Preparation of W-Al alloys by mechanical alloying

W1-xAlx (x=0-0.86) alloys were synthesized by mechanically alloying the pure metal powder mixtures at designated compositions by conventional high-energy ball milling. The W-Al alloys were stable under high pressure and high temperature. The alloys were lighter than W. The hardness and oxidation resistance of the alloys was greatly improved compared to both W and Al. (C) 2002 Elsevier Science B.V. All rights reserved.

Formation of epsilon-FeXN/BN magnetic nanocomposite and its thermodynamic and kinetic analyses

A nanocomposite of nanometer-sized magnetic granular epsilon-FeXN embedded in a nonmagnetic amorphous boron nitride matrix was prepared by ball milling mixture of alpha-Fe and hexagonal boron nitride in argon atmosphere. The grain size of the epsilon-FeXN alloy was about 10-20 nm. The nitrogen concentration in the epsilon-FeXN alloy increases with extending milling time. Both thermodynamic calculation and the present experiment show that iron and nitrogen atoms have higher alloying driving force than iron and boron atoms. Analyses of thermodynamics and kinetics about formation of the epsilon-FeXN alloy suggested that the formation of the epsilon-FeXN alloy is related to amorphization of the hexagonal boron nitride and refinement of the alpha-Fe. II was found from the present experiment that a critical grain size of the alpha-Fe reacting with nitrogen in the amorphous boron nitride is about 8 nm.

一种混合型4自由度并联机床的位置分析

针对原沈阳自动化研究所研制开发的五轴并联铣床的结构特点 ,提出了一种改进方案 ,并对这种新的构型的运动学进行了分析 ,针对其特点 ,从新的角度给出了位置正解及反解的方程。该构型的位置正解由于使用了附加传感器并充分考虑到机构特点而使得正解方程形式非常简单并且其中只存在一次项 ,从而避免了对复杂数值解法的采用