资源描述:
《AZ91D镁合金半固态坯料制备及角框件模锻工艺研究》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、一-—一一一二彭塑竺生笠兰理三进鱼鲤二一~-一.一摘要镁合金是实用余属中最轻的有色金属材料,并且可以100%回收,已成为汽车、电子、通讯等行业的热门材料。传统的镁合金成形方法多采用压铸法,但压铸法成品率低,并且容易产生冷隔、气孔、收缩、变形等缺陷,本文采用半固态模锻进行镁合金的成形研究,以期解决传统成形方法的不足。半固态模锻成形工艺中,获得被液相包裹着的均匀近球形晶粒的触变组织是整个工艺的基础和关键。本文以商业化生产的镁合金AZ91D铸态棒材为原料,首先研究了镁合金非枝晶组织的制备方法。在研究了半固态等温热处理法制坯后,分别使用徽粗和等径弯曲通道
2、挤压的方法对镁合金原始坯料进行预变形,利用应变诱发熔化激活法制备出了理想的半固态坯料,获得了细小而均匀的半固态球状组织,并分析了坯料预变形程度、等温热处理温度和保温时间对非枝晶组织形成的影响。在此基础上,对镁合金坯料经预变形处理,再经半固态等温热处理后,坯料中非枝晶组织形成的机理进行了探讨。在合理选择半固态模锻工艺参数的基础上,利用自行设计的模具成形出了壁厚为3mm、充型完美、表面光滑的角框件,对镁合金制件的微观组织进行了分析,并进行了热处理改善制件力学性能的研究。关键词AZ91D镁合金;SIMA法;非枝晶组织;半固态模锻哈尔滨工业大学工学硕士学
3、位论文AbstractMagnesiumalloyisthelightestnonferrousmaterialofthepracticalmetals,andcanberecycledfully,soitbecomesthehotmaterialofautomobile,electronsandcommunications.Thecommonformingprocessofthisalloyisdie-castmethod,butitcannotavoidthedisadvantageoflowyield,andeasytogenerateco
4、ldlap,gascavity,shrinkageanddeformation.Itisexpectedinthisdissertationtosolvethesethroughsemi-solidforgingandovercomethedeficiencyofthecommonmethodItisfoundthatthebasisandthekeyfortheentiresemi-solidprocessisthixo-microstructurewithmean-smallgrainsapproachingthesphericalshape
5、andwellbeingisolatedfromeachotherbyacontinuousliquidfilm.Inthisdissertation,thecommercialAZ91Dmagnesiumalloywasemployedasrawmaterial,andthepreparationmethodofnon-dendriticstructurewasstudiedfirstly.Afterthestudiesofsemi-solidisothermalheat-treatment,therawbilletswerepre-defor
6、medthroughupsetandequal-channelangularpressingseparately,andthentheideal,thinandmeansemi-solidmicrostructurewereobtainedthroughthestrain-inducedmeltactivationmethod,andtheinfluencesofpre-deformation,thetemperatureoftheisothermalheat-treatmentandtheholdingtimeonthenon-dendriti
7、cmicrostructurewereanalyzed.Basedonthese,themechanicsoftheformationofnon-dendriticmicrostructureinthemagnesiumbilletwasalsostudied.Aftertheproperselectionoftheprocessingparametersofthesemi-solidforging,theangle-frameswith3mmwallthicknesshavebeensuccessfullyformedthroughthemol
8、ddesignedbyourselves,whichareslipperandfull.Afterthat,themicrostruct