石墨烯增强金属基复合材料的研究进展

石墨烯由于独特的结构和优异的性能已成为金属基复合材料中最具吸引力的碳质材料增强体。综述了近年来石墨烯增强金属基复合材料的研究进展、强化机制及石墨烯表面改性进展,分析了石墨烯增强金属基复合材料研究存在的问题,并对石墨烯增强金属基复合材料的研究方向及发展趋势进行了展望。     

Mg-Nd-Y-Zr合金的无熔剂保护制备工艺研究

以金属镁、金属钕、镁钇中间合金和镁锆中间合金为原料,进行Mg-Nd-Y-Zr合金的无熔剂制备工艺的研究。通过考察熔炼温度、熔炼时间、合金液静置时间以及浇铸温度等工艺参数对合金收率、合金元素收率以及合金元素偏析程度等技术指标的影响,结合对合金铸态组织结构的研究,确定Mg-Nd-Y-Zr合金的均质纯净化制备工艺条件为:熔炼温度770℃、熔炼时间150 min、物料加入速率50 g/min、保护气中SF6体积分数0.1%、合金液静置时间60 min以及浇铸温度740℃。该工艺条件下,合金收率大于96%,合金元素偏析程度为±(0.05~0.15)%(质量分数),合金元素含量偏差±(0.03~0.10)%(质量分数),合金内部无氧化缺陷,无杂质元素的引入富集。合金中的典型强化相为Mg41Nd5、Mg12Nd及Mg2Y相,呈网状分布,钕和钇元素对合金具有弥散强化作用;锆元素在合金中具有晶粒细化和铁杂质去除的双重作用。     

220 kV断路器合闸储能弹簧内嵌紧固件断裂分析

分析某一断路器合闸储能弹簧内嵌紧固件断裂的原因,通过宏观检查、金相组织、硬度值及化学成分等手段研究。结果显示,该部件显微组织中存在有非金属夹杂物,导致其组织成分不均匀,同时热处理工艺(固溶和强化)不当,使得构件的塑性和韧性恶化,最终在多次动作后出现变形损伤,脆性断裂。     

Reinforcement in Al Matrix Composites: A Review of Strengthening Behavior of Nano‐Sized Particles

Aluminum matrix composites (AMCs) reinforced with the nano‐sized particles are very important materials for the applications in industrial fields. These aluminum matrix composites consist of an aluminum matrix and nano‐sized particles, which own very different physical and mechanical properties from those of the matrix. Nano‐sized particles show a more obvious strengthening effect on the matrix than the micro‐sized particles do, because of the high specific surface area which is positive for the pinning effect during the deformation process. Thus, the nano‐sized particle‐reinforced AMCs usually exhibit a good ductility. The main issues of the fabrication methods are the low wettability between the nano‐sized particles and the molten aluminum alloys, which is fatal to the conventional casting methods, and the agglomeration of nano‐sized particles which happened easier than the larger particles. Several alternative processes have been presented in literature for the production of the nano‐sized particle‐reinforced aluminum composites. This paper is aimed at reviewing the feasible manufacturing techniques used for the fabrication of nano‐sized particle‐reinforced aluminum composites. More importantly, the strengthening mechanisms and models which are responsible for the improvement of mechanical properties of the nano‐sized particle‐reinforced aluminum composites have been reviewed.

