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试样薄化导致的Cu—Al贝氏体/马氏体组织变化 总被引:1,自引:1,他引:0
加热到1173K的Cu-25at.%Al合金块状试样经723K60S等温淬火后其组织由片状的“羽毛状贝氏体(9R结构)和β1'马氏体(18R结构)组成。当试样被离子束轰去进一步薄化后,在足够薄的区域内生成了许多2H结构的簿片马氏体。初步分析认为该薄片马氏体形成的原因是由于贝氏体生成时在试样内留下了高的应力场,当试样薄化到一临界厚度以下时,试样区的三维约束条件松弛使试样内的应力场触发了簿片马氏体的生 相似文献
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用电子衍射方法在Al-Cu-Fe合金系中发现了一个新相,它属四方晶系,a=b≌8.6A,c=21A。图1和2分别是其沿[001],[010]带轴拍摄的电子衍射花样。但是,不同晶粒[010]电子衍射花样上斑点间距和强度往往不同。例如图3中沿箭头所指方向看去,衍射斑点不在一条直线上。对所有衍射斑点的指标化都需要三个以上的指数。很显然,它具有一维无公度调制结构的特征。另一方面,这个特征又不同于一般。其一是从各个不同带轴的电子衍射花样上很难确定哪些衍射斑点是主衍射斑点,哪些是卫星衍射。因为在一般调制结构中,主衍射的强度都比其卫星斑点强。其二是如果不考虑强度,在图3中将 相似文献
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难互溶Cu-Fe系机械合金化过程中的结构变化研究 总被引:1,自引:0,他引:1
机械合金化可使室温下几乎不互溶体系Cu_xFe_(100-x)形成过饱和国溶体。fee相区的固溶度范围扩展到X>35at.%。对Cu_(40)Fe_(60)进行的高分辨电镜观察表明:球磨3小时后bee相与fee相之间存在N-W关系,即〈001〉_α//〈110〉_γ,〈110〉_α//〈111〉_γ。表明在球磨的过程中可能发生了逆马氏体相变,fee相区的扩展与此密切相关。球磨60小时后形成了尺寸比较均匀的纳米晶结构。高分辨电镜同时观察到了层状结构的形成。 相似文献
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Haluk E. Karaca Ibrahim Karaman Burak Basaran Yang Ren Yuny I. Chumlyakov Hans J. Maier 《Advanced functional materials》2009,19(7):983-998
Magnetic shape memory alloys (MSMAs) have recently been developed into a new class of functional materials that are capable of magnetic‐field‐induced actuation, mechanical sensing, magnetic refrigeration, and energy harvesting. In the present work, the magnetic &!hyphen;field‐induced martensitic phase transformation (FIPT) in Ni45Mn36.5Co5In13.5 MSMA single crystals is characterized as a new actuation mechanism with potential to result in ultra‐high actuation work outputs. The effects of the applied magnetic field on the transformation temperatures, magnetization, and superelastic response are investigated. The magnetic work output of NiMnCoIn alloys is determined to be more than 1 MJ m?3 per Tesla, which is one order of magnitude higher than that of the most well‐known MSMAs, i.e., NiMnGa alloys. In addition, the work output of NiMnCoIn alloys is orientation independent, potentially surpassing the need for single crystals, and not limited by a saturation magnetic field, as opposed to NiMnGa MSMAs. Experimental and theoretical transformation strains and magnetostress levels are determined as a function of crystal orientation. It is found that [111]‐oriented crystals can demonstrate a magnetostress level of 140 MPa T?1 with 1.2% axial strain under compression. These field‐induced stress and strain levels are significantly higher than those from existing piezoelectric and magnetostrictive actuators. A thermodynamical framework is introduced to comprehend the magnetic energy contributions during FIPT. The present work reveals that the magnetic FIPT mechanism is promising for magnetic actuation applications and provides new opportunities for applications requiring high actuation work‐outputs with relatively large actuation frequencies. One potential issue is the requirement for relatively high critical magnetic fields and field intervals (1.5–3 T) for the onset of FIPT and for reversible FIPT, respectively. 相似文献
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纳米晶软磁合金(Fe73.5Cu1Nb3Si13.5B9)的典型结构为两相:即大小为15nm的FeSi小晶粒相弥散分布于剩余非晶基体相中。在离子减薄制备的电镜样品中,孔的边缘往往有一些无颗粒区。我们用EDS研究了其化学成分,发现这些无颗粒区的成分不同于理论估计的非晶基体相的化学成分,也不同于材料原来的平均成分。其电子选区衍射(SAD)花样既和两相区的衍射花样不同,表现为d=0.27nm附近的一个非晶衍射环,也和制备态的非晶衍射环不同,说明这些非晶区可能是在样品的离子减薄过程中二次非晶化引起的。 相似文献