Processing, microstructure, and mechanical properties of cast In-Situ Al(Mg, Ti)-Al2O3(TiO2) composite

In-situ particle-reinforced aluminum alloy-based cast composites have been synthesized by solidification of the slurry obtained by dispersion of externally added titanium dioxide (TiO₂) particles in molten aluminum at different processing temperatures. Alumina particles (Al₂O₃) form in situ through chemical reaction of TiO₂ particles with molten aluminum. Simultaneously, the chemical reaction also releases titanium, which dissolves into molten aluminum and results in the formation of intermetallic phase Ti(Al_1−x ,Fe _x )₃ during solidification. Increasing the processing temperature increases (1) the amount of elongated as well as blocky intermetallic phase Ti(Al_1−x ,Fe _x )₃, (2) the proportion of alumina particles in the reinforcing oxides, and (3) the porosity content in the resulting cast in-situ composite. The difference in particle content and porosity between the top and the bottom of the cast ingot increases with increasing processing temperature. The hardness of the cast in-situ composite is significantly more than that of the matrix alloy due to the presence of reinforcing particles, but the hardness is greatly impaired by the presence of porosity at the top of the cast ingot. The percent elongation of the cast in-situ composite decreases with increasing processing temperature possibly due to increasing porosity as well as an increasing amount of elongated intermetallic phase, which affects the percent elongation of the matrix alloy. The tensile and yield stresses of the cast in-situ composite decreases with increasing processing temperature again due to increasing porosity, which affects the ultimate tensile stress more than the yield stress. In the cast in-situ composite containing 3.31 ± 0.77 vol pct of porosity, the Brinell hardness is about 6 times its yield stress. The estimated yield stress of the cast in-situ composite at zero porosity as given by the linear least-squares fit appears to increase with particle content at a significantly higher rate than that predicted by the shear-lag model.     

Transformation Behavior and Mechanical Properties of Al2O3/ZrO2(2Y) Ceramic Composites

The content of zirconia has a remarkable influerce on transformation behavior and mechanical properties of Al2O3/ZrO2 (2Y) composites. When 15% and 20% ZrO2(2Y) was added to Al2O3, the bending strength and fracture of the content of ZrO2 (2Y) on transformation and mechanical properties was investigated. The changes of m-ZrO2 and t-ZrO2 phases content before and after fracture were measured by X-ray diffraction quantitative phase analysis, It is shown that improvement in bending strength and fracture toughness of the Al2O3/ ZrO2 (2Y) composites is due to the phase transformation toughening mechanism of ZrO2 (2Y) and thermal expansion mismatch.     

Characterization and tribological behavior of cast In-Situ Al (Mg,Mo)-Al2O3 (MoO3) composite

Aluminum alloy—based cast in-situ composite has been synthesized by dispersion of externally added molybdenum trioxide particles (MoO₃) in molten aluminum at the processing temperature of 850 °C. During processing, the displacement reaction between molten aluminum and MoO₃ particles results in formation of alumina particles in situ and also releases molybdenum into molten aluminum. A part of this molybdenum forms solid solution with aluminum and the remaining part reacts with aluminum to form intermetallic phase Mo(Al_1−x Fe _x )₁₂ of different morphologies. Magnesium (Mg) is added to the melt in order to help wetting of alumina particles generated in situ, by oxidation of molten aluminum by molybdenum trioxide, and helps to retain these particles inside the melt. The mechanical properties of the cast in-situ composite, as indicated by ultimate tensile stress, yield stress, percentage elongation, and hardness, are relatively higher than those observed either in cast commercial aluminum or in cast Al-Mo alloy. The wear and friction of the resulting cast in-situ Al(Mg,Mo)-Al₂O₃(MoO₃) composites have been investigated using a pin-on-disc wear testing machine under dry sliding conditions at different normal loads of 9.8N, 14.7N, 19.6N, 24.5N, 29.4N, 34.3N, and 39.2 N and a constant sliding speed of 1.05 m/s. The results of the current investigation indicate that the cumulative volume loss and wear rate of cast in-situ composites are significantly lower than those observed either in cast commercial aluminum or in cast Al-Mo alloy, under similar load and sliding conditions. Beyond about 30 to 35 N loads, there appears to be a higher rate of increase in the wear rate in the cast in-situ composite as well as in cast commercial aluminum and cast Al-Mo alloy. For a given normal load, the coefficient of friction of cast in-situ composite is significantly lower than those observed either in cast commercial aluminum or in cast Al-Mo alloy. The coefficient of friction of cast in-situ composite increases gradually with increasing normal load while those observed in cast commercial aluminum or in cast Al-Mo alloy remain more or less the same. Beyond a critical normal load of about 30 to 35 N, the coefficient of friction decreases with increasing normal load in all the three materials.     

