Crystallographic and electrochemical characteristics of Ti45Zr35Ni13Pd7 melt-spun alloys

Ti₄₅Zr₃₅Ni₁₃Pd₇ alloys are prepared by melt spinning at different cooling rates (v). The phase structure and electrochemical hydrogen storage performance are investigated. When v is 10 m/s, the alloy consists of icosahedral quasicrystalline phase (I-phase), C14 Laves phase and a little amorphous phase. When v increases to 20 or 30 m/s, a mixed structure of I-phase and amorphous phase is formed. Maximum discharge capacity of alloy electrode decreases from 156 mAh/g (v = 10 m/s) to 139 mAh/g (v = 30 m/s) with increasing v. High-rate dischargeability at the discharge current density of 240 mA/g decreases monotonically from 61.2% (v = 10 m/s) to 56.8% (v = 30 m/s). Cycling retention rate S₂₀ increases from 62.2% (v = 10 m/s) to 66.1% (v = 30 m/s) with increasing v, which is ascribed to the increase in amorphous phase.     

立方准晶材料的裂纹问题

本文通过引入位移函数使得立方准晶的轴对称弹性问题化为求解一高阶偏微分方程。作为轴对称问题的例子,得到了立方准晶含有圆盘状裂纹时其弹性场的分析解,并由此确定了应力强度因子和能量释放率。     

Al-Cu-Fe系初生准晶相凝固过程的热力学分析

采用XRD,SEM和TEM等方法,研究了铸态 Al58.8Cu36.6Fe3.5Si1.1合金(973K保温2.5h后水淬)的显微组织及相组成.观察到铸态样品中存在4种不同的相,即初生准晶I相、Φ相、θ-Al2Cu相和η-AlCu相.对准晶I相及其晶体近似相R相,提出相应的自由能计算模型及算法,从理论上说明准晶(Al61.89Cu25.61Fe11.10)I相是高温稳定相,当温度低于938K时,将形成其晶体近似相R相.     

AlMn二十面体准晶的凝固形貌与固液界面稳定性

根据已经报导的实验结果对在典型的AlMn二元合金中二十面体准晶的凝固形貌及合金成分、冷速的关系进行了研究,对二十面体准晶与相应的晶体的凝固形貌进行了比较。实验结果与理论分析表明,在晶体凝固中适用的形貌稳定性理论也可以应用了二十面体准晶的凝固形貌予测及控制。     

一个与准晶相关的新Al—Cu相

本文报道一个新Ａｌ－Ｃｕ相，具有正交结构，空间群Ｆｄｄｄ，点阵常数为：ａ＝０．８１６６ｎｍ，ｂ＝０．９９９５ｎｍ，ｃ＝１．４１４９ｎｍ，表达式为Ａｌ４３．２Ｃｕ５６．８，该相与Ａｌ－Ｃｕ－Ｆｅ准晶的价电子浓度相同，是一个由ＣｓＣｌ结构衍生的类似相。     

PHASE TRANSFORMATION IN RAPIDLY SOLIDIFIED AI-Cu-Fe ALLOY

By means of rapid solidification, two Al_(65)Cu_(20)Fe_(15) powders were prepared with water and liquid N_2 as the respective cooling agent. Both powders are composed of a qnasicrystalline icosahedral phase and a crystalline hexagonal phase, with the water-cooled alloy having a higher crystalline phase content. In the isothermal an nealing process, the crystalline phase in the water-quenched alloy begins to decrease at 500℃ and then disap pears at 600～700℃. At about 800℃, new crystalline phases form, and at 900℃, the quasicrystalline phase disappears. Conversely, in the liquid N_2 quenched alloy, the quasicrystalline phase starts to decrease at about 500℃. and the hexagonal phase decomposes into new crystalline phases. At 700～800℃, the quasicrystalline phase disappears. For the water-cooled sample, the quenching at 100～200C makes the crystalline to quasicrystalline phase transformation start at a lower temperature and the crystallization of the quasicrystal occur at a higher temperature. For the liquid N_2 quenched alloy, the quenching at 100～400℃, did not affect its phase transformation at high temperature.     

Zr-二十面体准晶-十次准晶伪三元系中非晶的形成

分析了块状非晶与稳定准晶结构上的异同点，选择两种稳定准晶(二十面体准晶和十次准晶)相互混合，在保持准晶二十面体基本结构单元的基础上，增加元素组成的混乱度，再添加有利于形成高配位多面体的元素Zr，用急冷方法制备出非晶合金．对此非晶合金的热力学测试表明，该非晶形成能力和稳定性与Inoue的Zr65Al7.5Cu17.5Ni10非晶相近．     

Al－Cu－Co－Ge十边形准晶单晶的定向生长

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．