飞灰空心微珠/铝基复合材料的国内外发展概况

综述了近年来国内外飞灰空心微珠-铝基复合材料的研究进展,包括飞灰空心微珠-铝基复合材料的制备方法和材料性能等,并指出了飞灰空心微珠-铝基复合材料的发展趋势.     

不同铸造方法下废玻璃-铝基复合材料的组织和性能

采用半固态搅拌铸造法制备了废玻璃-废铝复合材料,分别对金属重力铸造和挤压铸造方法制备得到的该复合材料的组织和性能进行了研究,并对其拉伸断口形貌进行了扫描电镜分析。结果表明:随玻璃加入量的增加,复合材料的抗拉强度、硬度均先上升后下降,磨损量先下降后上升。该复合材料韧性降低,使其断裂形态从塑性断裂转变为脆性断裂。     

粉煤灰微珠增强铝基复合材料的研究

采用搅拌铸造法,在纯铝中加入粉煤灰微珠颗粒作为增强体,制备铝基粉煤灰微珠复合材料。以L9（3^4）型正交试验数据为依据,研究增强体含量和工艺参数对铝基复合材料性能的影响。结果表明,在试验条件下,制备铝基粉煤灰微珠复合材料的最佳工艺为,在700℃加入粉煤灰微珠13％,以1200r／min的速度搅拌6min。制备的铝基复合材料密度达2．2g／cm^3,抗拉强度为89MPa。     

粉煤灰微珠增强铝基复合材料的断裂力学行为

对粉煤灰微珠增强铝基复合材料的力学性能进行了研究,并对其拉伸断口形貌进行了扫描电镜观察.研究结果表明,复合材料的抗拉强度高于纯铝,随着粉煤灰微珠加入量的增加,复合材料的抗拉强度不断增加,但塑性下降.复合材料的断口出现较明显的"河流花样" 和撕裂棱,断裂形态由塑性断裂向脆性断裂转化.     

铝/空心微珠复合材料弹性性能的预测研究

根据复合材料的基本原理建立了复合材料弹性模量的本构方程，在这基础上利用有限元的方法预测了空心微珠增强铝基复合材料的弹性模量，并在模拟中考察了空心微珠体积百分比（Vf）、空心微珠壁厚与空心微珠半径的比值（t／R）两个参数对弹性模量的影响。通过将有限元模拟结果与理论计算结果相比较，发现结果具有较好的一致性。由于有限元模型和公式是理想模型，其结果比实验值要高，为此，通过考虑空心微珠增强铝基复合材料的主要缺陷，从而使模拟值更接近于实验值。     

空心微珠增强铝基复合材料细观力学性能的数值模拟

基于代表性体积元的细观力学有限元的方法预测了空心微珠增强铝基复合材料的有效弹性模量、弹塑性应力应变和空心微珠与基体的界面性能.研究表明:影响复合材料有效弹性模量的重要参数为:空心微珠体积百分比(V4)和空心微珠壁厚与空心微珠半径的比值(t/R).同时也发现复合材料的颗粒增强金属基材料的特性随着空心微珠Vf的增加而减弱.     

半固态搅拌铸造SiC_p/6061铝基复合材料的组织与性能

采用半固态搅拌铸造方法制备了SiCp粒径为20~50μm的SiCp/6061铝基复合材料,研究了SiCp粒径对铝基复合材料显微组织、力学性能及耐磨性能的影响。结果表明,随着SiCp粒径增大,SiCp在铝基复合材料内的分散均匀性提高,但铝基复合材料的抗拉强度和伸长率下降。铝基复合材料的断裂机制为SiCp与基体合金之间界面脱粘和SiCp断裂共同作用。复合材料的耐磨性随着SiCp粒径的增大而逐渐提高,其磨损机理为粘着磨损和磨粒磨损共同作用,且随着SiCp粒径的增大,磨粒磨损作用起主导作用。     

空心微珠增强铝基复合材料弹塑性性能的模拟预测

基于代表性体积元的细观力学有限元的方法预测空心微珠增强铝基复合材料的弹性模量、弹塑性应力应变。研究了空心微珠体积百分比(Vf)和空心微珠壁厚与空心微珠半径的比值(t/R)对弹塑性性能的影响。研究表明复合材料有效弹性模量随着Vf的增大而减小,随着t/R的增大而增大;另外,随着Vf的增加复合材料逐渐表现出泡沫金属材料的特性。     

