Characteristics of AA6061/BN composite fabricated by pressureless infiltration technique

Spontaneous infiltration and strengthening behaviors were analyzed in terms of microstructures and tensile properties of AA6061/BN composite fabricated by pressureless infiltration technique in the presence of both Mg and nitrogen. The microstructure and properties were compared with control AA6061 without BN fabricated by the same method. The Mg₃N₂ formed by the reaction of Mg vapor and nitrogen gas, which coated the particles in the powder bed, is believed to induce spontaneous infiltration through greatly enhancing wetting by means of the reaction Mg₃N₂ + 2Al → 2AlN + 3Mg. This was identified by the finding of AlN particle layers on the surfaces of prior Al particles in the powder bed, which made contact with the infiltrating melt. In addition, unreacted Mg₃N₂ was observed outside the composite, where the Al melt did not come into direct contact. Fine AlN particles formed in situ resulted in significant strengthening, even in the control alloys with no addition of BN. In the composite reinforced with BN, additional AlN was formed by the interfacial reaction of the BN and Al melt as well as by the in situ reaction. Consequently, both the BN particles and the additional AlN particles formed by the interfacial reaction led to a further strengthening in the composite, as compared to the control alloy, which was strengthened only by the AlN particles formed in situ. In addition, the flake shape of BN may have lent considerable strength, due to the high aspect ratio it demonstrates, as compared with that of a spherically shaped particle.     

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Abstract

Transmission electron microscopy (TEM) as well as corresponding analytical techniques, such as high resolution TEM (HRTEM), energy dispersive X-ray (EDX) analysis, electron energy loss spectroscopy (EELS) and elemental mapping via a Gatan imaging filter (GIF), have been used to study the complex precipitation morphology of the commercial Fe–Cr–Al based oxide dispersion strengthened (ODS) alloy PM 2000. Formation of homogeneously distributed Y–Al–O ODS particles from Y₂O₃ added to the metal powder is shown. Besides these ODS particles, a large amount of complex Y–Al–O/Al₂O₃ and Y–Al–O/TiC as well as pure Al₂O₃ inclusions with sizes significantly larger than ODS particles have been identified. A typical feature is the growth of Al₂O₃ and Y–Al–O particles on the surface of small Ti(C,N) nuclei. Some implications of the results obtained from the mechanical properties of PM 2000 steel are discussed.     

Fe2O3对氧化物弥散强化Fe12CrWTiY合金的显微组织和高温拉伸性能的影响

采用气体雾化Fe-12Cr-2.5W-0.4Ti-0.25Y合金粉末,添加1%(质量分数)的Fe2O3作为携氧剂,制备氧化物弥散强化Fe-12Cr-2.5W-0.4Ti-0.25Y高温合金。测定该合金在室温以及550~850℃的高温抗拉强度,采用X射线衍射仪分析合金的物相组成,通过扫描电镜和透射电镜观察合金的组织和拉伸断口形貌。结果表明,添加Fe2O3后,合金晶粒细化,平均晶粒尺寸由8.6μm减小到7.3μm。基体中第二相除纳米尺寸的Ti2Y2O7外,还形成20~200nm和1~10μm两种尺度的Y3Fe5O12、Cr1.3Fe0.7O3和(Cr0.88Ti0.12)2O3等多种复合氧化物,以及宽度分别为200~300nm和5~30 nm的板条组织,室温、550℃和850℃下的抗拉强度分别为1 257、1 108、和128 MPa,比未添加Fe2O3的合金分别提高50.7%,39%和30.6%。添加Fe2O3增加了氧化物的数量,提高了弥散强化效果,但微米尺度氧化物第二相的膨胀系数与基体不同,在高温下与基体的界面产生分离,优先形成裂纹源,降低高温强化效果。     

ICP-AES法测定锆英砂、电熔脱硅锆中Fe_2O_3、Al_2O_3、TiO_2、Cr_2O_3的质量分数

为测定锆英砂、电熔脱硅锆中Fe_2O_3、Al_2O_3、TiO_2、Cr_2O_3的含量,研究了用无水碳酸钠、无水碳酸钾、四硼酸钠混合熔剂熔融试样,在一定酸度下,用锫基体打底绘制工作曲线,将溶液雾化导入ICP,同时测定Fe_2O_3,Al_2O_3,TiO_2,Cr_2O_3发射光强度,计算各元素的质量分数。经实践该方法可操作性强,测量精确,可及时指导生产。     

