ti 55钛合金板材超塑性变形行为

第20卷专辑 2010年10JournalofNonferrousOct.1，1,2，1，王清江1，1(1.中国金属，沈阳2.沈阳大学机械，沈阳在高应变速率下，Ti-55板材的最大伸长率向高温区移动；超塑性变形过程中晶粒呈相互聚合长大的现象，应变号：TG ZHAOZi-bo1,GEJing-lu1,2,CHENZhi-yong1,WANGQing-jiang1,LIUJian-(1.InstituteofMetalResearch,TheAcademyofSciences,Shenyang110016,2.CollegeofMechanicalEngineering,ShenyangUniversity,Shenyang110044,:Thesuperstictensiletestswereperformedatvarioustemperatures(890−910℃)andinitialstrainrates(4.4×10−4−1.76×10−3s−1).Theresultsshowthatthefine-grainedTi-55sheet,withanaveragegrainsizeabout4µm,exhibitsexcellentsupersticity.Ontheoptimalsupersticconditionof900℃andinitialstrainrate8.8×10−4s−1,aumelongationof1300%canbeachieved.Thereexistsanoptimalstrainrateof8.8×10−4s−1foreachtesttemperaturetogetthehigheststrain,andthesupersticelongationwouldbesignificantlyreducedatstrainrateshigherorlowerthantheoptimumstrainrate.ThetemperatureforthebestsupersticityofTi-55sheetmovestohighertemperaturesathighstrainrates.Theinfluenceofthedeformationonmicrostructureisobviously.Thestraininducegraingrowthisoneofthemostprominentcharacteristicduringsupersticdeformation.:Ti-55titaniumalloy;supersticity;strainrate;deformationtemperature;Ti-55550℃下长期服役的

之一而日益引起人们的重视。目前Ti-6Al-4V合和领域中[2]。高温钛合金由于具有比Ti-6Al-4V高的 Ti-55板材超塑性的影1，可见由等轴细4µm左右。

3个阶段：的。图2所示为Ti-55试样超塑变形前、后的，33可可由Hart准则得到很好解释。F都是相同的。由1Fig.1Originalstructureof

FFAF

本试验所有超塑性拉伸试验均在岛津DCS−25T3个变形温度：890，900910℃，变形时采用恒定夹头速度拉伸。8mm×4mm×1.37mm。每0.210.428.8×10−41.76×10−3s−1。试样均沿垂直于轧制方向ZZeissAxiovert200MAT金相显微镜观察变形前后显微组织的变化。

2试样变形前、后的 Photosofspecimensbeforeandaftersuperstic即dlnδdt，Hart3Fig.3Relationshipbetweenelongationandinitialstrain

力F及其变化率F都相同，所以由式(2)得：

δFdAAδδAAδddA δAδ δAδ ≥dln

超塑变形温度对伸长率及显微组织的影响如图5所示。可见，在低应变速率时材料的伸长率随温聚合[10−12](5所示)，又会大幅度降低材料超塑性匀性，则dlnδdt截面上应变速率增加，使其强化速率大于松弛速率从而变形减慢，未发生细颈的部分应变速率较慢，

4Fig.4Relationshipbetweenelongationand5 Microstructureoftensiledspecimen:(a)Chuckpartofspecimen,890℃,4.4×10−4s−1;(b)Chuckpartofspecimen,8908.8×10−4s−1;(c)Chuckpartofspecimen,910℃,4.4×10−4s−1;(d)Fracturepartofspecimen,890℃,4.4×10−4s−1;(e)Fracturepartofspecimen,890℃,8.8×10−4s−1;(f)Fracturepartofspecimen,910℃,4.4×10−4s−1材料内部的协调变形能力进一步增强，所以在较高初始应变速率17610−3−1)条件下，T-55板材的最大9044×0−4−189088×0−4−1条件下样品夹持部位与标距5(),(d和(be(约4h)1组织明显粗化13−15]，其平均晶粒尺寸长大到8m左右。在应变速率较快(保温时间较短)的条件下，夹持端晶粒明显比应变速率较慢(保温时间较长)时的细。这一晶粒长大过程采用经典晶粒长大模型中大晶粒吞

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