Cu/Al2O3复合材料的制备工艺、性能和组织研究

采用快速凝固离心雾化,原位反应和热挤压成形等工艺技术,制备了Cu/Al2O3复合材料,进行了Cu-Al系列合金粉末原位反应的热力学条件分析,确定了反应温度,研究了粉末成型压力与压坯密度,压坯烧结密度与电导率、硬度的关系,电导率、硬度随烧结时间的变化规律,以及材料显微组织随烧结时间的变化等,并与国内外有关行业制备的同类材料进行了综合性能比较.研究结果表明:Cu/Al2O3复合材料具有良好的物理、力学性能和较高的软化温度,为其生产应用提供了新途径.     

Microstructure and properties of Al2O3-Al(Si) and Al2O3-Al(Si)-Si composites formed byin situ reaction of Al with aluminosilicate ceramics

Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites have been formed byin situ reaction of molten Al with aluminosilicate ceramics. This reactive metal penetration (RMP) process is driven by a strongly negative Gibbs energy for reaction. In the Al/mullite system, Al reduces mullite to produce α-Al₂O₃ and elemental Si. With excess Al (i.e., x > 0), a composite of α-Al₂O₃, Al(Si) alloy, and Si can be formed. Ceramic-metal composites containing up to 30 vol pct Al(Si) were prepared by reacting molten Al with dense, aluminosilicate ceramic preforms or by reactively hot pressing Al and mullite powder mixtures. Both reactive metal-forming techniques produce ceramic composite bodies consisting of a fine-grained alumina skeleton with an interpenetrating Al(Si) metal phase. The rigid alumina ceramic skeletal structure dominates composite physical properties such as the Young’s modulus, hardness, and the coefficient of thermal expansion, while the interpenetrating ductile Al(Si) metal phase contributes to composite fracture toughness. Microstructural analysis of composite fracture surfaces shows evidence of ductile metal failure of Al(Si) ligaments. Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites produced byin situ reaction of aluminum with mullite have improved mechanical properties and increased stiffness relative to dense mullite, and composite fracture toughness increases with increasing Al(Si) content. This article is based on a presentation made in the “In Situ Reactions for Synthesis of Composites, Ceramics, and Intermetallics” symposium, held February 12–16, 1995, at the TMS Annual Meeting in Las Vegas, Nevada, under the auspices of SMD and ASM-MSD (the ASM/TMS Composites and TMS Powder Materials Committees).     

Mechanical Behaviors of ZrO2-Al2O3 Ceramic Composites with Y2O3 as Stabilizer

Forlongthebrittlenessofceramicmaterialshasstoodinthewayofindustrialapplicationanddevelop ment.However ,inrecentyears ,suchprogressasthephasetransformationtougheningofzirconia ,thedis persionofparticletougheningandthefiberorwhiskertougheninghavewellimprove…     

Al2O3短纤维增强Al-Cu合金的微观组织结构和机械性能研究

为了研究铜元素含量变化对复合材料界面反应、微观组织结构和机械性能的影响，利用挤压铸造法制备了体积分数均为40％的Al2O3纤维增强纯铝和Al—Cu合金（1％，3％和5％）复合材料。采用X射线、TEM、SEM和拉伸实验手段，观察和测试了4种复合材料的微观组织和机械性能。结果表明，Al2O3纤维表面含有非晶SiO2成分，在高应力下易于开裂。铜元素的加入对材料的析出产生和机械性能有重要影响。铜元素引入后在复合材料中纤维表面处偏聚和富集，促进了界面θ相析出，并随基体中Cu含量提高而增加。当铜含量增加到5％后，基体内部也出现明显的析出相。拉伸实验结果表明随着Cu含量的增加复合材料的抗拉强度增高，Al2O3f/Al-Cu与Al2O3f／纯Al相比，抗拉强度分别增加了102％，146％和171％。SEM断口观察表明：基体合金的断口基本上都呈宏观脆性断口，具有低的展延性和撕裂纹理；大量的纤维从复合材料基体中拔出，一些纤维被拉断，这些特点与界面结合物和多晶的Al2O3纤维结构密切相关。     