原位反应法制备(Al_2O_3)_P/Al复合材料的研究

通过加入TiO2粉末原位制备了Al2O3颗粒增强铝基复合材料,分析了（Al2O3）p／Al材料的微观结构,测试了材料的布氏硬度和抗拉强度随所加TiO2粉未重量百分数的变化。结果表明：Mg的加入改善了颗粒与基体的浸润性,加入5％的TiO2时,复合材料具有最好的综合性能,随着Al2O3颗粒体积分数的升高,材料性能下降,Al2O3颗粒的偏聚是其主要原因。     

铁 铬 铝合金中铬的第三组元作用

 研究了Fe 10Al、Fe 5Cr 10Al和Fe 10Cr 10Al合金在1 000 ℃的氧化行为，利用电子显微镜和俄歇电子谱分析了合金表面氧化膜的形貌及组成。讨论了三元Fe Cr Al合金形成保护性氧化膜的机理，对于不发生铝的内氧化情况提出了合金中第三组元铬的作用机制：在氧化初始阶段，铬与合金中其它两组元——铁和铝一起氧化形成各自的氧化物，铬在氧化膜内最大含量的位置处于铁和铝的最大含量位置之间；铬降低了氧化膜内的铁含量，提高了初期氧化膜的保护性，从而促进选择性氧化铝膜的形成。     

纳米TiO2改性彩色涂层钢板的涂层老化性能

 采用超声预分散结合湿球磨法和分散剂复配方式对纳米TiO2进行表面改性处理,研制了均匀稳定分散的纳米TiO2分散液,表征了纳米TiO2改性后的彩涂板涂料及涂层性能。结果表明：纳米TiO2在分散液中的粒径集中分布在60~100 nm范围,可完全吸收330 nm左右的紫外线,对长波紫外线的散射吸收作用强于对短波紫外线的散射吸收。纳米TiO2改性彩涂板涂料用量为w(TiO2)=20%~30%。纳米TiO2改性处理可提高涂层柔韧性和附着力,减少涂层色差变化,降低失光率。涂层抗紫外老化性能优于同类传统彩涂板涂料涂层。     

陶瓷颗粒强韧化Fe基非晶合金复合涂层硬度的研究

通过大气等离子喷涂技术（APS）在Q235基体上制备了一种Al2O3-13%TiO2颗粒增强的Fe基非晶态合金涂层。利用光学显微镜（OM）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）、显微硬度计（MHT）和纳米压痕仪对该涂层的显微组织结构、相组成以及弹性模量等进行了研究。结果表明：采用APS喷涂技术制备的该涂层由...     

稀土氧化物粒子对钼合金粉末冶金过程及力学性能的影响

试验研究了掺杂La2O3、Y2O3、CeO2稀土氧化物颗粒对钼合金的粉末物性、烧结进程、制品的烧结致密度及压力加工丝材的室温力学性能的影响规律。试验结果表明,掺杂稀土氧化物粒子细化了钼粉的粒度,降低了松装密度和粒度分布范围,同时导致粉末团聚现象增多;稀土氧化物粒子延迟了钼合金的烧结进程,降低了烧结制品的致密度,同时细化了烧结体晶粒尺寸。稀土氧化物粒子以弥散强化和细晶强化的形式,提高了钼合金丝的室温强度。CeO2显著提高了钼合金丝的室温韧性,La2O3、Y2O3则降低了钼合金丝的室温韧性。     

氮在Fe Cr V液态高氮合金中的溶解行为

 采用MgO坩埚高频真空/加压感应炉在氮气压力04~10 MPa、温度1 570~1 640 ℃下,对加压感应熔炼Fe Cr V系高氮不锈钢进行了实验研究。结果表明,在30CaO 45Al2O3 25SiO2渣覆盖的情况下,氮在Fe 15Cr 10V、Fe 18Cr 10V、Fe 18Cr 15V和Fe 20Cr 20V液态合金中的溶解度分别为0595%、0736%、0776%和1020%,溶解度与氮分压的关系基本符合Sievert定律。渣对钢液吸氮和铝脱氧都起重要的作用,1 873 K、10 MPa氮气氛中,在30CaO 45Al2O3 25SiO2、40CaO 40Al2O3 20SiO2、40CaO 50Al2O3 10SiO2三种不同渣系作用下氮在液态Fe 18Cr 15V中的浓度分别是0776%、0849%和0884%。     

