一场学生宿舍火灾引起的思索

最近上海某高校的一幢女研究生宿舍楼发生了一起火灾事故,虽然此火灾损失不大,但由于发生在高等院校内的学生宿舍区,住宿的又都是天之骄子而且加上该楼系木结构建筑,着火的房间在顶层,着火后烟雾进入屋顶的三角夹层向四周弥漫,给施救带来了一定的困难,加上其它一些原因使施救时间较长,导致屋顶烧穿,往社会上造成了较大的影响。现经市消防局调查,火灾原因是违章使用电热器具引起的。应该说,该校对消防工作还是比较重视的,尤其是校     

轧制和退火态的Mg-Y-Zr-xNd合金的组织和力学性能

通过光学显微组织(OM),扫描电子显微镜(SEM),X射线衍射(XRD),电子背散射衍射(EBSD)和拉伸试验研究了不同热处理条件下Mg-5Y-0.6Zr-xNd (x = 0, 0.5和1wt.％) 合金的组织和力学性能。结果表明,随着Nd含量的增加,第二相Mg24Y5和Mg14Nd2Y (β)在基体中的含量增加。添加少量Nd可以降低α-Mg的堆垛层错能,促进热轧过程中的动态再结晶。随着Nd含量的增加,静态再结晶的体积分数明显增加。退火处理后Mg-5Y-0.6Zr-0Nd合金的平均晶粒尺寸可细化至3.73μm。轧制合金的抗拉强度随着Nd的增加而增加,而伸长率则表现出相反的变化趋势。含有1.01wt.％Nd的轧制合金具有优良的机械性能,其拉伸强度,屈服强度和伸长率分别为336MPa,278MPa和16.3％。在微观结构观察的基础上,讨论了力学性能的变化。     

冷轧及热处理对AA 5052铝合金组织及力学性能的影响

通过光学显微镜、扫描电镜、X射线衍射分析、硬度实验和拉伸实验等方法,研究不同轧制变形量及后续退火处理对均匀化态5052铝合金组织与性能的影响。研究结果表明,随着轧制变形量的增加,等轴晶沿着轧制方向明显地被拉长。由于轧制变形量的增加,加工硬化效应导致合金强度升高,硬度下降。当轧制变形量为87%时,抗拉强度可达325 MPa,但是伸长率只有2.5%。经退后处理后,大量的第二相析出。随着退火温度的升高,第二相析出增多,并且明显弱化加工硬化效应。当经过300°C处理4 h后,伸长率可达~23%,抗拉强度降至212 MPa,此时综合力学性能恢复到均匀化状态。     

静力触探指标在桩基评价中的应用

结合梧州大塘３＾＃综合楼工程，通过理论计算和试验结果的对比分析，得出利用静力触探指标来评价钢筋混凝土预制桩在梧州地区的适用性的方法。其既简便可行又经济合理。     

Influence of impurities on microstructure and mechanical properties of ZK60 magnesium alloy

The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy, scanning electron microscopy and tensile test. ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements. The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state. However, in the as-extruded state, reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa, while the elongations in the as-extruded alloys with different contents of impurities are almost the same. After T5 treatment, impurity content is found to have more obvious effect on the yield strength of ZK60 alloy. The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.     

Influence of impurities on damping properties of ZK60 magnesium alloy

The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast, as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature. Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys. It is found that reducing impurity content can decrease the amount of second-phase particles, increase grain size and improve damping capacity of the as-cast alloy slightly. The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration, which appears to originate mainly from different dislocation characteristics. The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile, the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.     

稀土元素对ZK60镁合金组织和性能影响的研究现状

简述了稀土元素在镁合金中的作用,重点介绍了Y、Ce、Er、Nd、Dy、Gd、Yb等稀土元素对ZK60镁合金的晶粒尺寸、第二相化合物、室温力学性能以及高温性能的影响,指出了在ZK60镁合金中添加稀土元素的研究存在的问题与不足,并对其发展方向进行了展望.     

热轧变形对5052铝合金组织与力学性能的影响

通过光学显微镜、扫描电镜、能谱和X射线衍射分析和拉伸实验等试验分析方法,研究不同热轧变形量(54％、75％)对5052铝合金微观组织和力学性能的影响.结果显示,变形量可显著影响5052铝合金的热变形组织及其力学性能.随着轧制变形量的增加,晶粒被显著拉长,晶界处粗大第二相沿晶界被拉长,甚至被破碎.但是其第二相的组成并没有随着轧制变形量的增加而变化,铸态和轧制态的5052铝合金均由α-Al、Al82Fe18和Mg2Si三相组成.同时随着轧制变形量的增加,其综合力学性能提高,即沿轧制方向且轧制量为75％时的5052铝合金呈现出最优的综合力学性能.     

水泥搅拌桩复合地基沉降的探讨

本文就深厚软土地基常用的水泥搅拌桩复合地基处理方法做介绍,主要分析水泥搅拌桩地基沉降的相关因素,供同类施工参考。     

镁合金热处理的研究现状及发展趋势

热处理对镁合金的影响已受到广泛关注.综述了当今国内外现有的镁合金热处理的方法(如退火、固溶、时效、形变热处理、氢化处理、表面热处理等)以及特点,阐述了热处理工艺对镁合金显微组织、力学性能、腐蚀性能的影响,最后展望了镁合金热处理的发展方向.