Activities of SiO2 and Al2O3 and activity coefficients of FetO and MnO in CaO-SiO2-Al2O3-MgO slags

The activities of SiO₂ and Al₂O₃ in CaO-SiO₂-Al₂O₃-MgO slags were determined at 1873 K along the liquidus lines saturated with 2CaO · SiO₂, 2(Mg,Ca)O · SiO₂, MgO, and MgO · Al₂O₃ phases using a slag-metal equilibration technique. Based on these and previous results obtained in ternary and quaternary slags, the isoactivity lines of SiO₂ and Al₂O₃ over the liquid region on the 0, 10, 20, 30, and 40 mass pct Al₂O₃ planes and those on the 10 and 20 mass pct MgO planes were determined. The activity coefficients of Fe _t O and MnO, the phase boundary, and the solubility of MgO were also determined.     

铬酸镧/氧化铝复合材料的烧结机制与性能

将掺Ca铬酸镧与Al2O3混合,在1650℃烧结得到氧化铝量从0~100%(摩尔分数)的系列Al2O3/La0.9Ca0.1CrO3复合材料烧结体。研究得出Al2O3/La0.9Ca0.1CrO3系统是热力学不稳定的,高温烧结时存在离子扩散,烧结体的最终相组成与Al2O3量有关。复合材料中氧化铝含量较低时(≤20%,摩尔分数)可以提高铬酸镧粉体的烧结性能;当氧化铝含量在30%~70%(摩尔分数)之间时,生成的层片状六铝酸镧使烧结致密度降低,并在氧化铝含量为70%(摩尔分数)时达到最低值,随后试样的相对密度又逐渐增大。     

铸造氧化铝／锌合金复合材料界面的SEM观察

利用挤压铸造制备氧化铝／锌合金复合材料,在扫描电镜（SEM）上观察复合材料的界面。在复合材料中纤维与基体间存在致密界面层,合金元素通过适当的化学反应可改善纤维与基体间的结合,在凝固过程中,纤维／基体界面上的硅在共晶体的生长过程中起到领先作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两者组成。     

La2O3, Ce2O3掺杂对原位合成Al2O3(p)/TiAl复合材料显微组织与性能的影响

借助XRD, SEM分析及力学性能测试, 分析了La2O3, Ce2O3掺杂对原位合成Al2O3颗粒强化钛铝基复合材料组织与性能的影响, 探讨了稀土氧化物（La2O3, Ce2O3）的细化机制. 研究结果表明： 掺杂稀土氧化物后产物由γ-TiAl/α2-Ti3Al双相、 Al2O3及Al4La或Al4Ce相组成;Al2O3颗粒分布于晶界处, 使基体晶粒得以细化;引入稀土元素后材料的密度明显增强, 氧化铝的团聚现象减弱. 力学性能测试表明, La2O3, Ce2O3的引入, 有效改善了复合材料的力学性能, 尤其是掺杂Ce2O3后, 材料的抗弯强度比未掺杂时提高了160%以上.     

Thermal Shock Resistance of Al2 O3/ZrO2 (Y2O3) Composites

ZrO₂ containing 2% (mol fraction) Y₂O₃ and 3% (mol fraction) Y₂O₃ were added into Al₂O₃ matrix, compositing composites with 15% volume fraction of addictives mentioned above. The testing of property and analysis of SEM presented that, after vacuum sintering at 1550 °C, thermal shock resistance of two composites was superior to Al₂O₃ ceramic. The experiment showed that the properties of Al₂O₃ composites was higher than Al₂O₃ ceramic, and Al₂O₃/ZrO₂(3Y) was higher than Al₂O₃/ZrO₂(2Y) in thermal shock resistance. Improvement of thermal shock resistance of composites was attributed to many toughness machanisms of ZrO₂(Y₂O₃). By calculation, the fracture energy of Al₂O₃, Al₂O₃/ZrO₂ (2Y) and Al₂O₃/ZrO₂(3Y) was 38100.8 and 126.2 J·m⁻², respectively. Cracks initiation resistance (R') of Al₂O₃/ZrO₂(3Y) and Al₂O₃/ZrO₂(2Y) was higher than Al₂O₃ ceramic by 1.57 and 1.41 time, respectively, and cracks propagation resistance (R″″) was higher than Al₂O₃ ceramic by 1.46 and 1.38 time, respectively, which was corresponding to the results of residual strength.     

