碳纤维增强铝基复合材料熔体真空除气

为解决搅拌铸造法制备的碳纤维增强铝基复合材料气孔率过高对材料性能的破坏问题,在熔体搅拌混合结束后,增加真空除气的工艺减少复合材料中的气体。采用阿基米德法测量了复合材料铸锭的相对密度,研究了碳纤维增强A356合金基复合材料熔体在0.03MPa的真空度下,真空炉温度、除气时间对复合材料铸锭致密度的影响。结果表明,当炉温为700℃、除气2min,即可将复合材料铸锭的气孔率降低至2%以下。通过扫描电镜观察了复合材料铸锭的组织,结果显示界面完好,未发现气孔。     

铝及铝合金中氢的快速测定

除气是铝合金熔炼过程的主要操作。若对气体缺乏控制,无论是铸锭或铸件都会因气孔和疏松而成批报废。因此,在铸造前快速测定熔铝中的气体含量,确定精炼除气程度,是保证质量,提高效率的重要手段。测定金属中气体含量的方法很多,但大部分都采用固体试样在真空下重熔测量,不适     

CNTs/ZL114A复合材料通孔铸件的熔化及浇注工艺研究

对CNTs/ZL114A复合材料通孔铸件的熔化、浇注工艺进行了试验研究,得到了无铸造缺陷的CNTs/ZL114A通孔铸件。结果表明:在800℃进行熔化时,CNTs/ZL114A复合材料有较好的流动性,除渣方便;集过滤、动态真空除气与浇注为一体的浇注方法使熔体得到了很好的净化;缝隙式浇冒系统的铸型设计合理,适合CNTs/ZL114A复合材料成型。     

（Al2O3）p和SiCp多元增强铝基复合材料

利用Ａｌ２（ＳＯ４）３ 分解反应所制备的多元增强铝基复合材料,其中Ａｌ２Ｏ３ 和ＳｉＣ 颗粒和基体结合良好,分解的ＳＯ３ 对ＳｉＣｐ／ Ａｌ 复合材料熔体进行精炼、除气,试样中没有发现气孔、团聚、集聚、偏析,克服了传统搅拌铸造所带来的铸造缺陷,解决了回收利用重熔过程中的吸气、精炼问题;从而为颗粒增强铝基复合材料走向实用化打下了基础。     

铝基复合材料镶嵌铸造工艺

研究了在铝合金铸件中镶嵌铝基复合材料的镶嵌铸造工艺，并通过镶嵌件表面处理（喷砂、镀锌、镀镍）和控制浇注工艺参数（铸模温度、镶嵌件预热温度、铝合金浇注温度和浇注操作时间）获得了复合材料镶嵌件和铸件本体铝合金之间良好的界面结合     

挤压铸造SiC_p/ZL111铝基复合材料

研究了含量为20%的SiC颗粒增强ZL111铝基复合材料锭重熔后,挤压铸造件的组织和性能。结果表明,可以采用卧式挤压铸造方法制备铝基复合材料铸件,浇注温度为710℃,挤压冲头速度为0.4m/s,比压为135MPa;组织内SiC颗粒分布仍然保持分散,没有发生团聚,铸件不同部位SiC含量基本一致;但是SiC颗粒只分布在共晶组织内;铸件耐磨性显著提高,导致切削加工刀具磨损急剧增加,但布氏硬度(HB)为76.7～94.4,与ZL111铝合金相差不多。     

铝合金壳体铸件翻转浇注工艺研究

翻转浇注是重力浇注的一种特殊形式,它有许多优点,有利于解决复杂铸件浇注过程产生的缩孔、缩松、气孔、夹杂等铸造缺陷.对航空用铝合金壳体铸件的浇注工艺进行了研究,分析了传统重力底注铝合金壳体铸造缺陷的原因,提出了翻转浇注工艺并进行了改进.结果表明,改进后的工艺使铝合金壳体铸件的合格率增至90％,获得了无夹渣和气孔的铸件.     

