简介:2016年在留给人一种变化莫测、捉摸不定的感觉中,终于要结束了.首先,2016年的天灾太可怕了。世界气象组织总干事PetteriTaalas先生称:'由于气候变化,极端事件的频率和影响都已经增加。一代人才会发生一次的热浪和洪水变得更加常见。而且热带气旋所带来的风暴潮也让海平面上升变化明显。'据世界气象组织初步统计数据显示,2016年全球平均气温预计将比工业化前水
简介:ScanningElectronMicroscopyStudiesofYBa_2Cu_3O_(7-δ)SuperconductorsShaWei(沙维)(DepartmentofCivilEngineering,TheQueen′sUniversit...
简介:Thequenchsensitivityandtheirinfluentialfactorsof7,021,7,085,and7,050alloyswereinvestigatedbytheendquenchingtestmethodandthemeasurementofelectricalconductivity,hardness,andmicrostructureafteraging.Theresultsindicatethat7,050alloyhasthelargestchangeswithhardnessdecreasingfromHV199toHV167,andelectricalconductivityincreasesfrom16.6to18.2MSm-1whenthedistancefromquenchedendincreasesfrom2to100mm.Alloys7,085and7,021haverelativelysmallerchanges.Accordingtotherelationshipbetweenthehardnessandelectricalconductivityofasupersaturatedsolidsolution,7,050alloyhashigherquenchsensitivitythan7,085and7,021alloys.Themicrostructureof7,050alloywithhighermajoralloyelement(Zn+Mg+Cu)additionandCuelementadditionismostlyaffectedbythechangesofdistancefromquenchedend.In7,050alloy,thesizeofintragranularprecipitatesisfromabout10–200nm,andthe(sub)grainboundaryprecipitatesareabout20–300nm.Alloy7,085withlowerCucontentismoderatelyaffected,while7,021isleastaffected.Itisfoundthatwiththeincreaseofdistancefromquenchedend,quenched-inducedprecipitatepreferentiallynucleatesandgrowsinthe(sub)grainboundaryandthenonthepre-existingAl3Zrparticles.
简介:ThemixturemodelofAl85Y4Nd4Ni7alloyinwhichapartiallycrystallizedamorphousalloyisregardedasananocompositeofanAlnanoparticleandaremainingamorphousmatrixispresented.Itsevolutionintheprocessofcrystallizationhasbeeninvestigatedbydifferentialscanningcalorimetry(DSC),X-raydiffraction(XRD),andtransmissionelectronmicroscopy(TEM).Mainlyamorphousstructurewithα-Alnanocrystalsembeddedintheamorphousmatrixhasbeenrevealedbymeltspiningthealloy.Crystallizationisshowedtooccurinthreestages:(1)crystallizationofamorphousalloyandformationofAlNiY,AlNdNiandunknowncrystallinephases,(2)formationofAl3YandAl3Nd,and(3)formationofAl3Ni.