镍基单晶铸造气膜孔低周疲劳断裂特征研究

气膜孔结构作为一种重要的热防护技术广泛应用于涡轮叶片中。气膜孔的存在会引入制造缺陷、应力集中等不利因素,成为疲劳失效的主要诱因之一。本研究开展不同温度下镍基单晶铸造气膜孔低周疲劳试验,分析熔模铸造直接成型的气膜孔疲劳断裂特征。结果表明:不同温度下疲劳寿命取决于应力幅值;随温度降低,疲劳断裂路径由Mode-I型转换为晶体学平面断裂,断口形貌呈现出从类解理至韧性断裂特征。气膜孔周围微结构分析表明,在1000℃及循环应力作用下,氧化膜发生破裂形成氧化裂纹;在700℃条件下,疲劳裂纹形核主要由滑移累积导致;在850℃条件下,疲劳损伤由氧化损伤和滑移累积共同作用。晶体塑性有限元分析揭示铸造气膜孔疲劳断裂特征主要受气膜孔附近应力分布的影响。

大型铝合金箱体中的深孔铸造技术研究

介绍了一种新的大型复杂铝合金箱体高压油道的铸造过程,研究了箱体高压油道选用不同的制芯材料和工艺对油道致密度及性能的影响,并试验验证了这种新型复合材料和工艺。结果表明,这种材料具有较强的激冷作用,还具有高的热导率、比热容和密度。使用这种材料所制成的油道芯不仅发气量低,而且透气性较好和良好的溃散性,同时有较高的强度和耐火度。这种新工艺既能保证了油道芯的刚度,又保证其具有良好的透气性,可以满足各种大型铝合金箱体深孔的铸造成形。

埋管铸造成形油道孔的工艺试验

针对砂型铸造中利用砂芯成形细长的油道孔容易出现断芯、烧结和清砂困难的问题,研究了预埋空心油道管和预埋油道管内填充铬矿砂成形铸钢件中细长油道孔的两种工艺方案,分析了预埋油道管与铸件界面结合状况、影响油道管熔合的因素以及油道管重量与热节部位重量的关系。结果表明:对于20～100 kg的铸件,采用预埋空心油道管可以有效解决断芯问题,而对于100～300 kg的铸件,采用预埋油道管内填充铬矿砂的工艺不仅可以解决预埋管熔穿的问题,还可以提高铸件的品质。

深孔铸造一例

深孔铸造一例中国南方航空动力机械公司张春永铸孔对于熔模铸造而言并不困难，但是有些弯孔和深孔的铸造却非易事。例如图１所示的某机轴承机匣，外形看似简单，当要求把全部弯孔深孔铸出来就有些棘手。图中的Ｇ—Ｇ剖面（未给出剖面图）上有深３５３ｍｍ的直通孔一个；Ｆ...

冲压模具实型铸造的铸件结构

着重介绍了冲压模具设计过程中,实型铸造的铸件结构设计要点。

ZJH整铸机体工艺设计及其铸孔弯曲问题改进措施

为了生产出12VZJH机体铸件,并解决油道管弯曲的关键技术问题,通过设计合理的铸造工艺方案,以及"预提芯组芯"操作方法,解决难点。最终生产出合格产品。并为同类产品生产提供借鉴。

绩效技术指导注塑机定模板铸件结构的优化设计

简述了全液压注塑机重要零部件—定模板铸件的结构及其工作状态。分析了原定模板结构存在的问题:壁厚设计不合理、预埋钢管结构及其位置不正确、加强筋结构不合理、铸造工艺孔大小及其位置不合适等诸多不足;阐述了运用绩效技术等新理念设计出的定模板铸件的结构特征,及其预埋钢管镶铸可靠、铸件合格率高等优点。其设计理念可推广于其类似铸件之结构设计过程中。

360m^2烧结机筛分系统优化及改造

介绍了安钢烧结厂在降低铺底料和烧结矿中小粒度比例时采取的措施，改造取得了预期的效果。

Effects of compocasting process parameters on microstructural characteristics and tensile properties of A356-SiC_p composites

The effects of compocasting process parameters on some structural and tensile characteristics of the A356-10% SiCp (volume fraction) composites were studied. Semisolid stirring was carried out at temperatures of 590, 600 and 610 °C with stirring speeds of 200, 400 and 600 r/min for 10, 20 and 30 min. The distribution of the SiC particles within the matrix, porosity content and tensile properties of the obtained samples were examined. The structural evaluations show that by increasing the stirring time and decreasing the stirring temperature, the uniformity in the particle distribution is improved;however, by increasing the stirring speed the homogeneity firstly increases and then declines. It is also found that by increasing all of the processing parameters, the porosity content is enhanced. From the tensile characteristics viewpoint, the optimum values of the speed, temperature and time are found to be 400 r/min, 590 °C and 30 min, respectively. The contribution of the reinforcement distribution uniformity prevails over that of the porosity level to the tensile properties.

