SiC_(p)/Al复合材料研究进展

SiC_(p)/Al复合材料综合了铝合金与陶瓷颗粒碳化硅的优点,具有轻质、高强、高模量以及摩擦磨损性能和热物理性能优异等优良性能,具有广阔的应用前景,是金属基复合材料领域研究的重点之一。针对SiC_(p)/Al复合材料的特点,综述搅拌铸造、挤压铸造、粉末冶金、喷射共沉积等制备方法的优缺点,论述热挤压、热轧制、等径角挤压等二次塑性变形对其组织性能的影响,并围绕SiC_(p)/Al复合材料的组织特征,阐述Al基体中引入不同数量与状态的SiC颗粒与其性能之间的关系,论述其断裂行为与强韧化机制。最后,举例说明SiC_(p)/Al复合材料的广泛应用,并展望其发展前景。

SiCp/2014Al复合材料的热变形行为及本构模型

在Gleeble-3180热模拟机上对碳化硅颗粒增强铝基(SiCp/2014Al)复合材料进行热压缩试验,研究其在变形温度为350,400,450℃和500℃,应变速率为0.001,0.01,0.1s^(-1)和1.0 s^(-1)条件下的热变形行为。根据热压缩实验的真应变-真应力数据,在考虑应变、应变速率和变形温度对流动应力的耦合影响下构建修正的Johnson-Cook(JC)本构模型,同时建立人工神经网络模型(ANN)。结果表明:SiCp/2014Al复合材料的流变应力随应变速率的增加和温度的降低而增大。与修正的JC模型相比,ANN模型具有较低的均方根误差(0.51 MPa)和平均绝对误差(1.43%),以及较高的相关系数(0.9997),表明其对SiCp/2014Al复合材料热变形流变应力的预测具有更高的预测精度和可靠性。

增强体表面镀钛对SiCP/Al2014复合材料组织和性能的影响

为了提高SiCP/Al2014复合材料的界面结合强度,分别采用盐浴法和真空微蒸发法对SiCP进行表面镀钛处理,并通过热压烧结+热挤压工艺制备了SiCP增强Al2014复合材料(10%SiCP/Al2014),研究了SiCP表面镀钛对SiCP/Al2014复合材料微观组织、抗拉强度和耐磨性能的影响。结果表明:经过表面镀钛处理后,SiCP表面均形成了TiC+Ti5Si3的化合物层,使复合材料中SiCP与铝基体的界面结合由物理缩合转化为化学结合,故改善了SiCP与铝基体的润湿性,减少了界面缺陷,从而提高了界面结合强度。盐浴镀钛和微蒸发镀钛10%SiCP/Al2014复合材料的拉伸强度(407 MPa和394 MPa)相比未镀钛10%SiCP/Al2014复合材料分别提升了12.1%和8.0%,磨损量分别降低了58.3%和50.0%。

镍包覆碳化硅颗粒增强Al2519复合材料的制备和性能研究

采用化学镀方法在SiCp表面镀镍,然后采用真空热压法烧结出不同体积分数(5%~20%)的镀镍和未镀覆SiCp增强Al2519复合材料,之后对复合材料进行热挤压和热处理。SEM、XRD及布氏硬度计测试和拉伸试验结果表明,SiCp镀镍可提高SiCp与基体的润湿性,减少复合材料中的孔隙,提高致密度。与未镀覆SiCp相比,镀镍SiCp分散性变好,镍镀层与基体Al发生化学反应,生成稳定的新相Al3Ni。复合材料的力学性能得到很大提高,其硬度、抗拉强度和延伸率分别提高了15.6%~20%、5.5%~8.42%和9.45%~40.55%。

Preparation and characterization of different surface modified SiCp reinforced Al-matrix composites

The effects of SiCp surface modifications(Cu coating,Ni coating and Ni/Cu coating)on the microstructures and mechanical properties of Al matrix composites were investigated.Surface modification of SiC particles with Cu,Ni and Cu/Ni,respectively,was carried out by electroless plating method.SiCp/Al composites were prepared by hot pressed sintering followed by hot extrusion.The results show that the surface modification of SiC particles plays an effective role,which is relative to the type of surface coating,and the interfacial bonding become stronger in the following order:untreated SiCp<Ni(Cu)-coated SiCp<Ni/Cu-coated SiCp.The Ni/Cu-coated SiCp/Al composites exhibit the best comprehensive mechanical properties,with ultimate tensile strength(σUTS)and fracture strain(εf)of 389 MPa and 6.3%,respectively.Compared with that of untreated-SiCp/Al composites,theσUTS andεf are enhanced by 19.3%and 57.5%.

