高压下Fe_(84)Nb_7B_9纳米晶软磁块体合金的形成

采用机械合金化(MA)以及低温高压烧结工艺制备了Fe84Nb7B9软磁合金粉末及其块体合金,并利用XRD、DSC、SEM对MA合金粉末和块体合金的相结构、晶粒大小以及组织的热稳定性进行了研究。结果表明:经过15hMA后,可获得单相bcc结构的粒径小于10nm的纳米晶过饱和固溶体粉末;在常压状态下,单相纳米晶过饱和固溶体合金在温度小于550℃时具有良好的组织热稳定性,温度小于770℃时具有良好的相热稳定性;在p=5.5GPa,t=3min条件下,当Pw≥820W时,可获得相对密度大于98.4%、单相bcc结构的纳米晶(粒径小于10nm)块体合金。

Heusler型Ni2MnGa合金的有序化处理

研究了热处理工艺条件对非化学计量比的Ni48Mn31Ga21合金的结构有序度的影响.结果表明:对于非化学计量Ni48Mn31Ga21合金,其结构有序化处Ζ理工艺宜选用900℃×4d+400℃×50h.

热处理工艺对Heusler型Ni_2MnGa合金马氏体相变的影响

采用电弧熔炼法熔炼Ni48Mn31Ga21和Ni50Mn25Ga25两种合金,并对这两种合金进行了热处理,借助交流磁化率测定、金相显微镜观察、X射线衍射等手段研究了热处理工艺条件对非化学计量比的Ni48Mn31Ga21合金马氏体相变和结构有序度的影响。结果表明:(1)Ni48Mn31Ga21合金相变特征温度为:Ms=305K,Mf=297K,As=313K,Af=318K,居里温度Tc=366K;(2)与空冷态相比,淬火态的马氏体转变量降低,经过400℃退火后,随着保温时间t的延长,马氏体转变量上升,当t=50h时达到最大值;(3)Ni48Mn31Ga21合金经过900℃×4d+400℃×50h热处理后,有序度明显提高。

Formation of texture of Ni_(48)Mn_(31)Ga_(21) polycrystalline alloy by thermal simulation pack rolling technology

The hot deformation behavior of Ni48Mn31Ga21 alloy was studied by thermal simulation rolling technology. Microstructure evolution of the alloys under different rolling processes was studied by optical microscopy(OM) and X-ray diffractometry(XRD).The results show that, by thermal simulation pack rolling technology, textures appear in polycrystalline Ni48Mn31Ga21 alloy, and big cracks can be avoided under large deformation ratio. The rolling process with few passes and strong deformation makes Ni48Mn31Ga21 alloy obtain (202), (400) and (323) textures of martensitic variants more easily, especially (400) texture. Besides the interface between package materials and the Ni48Mn31Ga21 alloy is clear, which is beneficial for Ni48Mn31Ga21 alloy to separate from pack.