机械合金化制备纳米材料

纳米科技的发展推动了社会乃至全球的经济发展.机械合金化(Mechnical Alloying简称MA)作为一种极具价值的制备纳米材料的方法被越来越多的人所采用.本文对纳米材料的结构、材料的球磨技术、机械合金化制备纳米材料的过程及原理、利用机械合金化制备电触头材料及扩展端际固溶度等进行了阐述.     

机械合金化合成Fe_3O_4/Fe磁性复合材料

机械合金化合成Ｆｅ３Ｏ４／Ｆｅ磁性复合材料高能球磨机，机械合金化，已广泛用于生产非晶和纳米晶材料，并已用来制取磁性材料，为了有效地利用机械合金化技术开发新型磁性材料，研究了利用机械合金化热处理方法合成的Ｆｅ３Ｏ４／Ｆｅ纳米复合材料的组织和磁性能，研究...     

机械合金化及其应用

<正> 什么是机械合金化 机械合金化（Mechanical Alloy-ing,简称MA）方法是由本杰明于1970年在研究镍基高温合金氧化物弥散强化时所创造的一种制造氧化物颗粒的新方法。该法系将含有欲制得氧化物成分的各种粉末,置于高能球磨机球磨罐内,进行长时间球磨处理,得到欲期组成或新组成的氧化物颗粒,或新组成的固溶     

机械合金化用的球磨机“Uni BallMill”

机械合金化用的球磨机“Ｕｎｉ　ＢａｌｌＭｉｌｌ”英国斯坦莫尔的ＧｌｅｎＣｒｅｓｔｏｎ公司新开发成功一种专门用于机械合金化的球磨机‘ＵｎｉＢａｌｌＭｉｌｌ’。这种新型球磨机能够通过改变在其四周安装的高能磁体的位置及磁场强度、改变旋转速度以及改变球磨机机...     

机械合金化制备金属间化合物MoSi2

以Si粉和Mo粉为原料采用机械合金化的方法制备了金属间化合物MoSi2。研究了球磨过程中球磨时间、球料比、转速及不同球磨机类型对机械合金化产物的影响。利用SEM观察粉末表面形貌及颗粒大小，利用XRD测定物相结构。研究结果表明，当球磨机提供的能量达到相变所需的能量时，粉末中有MoSi2相生成。通过XRD分析可以看出，随着球磨时间的延长，合金化程度逐渐提高：球磨转速的提高有助于生成MoSi2：较高的球料比可以使生成MoSi2的时间提前。在机械球磨过程中，粉末的颗粒尺寸经历了一个由较粗且不规则、不均匀粉末向细小、均匀、接近球形粉末，然后团聚增大的转化过程。此外，还研究了助磨剂对合金化产物的影响，结果表明助磨剂的加入并不能促进MoSi2的生成，但可以对颗粒的细化起到一定作用。     

机械合金化对MoSi2烧结致密化的影响

利用粉末烧结理论对比分析了机械合金化（MA）和高温自蔓延（SHS）合成的MoSi2粉末的烧结性能，并阐明了原因。结果表明，二者合成粉末的烧结性能存在较大差别。机械合金化法比高温自蔓延法至少降低了MoSi2的烧结温度的250℃，机械合金化MoSi2粉末细、晶粒缺陷密度大，具有较高的活性，其烧结表观活化能仅为高温自蔓延粉末的37%，起到了显著的机械活化烧结作用。实际中采用SHS 球磨的工艺有利于在较低烧结温度获得较致密的MoSi2材料。     

添加W对机械合金化TiAl合金显微组织和性能的影响

采用机械合金化结合粉末冶金技术制备了Ti-44．7A1-xW（at％）合金材料。采用透射电镜、扫描电镜和金相显微镜研究不同W添加量对机械合金化TiAl基合金的显微组织和高温抗氧化性能的影响，并对合金的力学性能进行测试。研究表明，通过机械合金化在TiAl基合金系统中添加微量W元素会形成新的固溶体相，这种新成分相大大提高TiAl基合金的抗弯强度σb当W添加量为1．0at％时，σb达到峰值；随后随着W含量的增加，抗弯强度降低。W元素的添加有效的制约了合金基体的内部氧化，使TiAl合金的高温抗氧化性能明显提高。     

