Al-Li合金时效-回归-再时效析出δ′相的行为

应用小角X射线散射技术研究二元Al-Li(Li的质量分数为2.70%)合金时效-回归-再时效析出δ′相的行为.发现再时效8h析出的δ′相与基体之间存在明显的过渡界面层,再时效16h以后过渡界面层消失.表明δ′相粒子的长大首先是吞噬过渡界面层长大,然后是互相吞并长大. 关键词： Al-Li合金 时效－回归－再时效 过渡界面层     

Small-angle x-ray scattering study of the formation and growth of δ' in binary Al－7.87at% Li alloy

The formation and growth of δ' particles in an alloy of Al－7.87at% Li have been investigated using the small angle x-ray scattering technique. It has been shown that a transition zone, which exists between the δ' phase and the matrix after ageing for 16 h, disappears after ageing for 32 h. The existence of a transition zone indicates that the δ' phase is precipitated in the process of spinodal decomposition. This result also indicates that the growth of δ' particles should be divided into two stages. During the first stage, the δ' phase increases eating up the transition zone before ageing for 32 h, and in the second stage it grows by swallowing up each other after ageing for 32 h. In the latter stage, the larger and smaller δ' particles can coexist in the alloy.     

我国股指期货延长交易对股市现货市场影响的实证分析

采用价格加权贡献方法(WPC)和GARCH模型分析我国股指期货提前开盘和推迟收盘这两个阶段的价格发现功能和对股市现货市场的影响。实证研究表明,这两个延长交易阶段皆具有显著的价格发现作用且提前开盘阶段的价格发现效应要大于推迟收盘阶段的;在推迟收盘阶段分离出的非预期收益率所蕴含的私人信息已在这一阶段的价格中得到了反应,但提前开盘阶段的非预期收益率中的私人信息则需要通过当天的股市交易才能被吸收。同时本文还发现取样期间我国股市的周一效应较为显著,这与普遍认为的股市具有周五效应不太一致。     

钴铝和锌铝水滑石的合成

采用低过饱和共沉淀法合成了一系列锌铝和钴铝水滑石,其结构经IR和XRD表征。研究结果表明,两类水滑石晶体结构相似;钴铝水滑石的稳定性高于锌铝水滑石。