原位颗粒增强钛基复合材料高温流变行为

通过等温热压缩实验,研究了原位合成TiB和TiC增强Ti基复合材料在550°C~750°C、0.0001s~(-1)~0.0004s~(-1)应变速率条件下的高温流变行为。结果表明:该复合材料在高温塑性变形时,压缩流变应力随变形温度的提高而降低,随应变速率的提高而提高;材料的软化机制以动态回复为主,动态再结晶为辅;利用Arrhenius方程模型结合Zener-Hollomon修正参数计算出材料的热变形参数,建立了双曲正弦形式的本构方程。     

Friction and Wear Characteristics of Mg-Al Alloy Containing Rare Earths

The influence of rare earth on the friction and wear characteristics of magnesium alloy AZ91 and AM60 were studied. The results show that the wear resistance properties of rare earth magnesium alloys are better than those of matrix alloy under the testing conditions. The anti-wear behaviour of AZ91 alloy is much better than that of AM60 alloy. In dry sliding pmcess, magnesium alloys undergo a transition from mild wear to severe wear. The addition of rare earths refine the structure of alloys, improve the comprehensive behaviors of magnesium alloys,increase the stability of oxidation films on worn surfaces,enhance the loading ability of rare earth magnesium alloys,and delay the transition from mild wear to sevre wear effectively.     

白云石煅烧组织的转变过程

以长白山地区白云石为实验对象,在不同温度、不同时间下进行煅烧实验,通过TG和DTA等热分析手段,以及利用XRD和SEM对白云石分解前后的组织结构进行观察分析,确定了白云石分解过程及相应的组织转变过程.结果表明:长白山地区白云石中的MgO和CaO的分子比为1∶1,矿物呈隐晶质组织.热分解过程分两步完成:第一步反应:CaMg(CO3)2=CaCO3+MgO+ CO2↑,第二步反应:CaCO3=CaO+ CO2↑;最佳煅烧参数是:煅烧温度700℃,恒温时间3h.此外,在930℃下恒温煅烧3h开始形成团聚结构,白云石表面过烧活性降低.     

压铸镁合金AZ91D高周疲劳性能研究

研究了压铸镁合金AZ91D在应力比R=0．1条件下的高周疲劳性能。结果表明：AZ91D压铸镁合金的室温条件疲劳强度在应力比R=0．1时大约相当于其抗拉强度的44％；AZ91D合金内部的一些缺陷如夹杂等，容易引起应力集中，从而导致裂纹的萌生；AZ91D合金的疲劳断口可以观察到3个典型区域：疲劳源区、疲劳裂纹扩展区和瞬断区。疲劳裂纹扩展区的疲劳裂纹不明显，疲劳断口呈现出准解理断口的形貌。     

Surface modification of Al-Pb alloy by high current pulsed electron beam

Al-Pb alloy was modified by high current pulsed electron beam and the microstructure, hardness and tribological characteristics were characterized by scanning electron microscopy, electronic microanalysis probe microanalysis, Knoop hardness indentation and pin-on-disc type wear testing machine. The results show that the microstructure and hardness can be greatly improved, and the modification layer consists of a molten zone, an overlapped zone of heat-affected and quasistatic thermal stress-affected zone and a transition zone followed by the substrate. The tribological properties of high current pulsed electron beam irradiated Al-Pb alloy are correspondingly improved largely. Optical observation and scanning electron microscopy analysis reveal that the low wear rate and lowest level in coefficient of friction at high load level for irradiated Al-Pb alloy are due to the formation of a lubricious tribolayer covering the worn surface, which is a mixture of Al2O3, Pb3O4 and silicate. The wear mode varies from oxidative wear at low load to film spalling at high load and, finally, adhesive wear.     

宽带激光扫描铁基烧结材料的耐磨性研究

研究了两种不同成分铁基烧结材料激光扫描后的显微组织和摩擦学特性。结果表明，经宽带激光表面处理后，铁基烧结材料的耐磨性显著提高。两种材料比较，在较低载荷下，具有孪晶马氏体／位错马氏体混合组织的材料具有较好的摩擦学特性；而在较高载荷下，具有马氏体／下贝氏体复相组织的材料具有较好的摩擦学特性。     

压铸铝合金AlSi_9Cu_3的铁金属间化合物对高速钢刀具钻削磨损特性的影响

研究了在无润滑条件下,压铸铝合金A lSi9Cu3的铁金属间化合物对高速钢刀具钻削磨损特性的影响。结果表明:当合金中铁的质量分数较低时(w(Fe)<0.6%),铁金属间化合物以细小的多边形形状铁相为主,刀具后刀面磨损机制主要为塑性变形磨损,磨损量较大;当0.6%0.8%时,汉字状和多边形状铁相明显增多,呈薄片晶状的β相A l5FeSi出现,磨粒磨损成为主要的磨损机制,磨损量变大。粘着磨损和磨粒磨损共存的磨损机制是钻削压铸铝合金刀具合理的磨损机制。     

High Cycle Fatigue Properties of Die-Cast Magnesium Alloy AZ91D with Addition of Different Concentrations of Cerium

Recently , magnesiumalloy has become a very at-tractive material because of its lowdensity ,high spe-cific strength, and easy recyclability compared withother metals[1].As alight structural material ,recentlythere has been a significantincreaseinthe use of mag-nesiumalloy for automobiles ,aerospace components ,computers , mobile phones , and household equip-ments[2 ,3]. Mg-Al-Zn (AZ91D) alloyis the most wide-ly used die-cast magnesiumalloyin automotive applica-tions due toits excellent casta…     

WAP协议栈总体设计及WTP层的Petri网描述与实现

简介了WAP协议并设计了实现该协议的总体方案，然后用petri网的有关理论对WTP层进行了描述，最后具体实现了WTP层．     

纳米Cu粉末的SPS烧结与晶粒长大行为的研究

为了研究金属材料在放电等离子烧结(SPS)过程中晶粒的长大行为和激活能的变化情况,利用SEM、FESEM、TEM等技术分析测定了纳米Cu粉坯体在SPS过程中组织形貌和晶粒尺寸的变化情况.研究表明:特定的工艺和烧结制度下,应用SPS技术可以得到均匀、致密的组织;脉冲电流的作用使晶粒表面大大活化,晶粒长大激活能大大降低,材料在迅速烧结的同时,晶粒也迅速长大.