机械合金化合成TiB2/Fe3Al纳米复合粉体

采用铁、铝、钛、硼四元粉体机械合金化与后续热处理的方法合成纳米TiB_2／Fe_3Al复合粉体,并利用XRD、DSC、SEM和TEM等对粉体进行了表征。结果表明：在球磨过程中,四元粉体形成了Fe(Al,Ti,B)过饱和固溶体,有序度不断降低,逐渐向非晶态转变,同时粉体晶粒尺寸逐渐细化,球磨40h后Fe(Al,Ti,B)的晶粒尺寸为9．6nm;并在热处理过程中Fe(Al,Ti,B)分解生成纳米Fe_3Al和TiB_2复合粉体,同时发生组成相晶粒生长,结构有序度提高等转变。     

热压烧结Fe3Al金属间化合物的结构和摩擦学特性

采用机械合金化结合热压烧结的方法制备了Fe3Al金属间化合物块体材料，对其烧结后的物相、力学性能、微观结构以及干滑动摩擦磨损性能进行了试验研究。结果表明，热压烧结Fe3Al金属间化合物材料以有序度较低的B2结构为主，具有较高的强度和硬度。在不同的载荷和滑动速度下具有不同的摩擦学特性，不同摩擦阶段的磨损机制主要包括磨粒磨损、塑性变形、裂纹萌生与扩展、微区脆性剥落以及氧化磨损等。     

纳米Fe3Al粉体及块体材料的制备及表征

分别利用氢电弧等离子体法及机械合金化制取纳米Fe3Al粉体.氢电弧等离子体法制备的纳米Fe3A1粒子为球形,粒径为50～100 nm,粒度分布较均匀,呈部分有序的B2相结构.由机械化合金化制得的Fe3A1粉体存在着较高的缺陷浓度及晶格畸变.热压烧结制备Fe3AI块体材料的洛氏硬度为61 HRC,室温抗弯强度和断裂韧度分别高达1 300MPa和49MPa·m1/2.     

粉末硼铝共渗层的显微组织和性能

本文研究了20、45、T8、GCr15、3Cr2W8V钢用不同粉末渗硼剂与渗铝剂配比所形成的硼铝共渗层的组织和性能。结果表明,硼铝共渗层主要由硼化物(Fe、Al)B、(Fe、Al)_2B和超结构铝化物β_1(Fe_3Al)以及α(Al、B)组成。硼铝共渗层具有高硬度、高耐磨性、耐蚀性、抗高温氧化性和热硬性。因此,它是一种值得推广的新型化学热处理工艺。     

Fe3A1金属间化合物的机械合金化

利用X射线衍射(XRD)、示差扫描量热计(DSC)以及透射电镜(TEM)研究了Fe-Al元素混合粉末球磨过程中的结构演变。结合Fe3Al各种相衍射规律的分析,阐述了合成的B2-Fe3Al在XRD中未出现超点阵衍射峰的原因。球磨中,加工硬化和回复这一相互矛盾的过程,决定球磨粉末具有极限晶粒度。     

压铸铝合金的铁金属间化合物对力学特性的影响

压铸铝合金AlSi9Cu3中含有三种FeSiAl类金属化合物,即:多边形状铁相Al8Si1.6(Fe,Mn)1.8 (CuZn)0.1、α铁相Al8Si1.5(Fe,Mn)1.7 (CuZn)0.2和β铁相Al5Si1.3(Fe,Mn)(CuZn)0.1 .当铁的含量从0.17 wt%～0.8 wt%变化时,压铸铝合金AlSi9Cu3以α铁相和多边形状铁相为主,其强度上升,塑性降低;当铁的含量达到0.8 wt%～1.3 wt%时,α铁相和多边形状铁相有明显的增加,同时β铁相也大量形成,从而使其强度增加5%,延伸率减少27%.     

渗硼的渗层组织和性能研究

渗硼过程中,随着硼浓度的增加,渗硼层的组织由内向外依次为芯部基体、过渡层和硼化物层.如碳钢的低温硼氮共渗层呈梳齿状,表层由FeB、Fe2B双相组成,内层为Fe2B单相.合金钢低温硼氮共渗层的针状变得平坦,渗层的相组成较为复杂,Cr12钢低温硼氮共渗表层由Fe2B、FeB、Fe4N组成,内层相由FeB、Fe2B、Fe3 (C,B)、(Fe,Cr)2B、Fe4N、Fe3C等组成,过渡区形成Fe3 (C,B)、Fe4N相及Cr的碳化物,有效地强化了对硼化物层的支撑作用.渗硼层具有良好的耐磨性、耐腐蚀性.     

