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页数:68页
时间:2020-06-19
《材料成型专业英语 Heat Treatment.ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、EnglishinMaterialsScienceandEngineering材料科学与工程专业英语2021/7/30合肥工大材料学院何顺荣制作2EnglishinMaterialsScienceandEngineeringInitialheatingtoatemperatureupto900℃giveslamellarpearlite,withmoredisperse*structurebeingobtainedatlowertempera-ture.Thestructureofthesamesteelatthesametemperatureoftransformationbutu
2、ponalowtemperatureheating(780℃)isgranularpearlite.Cementitegrainsthatareformedinthestructurearefineratalowertemperaturetransformation.2021/7/30合肥工大材料学院何顺荣制作3EnglishinMaterialsScienceandEngineeringConsequently,thesizeofcementiteparticlesdependsonthetemperatureofaustenitetransformationandtheirfor
3、mdependsonthetemperatureofheating(thetemperatureofaustenitization).ThetransformationattemperatureaboveandbelowthebendoftheCcurvedifferinthekineticsandtheshapeofdecompositionproducts.2021/7/30合肥工大材料学院何顺荣制作4EnglishinMaterialsScienceandEngineeringAbovethebendofCcurve,i.e.atsmalldegreesofundercooli
4、ng,thetransformationbeginsfromafewcentersandpearliticcrystalsfreelygrowtointerference.BelowthebendofCcurvethereformsanacicularmicrostructure,sinceacicularplateletscannotgrowfreelyandthetransformationmainlyoccursthroughtheformationofnewcrystals.[1]2021/7/30合肥工大材料学院何顺荣制作5EnglishinMaterialsScience
5、andEngineeringAsindicatedabove,therateofisothermaltransformationofausteniteisdeterminedbytherateofnucleationandcrystalgrowth,NandG.Therateofcrystalgrowthisquitesensitivetovariouschangesinthesteelstructureandcanbestronglyaffectedbythemetallurgicalnatureofthesteel,thedegreeofdeoxidization,thepres
6、enceofundissolvedparticles,thehomogeneityofaustenite,andthesizeofausteniticgrains.2021/7/30合肥工大材料学院何顺荣制作6EnglishinMaterialsScienceandEngineeringThepresenceofundissolvedparticlesincreasesthevalueofG,sincetheseparticlesserveasadditionalnuclei.ThevalueofGdiminisheswithincreasingsizeofausteniticgra
7、ins.Crystallizationnucleiappearmainlyongrainboundaries,therefore,theconditionsfornucleationareworseincoarsegrainedsteelwheretheextentofgrainboundariesissmaller.2021/7/30合肥工大材料学院何顺荣制作7EnglishinMaterialsScienceandEngineeringThefacto
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