形状记忆及热膨胀材料

Ti-Ni-Cu形状记忆合金机械合金化过程定量相分析伊朗Shiraz大学RasoolAmini等人借助高能球磨机械合金化法制备了Ti-41Ni-9Cu形状记忆合金,用X-射线衍射法对球磨态合金进行定性和定量相分析,用扫描电镜和高分辨率透射电镜分析了合金微结构。研究结果表明,在球磨周期,很快地发生纳米晶化,     

Ti-X-C(X=Si,Al)三元体系的元素机械合金化

采用Ti,Si,Al粉和石墨粉等元素作为主要原料,利用行星式球磨机,研究通过机械合金化法(MA)的反应球磨技术(RBM)活化烧结制备Ti3SiC2和Ti3A1C2粉末材料.通过X-射线衍射、扫描电镜等手段,分析研究了机械合金化过程中的元素组织结构变化和可能的机械化学反应.提出实验中机械合金化趋向于界面原子逐渐扩散的反应机制.     

纳米晶和纳米复合的SmCo_2Fe_2B磁体

纳米晶和纳米复合的ＳｍＣｏ_２Ｆｅ_２Ｂ磁体美国特技华大学通过球磨、机械合金化和熔体快淬方法制备了ＳｍＣｏ_２Ｆｅ_２Ｂ磁体，研究了合金的晶体结构、晶粒尺寸与磁特性的关系。合金由感应炉熔炼，利用１５０μｍ合金粉末在高能球磨机上实现机械合金化。在辊速大于４...     

低温球磨和真空热压技术制备的纳米晶纯铝块体的强化机理

利用液氮球磨和真空热压技术制备了纳米晶纯铝块体材料。采用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)对材料的晶粒尺寸和微观组织进行研究,分析了影响热稳定性的因素和强化机理。研究表明,液氮球磨以后材料晶粒尺寸为37nm,经过真空热压和热挤压后晶粒有所长大,晶粒大小约300nm,纳米晶结构基本得到保持。分析晶粒热稳定性的原因在于球磨过程中生成的AlN等粒子的晶界钉扎以及引入的杂质溶质的拖拽作用。纳米晶纯铝块体的拉伸强度极限σb为173MPa,伸长率fε为17.5%。     

Grain growth in nanocrystalline iron and Fe-Al alloys

The effects of the annealing temperature and time, cryomilling in liquid nitrogen, and the addition of aluminum powder on the thermal stability and grain growth behavior of nanocrystalline iron were modeled using the Artificial Neural Network (ANN) technique. The developed model can be used as a guide for the quantification of the grain growth by considering the effects of annealing temperature and time. The model also quantified the effect of Al on the thermal stability of cryomilled nanocrystalline Fe. The model results showed that the cryomilling of Fe has a tangible effect on the stabilization of the nanostructure.     

液氮球磨Sm-Fe合金的组织演变

利用低温液氮球磨技术制备了Sm-Fe合金粉体,采用XRD、HRTEM和惰性气脉冲-红外-热导等方法对Sm2Fe17合金粉体在液氮球磨过程中的组织演变进行了研究。结果表明,液氮球磨可加速细化Sm-Fe合金粉体。球磨5 h后,Sm-Fe合金的晶粒尺寸约为10 nm,9 h后晶粒尺寸约为5 nm。Sm-Fe合金中的氮含量随着球磨时间的延长而增加,主轴转速150 r/min球磨9 h后,氮含量达1.62% (质量分数, 下同)。随着球磨时间的延长,Sm2Fe17相向非晶态转变,降低球磨转速可以延缓非晶的形成过程     

Evidence for the formation mechanism of nanoscale microstructures in cryomilled Zn powder

Nanocrystalline Zn powder has been synthesized by a cryomilling method. The average grain size decreased exponentially with the cryomilling time and reached a minimum average grain size of around 17 nm. Large numbers of small grains (2∼6 nm) have been found in the very early stages of cryomilling. Dynamic recrystallization was used to explain the observed phenomena. The exothermic peaks revealed in the differential scanning calorimetry (DSC) results were correlated with the release of microstrain as confirmed by the x-ray diffraction measurements.     

