粉末增塑挤压制备Al2O3/430L复合型蜂窝材料的组织与性能

为制备性能优良的Al_2O_3/430L复合型蜂窝载体材料,本文以430L不锈钢合金粉末、Al_2O_3粉末、粘结剂为原料,采用粉末增塑挤压技术挤压成形,并在1 100℃真空中烧结2 h获得Al_2O_3/430L复合型蜂窝材料.借助SEM、XRD及万能试验机,研究了添加Al_2O_3对Al_2O_3/430L复合型蜂窝材料的组织与性能的影响.研究表明:金属粉末颗粒在烧结过程中结合形成的基体组织为α-Fe(Cr),在基体晶粒间孔隙处和表面弥散分布着Al_2O_3颗粒.添加少量的Al_2O_3可提高烧结密度,制件表面光滑.随着Al_2O_3添加量增加,蜂窝材料表面负载催化涂层的能力增强;抗压强度随Al_2O_3添加量的增加先升高后降低,在Al_2O_3含量为2.5wt.%时,最大抗压强度达27 MPa.添加2.5wt.%Al_2O_3所制备的Al_2O_3/430L复合型蜂窝材料力学性能最佳、表面负载催化涂层的能力优良.     

激光引燃合成Fe-Al掺杂Cr粉合金的组织及性能

采用激光引燃自蔓延高温合成的方法,在Fe70Al30粉末中分别添加质量分数为0%、5%、10%、15%和20%的Cr粉,压制成坯,制备出Fe-Al复合材料。利用X射线衍射仪、金相显微镜等表征手段及孔隙率、硬度、磨损和腐蚀性能等性能测试方法,得到了不同Cr含量对烧结合金显微组织及性能的影响规律。结果表明:烧结合金主要物相为Fe_3Al、FeAl、AlCrFe_2、Al_8Cr_5、Al_2O_3和Cr_2O_3。随着Cr含量增加,合金的孔隙率先减小再增大,最小值为12.58%。当Cr含量为10%时,合金显微硬度最高,达到876.4HV,磨损率最低为0.65g/mm~2,自腐蚀电流密度最小为20.32mA/cm~2,耐腐蚀性能最好。     

挤压316L金属蜂窝的烧结及其组织性能研究

以金属粉末、粘结剂为原料,经炼料制成膏状挤压料,通过挤压模成型为蜂窝状,再经高温烧结制备成316L不锈钢蜂窝.研究了烧结气氛、烧结温度对蜂窝烧结组织结构的影响,并对烧结后的蜂窝进行力学性能测试.结果表明,在氢气中烧结的316L蜂窝组织,金属颗粒间形成烧结颈,呈网状连接在一起,并随温度升高颗粒合并长大成晶粒,基体组织为Fe-Cr-Ni-C(γ-Fe)固溶体,第二相球形颗粒为富含硅的低熔点化合物;在真空中烧结,金属颗粒表面形成氧化物Fe2Cr4O4、Cr2O3,以及SiO2,大量的表面氧化物阻碍了金属粉末颗粒的结合,直接影响烧结蜂窝的强度,致使烧结蜂窝强度远低于氢气中烧结的蜂窝.在氢气中烧结的316L金属蜂窝,其径向抗压强度可达40～50 MPa,远高于目前广泛应用的陶瓷蜂窝载体,是作为载体材料的一种理想选择.     

PS45/CuAl8伪合金复合涂层高温循环氧化行为

采用超音速活性电弧喷涂技术在Q235钢基体表面制备PS45/CuAl8伪合金复合涂层,将该涂层在600℃和800℃进行循环氧化,采用XRD、SEM和精密天不等手段对涂层的显微结构进行表征,研究了涂层的循环氧化性能。结果表明:PS45/CuAl8伪合金复合涂层主要由Al_2O_3、Cr_2O_3、α-Cu和γ-Ni固溶体组成,组织致密,颗粒成扁平状且扁平化程度高、分布均匀。经高温循环氧化后在涂层表面形成了一层致密的Al_2O_3+Cr_2O_3+Ni(Al,Cr)_2O_4薄膜,避免了Al_2O_3薄膜的剥落,从而降低了涂层氧化速率,提高了基体的抗高温循环氧化性能。     

Fe/Al2O3陶瓷梯度涂层的结合性能

以FeAl和FeAlNi两种混合粉体作为底层材料,将喷涂法和溶胶-凝胶相结合制备了Fe/Al_2O_3梯度涂层,分析了其与钢基表面的结合性能。结果表明:当烧结温度为1220℃时,两种过渡底层Fe/Al_2O_3陶瓷梯度涂层的界面结合强度分别达到21.2 MPa和25.3 MPa,涂层的物相组成分别为α-Al_2O_3、AlFeO_3、Al_2Fe_2O_6、Al_3Fe_5O_(12)和α-Al_2O_3、AlFeO_3、NiFe_2O_4等。与FeAl相比,以FeAlNi作为过渡底层制备的Fe/Al_2O_3梯度涂层材料结构致密度高、没有明显孔洞与宏观界面,且有树枝状组织生成,有利于涂层结合性能的提高。     

