基于外场辅助的机械合金化研究

机械合金化（MA）技术作为一种制备纳米材料的有效方法已获得广泛的应用。把机械合金化过程中的磨球机械能与其它物理能有机地结合起来,能够增强对粉末的作用,有效提高机械合金化效率。本文简单回顾了机械合金化的发展,对外加物理场辅助作用下的几种高能球磨工艺进行了详细分析。采用物理能辅助机械球磨,从而使粉末得到复合作用或活性激活,是机械合金化效率提高的原因。     

(TiB2+Al2O3)增强铜基复合材料的研究

研究了Cu-Al-TiO2-B2O3粉末在机械合金化和随后的烧结过程中结构的变化，结果表明：Cu-Al-TiO2-B2O3粉末通过机械合金化可以形成Cu(Ti,B）及Al2O3和少量的TiCu3粉末，Al2O3是通过机械合金化过程中的自维持反应形成的，采用Cu,Al,TiO2和B2O3作为原料，通过机械合金化和随后的加压烧结，可以制备性能较好的（TiB2 Al2O3）增强铜基复合材料。     

机械合金化研究的新进展

简要介绍了机械合金化法的发展历程，重点评述了机械合金化法在新材料制备领域的应用，介绍了一种新型的机械合金化法－－摩擦法。分析了国内外研究现状，并对其发展趋势作了展望。     

机械合金化─研制生产金属材料的一种新工艺EI

本文介绍了机械合金化的工艺特点。用机械合金化技术可以获得一些常规方法难以制备的新型合金及难以获得的独特性能，如生产ＯＤＳ合金和弥散强化复合材料，扩大合金元素在基体中的固溶度，获得非晶态合金（金属玻璃），合成金属间化合物材料，获得纳米结构材料。在金属材料研制生产中，机械合金化是一项值得大力研究开发的新技术。     

机械合金化─研制生产金属材料的一种新工艺

本文介绍了机械合金化的工艺特点。用机械合金化技术可以获得一些常规方法难以制备的新型合金及难以获得的独特性能，如生产ＯＤＳ合金和弥散强化复合材料，扩大合金元素在基体中的固溶度，获得非晶态合金（金属玻璃），合成金属间化合物材料，获得纳米结构材料。在金属材料研制生产中，机械合金化是一项值得大力研究开发的新技术。     

机械合金化制备MOSi2基复合材料

总结了近年来国内外大于机械合金化制备MoSi2基复合材料的研究成果，重点讨论了MoSi2的概械合金化合成过程和机理，以及机械合金化制备的MoSi2基复合材料的力学性能。机械合金化是一种合成MoSi2及其复合材料的行之有效的方法，其合成过程和机理与球磨条件有关，系统地研究了不同增强体对MoSi2的机械合金化合成过程和机理的影响是必要的，利用微合金化，合金化和复合化三方面的综合作用将成为改善MoSi2基复合材料性能的新发展趋势。     

机械合金化法制备镁基储氢合金的研究进展

机械合金化法是制备镁基储氢合金的较佳工艺。对近年来机械合金化法制备镁基储氢合金的研究开发,特别是在多元合金化、复合储氢合金等方面的发展进行了系统阐述。总结认为,机械合金化法可以显著改善镁基储氢合金的动力学性能和电化学性能,提高储氢量。未来镁基储氢合金应向复合材料、新方法与机械合金化法相结合、材料的计算机设计等方面发展。     

机械合金化过程中各种因素对储氢合金结构和性能的影响

机械合金化是最近发展起来的制备储氢材料的新型工艺,在改善材料结构和储氢性能方面显示出非常有效的作用.然而,在机械合金化过程中的各种因素,包括球磨时间、球磨环境、球料比等,对合金的结构和储氢性能有不同程度的影响.综述了国内外在机械合金化方面的研究,为更进一步探索通过调整这些因素来改善储氢合金性能有一定的指导意义.     