一种配制不同含氢量铝合金熔体装置研制

氢是唯一大量溶于铝熔体的有害气体,极易使铸件产生气孔等缺陷。为提高铝合金铸件的质量,铝熔体的除气和炉前检测是必不可少的。在评价除气效果或测氢精度时,需提供全量程内不同氢含量铝熔体作为样本。基于此,研制出用于配置不同含氢量的铝合金熔体装置,介绍了装置的原理、组成及不同含氢量铝熔体的配制试验结果。     

铝合金铸锭生产中熔体净化

铝合金熔炼铸造是生产铝材的第一道工序,铸锭中的缺陷会传递到铝材中,因此铝合金熔体的除气除渣净化处理非常重要。论述了铝合金熔体中气体、夹杂的来源,介绍了铝加工行业现在采用的各种除气除渣的技术、装置及其原理,各自的除气除渣净化效果、优缺点、应用情况,以及检测除气除渣效果的仪器。     

真空差压铸造控制系统

系统应用单片微机控制技术,采用真空熔炼、真空差压铸造工艺,有效地消除了气体的有害影响,克服了铝基复合材料熔体流动性差的缺点,保证了复杂、薄壁、精密铸件的工艺要求。文中介绍了熔炼铸造炉控制系统的结构组成及各部分功能,并介绍了在单片微机控制下的充型调压过程。     

铝合金熔体在SiC陶瓷颗粒间的流动浸渗行为

报道了挤压铸造条件下铝合金熔体在自然堆积的SiC颗粒预成形块中的单向浸渗行为。观察结果表明,挤压浸渗过程中铝合金熔体流动前沿与SiC颗粒表面间呈动态不浸润;熔体对颗粒间间隙的浸渗受润毛细现象控制,是一个随浸渗压力增加而逐渐对不同尺寸间隙实现浸渗的选择性浸渗过程,并据此解释了观察到的复合材料组织的形成条件。     

颗粒增强铸造铝基复合材料的研究

本文探讨了用搅拌铸造法,采用常规的熔炼加工设备和工艺,制造ＳｉＣ颗粒增强铝基复合材料的可行性;研究了不同ＳｉＣ含量的复合材料的显微组织;试验表明：复合材料中ＳｉＣ颗粒分布较为均匀,其力学性能均优越于基体合金,弥散分布的ＳｉＣ颗粒是复合材料力学性能优异的主要原因。     

Weibull analysis of fluidity and hardness of ultrasonically degassed secondary Al7Si0.3Mg aluminum alloy

The influence of ultrasonic degassing process on fluidity and hardness of secondary Al7Si0.3Mg alloy castings was studied by Weibull analysis. This work makes a contribution about fluidity and hardness distribution of secondary aluminum alloys with ultrasonic degassing phenomena using a two-parameter form of Weibull analysis. Results show that both hardness and fluidity of alloy are improved after the ultrasonic degassing process. Average efficiency of ultrasonic degassing on fluidity measurements is 31.71%, whereas on hardness values is 8.48%. The Brinell hardness of 45.7 and fluidity of 19.5 of Weibull modulus were achieved as the most reliable and reproducible after 45 s ultrasonic degassing process against 15 s and 30 s ultrasonic degassing processes. The value of 70.08 HB is obtained from ultrosonic degassing, which is equivalent to sand casting of primary Al7Si0.3Mg aluminum alloy, and the highest value of 56.4 cm for 45 s after ultrasonic degassing of fluidity was measured.

     

Weibull analysis of fluidity and hardness of ultrasonical y degassed secondary Al7Si0.3Mg aluminum alloy

The influence of ultrasonic degassing process on fluidity and hardness of secondary Al7 Si0.3 Mg alloy castings was studied by Weibull analysis. This work makes a contribution about fluidity and hardness distribution of secondary aluminum alloys with ultrasonic degassing phenomena using a two-parameter form of Weibull analysis. Results show that both hardness and fluidity of alloy are improved after the ultrasonic degassing process. Average efficiency of ultrasonic degassing on fluidity measurements is 31.71%, whereas on hardness values is 8.48%. The Brinell hardness of 45.7 and fluidity of 19.5 of Weibull modulus were achieved as the most reliable and reproducible after 45 s ultrasonic degassing process against 15 s and 30 s ultrasonic degassing processes. The value of 70.08 HB is obtained from ultrosonic degassing, which is equivalent to sand casting of primary Al7 Si0.3 Mg aluminum alloy, and the highest value of 56.4 cm for 45 s after ultrasonic degassing of fluidity was measured.     

Fabrication and characterization of cast magnesium matrix composites by vacuum stir casting process

