的变化规律，以期使镁合金表面改性技术的研究　　结果表明：随着激光扫描速度的增加，改性层中?-Mg17Al12的含量降低，树枝状晶的尺寸也随之减小且具有定向凝固的分布特征改性层均由α-Mg固溶体和β-Mg17Al12金属间化合物组成，随着扫描速度的升高，改性层中的β-Mg17Al12，含量减少这主要是因为扫描速度升高后，熔池中镁合金单位面积上吸收的能量降低，这样单位面积镁的烧损量减少，元素铝的相对含量减少，从而导致β-Mg17Al12的相对含量降低不同扫描速度下熔凝层组织皆呈现典型的树枝品形貌。

但随扫描速度的升高，由于熔池中冷却速度增加，枝晶尺寸逐渐减小以不同扫描速度得到的熔凝层的显微硬度都明显高于基体，随扫描速度增加，由于熔凝层硬度提高，抗磨粒磨损能力增强，耐磨性随之增大　　关键词:镁合金；激光熔凝；激光扫描速度；组织；性能　　I　　Magnesium(Mg)alloysareregardedastheidealengineeringmaterialsinthe21thcenturybecauseoftheirlowdensity，highspecificstrengthandrigidity，goodheatandelectricalconductivity.However，thepoorcorrosionresistanceandmechanicalpropertiesofMgalloyslimittheadvantagesoftheirperformance.Therefore，bytakingthesurfacemodificationtechnology，theimprovementofthechemicalandmechanicalpropertiesofMgalloyshastheimportantpracticalsignificance.Inthisdissertation，thetechniques，suchaslasersurfacemeltingandlasersurfacecladding，arecarriedouttoimprovethesurfacepropertiesofAZ91HPMgalloy.thestructureandpropertiesofthemeltedlayer，thelowmeltingpointAlalloycoating，aswellasthechangingrelationstothelasertechnologyparameters，arestudiedsystematically.ItisexpectedtomakeadeeperresearchonthesurfacemodificationtechnologyimprovingthewearandcorrosionresistanceofMgalloys.　　Themresultsshowthat:withtheincreaseoftheLaserscanningspeed，thecontentof?-Mg17Al12inmodifiedlayerandthesizeofthedendritesreduce，andithasthedistributioncharacteristicsofdirectionalsolidification.Themodifiedlayerbytheα-Mgsolidsolutionand?-Mg17Al12intermetalliccompounds，withthescanspeedincreases，themodifiedlayerof?-Mg17Al12contentdecreased.Thisismainlybecausethescanningspeedisincreased，theenergyabsorbedinthemoltenpoolofmagnesiumalloyperunitareasothattheunitareaburningofmagnesiumreducedtherelativecontentoftheelementaluminumreduction，leadingtolowerrelativecontentof?-Mg17Al12.Surfacemeltingatdifferentscanratesareshowingthetypicalmorphologyofthebranchesofproducts.However，withincreasingscanrate，coolingrateduetothemoltenpoolincreases，thedendritesizedecreases.Themicrohardnessofthemeltedlayeratdifferentscanratesaresignificantlyhigherthanthematrix，withtheincreaseinscanningspeed，Abrasivecapacityenhancementduetothemeltinglayerhardness，wearresistanceincreases.　　Keywords：magnesium；magnesiumalloy；lasermelting；laserscanningspeed；Structure；Mechanical　　II　　目录　　目录　　摘要..............................................................................................................................................IAbstract...........................................................................................................................................II目录............................................................................................................................................III　　第一章绪论..........................................................................................................................-19-　　概述................................................................................................错误！未定义书签。

　　镁................................................................................................................................-19-　　镁合金........................................................................................................................-20-　　镁合金的性能特点....................................................................................................-21-　　良好的减震性能及流动性.............................................................................-21-　　良好的高温性能.............................................................................................-21-　　良好的机械加工性能.....................................................................................-21-　　高散热性.........................................................................................................-21-　　镁合金的优缺点........................................................................................................-22-　　镁合金的优点.................................................................................................-22-　　镁的缺点.........................................................................................................-22-　　镁合金的应用............................................................................................................-23-　　在轿车上的应用.............................................................................................-23-　　在电子工业的应用.........................................................................................-25-　　镁合金的表面处理技术............................................................................................-26-　　化学转化处理.................................................................................................-26-　　阳极氧化技术...........................。