简介:ThehotdeformationbehaviorofTC18alloyatstrainratesrangingfrom1910-4to1910-2s-1andtemperaturesrangingfrom25to800°CwasstudiedusingaWDW-300electronicuniversaltestingmachine.Therelationshipsbetweentruestressandtruestrainshowthatflowstressdecreaseswiththeincreaseoftemperatureandincreasesasstrainrateincreases.Theeffectofstrainrateontheflowstressbecomespronouncedathighertemperatures.Atroomtemperature,theriverpatterncharacteristicofbrittlefractureandthedimplepatterntypicalofductilefracturearefoundtoexistindifferentregionsoffracturesurfacesofthesamples.AnimprovedconstitutiverelationshipisproposedtoaccuratelydescribetheflowstressofTC18byconsideringtheeffectofstrain.Andamicroscopicmodelisalsodeducedwhichcanlinkthephysicalmechanismstothemacroscopicexperimentalresults.Agoodagreementisobtainedbetweenthepredictionsofthemicroscopicmodelandtheresultsofthemacroscopicexperiment.
简介:HINAPLAS2014国际橡塑展(第二十八届中国国际塑料橡胶工业展览会)已于4月26日在上海落下帷幕,本届展会无论从入场人数还是规模上,都刷新了多项纪录。
简介:Nb-24Ti-18Si-2Al-2Hf-4CrandNb-24Ti-18Si-2Al-2Hf-8Cralloyswerepreparedbyarcmeltinginawater-cooledcrucibleunderargonatmosphere.Microstructuralcharacteristicsandoxidationresistanceofthealloysat1250℃wereinvestigated.Theresultsshowthat,whentheCrcontentis4at%,themicrostructuresconsistof(Nb,Ti)_(ss)andNb_5Si_3;asCrcontentincreasesto8at%,C14LavesphaseCr_2Nbisformed.Theisothermaloxidationtestsshowthattheoxidationkineticsofthetwoalloysfollowsimilarfeatures.Theweightgainsofthetwoalloysafteroxidationat1250℃for100hare235.61and198.50mg·cm~(-2),respectively.Duringoxidation,SiO_2,TiO_2,Nb_2O_5andCrNbO_4areformedatfirst.Then,Ti_2Nb_(10)O_(29)isformedafteroxidationfor20minandbeginstochangeintoTiNb_2O_7astheoxidationproceeds.SiO_2isformedassolidstateatfirstbutlaterevolvesintoglassystatetoimprovethecohesionofthescale.Afteroxidationfor100h,oxidationproductsconsistofSiO_2,TiNb_2O_7,Nb_2O_5andCrNbO_4.
简介:TiC/Cr18Ni8steelbondedcarbidesweresynthesizedbyvacuumsinteringwithmixedpowdersofiron,ferrotitanium,ferrochromium,colloidalgraphiteandnickelasrawmaterials.Themicrostructureandmicrohardnessofthesteelbondedcarbideswereanalyzedbyscanningelectronmicroscope(SEM),X-raydiffraction(XRD)andRockwellhardometer.ResultsshowthatthephasesofsteelbondedcarbidesmainlyconsistofTiCandFe-Cr-Nisolidsolution.ThesynthesizedTiCparticlesarefine.Mostofthemarenotmorethan1μm.Withtheincreaseofsinteringtemperature,theporosityofTiC/Cr18Ni8steelbondedcarbidesdecreasesandthedensityandhardnessincrease,butthesizeofTiCparticlesslightlyincreases.Underthesamesinteringconditions,thedensityandhardnessofsteelbondedcarbideswithC/Tiatomicratio0.9arehigherthanthosewithC/Tiatomicratio1.0.TheTiCparticleswithC/Tiatomicratio0.9aremuchfinerandmorehomogeneous.