A vacuum stir casting process is developed to produce SiC_p reinforced cast magnesium matrix composites. This process can eliminate the entrapment of external gas onto melt and oxidation of magnesium during stirring synthesis. Two composites with Mg-Al9Zn and Mg-Zn5Zr alloys as matrices and 15 vol.% SiC particles as reinforcement are obtained. The microstructure and mechanical properties of the composites and the unreinforced alloys in as-cast and heat treatment conditions are analyzed and evaluated. In 15 vol.% SiC_p reinforced Mg-Al9Zn alloy-based composite (Mg-Al9Zn/15SiC_p), SiC particles distribute homogenously in the matrix and are well bonded with magnesium. In 15 vol.% SiC_p reinforced Mg-Zn5Zr alloy-based composite (Mg-Zn5Zr/15SiC_p), some agglomerations of SiC particles can be seen in the microstructure. In the same stirring process conditions, SiC reinforcement is more easily wetted by magnesium in the Mg-Al9Zn melt than in the Mg-Zn5Zr melt. The significant improvement in yield strength and elastic modulus for two composites has been achieved, especially for the Mg-Al9Zn/15SiC_p composite in which yield strength and elastic modulus increase 112 and 33%, respectively, over the unreinforced alloy, and increase 24 and 21%, respectively, for the Mg-Zn5Zr/15SiC_p composite. The strain-hardening behaviors of the two composites and their matrix alloys were analyzed based on the microstructure characteristics of the materials.     

A new high shear degassing technology and mechanism for 7032 alloy

Degassing is very important for aluminum alloys especially for 7xxx series alloys.In the present study,a high shear technology was used to degas 7032 aluminum alloy in order to study its degassing efficiency.The experimental results showed that the high shear technology can significantly degas 7032 aluminum alloy.By applying intensive melt shearing and an Ar injection of 60 seconds,the density index,D_i,was reduced from13.25%to 0.28%and the hydrogen concentration was significantly reduced from 0.31 to 0.10 mL/100 g Al.Compared with the conventional rotary degassing,high shear technology showed a much higher degassing efficiency,achieving a lower concentration of hydrogen in a shorter time.The water simulation experiment was used to study the mechanism of the high degassing efficiency.The small bubble size and the uniform distribution of Ar bubbles with the application of high shear technology are believed to be the main cause for the high degassing efficiency.     

SiCp/A357复合材料流动性数值模拟与实验研究

搅拌铸造方法易于成型大尺寸复杂的复合材料零件,但是碳化硅颗粒加入使得复合材料的流动行为变得更加复杂,开展复合材料流动性研究至关重要。本文建立了SiCp/A357复合材料的流动模型,采用数值模拟及实验研究相结合的方法,研究了浇注温度及碳化硅体积分数对SiCp/A357复合材料流动性及流动充型过程碳化硅分布的影响。结果表明,随着浇注温度的提高SiCp/A357复合材料的流动性升高,这一趋势在半固态区间更为明显;但是随着浇注温度的提高,试样前端的碳化硅体积分数较末端减少加剧,复合材料中碳化硅的整体分布均匀性降低;随着碳化硅体积分数的增加SiCp/A357复合材料的流动性降低,且随着碳化硅体积分数的增加,试样前端碳化硅的体积分数减少程度减弱,整体的均匀性提高。上述的模拟结果与实验结果具有较好的一致性。     

改善颗粒增强金属基复合材料塑性和韧性的途径与机制

评述了影响颗粒增强金属基复合材料塑性和韧性的各种因素,在此基础上深入研究了颗粒形状对ＳｉＣｐ／ＬＤ２复合材料塑性和断裂韧性的影响规律。采用有限单元法分析不同形状的ＳｉＣ颗粒增强的ＬＤ２复合材料的微区力学环境和整体力学行为,结果表明颗粒的尖锐化导致基体内应变集中和颗粒尖端断裂的可能性加剧,因而降低材料的塑性;而在外加载荷的作用下,由于复合材料基体整体均处于较高的加工硬化状态,因此颗粒形状对材料断裂韧     

铸造ZL101A／SiCp复合材料的研究

采用真空搅拌复合工艺制备了铸造ZL101A／SiC复合材料,研究了变质和细化处理对复合材料组织的影响。结果表明：变质和细化处理铸造 ZL101A／SiC复合材料制备工艺的重要处理措施,可明显改善复合材料的组织。利用透射电镜对AL／SiC界面特征及界面反应进行分析,同时对该复合材料的铸造性能（熔体合金流动性能、线收缩、体收缩和热裂倾向）以及力学和物理性能进行了测试。     

Fabrication and fracture toughness of macro-toughening-designed composite

lINTR0DUCTIONParticleReinforcedMetalMatrixC0mp0s-ites(PMMCs)havehighspecificstrength,spe-cificmodulus,elevatedtemperatureproperties,res1stancetowearandlowcost.However,com-paniedlowductilityandtoughnessisonemainobstacletotheirapplicationforengineeringL','j.ManystudiesonSiCparticlereinforcedalu-.minum.ll.y.['v']showthattheadditionofpar-ticlenotonlyrefinesmatrixgrainbutalsoresultsinhighdensitydislocationsinthematrixneartheinterface.Particlesblocklong-distance-slipofthedislocationsinthema…