热重分析仪TGA测定磁性材料的相转变

本文利用带有磁场的热重分析仪(M -TGA)对Fe3B合金中加入元素Nd造成的合金相转变和各相含量等进行研究。研究发现,在Fe3B合金中加入适量的稀土元素Nd将导致合金相组成由四角Fe3B(t-Fe3B)变为t-Fe3B和亚稳相Nd2 Fe2 3B3。与常规热分析仪器DTA相比,高灵敏的M -TGA可以更加清楚地观察到具有铁磁性转变的磁性材料相变过程     

Fe3Al金属间化合物多孔材料的孔隙特征

通过在Fe3Al粉末中添加挥发性造孔剂,利用粉末冶金技术制备了Fe3Al金属间化合物多孔材料,研究了其孔隙特性和成孔机理,并通过计算分析了孔隙比表面积及平均有效孔径.结果表明:随着Fe3Al多孔材料的开孔隙率不断增加,材料比表面积不断减小,平均有效孔径不断增大;通过近似计算,得出添加25%聚甲基丙烯酸甲酯(PMMA)的试样平均有效孔径达到21.6μm,比表面积超过2000cm2·cm-3;Fe3Al多孔材料内部大孔壁上的微孔可以帮助造孔剂顺利挥发排除,也可以增加Fe3Al多孔材料比表面积和渗透性能.     

AlN-TiB_2复相导电陶瓷的制备及性能研究

以微米Al N、微米Ti B2以及纳米Si C为主要原料,以微米Y2o3和微米Al2o3为添加剂,采用真空N2气氛保护热压烧结工艺制备了Al N-Ti B2复相导电陶瓷材料。测试和分析了烧结样品的相对密度、弯曲强度、硬度值以及导电性能。结果表明,当微米Al N添加量为55wt%,微米Ti B2为20wt%,纳米Si C为20wt%,微米Y2o3为3wt%以及微米Al2o3为2wt%时,且烧结温度为1880℃时,所制备的Al N-Ti B2复相导电陶瓷材料性能最佳,其相对密度为94.45%,弯曲强度为512.35MPa,洛氏硬度为104.25,电阻率值为1526μΩ.cm。     

Fe3Al金属间化合物基摩擦材料的制备工艺与性能

采用机械合金化结合加压烧结的方法制备了一种新的Fe2Al金属间化合物基摩擦材料，并对其制备工艺、微观结构和力学性能、抗氧化性以及千滑动摩擦磨损性能进行了试验研究。结果表明：Fe3Al金属间化合物基摩擦材料密度低，强度高，抗氧化性好，摩擦因数稳定，耐磨性好；不同摩擦阶段具有不同的磨损机制，主要包括磨粒磨损、裂纹萌生与扩展、微区脆性剥落以及氧化磨损等。     

EFFECT OF Fe_2O_3 ON WELDING TECHNOLOGY AND MECHANICAL PROPERTIES OF WELD METAL DEPOSITED BY SELF-SHIELDED FLUX CORED WIRE

Five experimental self-shielded flux cored wires are fabricated with different amount of Fe2O3 in the flux. The effect of Fe2O3 on welding technology and mechanical properties of weld metals deposited by these wires are studied. The results show that with the increase of Fe2O3 in the mix, the melting point of the pretreated mix is increased. LiBaF3 and BaFe12O19, which are very low in inherent moisture, are formed after the pretreatment. The mechanical properties are evaluated to the weld metals. The low temperature notch toughness of the weld metals is increased linearly with the Fe2O3 content in the flux due to the balance between Fe2O3 and residual Al in the weld metal. The optimum Fe2O3 content in flux is 2.5%-3.5 %.     

Investigations on field-ion image formation and field evaporation sequences of DO3-ordered Fe3Al

The field-ion image formation of DO3-ordered Fe3Al was reinvestigated performing the atomic plane counting technique and the analysis of field evaporation sequences of different crystallographic plane sets with supporting atom probe microanalysis. For comparative studies a hypostoichiometric iron aluminide with B2 ordering was also imaged in the field-ion microscopy (FIM). The results show that Al atoms are the brightly imaging species. However, on DO3 superlattice plane sets, such as (222) and (226), iron atom layers have been imaged with atomic resolution. The B2-ordered iron aluminide does not exhibit prominent (222) and (226) poles in the FIM image. Video controlled field evaporation sequences of different atomic planes and image analysis lead to the conclusion that preferential field desorption of Fe atoms and the stronger field-ionization of Al atoms are the important mechanism for the formation of field-ion images of Fe3Al. The B2-ordered iron aluminide exhibits preferentially double layer field evaporation, and topmost Fe atom layers are not visible in the FIM.     

Fretting wear of mechanically alloyed AlFe and AlFeMn alloys

A double mechanical alloying process (dMA) was employed to fabricate AlFe and AlFeMn alloys containing finely distributed intermetallic compounds and inert dispersoids (Al₄C₃ and Al₂O₃). The tribological properties of the produced alloys were investigated under fretting conditions. It was shown that the fretting behaviour strongly depends on contact conditions which are mainly determined by displacement and normal load, and the wear resistance of Al alloys can be improved by dispersion of large amount of intermetallics and inert dispersoids. Compared with current and competitive wear resistant Al alloys, the dMA AlFeMn alloy shows attractive wear and friction properties. The results indicate that Al alloys fabricated by dMA are promising for wear-resistance applications.     