Fabrication of Al-3.7?Pct Si-0.18?Pct Mg Foam Strengthened by AlN Particle Dispersion and its Compressive Properties

Al-3.7 pct Si-0.18 pct Mg foams strengthened by AlN particle dispersion were prepared by a melt foaming method, and the effect of foaming temperature on the foaming behavior was investigated. Al-3.7 pct Si-0.18 pct Mg alloy containing AlN particles was prepared by noncompressive infiltration of Al powder compacts with molten Al alloy in nitrogen atmosphere, and it was foamed at different foaming temperatures ranging from 1023 to 1173 K. The porosity of prepared foam decreases and the pore structure becomes homogeneous with increasing foaming temperature. When the foaming temperature is higher than 1123 K, homogeneous pores are formed in the prepared ingot without using oxide particles and metallic calcium granules, which are usually used for stabilizing a foaming process. This stabilization of the foaming at high temperatures is possibly caused by Al₃Ti intermetallic compounds formed at high temperature and AlN particles. Compression tests for the prepared foams revealed that the absorbed energy per unit mass of prepared Al-3.7 pct Si-0.18 pct Mg foam is higher than those of aluminum foams strengthened by alloying or dispersion of reinforcements. It is remarkable that the oscillation in stress, which usually appears in strengthened aluminum foams, does not appear in the plateau stress region of the present Al-3.7 pct Si-0.18 pct Mg foam. The homogeneity in cell walls and pore morphology due to the stabilization of pore formation and growth by AlN and Al₃Ti particles is a possible cause of this smooth plateau stress region.     

镁砂中Fe2O3、Al2O3、P2O5、TiO2的联合测定

镁砂产品检验中,采用碱熔融法共同预处理样品,在同一母液中,联合测定铁、铝、磷、钛的含量,缩短了检测时间。通过分别控制各元素的显色酸度,各元素线性良好,测得的Fe2O3、Al2O3、P2O5、TiO2的相对标准偏差分别小于1.11%、2.78%、4.84%、5.88%。实验结果表明,方法的准确度和精密度都较高。     

加压感应熔炼Fe Cr V系高氮钢及其铝脱氧

 真空/加压感应炉以10 MPa高纯氮(体积分数≥99999%)为氮源熔炼了Fe Cr V高氮钢,分析了氮的溶解度与氮分压和铬、钒含量的关系。氮在Fe Cr V合金中的溶解服从Sievert定律,氮的溶解度随铬和钒含量的增加而增加。用Al和Fe Al(铝的质量分数为50%)合金加顶渣对Fe Cr V合金进行了脱氧实验,Fe Al合金加CaF2 CaO Al2O3(各成分比例为1∶4∶1)顶渣40 min可使Fe 20Cr 193V合金的氧的质量分数降低到0007 2%。     

不锈钢酸洗污泥碳还原过程中的物相变化及元素迁移行为

摘要：不锈钢酸洗污泥是危险废弃物,但其中含有大量有价值重金属,因而如何对其资源化利用具有重要意义。研究不锈钢污泥在碳热还原反应过程中铁、铬、镍等元素在物相间的相互作用及转化,探究铁、铬、镍元素在污泥中分布的影响因素。利用XRD分析污泥在还原过程中的矿相变化,金相显微镜、SEM EDS分析污泥还原过程中金属颗粒的形貌及其迁移行为。结果表明,在污泥升温碳还原的过程中,NiO与Fe2O3形成NiFe2O4尖晶相并被还原形成Ni-Fe金属相;FeO与Cr2O3形成FeCr2O4并与碳还原形成Fe-Cr--C金属固溶体;含碳的Ni-Fe-Cr-C等合金颗粒在高温下熔化并汇聚长大。当温度为1300℃时,渣相内部结构软化形成微熔池,使得金属液滴具备更好的迁移长大条件,非金属元素形成了以［Si-O］为主要网络结构的熔渣球团,这些网络结构由Ca2Al(AlSiO7)组成。     

Cu－Al粉末烧结合金内氧化后的组织与性能

通过测定内氧化强化型Ｃｕ－Ａｌ合金的电阻率、耐蚀、耐磨、抗压性能及ＳＥＭ、ＴＥＭ形貌观察，研究了内氧化对合金组织与性能的影响。结果表明：内氧化层中，内氧化物沿晶界呈网状生长，晶内是Ｃｕ基体加弥散分布的氧化物质点。内氧化使基体Ａｌ原子的固溶量减少，降低了合金的电阻车，增加了合金的致密度及弥散强化效果，因而使５％Ａｌ－Ｃｕ粉末烧结合金的耐蚀、耐磨及抗压性能明显提高。     

