Production of NiTi shape memory alloys via electro-deoxidation utilizing an inert anode
摘要:
NiTi shape memory alloys (SMA) with equiatomic composition of Ni and Ti were prepared by electro-deoxidation, in molten calcium chloride, at 950 degrees C. Constant voltage electro-deoxidation was conducted using a NiTiO(3) cathode, and either a carbon anode or a novel CaRuO(3)/CaTiO(3) composite inert anode. Both anode materials successfully allowed NiTi shape memory alloy to be obtained. The primary difference is that molecular oxygen was produced on the inert anode, instead of environmentally undesired CO(2) greenhouse gases on the carbon anode. Indeed, it was found that carbon could successfully be substituted with conductive calcium titanate-calcium ruthenate composites for electro-deoxidation. Furthermore. DSC was used to analyze the phase transformation of NiTi shape memory alloys, with results revealing the existence of reversible martensite-austenite phase transformations during the cooling and heating process. (C) 2010 Elsevier Ltd. All rights reserved.
Influence of heat of formation of B2/L12 intermetallic compounds on the milling energy for their formation during mechanical alloying
作者:N.C. Abhik、R. Vivek、V. Udhayabanu、B.S. Murty
DOI:10.1016/j.jallcom.2007.10.076
日期:2008.10
heat of formation of an intermetallic and the milling energy required for its formation during mechanical alloying. This has been demonstrated in case of B2 intermetallic compounds, namely, NiAl, FeAl, CoAl and MnAl. The milling energy corresponding to the start of formation of the compounds during mechanical alloying of the elemental blends is found to decrease linearly with the heat of formation of the
for which few additions have been obtained, probably due to the understanding being confounded by other impurity phases. This alteration intrinsically results in enhanced desorption properties of Mg2NiH4 when Ti is dissolved, i.e., not only does it exhibit a decreased peak desorption temperature with a reduction in the activation energy, but it also positively changes the enthalpy value in comparison
The experimental evaluation of phase equilibria in the Ti–Ni–Al–N and Ti–Ni–Al–O phase diagrams are based on alloy samples, which were prepared of elemental powder blends by argon-levitation melting in a Hukin crucible. The experimentalinvestigation employed X-ray powder diffraction, metallography, SEM, and EMPA techniques in the as-cast state as well as after annealing at 900°C. Two quaternary compounds
Ti-Ni-Al-N和Ti-Ni-Al-O相图中的相平衡实验评估是基于合金样品,这些合金样品是通过在Hukin坩埚中通过氩气悬浮熔炼元素粉末混合物而制备的。实验研究采用铸态和在900°C退火后的X射线粉末衍射,金相,SEM和EMPA技术。两种季铵化合物的Ti 3的NiAl 2 N和钛3的NiAl 2 O,使其脱离填充钛导出2 -Ni型(η观察相)。新型相与Ti 2 Ni型固溶体相(Ti 1- x Al x)2 Ni,在二元Ti 2 Ni中的最大溶解度为14 at。%。通过定量X射线粉末衍射(Rietveld分析)监测所有这些阶段的原子顺序。分析了由母体Ti 2 Ni类型衍生的各相之间X射线光谱的差异,并根据η相的一般分类方案讨论了复杂原子位点占据模式。
Engineering the porosity and superelastic behaviors of NiTi alloys prepared by an electro-assisted powder metallurgical route in molten salts
Abstract An Electro-Assisted PowderMetallurgical (EPM) route is able to prepare porous NiTi alloys with controllable porosities and pore sizes using nickel (Ni) and titanium (Ti) powders at a temperature ranging from 850 to 950 °C. Ammonium hydrogen carbonate (NH4HCO3) was used as a sacrificial space holder to tailor the porosity and pore size of the NiTi alloy and its properties, i.e., elastic modulus
摘要 电辅助粉末冶金 (EPM) 路线能够使用镍 (Ni) 和钛 (Ti) 粉末在 850 至 950 °C 的温度范围内制备孔隙率和孔径可控的多孔 NiTi 合金。碳酸氢铵 (NH4HCO3) 被用作牺牲空间保持器来调整 NiTi 合金的孔隙率和孔径及其特性,即弹性模量、相变温度、形状记忆效应和超弹性。通过优化牺牲空间支架的合成温度和含量(0-30%)、孔隙率(41-75%)、孔径(22-174 μm)、弹性模量(4.77-0.87 GPa)和恢复应变( >2%)的EPM-NiTi可以达到或接近天然骨的标准(孔隙率:30%–80%,孔径:100–600 μm,松质模量:2%)。所以,
Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti–Ni–Sn and Ti–Ni–Sb ternary systems
The phase equilibria of the Ti–Ni–Sn and Ti–Ni–Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi2−xSn (MnCu2Al-type), Ti2Ni2Sn (U2Pt2Sn-type), and Ti5NiSn3 (Hf5CuSn3-type) are formed in Ti–Ni–Sn system at 1073 K. The TiNi2Sn stannide is characterized