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61.
Growth morphology and evolution of quasicrystal in as-solidified Y-rich Mg-Zn-Y ternary alloys 总被引:1,自引:0,他引:1
WAN Diqing YANG Gencang CHEN Sulin ZHU Man ZHOU Yaohe 《稀有金属(英文版)》2007,26(5):435-439
A petal-like icosahedral quasicrystal with five branches,which is considered to be the representative morphology of the icosahedral quasicrystal,has been observed in the Y-rich Mg-Zn-Y ternary alloys. Moreover,the polygon-like morphology,another pattern of the icosahedral quasicrystal,has also been found in the Y-rich Mg-Zn-Y ternary alloys. The latter morphology results from the evolution of the former one. The growth mechanism of the petal-like morphology of the icosahedral quasicrystal was also discussed. Alloying composition,i.e.,Y element content,is a major factor inducing the morphology evolution of the icosahedral quasicrystal. 相似文献
62.
Al-Cu-Co-Ge十边形准晶单晶的定向生长 总被引:1,自引:0,他引:1
利用控制凝固过程的定向凝固技术生长出了直径0.8长10mm的Al-Cu-Co-Ge十边形准晶单晶.在准晶生长过程中,所有准晶单晶形成了单一取向的择优生长结构,其棱柱的中心轴为十次旋转对称轴.在温度梯度为95℃/cm的条件下,随着定向凝固速度的增大,生长界面出现的成分过冷越来越大,从而导致生长界面的扰动也逐渐加剧并使成分偏析,界面形态由平面向胞状和树枝状转化,出现大量非准晶相,最后无法生长出所需要的高质量准晶单晶. 相似文献
63.
Al-Cu-Fe准晶及其晶体类似相与纯Mg的界面反应 总被引:2,自引:0,他引:2
分析了按照Al63Cu25Fe12配比常规凝固制备的AlCuFe准晶材料的相组成, 研究了块状AlCuFe准晶材料与熔融纯镁的界面反应,发现在界面处存在物质交换作用. 镁与AlCuFe准晶材料有良好的浸润性, 这归因于准晶材料中孔隙的存在、亚稳相的分解和表面氧化层与Mg的反应. 相似文献
64.
An Al86 Mn3 Be11 alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be4 AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. The composition of the Be4 AlMn slightly deviated from the stoichiometric composition, whereas the composition of the i-phase was approximately Al52 Mn18 Be30 , containing an appreciable amount of Be. The average composition of the hexagonal phase was Al66 Mn21 Be13 . Deep etching and particle extraction provided a deep insight into the three-dimensional morphology of the i-phase and the hexagonal phase, whereas Be4 AlMn was slightly attacked by the etchant. The i-phase was present predominantly in the form of dendrites and a rodlike eutectic phase. The hexagonal phase was primarily in the form of hexagonal platelets, whereas Be4 AlMn was rather irregular in shape. The morphology of the i-phase can be explained by predominant growth in 3-fold directions and the lowest energy of the 5-fold planes, leading to the faceting and adopting a pentagonal dodecahedron shape. The brightnesses of phases in the backscattered electron images were rationalized by determining their backscattering coefficients. TEM investigation showed considerable phason strain in the i-phase, and the polycrystalline nature of the Be4 AlMn phase. 相似文献
65.
66.
67.
铸态Ti-Zr-(Ni,Co)伪三元准晶合金研究 总被引:2,自引:0,他引:2
沿Ti9(Ni,Co)4-Zr变电子浓度线设计系列合金成分.用吸铸方法可制备出Ti-Zr-(Ni,Co)准晶,其中Ti42Zr40(Ni,Co)18为形成准晶的最佳成分点,Ti-Zr-(Ni,Co)伪三元准晶系列的准点阵常数介于0.506~0.518nm之间。实验结果表明,Co是形成准晶的不利组元,其含量的增加将促使Ti2Ni、fcc-Zr2Ni和β-Zr(Ti)固溶相的形成,使合金中准晶相的含量大为降低;但适量Si的加入(~2at%)能促进Ti-Zr-(Ni,Co)准晶的形成。 相似文献
68.
热处理工艺对Al65Cu20Cr15准晶颗粒/Al基复合材料组织与性能的影响 总被引:1,自引:0,他引:1
采用热压方法制备了Al65Cu20Cr15准晶颗粒/Al基复合材料,对热处理前后复合材料的显微组织及硬度进行分析,结果表明:在500%高温退火过程中,准晶颗粒中的Cu和Cr原子向纯铝基体中扩散,基体中的Al原子向颗粒中扩散,从而使二十面体准晶相颗粒转变为十次准晶及其类似相,硬度有所降低;基体中,退火过程高温过饱和的Cu以Al2Cu的形式析出,而淬火过程高温过饱和的Cu来不及充分析出,产生固溶强化效应,使淬火后基体的硬度显著增加。 相似文献
69.
A composite consisting of a brittle multiphase matrix containing both an Al-based quasicrystalline phase (ψ) and an ordered body centred cubic phase (β) and a relatively ductile ordered body centred cubic intermetallic FeAl phase has been developed as an abrasive wear-resistant coating material. It is applied as a 500 μm thick layer onto stainless steel substrates through plasma spray processing. The microstructure of such materials can be readily examined by optical and scanning electron microscopy, but the inherent difficulty of preparing transmission electron microscope (TEM) samples has inhibited higher resolution studies. However, the relatively recent development of the focused ion beam (FIB) miller as a tool in materials science provides a method ideal for the preparation of TEM specimens of these materials. In this study a coating consisting of a mixture of an Al–Cu–Fe based quasicrystal and FeAl+Cr was deposited on to a 304 stainless steel substrate. TEM specimens were prepared using a FIB and subjected to detailed microstructural characterization. The structure consisted of elongated bands of a FeAl phase about 100 nm in width and several micrometres in length, which enclosed more equiaxed regions about 1 μm in diameter that consisted of fine mixtures of quasicrystal and two Al-Fe-Cu phases isostructurally related to FeAl. 相似文献
70.