低温反应自熔法制备镁基复合材料的新工艺

为克服粉末冶金法(PM)和铸造法(Casting)在制备镁基复合材料过程中的缺点，尝试采用低温反应自熔(RSM)新工艺制备颗粒增强镁基复合材料。经低温反应自熔制备的颗粒增强镁基复合材料，在一定程度上消除了粉体颗粒的氧化膜，减小了对合金元素扩散的阻碍作用，使颗粒间的结合得到改善；SEM断口观察及X射线衍射物相分析表明，基体与增强体界面处有轻微的反应存在，反应产物为MgTiO3，推测为MgO-Ti、Mg-TiO3或MgO-TiO2的反应所生成。     

二氧化硅原位反应在制备镁基复合材料中的应用

在熔融镁合金中加入活化SiO2颗粒，由其与镁反应生成Mg2Si原位合成镁基复合材料；用X射线衍射仪(XRD)、电子探针显微分析仪(EPMA)、能谱仪(EDX)对制备的复合材料进行了分析。结果表明，SiO2原位反应制备的镁基复合材料中的增强相Mg2Si颗粒分布均匀，与基体结合较好，复合材料硬度得到提高。     

原位合成增强镁基复合材料的制备方法

镁基复合材料以高强度、高弹性模量的陶瓷颗粒或硬质相为增强相,从而具有好的力学性能和物理性能。原位合成法增强镁基复合材料中的增强体具有热稳定性好、组织细小、与镁基体界面结合良好等优点,因而原位合成法成为制备镁基复合材料研究发展的方向之一。本文重点介绍了原位颗粒增强镁基复合材料的制备方法以及其优缺点,并分析了原位制备镁基复合材料过程中存在的问题,展望了发展趋势。     

颗粒增强镁基复合材料研究进展

综述了不同种类颗粒增强镁基复合材料的最新研究进展，着重介绍了这些复合材料的组织、结构、性能及界面问题。针对目前颗粒增强镁基复合材料研究领域存在的问题，提出了该领域的研究方向：探索控制增强颗粒和基体界面行为的有效手段：研究低成本、短流程的原位颗粒增强复合材料制备技术；实现多种材料制备和加工技术的紧密结合；借助现代计算机模拟技术对增强颗粒强化和失效机制进行研究将是该领域的研究方向。     

颗粒增强镁基复合材料的制备技术与展望

介绍了颗粒增强镁基复合材料的制备方法,包括粉末冶金法、喷射沉积法、搅拌铸造法、熔体浸渗法和原位合成法等。阐述了各种制备方法的应用背景、基本原理以及应用情况,讨论了不同制备方法对复合材料的强度、耐磨性、耐蚀性等性能以及气孔率、杂质含量等缺陷的影响,评价了各种制备工艺的优缺点,剖析了各种制备方法的异同。结果表明,影响颗粒增强镁基复合材料性能的关键问题在于如何使增强体在基体中均匀弥散分布,展望了颗粒增强镁基复合材料的制备技术。     

纳米SiC颗粒增强AZ91D复合材料的制备及性能

利用高能超声辅助法制备纳米SiC颗粒(n-SiCp)增强AZ91D镁基复合材料(n-SiCp/AZ91D),并对其显微结构和室温力学性能进行测试分析。结果表明:纳米SiC颗粒的加入能够起到细化晶粒的作用,纳米颗粒在基体中的分布比较均匀,超声波辅助技术能够有效地分散纳米颗粒,在重力铸造下所制备的复合材料的抗拉强度、屈服强度和硬度均高于基体,尤其是屈服强度较基体提高了57%。     

镁基复合材料的分类与研究进展

综述了镁基复合材料基体的分类、快速凝固制备以及应变诱导晶粒细化,并概述了颗粒增强、晶须增强、短纤维增强、碳纳米管增强、非连续纤维增强以及连续纤维增强镁基复合材料的研究进展以及发展趋势。     

原位颗粒增强镁基复合材料的制备

综述了原位颗粒增强镁基复合材料的研究进展，重点介绍了原住反应法制备颗粒增强镁基复合材料的基本原理和过程，并分析了其组织和性能；同时还简述了传统铸造法制备原位颗粒增强镁基复合材料的特点。最后，对原位颗粒增强镁基复合材料的发展趋势作了展望。     

Al3Ti／Mg复合材料磨损行为的研究

研究了原位反应烧结法制备的Al3Ti/Mg复合材料的磨损行为,并且与纯镁和AZ91镁合金进行了比较.结果表明,原位内生Al3Ti颗粒能有效地增强镁基体,Al3Ti/Mg复合材料的耐磨性比纯镁和AZ91镁合金有明显的提高,且随Al3Ti颗粒增强相体积分数的增加,复合材料的耐磨性呈现上升的趋势;磨损表面的微观形貌显示,Al3Ti颗粒均匀分布在镁基体内部,且与基体结合牢固,起到了承担载荷和推迟复合材料磨损的作用.     