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiCp particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiCp/Al composites.Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing,hot extrusion and heat treatment.The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti5Si3 phases at the interface.Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles.The microstructure,relative density and mechanical properties of the composite are significantly improved.When the volume fraction is 15%,the hardness,fracture strain and tensile strength of the SiCp reinforced Al 2519 composite after Ti plating are optimized,which are HB 138.5,4.02%and 455 MPa,respectively.

Near-net shaped Al/SiCP composites via vacuum-pressure infiltration combined with gelcasting

To solve the problem of difficult machining, the near-net shaped Al/SiCP composites with high volume fraction of SiC particles were fabricated by vacuum-pressure infiltration. The SiCP preform with a complex shape was prepared by gelcasting. Pure Al, Al4Mg, and Al4Mg2Si were used as the matrices, respectively. The results indicate that the optimal parameters of SiCP suspension in gelcasting process are pH value of 10, TMAH content of 0.5 wt.%, and solid loading of 52 vol.%. The Al matrix alloyed with Mg contributes to improving the interfacial wettability of the matrix and SiC particles, which increases the relative density of the composite. The Al matrix alloyed with Si is beneficial to inhibiting the formation of the detrimental Al4C3 phases. The Al4Mg2Si/SiCP composite exhibits high relative density of 99.2%, good thermal conductivity of 150 W·m^-1·K^-1, low coefficient of thermal expansion of 10.1×10^-6 K^-1, and excellent bending strength of 489 MPa.

钨渗铜复合材料致密化机理研究

以粗细钨粉和铜丝为原料,采用粉末冶金工艺制备钨骨架,随后通过液态熔渗铜的方法制备低铜含量(质量分数低于10%)的钨渗铜复合材料。利用电子天平、金相显微镜和扫描电镜分析材料的致密度及显微组织,对材料在制备过程中的致密化机理进行探讨。结果表明:钨渗铜复合材料熔渗过程的驱动力既有毛细管力又有晶界扩散作用,熔渗路径可用根系模型来阐释;在钨骨架中加入Ni等诱导金属可强化熔渗过程;低铜含量的致密钨渗铜复合材料需制备高致密度且具有联通晶界或孔隙的钨骨架。

表面硅烷化改性秸秆吸油材料的制备及性能

玉米秸秆是低成本、环境友好的农业废弃物之一。以废弃秸秆为原料,用氢氧化钠、硫化钠、二氧化硅及乙烯基三乙氧基硅烷为表面改性剂对秸秆材料进行表面改性处理。利用扫描电镜(SEM)、红外光谱分析仪(FT-IR)、热重分析(TGA)及接触角测量仪对改性前后材料进行表征。结果表明,经表面改性后的秸秆材料表面改性均匀,与水的润湿角达到153°,表现出良好的疏水亲油性能;同时,与原始秸秆材料相比,其吸附率获得明显提高,在处理有机水体污染时表现出良好的选择吸附性。因此,低成本改性玉米秸秆作为天然吸附剂,在治理有机水污染方面具有很大的应用潜力。

表面改性水稻秸秆吸附有机污染物性能及机理研究

以废弃水稻秸秆为原料,采用氢氧化钠、双氧水对秸秆进行预处理,再以SiO2颗粒、乙烯基三乙氧基硅烷为表面改性剂对秸秆进行表面改性,使其具备良好的疏水和亲油特性。利用扫描电镜、红外光谱、热重及润湿角测试仪对改性前后水稻秸秆显微组织形貌及性能进行分析,探究了材料表面改性机理,并以机油、食用油、石油醚、二甲苯等有机污染物进行材料宏观吸附性能测定。结果表明:经表面改性后的秸秆材料表现出良好的疏水性,润湿角达到148.9°,吸附有机物的吸附量明显增加,在处理有机水体污染时表现出良好的选择吸附性。

添加Cu对SiC_(p)/Al-Si复合材料组织与性能的影响

利用X射线衍射仪、扫描电镜、电子天平、力学性能试验机等研究了Cu元素含量对粉末冶金法制备的SiC_(p)/Al-Si复合材料组织与性能的影响。结果表明:添加Cu元素后,材料的致密度、硬度、抗拉强度及耐摩擦磨损性能都获得了较大的提高,且强度在Cu含量为4%(质量分数)时达到最大值。由于在基体中以铜粉的形式添加Cu元素时,较低温度下即可在Al-Cu边界通过互扩散形成液相,从而填充基体及界面处的缝隙、孔洞等缺陷;并且在压坯快速冷却到室温的过程中,生成的α-Al和Al_(2)Cu相均对材料有强化作用,使得复合材料的综合力学性能获得提高。