定向凝固MnNi合金复合相变行为的阻尼特性  

Damping characteristics of directionally solidified MnNi alloy exhibiting multiply phase-transformation behavior

作　　者：王迪玮 牛红康 田青超 WANG Diwei;NIU Hongkang;TIAN Qingchao(State Key Laboratory of Advanced Special Steels,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学省部共建高品质特殊钢冶金与制备国家重点实验室,上海200444

出　　处：《航空材料学报》2022年第5期81-90,共10页Journal of Aeronautical Materials

摘　　要：在定向凝固过程中可通过改变拉速来改变合金的元素偏析程度以影响合金的相变行为。通过定向凝固手段,分别使用不同拉速制备4个MnNi合金试样。采用差示扫描量热分析(DSC)、X射线衍射(XRD)、热膨胀分析、动态力学分析(DMA)等研究合金相变行为;使用金相显微镜、扫描电镜、透射电镜观察合金的微观组织。结果表明:定向凝固MnNi合金的微观组织具有多形性的特征,合金中存在从微米级到纳米级的多尺度的孪晶,其协调运动使得孪晶内耗是轧制合金的3~6倍;在加热过程中合金在贫Mn区枝晶间发生fct_(1)→fcc相变,在富锰枝晶干发生fct_(2)→fco→fcc多阶相变,这种复合相变行为使得定向凝固态MnNi合金在宽温域内其阻尼能力是轧态MnNi合金的2~6倍。In the process of directional solidification,the degree of element segregation can be changed by altering the drawing rate to affect the phase transformation behavior of the alloy.In this paper,four kinds of MnNi alloy specimens were prepared by directional solidification at different drawing rates.The phase transformation behavior of the alloy was studied by differential scanning calorimetry(DSC),X-ray diffraction(XRD),thermal expansion analysis and dynamic mechanical analysis(DMA).The microstructure of the alloy was observed by metallographic microscope,scanning electron microscope and transmission electron microscope.The results show that the microstructure of directionally solidified MnNi alloy has the characteristics of polymorphy.There are multi-scale twins from micron to nanometer in the alloy,and their coordinated movement makes the internal friction of twins 3-6 times than that of rolled alloy.It is found that during heating,the alloy undergoes fct_(1)→fcc phase transformation in the interdendritic spacings of Mn-poor region while fct_(2)→fco→fcc multi-stage phase transformation occurs in Mn-rich dendrite.This multiply phase transformation behavior makes the damping capacity of directionally solidified MnNi alloy 2-6 times than that of rolled MnNi alloy in a wide temperature range.

关 键 词：MnNi阻尼合金 定向凝固 相变 孪晶组织 

分 类 号：TG146[一般工业技术—材料科学与工程]