搅拌铸造法制备SiCp／A356铝基复合材料的研究

利用搅拌铸造技术制备SiCp/A356铝基复合材料.通过金相观察(OM),扫描电镜(SEM)及力学性能测试对所制备的颗粒增强铝基复合材料的显微组织和力学性能进行了研究.结果表明,SiC增强颗粒较均匀地分布于基体中,SiC/Al界面处存在明显的Si溶质偏聚,复合材料的孔隙率为4.2%;与基体合金相比,SiC颗粒的加入提高了复合材料的硬度和屈服强度,抗拉强度及延伸率略有下降;断口分析表明,搅拌铸造SiCp/A356铝基复合材料主要的断裂机制为SiC/Al界面脱粘及基体合金的脆性断裂.     

颗粒尺寸对SiCp/6061铝基复合材料组织与性能的影响

采用搅拌铸造方法制备颗粒尺寸为20～50 μm的SiCp/6061铝基复合材料,研究了SiC颗粒尺寸对6061铝基复合材料显微组织、拉伸力学性能和耐磨性能的影响.结果表明:通过搅拌铸造方法制备6061铝基复合材料,SiC颗粒在6061铝基复合材料中分布较为均匀,且随SiC颗粒尺寸增大,6061铝基复合材料中SiC颗粒的分布均匀性提高.SiC颗粒尺寸越小,6061铝基复合材料的抗拉强度和伸长率越高.在SiC颗粒尺寸为20μm时,6061铝基复合材料的抗拉强度和伸长率分别为296MPa、5.5％.随SiC颗粒尺寸增大,6061铝基复合材料的耐磨性能提高,磨损率逐渐下降.     

Effects of forced cooling on mechanical properties and fracture behavior of heavy section ductile iron

To develop materials suitable for spent-nuclear-fuel containers, the effect of forced cooling on mechanical properties and fracture toughness of heavy section ductile iron was investigated. Two cubic castings with different cooling processes were prepared: casting A was prepared in a totally sand mold, and casting B was prepared in a sand mold with two chilling blocks placed on the left and right sides of the mold. Three positions in each casting with different solidification cooling rates were chosen. In-situ SEM tensile experiment was used to observe the dynamic tensile process. Fracture analysis was conducted to study the influence of vermicular and slightly irregular spheroidal graphite on the fracture behavior of heavy section ductile iron. Results show that the tensile strength, elongation, impact toughness and fracture toughness at different positions of the two castings all decrease with decreasing cooling rate. With the increase of solidification time, the fracture mechanism of conventional casting A changes from ductile fracture to brittle fracture, and that of casting B with forced cooling changes from ductile fracture to a mixture of ductile-brittle fracture.     

ECAP对连铸Cu-Ag合金断口形态及力学性能的影响

采用连续铸造和等径角挤压变形(ECAP)加工集成技术制备Cu-Ag合金,研究其力学性能和相应的拉伸断口形态。研究发现,Cu-Ag合金的强度随着ECAP加工道次和Ag含量的增加而增加,而延伸率却下降。连续铸造和ECAP加工的合金与传统浇铸和ECAP加工的合金相比,缩颈前静态韧性有所提高。同时发现,只有连铸的Cu-Ag合金在断裂前表现出缩颈现象,而经ECAP挤压后试样的断裂变为剪切模式,随着ECAP道次的增加出现不同的剪切断裂角。基于实验结果,讨论了经ECAP挤压后连铸Cu-Ag合金的拉伸断裂机制。     

亚微米级SiC颗粒增强铝基复合材料的拉伸性能与强化机制

用粉末冶金法制备了亚微米SiC颗粒增强纯铝基复合材料(Al MMC)，对该材料的微观结构和拉伸性能进行了研究，结果表明，15％SiCp(150nm)／Al MMC的拉伸强度和屈服强度分别为342．3和272．4MPa，比纯铝分别提高了89．0％和117．9％，其延伸率为6．3％．拉伸断口观察表明，SiCp／Al MMC断裂机制为界面脱粘和SiC团聚体的脆断，该复合材料具有高强度的原因是基体的微观结构发生了变化，用位错密度强化和弥散强化机制对Al MMC的强化作用进行了评估，预测结果与实验值符合得很好。     

Microstructure and mechanical properties of NZ30K alloy by semicontinuous direct chill and sand mould casting processes

The Mg-3.0Nd-0.2Zn-0.4Zr (NZ30K) alloys were prepared by direct-chill casting (DCC) and sand mould casting (SMC) processes,respectively and their microstructures and mechanical properties were investigated.The results indicate that casting method plays a remarkable influence on the microstructure and mechanical properties of as-cast NZ30K alloy.The grain size increases from 35-40μm in the billets made by the DCC to about 100-120μm in the billets by the SMC.The aggregation of Mg12Nd usually found at the trip...     