     

微量Mg元素添加对Cu-Cr合金析出行为及性能的影响

通过熔炼铸造工艺制备了Cu-Cr和Cu-Cr-Mg合金,评价了Mg元素对Cu-Cr合金硬度、导电和抗软化性能的影响,研究了Mg元素对Cu-Cr合金析出相的细化作用,探讨了Mg元素的迁移行为。结果表明,相比于Cu-Cr二元合金,时效态Cu-Cr-Mg合金具有更高的硬度和软化温度,且保持较高的导电性能。两种合金的主要时效强化相均为纳米Cr析出相,Mg元素的加入抑制了纳米沉淀相的长大和结构转变,峰时效态Cu-Cr-Mg合金的析出相与基体可能仍保持共格界面关系,过时效态合金中出现与Heulser相结构相同的析出相,且峰时效态Cu-Cr-Mg合金经过高温保温处理后,其强化相的尺寸明显小于Cu-Cr合金析出相。EDS的结果表明,在时效初期Mg和Cr共存于析出相内部,而在时效后期析出相内部只有Cr元素存在,Mg元素发生迁移,同时理论估算结果显示,Mg元素可明显降低Cu(fcc)/Cr(bcc)之间的界面能,导致其偏聚于基体/析出相界面处,这可能是Mg元素能够细化析出相和提高合金性能的主要原因。     

多步热处理对未掺杂LEC SI-GaAs特性的影响

对未掺杂ＬＥＣＳＩ－ＧａＡｓ进行了“三步热处理”。用霍尔测量、光激电流谱测量和化学腐蚀方法研究了这种热处理对电阻率、迁移率、电活性缺陷、位错密度及Ａｓ沉淀的影响。     

纳米碳酸钙粒子增韧增强不饱和树脂的研究

报道了纳米级碳酸钙填充不饱和树脂的性能研究，探讨了碳酸钙含量和钛酸酯偶联处理对不饱和树脂性能的影响，用扫描电镜（SEM）观察了试样的断裂口形貌，结果表明，用偶联剂处理的纳米碳酸钙粒子含量在4份左右时对复合材料的综合性能最佳，比未加纳米粒子的和未处理的材料冲击强度分别提高了370％和170％，拉伸强度分别提高了170％和150％，SEM分析说明未处理粒子增韧不饱和树脂的机理是粒子的“钉扎”效应和钝化裂纹，而偶联剂处理的纳米粒子增韧不饱和树脂的机理主要是料子导致基体产生了塑性变形。     

加固用复合材料力学性能的影响因素

在土木工程中，混凝土结构的加固补强要求连续纤维增强树脂基复合材料应具有较高的抗拉强度、弹性模量和一定的断裂延伸率，本文探讨了在一定成型工艺和环氧树脂基体的条件下，影响这些性能的因素．试验表明，纤维品种、纤维表面处理方法、片材厚度对这些性能有显著的影响；纤维束或纤维布与树脂基体复合固化后，由于固化应力的作用，其增强效率将大大下降。对此，在加固设计时应予以重视。     

某框架一核心简结构加强层位置的优化

本文研究了某带加强层框架一核心筒结构,利用有限元软件Midas building分别建立设置两道加强层的模型l、模型2和模型3,三种模型的区别在于加强层的楼层位置不同。通过在多遇地震作用下的弹性分析比较三个模型的周期比、层间位移角和位移比,结果表明模型2较之可以更有效地降低层间位移角突变,使得结构的受力更加均匀,不容易形成薄弱层,有效地缓解了刚度突变,有利于结构抗震。     

Strengthening steel joint of architectural structure under loading condition

Through the comparative analysis of steel plate reinforced,ceramics reinforced and non-reinforced joints under loading condition,the feasibility of strengthening steel joint of architectural structure was studied.By using element birth and death technology simulation of the fi nite element software ANSYS,it is found that when the reinforced structure is 10 mm in thickness and using steel structure to reinforce the concerned areas,the equivalent stress in concerned regionals reduces by 31.1% compared with that when the structure is not reinforced.When reinforced with ceramics,the equivalent stress in concerned regionals reduces by 24.1% compared with that reinforced with steels;when the reinforced structure is 20 mm in thickness using steels to reinforce the concerned area,the equivalent stress in concerned regionals reduces by 39.4% compared with that when the structure is not reinforced.When using ceramics to reinforce the concerned areas,the equivalent stress only decreases by 3.7% compared with that reinforced with steels.