纳米二氧化硅颗粒增强镁基复合材料在典型介质溶液中的耐蚀性研究

本文以纯镁粉末为基体材料,以纳米二氧化硅颗粒为增强相,按照原材料之间三种不同的体积配比,采用粉末冶金法制备出了三种纳米二氧化硅颗粒增强镁基复合材料样品。文中用扫描电子显微镜观察、对比了样品的显微组织,研究出了纳米二氧化硅颗粒的加入对镁基体产生的影响;用动电位极化试验法对三种样品在不同温度的典型介质溶液(Na_2SO_4溶液和Na Cl溶液)中的腐蚀行为进行了研究,从而分析出纳米二氧化硅颗粒增强镁基复合材料的腐蚀规律和腐蚀机理,进而建立其腐蚀模型。     

低温反应自熔法原位合成MgO颗粒增强镁基复合材料

采用低温反应自熔新工艺，由经过预氧化的Mg粉原位合成了MgO颗粒增强镁基复合材料，并对其显微组织和力学性能进行了检测。结果表明：低温反应自熔时，因Mg颗粒处于全熔或半熔状态，表面的氧化膜得到了有效地破碎、细化，并在液相熔蚀和自身表面张力的共同作用下，球化成微米和亚微米级MgO颗粒；形成的MgO颗粒不但与基体结合良好、分散均匀，而且因具有很高的强度和刚度，对基体产生了较好的增强效果。与粉末冶金法相比，采用低温反应自熔法制备的镁基复合材料的组织和性能均显示出明显优势。     

搅拌摩擦加工制备NiTip/WE43镁基复合材料

本研究提供了一种采用搅拌摩擦加工（FSP）制备NiTi颗粒增强WE43镁基复合材料的有效手段。采用SEM结合EDS对FSP试样的微观结构进行了研究，采用XRD进行了物相分析。结果表明，制备的复合材料具有形状记忆效应。较低的加工温度有效地阻止了NiTi颗粒与Mg基体在FSP过程中的界面反应。无论粒径大小，在FSP后，NiTi颗粒都均匀分布在Mg基体中。此外，与Mg基体相比，NiTi/WE43复合材料的屈服强度、极限拉伸强度和延伸率分别降低了33%、12%和18%。随着加入的NiTi颗粒尺寸的增大，该复合材料拉伸强度和延伸率均降低。复合材料的失效机理是颗粒之间的界面开裂以及增强颗粒的断裂。     

Strengthening Mechanism and Microstructure of Deformable Ti Particles Reinforced AZ91 Composite

In this study, the deformable titanium (Ti) particles reinforced AZ91 composite was successfully prepared by powder metallurgy and subsequent extrusion. The mechanical properties and microstructural evolution of pure AZ91 and 5Ti/AZ91 composite were studied. The yield strength, ultimate tensile strength, and elongation of 5Ti/AZ91 composite are measured to be 212 MPa, 323 MPa, and 10.1%, respectively. Microstructure analysis revealed that Ti particles are elongated along the extrusion direction, forming a discontinuous strip Ti particles, fine precipitated Mg₁₇Al₁₂ phase inhibits dynamic recrystallization (DRX) behavior through Zener pinning effect and hinders the growth of matrix grains, resulting in refiner grains of 5Ti/AZ91 composite. Heterogeneous deformed Ti particles and magnesium (Mg) matrix to generate additional heterogeneous deformation-induced (HDI) strengthening. Heterogeneous deformation-induced strengthening mainly contributed to the increment of yield strength for 5Ti/AZ91 composite.     

Preparation and mechanical properties of SiC／2024 composite by semisolid casting

A SiC/2024 composite was made by semisolid casting.The wetting between SiC and Al matrix is improved by treating SiC particles at a high temperature,coating K2ZrF6,and adding Mg to the Al melt,An effective way to remove the gas around SiC particles was also found.Microstructures were observed under optical microscope(OM) and scanning electron microscopy(SEM).The results show that SiC particles and Al matrix are well bonded and no gaps or cavities around the particles are observed.SiC particles distribute homogeneously in the Al matrix.The existence of SiC particles results in the increase of wear resistance and strength.     

(WC+SiCw)/Cu-Al2O3复合材料载流摩擦磨损行为

目的 研究相同载流条件下纳米Al2O3颗粒、微米WC颗粒和SiC晶须对(WC+SiCw)/Cu-Al2O3复合材料表面摩擦磨损性能的影响.方法 采用粉末冶金法和内氧化法相结合的方式,制备了(WC+SiCw)/Cu-Al2O3复合材料,并利用HST-100高速载流摩擦试验机进行载流摩擦磨损性能测试.采用透射电镜和扫描电镜...     