Rapidly solidified hypereutectic Al-Si alloys prepared by powder hot extrusion

Rapidly solidified hypereutectic Al-Si alloys were prepared by powder hot extrusion.By eliminating vacuum degassing procedure.the fabrication routine was simplified.The tensile fracture mechanisms at room temperature and elevated temperature were investigated by SEM fractography.Compared with KS282 casting material,the tensile strength of rapidly solidified Al-Si alloy is greatly improved due to silicon particles refining while its density and coefficient of thermal expansion are lower.than those of KS282.The wear resistance of RS AlSi is better than that of KS282.     

7075铝合金传动轴空心轴身的挤压铸造工艺研究

采用挤压铸造工艺制备了7075高强铝合金传动空心轴缩比件,并对其轴身的组织性能进行了研究.结果表明,在浇注温度与模具温度分别为700 ℃与250 ℃条件下,随着挤压压力的增大,可逐渐获得结构致密、晶粒细小、力学性能优异的挤压铸造高强铝合金管坯,当压力为160 MPa时,管坯的微观组织呈树枝状、颗粒状与蔷薇状相混合的结构形态,且其抗拉强度及伸长率均达到最大值,分别为545 MPa与8%;断口分析发现,随着挤压压力的增大,7075铝合金经挤压后的断裂模式由解理断裂逐渐转变为塑性断裂.     

电磁铸造2E12铝合金的铸态组织与力学性能

分别采用电磁铸造和普通连铸技术制备了2E12铝合金连铸锭.通过显微组织和力学性能的对比分析,研究施加电磁场对2E12铝合金连铸过程及铸锭性能的影响.结果表明,使用电磁铸造技术制备的2E12铝合金铸锭具有良好的表面质量和内部组织,以及优良的力学性能.其中,电磁铸造方法获得的2E12铝合金铸锭相对于普通连续铸造铸锭晶粒平均尺寸由58 μm减小至36 μm,抗拉强度提高了9.08%,伸长率提高了61.58%,断裂方式为准解理断裂.     

Weibull analysis of effect of T6 heat treatment on fracture strength of AM60B magnesium alloy

The effect of T6 heat treatment on the fracture strength and reliability of AM60B alloy was studied. The tensile specimens were poured at three different temperatures of 670, 685 and 700 °C for different holding times of 5, 10 and 15 min. The fluidity test was also conducted to determine the fluidity length under different pouring temperatures and holding times. According to the results, the optimum pouring temperature and holding time were determined as 685 °C and 10 min, respectively. SEM fractography of the tensile specimens reveals that the entrained oxides and oxide-related porosities are the main factors responsible for the reduction of fracture strength under the non-optimal casting conditions. The Weibull statistical approach was used to quantify the scatter of fracture strength in as-cast and heat-treated conditions. For this purpose, T6 schedule was applied to the specimens prepared under the optimal casting condition. It is found that, despite minor effect on the average fracture strength, T6 heat treatment improves the reliability of castings, where the Weibull modulus is increased by 75%. According to the microstructural and fractography observations, this improvement is related to the evolution of more uniform microstructure and the elimination of coarse brittle β-particles in heat-treated samples.     

纳米SiC增强AZ91D复合材料高温拉伸及断裂行为

采用复合分散铸造法制备了纳米SiC颗粒(n-SiCp)增强AZ91D复合材料,研究了复合材料在高温下的拉伸及断裂行为。结果表明:n-SiCp的加入可以提高复合材料的高温拉伸强度,高温下n-SiCp对复合材料的增强效果比室温更加明显;n-SiCp的加入还显著提高了复合材料在高温下的断后伸长率,复合材料具有较好的高温塑性。断口分析表明,n-SiCp的加入使复合材料在高温下的断裂行为由室温的脆性断裂为主转化为典型的韧性断裂。