简介:将T700或Nicalon-SiC短纤维、碳粉、硅粉和少量碳化硅粉混合,在1900℃热压烧结制备短纤维增强C-SiC复合材料,并对其组织、结构及性能进行了研究.结果表明:SiCf/C-SiC的相对密度和室温强度分别为95.3%和24.38MPa,均高于Cf/C-SiC的相对密度和室温强度,热压烧结过程中Cf的损伤严重.短纤维增强C-SiC复合材料中,由于C相和SiC相的同时存在,在同一温度下的氧化行为表现为在氧化初期氧化质量损失率较大,C相的氧化起主要作用;随氧化时间的增长,氧化质量损失率逐渐减小;在氧化后期则质量增加,SiC相的惰性氧化起主要作用.SiCf/C-SiC复合材料的抗氧化性能优于Cf-C-SiC复合材料的抗氧化性能.SiCf/C-SiC复合材料在温度为1100℃~1400℃时,温度越高,氧化质量损失率越小,抗氧化性能越强.
简介:Thehot-deformationbehaviorofFe-Mn-Ctwinninginducedplasticity(TWIP)steelwasinvestigatedbyconductinghotcompressiontestswithinarecommendedhotrollingtemperaturerangeatvariousstrainrates.Flowresistancecurvesduringhot-deformationwereobtained,andstrainratesensitivitiesandactivationenergiesforplasticdeformationwerecalculatedusingthepowerlaw.ItisfoundthattheadditionofAlandSiclearlyincreasesthepeakstressesforthepresentalloys,especiallyat950℃.ButMnhasaminoreffectonthestress-straincurvesandactivationenergywhenitscontentvariesfrom15mass%to22mass%forthepresentalloys.
简介:以钼粉及氧化锆粉为原料,采用不同的烧结工艺参数,在常压氩气气氛下烧结制备50%Mo-ZrO2金属陶瓷。采用四电极法测量该金属陶瓷的高温电导率,在1580℃下进行钢液和碱性熔渣侵蚀实验。结果表明:在烧结温度为1600~1650℃,保温时间为2~4h的条件下,随保温时间延长或烧结温度升高,烧结体更加致密,孔隙率下降;因而金属陶瓷的电导率提高,耐钢液和熔渣侵蚀性增强;在1600℃、保温4h条件下烧结的试样密度最大(6.49g/cm^3),高温电导率最高(1600℃下的电导率为101S/cm),耐钢液和熔渣侵蚀能力最强。钢液对金属陶瓷的侵蚀主要为Fe和Mo的相互溶蚀,熔渣对金属陶瓷的侵蚀主要作用于ZrO2陶瓷相,熔渣中的Al2O3取代金属陶瓷中的ZrO2。熔渣侵蚀过程中,CaO与金属陶瓷中的ZrO2发生反应生成高熔点CaZrO3相,阻止熔渣对金属陶瓷的进一步侵蚀。
简介:ItisfundamentallyimportanttounderstandtheinfluenceofstrainonthedensityofdeformationtwinsinTWIPsteelbecausetwinningisitsdominantdeformationmechanism.ThedeformationbehaviorofaFe-30Mn-4Si-3Al-0.097CsteelhasbeeninvestigatedbyX-raydiffraction(XRD),electronbackscatterdiffraction(EBSD)andtransmissionelectronmicroscopy(TEM)techniques.Samplewithanaveragegrainsizeof10μmwasdeformedincold-rollingwithareductionof10%,20%,30%,40%,50%,60%and70%,respectively.Themechanicalpropertiesofthecold-rolledsampleswerefurtherinvestigatedbytensiletests.Theyieldstrength(σy)andultimate-tensile-strength(σUTS)oftheas-preparedsampleis480MPaand850MPa,respectively.However,undercoldrollingdeformation,thetensilestrengthobviouslyincreaseswithanincreaseinrollingreduction.Thesamplewitharollingreductionof10%exhibitsσyof610MPaandσUTSof-1000MPa.Theyieldstrengthandtensilestrengtharefurtherenhancedupto1320MPaand1378MPaforthespecimenwitharollingreductionof70%,regardlessofthepoorductilityof6.7%.ThedeformationmicrostructureswerestudiedbyEBSDandTEMobservations.Itisfoundthat,withincreasingrollingreduction,theaveragedistancebetweendeformationtwinsdecreasesgraduallywhilethedensityofdeformationtwins(thelengthoftwinboundaryinunitarea)exhibitamaximumvalueat40%cold-rolling+tension.Carefullystatisticsanalysisrevealsgrainorientationiscloselyrelatedtothedeformationtwinsandtheunderlyingmechanismgoverningthetwinningisdiscussed.
简介:Resultspresentedinthisstudycontributetoinvestigationofthemicrostructureandmechanicalpropertiesofthehot-rolledFe16Mn0.6Csteelplates.Thesteelplateshavebeenproducedbybeinghot-rolledattemperaturesrangingfrom1100℃to850℃insevenpassesto97.5%reductioninthicknessandthencooledinafurnaceof650℃.Someplateshavebeenannealedattemperaturesrangingfrom300℃to1100℃for5minto60min,andthenfollowedbywaterquenching.Thereareannealingtwinsinthehot-rolledFe16M...
简介:利用Ta2O5-NaF-C混合粉末为原料,采用碳热还原法在石墨表面制备不同形态的碳化钽晶须,利用SEM和XRD对晶须的形貌、结构与成分进行观察与分析,采用热力学计算与实验验证相结合的方法研究不同形貌碳化钽晶须的生长机制。结果表明:TaC晶须存在不同的生长机制,当原料粉末添加量较少时,石墨表面主要生长出圆柱状晶须伴有头部液滴状结构,原料粉末添加量较多时得到规则的四方柱状结构晶须,也存在2种不同形貌晶须并存的情况。圆柱状晶须为VLS(气-液-固)生长机制;四方柱状TaC晶须为VS(气-固)生长机制。在VLS机制中,催化液滴的主要成分为NaTaO3。
简介:InordertoimprovethecorrosionandmechanicalpropertiesofAM50magnesiumalloy,1wt.%GdwasusedtomodifytheAM50magnesiumalloy.Themicrostructure,corrosionandmechanicalpropertieswereevaluatedbyX-raydiffraction(XRD),scanningelectronmicroscopy(SEM),energydispersivespectroscopy(EDS),electrochemicalandmechanicalstretchmethods.Theresultsindicatedthatβ-Mg17Al12phasedecreasedandAl2Gd3andAl0.4GdMn1.6phaseexistedafterGdaddition.BecauseoftheGdaddition,thegrainofAM50magnesiumalloywasrefinedsignificantly,whichimprovedthetensilestrengthofAM50magnesiumalloy.Thedecreasingofβphaseimprovedthecorrosionresistanceofthemagnesiumalloy.ThefracturemechanismoftheGdmodifiedAM50magnesiumalloywasquasi-cleavagefracture.Thecorrosionresidualstrength(CRS)ofAM50magnesiumalloywasimprovedafter1wt.%Gdaddition.