Fe-Ni机械合金化过程中马氏体的形成及相变

研究了Ni含量、机械合金化工艺参数对Fe-Ni机械合金化过程中马氏体相变的影响及其机理.结果表明:在Fe-Ni机械合金化过程中存在着马氏体相变,但继续机械合金化马氏体是否会发生逆转变主要由Ni含量决定.当Ni≤30%(质量分数,下同)时,机械合金化引起的材料局部温度未达到形变促使马氏体相变逆转变开始温度,因此继续机械合金化马氏体不转变.对于Fe-35Ni,形变促使逆转变的开始温度低于局部温升,马氏体将向奥氏体转变.当Ni含量为35%时,随着机械合金化时间的延长、球磨速度和球料比的提高,机械合金化可以提供的相变驱动力增大导致奥氏体的量逐渐增多.     

Cu-Cr机械合金化工艺研究进展

综述了机械合金化工艺制备Cu-Cr合金的研究进展。主要包括Cu-Cr机械合金化的基本原理;Cu-Cr粉末机械合金化过程的影响因素,包括球磨时间、球料比,填充率、球磨机转速、过程控制剂、球磨温度等;Cu-Cr合金机械合金化过程的缺陷。简要讨论了机械合金化方法生产Cu-Cr合金粉末的发展前景。     

X-ray Diffraction Investigation of the Formation of Nanostructured Metastable Phases During Short-Duration Mechanical Alloying of Cu-Al Powder Mixtures

Mechanical alloying is a powder processing technique used to process materials farther from equilibrium state. This technique is mainly used to process difficult to alloy materials in which the solid solubility is limited, and to process materials where non-equilibrium phases cannot be produced at room temperature through conventional processing techniques. In the present work, mechanical alloying/milling of selected compositions in the Al-Cu binary alloy system was carried out at a ball-to-powder weight ratio (BPR) of 2 : 1, to investigate alloying and subsequent heat treatment on microstructural changes as a result of short milling times. Copper-aluminum powder mixtures containing 5, 20, and 40 wt% Al (11, 37, and 61 at% Al, respectively) were subjected to mechanical alloying, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), after mechanical alloying and subsequent heat treatment. Nanometer-sized grains were observed in the as-milled crystalline powders in all compositions. Crystallite sizes were calculated using the Scherrer formula and found to be in the order of 10-20 nm after 360 minutes of milling time for all compositions. The XRD data show considerable solid solubility extension in these powders, and formation of intermetallic phases due to mechanical alloying and subsequent annealing. These changes are discussed in the context of the Al-Cu phase diagram.     

Effect of Fe content on the mechanical alloying and mechanical properties of Al-Fe alloys

Al-Fe alloys with Fe contents ranging from 5 to 12 wt% are produced by a double mechanical alloying process (DMA) which consists of a first step of mechanical alloying (MA1) applied to elemental Al and Fe powders, with subsequent heat treatment of MA1 powders to promote the formation of Al-Fe intermetallic phases, and a second mechanical alloying step (MA2) to refine the intermetallic phase, and consolidation of the produced powders by combination of degassing and hot extrusion. The effect of Fe content on the process, as well as on the mechanical properties of the extruded alloys, has been extensively studied. The alloys produced by this process show excellent tensile strength and stiffness at room and elevated temperatures due to the strengthening of Al by intermetallics, as well as to the stabilization of the structure by inert dispersoids.     

Amorphization reaction during mechanical alloying: influence of the milling conditions

Amorphous Ni-Zr powders have been prepared by mechanical alloying of elemental crystalline powders. The glass-forming range has been determined in detail at different milling intensities. Depending on the milling conditions, at least partial crystallization of the formerly amorphous material can occur from 66 to 75 at% Ni, due to a temperature rise during milling at high intensity. In comparison with isothermal annealing experiments at various temperatures on completely amorphous powder, a relation between milling temperature and milling time is shown. This confirms the similarity of the amorphization process during mechanical alloying with the solid-state interdiffusion reaction in alternating crystalline multilayers.     

