简介:ThemicrostructureandtensilepropertiesofSn-9Znsolderunderdifferentcoolingandagingconditionwerestudied.Duringsolidification,thedistributionofZn-richphasesandgrainsizeinthemicrostructureofSn-9Znsolderweredecidedbythecoolingrate.TheZn-richphaseinSn-9Znsolderunderfurnacecooling,aircoolingandwatercoolingmediawasseparatelyexistedascoarsendendriticandneedlelikeshape,fineneedlelikeshapeandveryfinerod-likeshape,respectively.Afteraging,thecoarsendendriticwasbrokenandthecoarsenneedlelikeZn-richphasewaspartlychangedintofinedistributionofZn-richphaseforSn-9Znsolderwithfurnacecooling,andtherod-likeZnphaseintheSn-9ZnsolderunderwatercoolingwaschangedtoconglomeratedZnwithneedleshape.DuringtensiletestingonSn-9Znsolder,tensilestrengthandductilityreachedthebestwithwatercooling,butdecreasedwithagingeffect.Meanwhile,theductilityofsolderwithaircoolingandthestrengthofsolderwithfurnacecoolingincreasedwithaging.Thefracturemodewasductileandwasindependentofcoolingmediaandagingeffect.Thesizeanddepthofdimplesdecreasedfromwater,furnacetoaircooling.Afteraging,numberandsizeofdimplesincreasedonthesolderwithfurnacecoolingandaircooling.ThechangeonthesizeofdimplesfortheSn-9Znsolderunderdifferentcoolingconditionandwithagingeffectwasaccordancetothetensileproperties.
简介:1Cr18Ni9Ti不锈钢球头在焊接后经酸洗,表面存在粗糙的腐蚀凹坑。通过采用S-3700N扫描电子显微镜、能谱分析仪、金相显微镜等对表面粗糙的腐蚀凹坑进行成因分析。结果表明:球头在焊接过程中产生了局部敏化现象,球头的晶粒组织细于与之配合的外套螺母组织,使得球头的耐腐蚀性低于外套螺母,在酸洗去氧化皮的过程中,外套螺母与球头的焊缝区、接管嘴的焊缝区之间形成缝隙,酸洗液中的正负离子移动受到了阻滞,导致缝隙处发生严重腐蚀,最终表现为球头表面的点状腐蚀形貌。定期更换酸洗槽液,降低Cl-浓度,以及在酸洗过程中活动零件,可以减少该类腐蚀的产生。
简介:Mg–9Li–3Al–1.6Yalloyswerepreparedthroughmixturemethod.Themicrostructure,mechanicalproperties,andcorrosionresistanceoftheas-castandasextrudedalloyswerestudiedbyopticalmicroscopy(OM),scanningelectronicmicroscopy(SEM),X-raydiffraction(XRD),mechanicalpropertiestesting,andelectrochemicalmeasurement.Theas-castMg–9Li–3Al–1.6Yalloywiththeaveragegrainsizeof325lmiscomposedofb-Limatrix,blocka-Mg,andgranuleAl2Yphases.Afterextrusion,thegrainsizeoftheas-castalloyisobviouslyrefinedandreachesto75lm;thestrengthandelongationoftheextrudedalloyareenhancedby17.20%and49.45%,respectively,owingtotheirfinemicrostructureandreductionofcastingdefects.Theas-extrudedalloyshowsbettercorrosionresistancecomparedtotheas-castone,whichmayberelatedtothelowstoredenergyanddislocationdensityintheextrudedalloy,alsothehomogenizationtreatmentbeforeextrusion.