复合材料Al/Al4C3/Al2O3的组织结构与力学性能

采用机械合金化（ＭＡ）球磨和热压烧结工艺制备了复合材料Ａｌ／Ａｌ４Ｃ３／Ａｌ２Ｏ３，对其组织结构和力学性能进行了研究。结果表明，发育良好的Ａｌ４Ｃ３棒状单晶体和等轴状γＡｌ２Ｏ３均匀分布在铝晶界或晶粒内部，二者体积含量约为６６ｖ％。Ａｌ／Ａｌ４Ｃ３和Ａｌ／Ａｌ２Ｏ３界面洁净，为直接的原子结合，但不存在确定的位向关系。复合材料的室温、高温强度及刚度比粉末冶金纯铝（Ｐ／ＭＡｌ）显著提高。     

Manufacturing of Aluminum Matrix Composites Reinforced with Iron Oxide (Fe3O4) Nanoparticles: Microstructural and Mechanical Properties

The purpose of this paper is to demonstrate the low-cost manufacturing of aluminum matrix composites reinforced with nano iron oxide as light and efficient materials for engineering applications. It is very desirable to use reinforced aluminum matrix composites in structural applications (automotive, aeronautical, etc.) because of their outstanding stiffness-to-weight and strength-to-weight ratios. In modern industry, it is increasingly important to develop new composites as alternative materials to fabricate multifunctional pieces. Detailed information is presented on the manufacturing process of this composite, and a preliminary study was performed on the cryogenic-cycling behavior to evaluate the interface between the matrix and the reinforcement. Microindentation tests were carried out to evaluate the micromechanical properties of these materials; a simple and practical finite element model is proposed to predict certain parameters related to the composition of the composite.     

Activity of MnO in MnO-CaO-SiO2-Al2O3-MgO Molten Slags

Metallurgical and Materials Transactions B - The activities of MnO in the MnO-CaO-SiO2-Al2O3 (10, 20, and 30 mass pct)-MgO (5 mass pct) melts at 1873 K...     

共沉淀法制备Al/Cr_2O_3复合粒子及其性能研究

采用共沉淀法将Cr2O3复合于片状金属铝粉表面获得了包覆效果好的Al/Cr2O3复合粒子。为了保证复合粒子的红外隐身性能,对前躯体粒子Al/Cr(OH)3进行了TG-DSC测试,确定了对前躯体的热处理温度;同时借助于XRD,SEM测试对制得的Al/Cr2O3粉末的相组成和形貌进行了表征,此外,将Al/Cr2O3粉末制成红外隐身涂层进行红外辐射率性能测试。结果表明,当铝粉含量为50%(质量分数)时制得的Al/Cr2O3复合粒子包覆较为完整,红外辐射率值最低为0.77。Cr2O3对片状Al粉的包覆在降低红外辐射率的同时不仅避免了Al粉的"显形"和氧化,其本身的绿色还可以起到可见光隐身的效果,在林地的迷彩隐身中具有重要的应用价值。     

(ZrO2)0.96(Y2O3)0.03(Al2O3)0.01陶瓷的制备及性能研究

采用化学共沉淀法制备（ZrO2）0.96（Y2O3）0.03（Al2O3）0.01的粉末, 在不同的升温速率、不同的烧结时间和不同的烧结温度等烧结工艺下制备出（ZrO2）0.96（Y2O3）0.03（Al2O3）0.01三相体系复合陶瓷. 经研究发现, 在升温速率和降温速率均为5 ℃·min^-1 的烧结制度下, 1550 ℃烧结时, 可以得到抗弯强度达998 MPa, 抗热震次数达33次, 相对密度达96%和电性能较好的烧结体.