Effect of ultrasonic degassing on performance of Al-based components

The effect of high intensity ultrasound based on the novel multi-frequency multimode modulated technology on the final density, porosity, mechanical and fatigue properties of an AlSi9Cu3(Fe) alloy after different processing time was studied. Reduced pressure test was used to evaluate the density of alloys. The tensile and fatigue tests were used to evaluate the static and dynamic properties for the different time of ultrasonic degassing, respectively. It is found that ultrasonic degassing is effective in reduction porosity as well as to improve the final density of castings. Furthermore, the experimental results suggest that the porosity level does not have a substantial influence on the static properties contrary to what is observed on fatigue properties.

Prediction of hot tearing susceptibility of direct chill casting of AA6111 alloys via finite element simulations

To predict hot tearing susceptibility(HTS)during solidification and improve the quality of Al alloy castings,constitutive equations for AA6111 alloys were developed using a direct finite element(FE)method.A hot tearing model was established for direct chill(DC)casting of industrial AA6111 alloys via coupling FE model and hot tearing criterion.By applying this model to real manufacture processes,the effects of casting speed,bottom cooling,secondary cooling,and geometric variations on the HTS were revealed.The results show that the HTS of the billet increases as the speed and billet radius increase,while it reduces as the interfacial heat transfer coefficient at the bottom or secondary water-cooling rate increases.This model shows the capabilities of incorporating maximum pore fraction in simulating hot tearing initiation,which will have a significant impact on optimizing casting conditions and chemistry for minimizing HTS and thus controlling the casting quality.

Microstructure and mechanical properties of aluminium metal matrix composites with addition of bamboo leaf ash by stir casting method

Al-4.5%Cu alloy was used as a matrix at2%,4%and6%of bamboo leaf ash(BLA)which was extruded from agro waste and was used as reinforcement.The composite which was fabricated by stir casting method possessed superior properties due to an effective bonding between matrix and reinforcement particles.The fabricated composite specimens were subjected to various tests to determine the mechanical properties such as density,porosity,hardness and tensile strength.The results were compared with basic matrix alloy.Furthermore,the OM,SEM with EDAX and XRD analyses were carried out to analyze the dispersion of the reinforced particles in the selected matrix alloy.It was observed that the homogeneous distribution of BLA particles in composites was intragranular in nature.Moreover,it was also observed that BLA particles were well bonded with matrix alloy with clear interface.It was also found that the density decreased with increase in mass fraction of BLA particles and porosity increased with increase in mass fraction of BLA particles.The hardness and tensile strength were increased up to4%of BLA in the composite,with a further increase in BLA content the hardness and tensile strength decreased.

Comparison of microstructure and wear resistance of A356-SiC_p composites processed via compocasting and vibrating cooling slope

The influences of SiC content on the microstructure, porosity, hardness and wear resistance of A356？SiCp composites processed via two different methods of compocasting and vibrating cooling slope （VCS） were compared with each other. In the as-cast condition, the matrix of VCS and compocast processed composites exhibited globular and dendritric structures, respectively. While a more uniform distribution of SiC particulates in the matrix alloy as well as higher hardness values were obtained for the VCS processed samples, the composites produced via compocasting exhibited less porosity. The increased SiC content （up to 20% in volume fraction） resulted in a more uniform distribution of SiC particles within the matrix alloy and improved wear resistance for both the composite series. However, for the VCS processed composites, the increased SiC content, resulted in the decreased size and shape factor of globules as well as better tribological properties when compared with compocast composites. It was concluded that the improved properties of the VCS processed composites when compared with their compocast counterparts was a consequence of a more uniform distribution of SiC particulates in the matrix alloy as well as the globular microstructure generated during the VCS process.

Nanospike surface-modified bionic porous titanium implant and in vitro osteogenic performance

This work aimed to prepare the nanospike surface-modified bionic porous titanium implants that feature favorableosteointegration performance and anti-bacterial functions.The implant was prepared using freeze casting,and nanospikesurface-modification of the implant was performed using thermal oxidation.The pore morphology and size,mechanical properties,and osteogenic performance of the implants were analyzed and discussed.The results showed that when the volume ratio of titaniumpowder in slurry was set to be10%,the porosity,pore diameter,compressive strength,and elastic modulus of the porous sampleswere(58.32±1.08)%,(126.17±18.64)μm,(58.51±20.38)MPa and(1.70±0.52)GPa,respectively.When the porous sample wassintered at a temperature of1200°C for1h,these values were(58.24±1.50)%,(124.16±13.64)μm,(54.77±27.55)MPa and(1.63±0.30)GPa,respectively.The nanospike surface-modified bionic porous titanium implants had favorable pore morphology andsize,mechanical properties and osteointegration performance through technology optimization,and showed significant clinicalapplication prospect.