Preparation of Cu-TiN alloy by external nitridation in combination with mechanical alloying

A copper alloy dispersion strengthened by TiN was prepared by external nitridation in combination with mechanical alloying. After mechanical alloying pure Cu and Ti powders, a Cu-3wt.%Ti solid solution was formed. These powders were nitrided at 1073 K, resulting in a TiN layer on the surface of the copper powders. Further mechanical alloying was very efficient in breaking down the TiN surface layers. A very fine uniform distribution of nanosized TiN was obtained. The resulting copper alloy had a grain size of about 150 nm in diameter after annealing at 1173 K in vacuum for 5.4 ks, and showed a very high room temperature hardness value of 251 kg mm⁻² which was independent of annealing temperature below 1173 K.     

机械合金化非平衡产物

机械合金化是一种非晶平衡态材料制备的新兴技术 ,利用机械合金化技术已制备出各种非平衡态材料 :如非晶、纳米晶、金属间化合物等。文中简要叙述了机械合金化非平衡过程的特点 ,着重介绍机械合金化过程中弥散强化合金、金属间化合物、非晶、纳米晶、过饱和固溶体等非平衡相的形成及其特点 ,提出该技术的开发亟待解决的关键问题     

Molecular dynamics investigation of mechanical mixing in mechanical alloying

Molecular dynamic simulation is exploited to obtain a deep insight of atomic scale mixing and amorphization mechanisms happening during mechanical mixing. Impact–relaxation cycles are performed to simulate the mechanical alloying process. The results obtained by structural analysis shows that the final structure obtained through simulation of mechanical alloying is in an amorphous state. This analysis reveals that amorphization occurs concurrently with the attainment of a perfectly mixed alloy. The results indicate diffusion and deformation are two important mechanisms for mixing during mechanical alloying. The rate of diffusion is controlled by the temperature and by the density of defects in the structure. Deformation enhances mixing directly by sliding atomic layers on each other and increases the number of defects in the structure. The results agree with mechanical alloying experiments described in the literature.     

Synthesis and formation mechanisms of molybdenum silicides by mechanical alloying

The synthesis and formation of MoSi₂, Mo₅Si₃, and Mo₃Si compounds by the mechanical alloying of MoSi powder mixtures has been investigated. Ball-milling experiments were conducted for the composition range of 10–80 at.% Si. The formation of molybdenum silicides, especially MoSi₂, during mechanical alloying and the relevant reaction rates markedly depended on the powder composition. The spontaneous formation of MoSi₂ during mechanical alloying at 67 at.% Si (MoSi₂ stoichiometry) proceeded by a mechanically-induced self-propagating reaction (MSR), the mechanism of which is analogous to that of the self-propagating high-temperature synthesis (SHS). At the compositions of 54 and 80 at.% Si, however, the formation of MoSi₂ proceeded by the gradual formation of both the and /gb phases instead of the MSR mode. The formation of Mo₅Si₃ during mechanical alloying was characterized by a slow reaction rate as the reactants and product coexisted over a long period. The milling of Mo-rich powder mixtures up to 150 h did not lead to the direct formation of Mo₃Si. The Mo₃Si phase appeared only after brief annealing at temperatures of 800°C and above.     

Synthesis of Mg-Ti alloy by mechanical alloying

Mg-based Mg-Ti binary alloys have been synthesized by mechanical alloying of Mg and Ti powder blends. It was found that mechanical alloying of Mg and Ti results in a nanocrystalline Mg-Ti alloy and an extended solubility of Ti in Mg, due to the favorable size factor and the isomorphous structure of Mg and Ti. In the case of Mg-20at.%Ti, about 12.5% Ti is dissolved in the Mg lattice when the mechanical alloying process reaches a stable state. The rest (about 7.5 at.%) remains as fine particles in the size of 50–150 nm in diameter. Dissolution of 12.5 at.% Ti in the Mg lattice causes a contraction of the unit cell volume from 0.0464 to 0.0442 nm³ and a decrease of the c/a ratio from 1.624 to 1.612 of the hexagonal structure. The supersaturated solid solution Mg-Ti alloy decomposes upon thermal annealing at temperatures above 200°C. Hydrogenation enhances the decomposition process at lower temperatures.