挤压铸造法对(Al63Cu25Fe12) p/ZL101复合材料性能的影响

研究了挤压压力和浇注温度对(Al63Cu25Fe12)p/ZL101复合材料性能的影响.结果表明:当挤压压力为50-100 MPa时,复合材料的抗拉强度、伸长率和硬度会随着压力的增加而增大,然而当挤压压力为100-150MPa时,随着压力的升高,其综合力学性能会随之下降.此外,复合材料的力学性能会随着浇注温度的升高而提高,但温度不能超过760℃.当挤压压力为100MPa,浇注温度为720℃时,复合材料的综合力学性能最优.最后,选择合适的热处理工艺来进一步提高复合材料的力学性能.     

Characterization & evaluation of Al7075 MMCs reinforced with ceramic particulates and influence of age hardening on their tensile behavior

Aluminium has a massive demand in the areas of automobile, aerospace and diverse engineering applications in order to furnish the requirement in those fields. But this technological evolution needs something more than aluminium. Materialogists are struggling hard to find out a material which owns sound mechanical and thermal properties and also superior than aluminium in each extent. Metal matrix composite (MMC) is a solution. Generally, metal matrix composites contain a low density material, i.e. aluminium or magnesium, reinforced with fibers or particulate of a ceramic material, i.e. silicon carbide or graphite. They show greater specific strength, high stiffness, elevated operating temperature, and superior wear resistance, along with the possibility to customize these properties for a specific use. In this study, Al 7075 is taken as a base matrix material, whereas ceramic materials like SiC, Al₂O₃, B4C and TiB₂ are used as reinforcements. There are different methods available for fabricating metal matrix composite materials and in this work, stir casting technique, which is a liquid state process, is used. Four different MMC specimens were produced with 15 % SiC, 15 % Al₂O₃, 15 % B4C and 15 % TiB₂. Mechanical properties i.e. tensile strength, hardness, and impact strength were studied for the prepared specimens. The results were charted and presented graphically to describe these materials characteristics.     

Structure and mechanical properties of NiAl and Ni3Al-based alloys

The investigation of Ni–Al–Fe–Ti–B alloys was carried out to determine the influence of iron and small titanium and boron additions on the phase composition, microstructure and mechanical characteristic, particularly with respect to high-temperature deformation conditions. These alloys, containing Al 35.8 at% and Fe 3.6–8.6–17.6 at% were prepared from high-purity components and Al master alloy containing Ti₂B particles. The influence of alloying additions of chromium and iron on the mechanical properties of directionally solidified Ni–Al–Cr–Fe alloy was investigated. Additions of both Cr 8 at% and Fe 2 at% result in higher strength than exhibited by unalloyed Ni₃Al. However, the ductility is reduced by the formation of the β′ phase. The typical, lamellar structure of Ni–20Al–8Cr–2Fe alloy undergoes coagulation during a high-temperature deformation process. The sequence of structural changes of NiAl and Ni₃Al-based alloys has been correlated with mechanical characteristics of high-temperature deformation process, determined in uni-axial compression tests. Two ranges of work hardening have been identified on the stress–strain curves of these alloys. It has been found that the first range of the deformation of Ni–Al–Fe–Ti–B alloys corresponds to the intergranular slip system operating within individual grains, while the second one is connected with transgranular slip. In the directionally solidified Ni–20Al–8Cr–2Fe alloy similar work hardening curves were observed in relation to the microstructural evolution from the lamellae shape, through elliptical shape into circular shape.     

Al-Cu合金片对钢/铝异种金属激光-MIG复合焊接头组织和性能的影响

采用PLC系统控制的激光-MIG复合焊接工艺对Q890钢/6063铝合金进行异种金属焊接,研究了钢侧坡口表面添加Al-Cu合金片对接头显微组织、硬度和拉伸性能的影响。结果表明:激光-MIG复合焊接接头具有典型的熔钎焊特征;未添加Al-Cu合金片的接头界面层由舌状相Fe2Al5和粗大针状相Fe4Al13组成,厚度约18μm,添加Al-Cu合金片后由舌状相(Fe,Cu)2Al5和细小絮状相(Fe,Cu)4Al13组成,厚度约为9μm,焊缝区与热影响区的组织与未添加Al-Cu合金片时的相似;添加Al-Cu合金片的接头界面层硬度比未添加Al-Cu合金片的低约59HV;添加Al-Cu合金片的焊接接头的抗拉强度比未添加Al-Cu合金片的提高了109.8%,未添加和添加Al-Cu合金片的焊接接头均在界面层断裂。