LC4铝合金断裂过程的动态观察

在扫描电镜上利用ＨＸ－ＴＳ２型拉伸台，对ＬＣ４高强铝合金常规热处理状态Ｔ６（时效至峰值强度）及退火状态拉伸时微裂纹的萌生及连接进行了原位动态观察。结果表明：在Ｔ６状态下，局部应力集中和应变引起的分散相（Ｐ）与基体（Ｍ）界面的分离及其本身开裂是微裂纹萌生的主要机制。退火样品除Ｐ／Ｍ界面分离和大块脆性相解理外还出现大量弯曲和扭折的滑移带。两种样品微裂纹的连接方式也不尽相同     

Influence of In Situ Reaction on the Microstructure of SiC<Subscript>p</Subscript>/AlSi7Mg Welded by Nd:YAG Laser with Ti Filler

The effect of in situ reaction on the microstructure of Nd:YAG laser welded joints of aluminum matrix composite SiC_p/AlSi7Mg was studied. Results showed that the laser welding with Ti filler improved the tensile strength of welded joints. Moreover, the laser welding with in situ reaction effectively restrained the pernicious Al₄C₃ forming reaction in the interface between aluminum matrix and reinforcement particles. Simultaneously, the reaction-formed TiC phase distributed uniformly in the weld. This permitted SiC_p/AlSi7Mg composite to be successfully welded by Nd:YAG laser.     

Correlation between tensile and indentation behavior of particle-reinforced metal matrix composites: an experimental and numerical study

The correlation between tensile and indentation behavior in particle-reinforced metal matrix composites (MMCs) was examined. The model composite system consists of a Al–Cu–Mg alloy matrix reinforced with SiC particles. The effects of particle size, particle volume fraction, and matrix aging characteristics on the interrelationship between tensile strength and macro-hardness were investigated. Experimental data indicated that, contrary to what has been documented for a variety of monolithic metals and alloys, a simple relationship between hardness and tensile strength does not exist for MMCs. While processing-induced particle fracture greatly reduces the tensile strength, it does not significantly affect the deformation under indentation loading. Even in composites where processing-induced fracture was nonexistent (due to relatively small particle size), no unique correspondence between tensile strength and hardness was observed. At very low matrix strengths, the composites exhibited similar tensile strengths but the hardness increased with increasing particle concentration. Fractographic analyses showed that particle fracture caused by tensile testing is independent of matrix strength. The lack of unique strength–hardness correlation is not due to the particle fracture-induced weakening during the tensile test. It is proposed that, under indentation loading, enhanced matrix flow that contributes to a localized increase in particle concentration directly below the indenter results in a significant overestimation of the overall composite strength by the hardness test. Micromechanical modeling using the finite element method was used to illustrate the proposed mechanisms under indentation loading and to justify the experimental findings.     

Improvement of high-temperature strength of 6061 Al matrix composite reinforced by dual-phased nano-AlN and submicron-Al2O3 particles

Nano-AlN and submicron-Al₂O₃ particles were simultaneously utilized in a 6061 Al matrix composite to improve the high-temperature strength. According to the SEM and TEM characterization, nano-AlN and submicron- Al₂O₃ particles are uniformly distributed in the Al matrix. Brinell hardness results indicate that different from the traditional 6061 Al matrix alloy, the aging kinetics of the composite is obviously accelerated by the reinforcement particles. The T6-treated composite exhibits excellent tensile properties at both room temperature and elevated temperature. Especially at 350 °C, the T6-treated composite not only has a high yield strength of 121 MPa and ultimate tensile strength of 128 MPa, but also exhibits a large elongation of 11.6%. Different strengthening mechanisms of nano-AlN and submicron-Al₂O₃ particles were also discussed in detail.     

Hierarchical magnesium nano-composites for enhanced mechanical response

In this work we have synthesized and investigated the mechanical performance of a hierarchical magnesium (Mg) nano-composite with a novel micro-architecture including a reinforcing constituent that is a composite in itself. Specifically, we developed a nano-composite (alternatively referred to as a level II composite) with monolithic Mg as the matrix, reinforced by another level I composite comprising a sub-micron pure aluminum (Al) matrix in which are embedded nano-alumina (n-Al₂O₃) particles. The level II composite was obtained by adding a small volume fraction (vf) of the ball-milled level I composite to Mg using the powder metallurgy route followed by microwave-assisted rapid sintering and hot extrusion. Compared with the monolithic pure Mg, the hierarchical composites exhibited significant simultaneous enhancement of strengthening, hardening and failure strain, and also non-monotonic mechanical performance as a function of level I vf. Among the different hierarchical formulations synthesized, the hierarchical level I composition with 0.972% Al and 0.66% Al₂O₃ by volume (Mg/0.972 Al–0.66 Al₂O₃) exhibited the best overall mechanical properties compared with monolithic Mg, with an improvement of 96% in the 0.2% yield strength, 80% in the ultimate tensile strength, 42% in failure strain and 147% in the work of fracture. We identified and quantified some of the strengthening mechanisms that may be responsible for the impressive performance of this hierarchical nano-composite.