热等静压Cr3 C2/Ni3 Al复合材料的微观组织及相组成

采用热等静压技术(HIP)在1160℃、100 MPa 条件下制备出 Cr3 C2/Ni3 Al 复合材料,研究了 Cr3 C2/Ni3 Al复合材料的微观组织和相组成。结果表明,Cr3 C2初始颗粒首先溶解成 Cr 和 C 原子,并往基体中扩散;冷却过程中,溶解的Cr和C原子转化为稳定的Cr7 C3结构;由于 Ni3 Al合金中的 Fe易与 C形成稳定碳化物,促使Fe原子从基体中往Cr7 C3结构中发生上坡扩散,并取代Cr7 C3结构中的部分Cr原子形成 M7 C3(M为 Cr、Fe,余同)结构的扩散相。当Cr3 C2初始颗粒较大时,在高温过程中,Cr3 C2颗粒未能全部溶解,而未溶解的 Cr3 C2颗粒芯部在冷却过程中仍保持为Cr3 C2结构。该条件下制备的Cr3 C2/Ni3 Al复合材料主要由Cr3 C2硬芯相、M7 C3扩散相和γ′-Ni3 Al基材相组成,其中Cr3 C2硬芯相和γ′-Ni3 Al基材相通过M7 C3扩散相形成良好的扩散连接;该结构的复合材料磨损后表面Cr3 C2颗粒末发生剥落且沟槽在铬碳化物处发生中断,表现出良好的耐磨性。     

Effect of Al2O3 on Structure and Wearability of Composite Coating

Asasurface strengtheningtechnology ,thether malsprayhasevolvedfromearlynormal protectivecoatingtocurrentfunctionalcoating .Thedevelopmentofcompositepowderisanimportantbreakthroughinthisfield .Particularly ,thenewlydevelopedmetal basedceramiccoatings ,such…     

合金元素Mg、Cr对5052铝合金性能和组织的影响

采用扫描电镜和能谱分析等检测手段,对不同Mg、Cr含量的5052铝合金主要物相的形貌、分布进行观察和分析,并对合金再结晶退火板材的性能比较分析。结果表明：合金中的主要物相为β（Al Mg）相和Al Cr相,大多呈不规则的块、条8 5 7状或粗骨骼状。Al Cr相尺寸和分布的数量随Cr含量升高而增大。合金元素Mg是5052合金的主要强化元素,合金元素Cr是补7充强化元素;在Mg含量处于合金范围的下限时,增加等量的Cr,合金的强化效果比增加等量的Mg好。     

铝质量分数对FeCrAl合金多孔材料性能的影响

铁铬铝（FeCrAl）合金是一种典型的耐热合金,由其开发而成的耐高温金属多孔材料已经在煤气净化、高温催化剂载体等方面获得了广泛的应用。在反应合成制备FeCrAl合金多孔材料过程中,铝质量分数在多孔材料孔结构、力学性能及抗氧化性能等方面具有重要影响。本文在Fe?20%Cr合金（质量分数）基础上添加不同质量分数的铝粉（0～20%）,以铁、铝、铬元素混合粉为原料,通过反应合成方法制备了一系列FeCrAl合金多孔材料（Fe?20Cr?xAl,x=0～20%,质量分数）,研究了铝质量分数对Fe?20Cr?xAl多孔材料物相、孔结构、力学性能以及抗氧化性能的影响。结果表明,添加5%铝（质量分数）的Fe?20Cr?xAl多孔材料具有较优的孔隙度和力学性能,同时在600～800 ℃高温氧化实验中表现出最优的抗氧化性能和力学性能稳定性。     

快凝AlCrYZr合金挤压成形与组织性能

添加Y合金化、配制AlCrYZr合金,采用金相、X射线衍射、透射电镜、扫描电镜、力学拉伸实验等研究手段,研究了快速凝固AlCrYZr合金粉末挤压成形工艺以及其对组织性能的影响。结果表明,实验合金中主要第二相为Al₂₀Cr₂Y(立方,a=1.44nm)和Al₃Zr;挤压成形时提高挤压比,降低挤压温度,有利于改善粉体结合状况,得到Ll₂Al₃Zr质点,同时细化Al₂₀Cr₂Y质点,使合金获得动态回复组织,从而使合金具有良好的低温、高温强度和塑性。