液氮球磨过程中钛粉的形貌和组织演变

采用液氮球磨技术制备出纳米晶钛粉。运用SEM、XRD和TEM研究了液氮球磨过程中钛粉的形貌和组织的演变。结果表明:钛粉颗粒在液氮球磨过程中以脆性开裂的方式细化,经8h液氮球磨后钛粉颗粒从球磨前的45μm减小到5μm左右,颗粒表面出现大量裂纹;采用液氮球磨方法制备纳米晶Ti粉仅需8h。     

液氮球磨制备纳米SiCp/Al基复合材料的研究

利用液氮球磨技术制备了纳米SiC颗粒增强铝基复合材料粉末,对该纳米粉末进行真空热压和热挤压,获得纳米铝基复合材料块体.采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)研究了纳米SiC粉和Al-Zn-Mg-Cu粉在液氮球磨过程中形貌、组织和相组成等.结果表明,液氮球磨可以使复合材料粉末达到纳米级,且纳米SiC可均匀地分布于铝合金中.     

Synthesis and characterization of nanocrystalline Ni produced by cryomilling in liquid nitrogen

NanocrystaUine Ni powders were successfully fabricated by mechanically milling at cryogenic temperature （cryomilling） with 1 wt.%Y2O3 particles. The experimental results have shown that the Ni grain size is reduced to 25 nm after 2 h of cryomilling in the presence of the Y2O3 particles. The cryomiUed Ni/Y2O3 powders can maintain their nanocrystalline structure up to 900℃, or 62% of the melting point of Ni. A bulk nanocrystalline Ni/Y2O3 material with a thermally stable grain size of approximately 100 nm was produced by cryomilling, cold isostatic pressing, followed by hot isostatic pressing. The microhardness of bulk nanocrystalline Ni/1wt.%Y2O3 is 315 DPH, which is two times as high as that of conventional Ni.     

Deformation twins and twinning at ambient temperature in cryomilled A1-Zn-Mg-Cu alloy powders

The nanocrystalline Al-Zn-Mg-Cu alloy powders were synthesized using cryomilling. Deformation twins and twinning at ambient temperature were observed in Al-Zn-Mg-Cu powders. Experimental results indicate that high strain rate at low temperature during cryomilling induces the formation of deformation twins by the climbing of the restricted dislocations in nano-scale grains, and the cryomilled powders at high energies and nonequilibrium state reduce the grain boundary energies by twinning.     

Nanostrucmred A1-Zn-Mg-Cu alloy synthesized by cryomilling and spark plasma sintering

Nanocrystallized Al-10.0%Zn-3.0%Mg-1.8%Cu (mass fraction) alloy powder was prepared by cryomilling, and then the nanostructured powder was consolidated into bulk material by spark plasma sintering (SPS). The microstructural evolution and phase transformation were studied. A supersaturated face-centered cubic solid solution is formed after cryomilling for 10 h, and the average grain size is 28 nm. Two typical nanostructures of the bulk nanostructured alloy are observed: primarily equiaxed grains with size of 150 nm, and occasionally occurring sub-micron grains up to 500 nm. Two types of MgZn₂ particles precipitate during consolidation. One is the sub-micron particles distributed along the boundaries of the powders, and the other is fine particles with size of several nanometers in the matrix, especially at the boundaries of sub-micron grains. These second phase particles can be completely dissolved into matrix by proper solid solution treatment.     

Microstructure and transformation of Al-containing nanostructured 316L stainless steel coatings processed using spark plasma sintering

Three austenitic stainless steel alloys containing 0, 2 and 6 wt.% Al were prepared by cryomilling and spark plasma sintering. It was shown that aluminum influences the strain-induced phase transformation that occurs during milling. The milled powders consisted of finely dispersed particles with the powder particle size distribution increasing with aluminum concentration. Consolidation of the SS0Al (stainless steel containing 0 wt.% Al) powder via the spark plasma sintering (SPS) process onto a solid stainless steel substrate yields an equiaxed structure due to the original particle morphology resulting from cryomilling. The SS2Al and SS6Al SPS consolidated powder coatings exhibit a lamellar structure due to the increased aspect ratio of the particles. The degree to which the BCC structure induced during cryomilling of all three powder systems reverted to FCC was dependent upon the Al content. The SPS process was found to minimally influence the FCC recovery compared to conventional powder consolidation heat treatments. The energy supplied by the SPS process was insufficient to overcome the activation energy governing the rearrangement of dislocations required to complete the FCC recovery. The microhardness of the coatings processing using SPS was found to be highly dependent on the Al content by controlling the ratio of the BCC/FCC crystals in the formed coating.