机械合金化后注射成形制备Cu/Al2O3复合材料的显微组织与力学性能

采用机械合金化后注射成形制备10%(体积分数,下同)Cu/Al_2O_3复合材料,研究机械合金化时间、烧结温度对复合材料显微组织和性能的影响,并分析复合材料的增韧机理。结果表明:通过机械合金化10h后注射成形、脱脂、1550℃烧结工艺制备的10%Cu/Al_2O_3复合材料具有良好的抗弯强度和断裂韧度,分别为532MPa和4.97MPa·m^1/2;烧结温度低于1550℃导致原子在固态下扩散能力不足,烧结温度高于1550℃则使颗粒边界移动速率大于孔隙逸出速率,二者都造成复合材料孔隙率增加,而导致材料的强度和韧度下降;机械合金化时间延长使复合材料晶粒细化、Cu与Al_2O_3之间的结合强度提高,材料强度和硬度提高,但断裂韧度下降;Cu粉末弥散分布于Al_2O_3基体中,抑制烧结过程中Al_2O_3晶粒粗化,且使裂纹在扩展过程中遇到延性的Cu产生裂纹桥联和偏转,提高材料的韧度。     

激光诱导自蔓延烧结Al80-(Fe-Cr)20合金组织及性能研究

将铝粉和高碳铬铁粉末按80∶20原子比混合压制成坯,并对压坯进行激光诱导自蔓延烧结,利用金相显微镜、X射线衍射仪等设备,表征烧结合金显微组织及物相结构;采用硬度计、磨粒磨损机及电化学腐蚀仪等,表征烧结合金宏观性能。研究合金表层区、中层区和底层区组织及性能变化规律。结果表明:烧结合金物相主要有α-Al、Fe_2AlCr、Al_(13)Cr_2、Al_(13)Fe_4及Al_2O_3等,且烧结合金中层区富Al相Al_(13)Cr_2和Al_(13)Fe_4的含量最多,α-Al相含量最少。烧结合金中层区显微组织最细小均匀;硬度值最高,为817.5HV;磨损率最低,为0.08mg/mm~2;耐蚀性能最好,钝化电流最小,为115.8μA/cm~2。     

TiO_2对挤压铸造Al_2O_(3p)/钢基复合材料组织与力学性能的影响

在预制坯中加入TiO_2粉末,利用挤压铸造法制备Al_2O_3颗粒增强1065钢基复合材料,研究TiO_2对复合材料组织与力学性能的影响。结果表明:TiO_2使基体与Al_2O_3的结合界面形成了TiO_2、Al_2TiO_5界面层;添加TiO_2的复合材料硬度和三点弯曲强度分别为39.0HRC,743.94MPa,比未添加TiO_2的复合材料分别提高了10.0%,26.4%;断口扫描表明,添加TiO_2的复合材料界面结合良好无裂纹,Al_2O_3颗粒表现为穿晶断裂。说明加入的TiO_2改善了Al_2O_(3p)/钢基复合材料界面结合强度,提高了复合材料力学性能。     

制备工艺对原位合成(Al_2O_3+Si)_p/Al复合材料显微组织影响及体系分析

以Al-SiO_2为反应体系,通过烧结反应原位合成了(Al_2O_3+Si)_p/Al复合材料。研究了第二相含量、烧结时间以及热锻压等工艺对(Al_2O_3+Si)_p/Al复合材料的第二相形貌、尺寸及分布的影响,探讨了原位合成(Al_2O_3+Si)_p/Al复合材料的生成机制。研究表明,Si相含量随着第二相含量的增多而增多且与Al和Al_2O_3相界限相对明显;随着烧结时间的延长,Si相面积相对减小,Al_2O_3相的数量相对增加;锻压后,Si相和Al_2O_3分布更加均匀且尺寸减小。复合材料在液相烧结的过程中,高温下的液相粘性流动以及在原位反应时发生的颗粒重排与固相的溶解和沉淀对材料的致密化产生了较大的作用,当烧结温度达到1000℃时,Al_2O_3颗粒数量、分布情况都得到明显地改善。     

CoO和Cr_2O_3复合掺杂对金属陶瓷的致密化及抗高温氧化性的影响

采用粉末冶金技术制备添加CoO和Cr_2O_3复合掺杂剂的17Ni/(10NiO-NiFe_2O_4)金属陶瓷,使用XRD、SEM等检测分析了不同含量、不同比例的复合掺杂剂对金属陶瓷材料的物相组成、组织形貌、烧结致密化和抗高温氧化性的影响。结果表明:CoO和Cr_2O_3复合掺杂后固溶到陶瓷基体相NiFe_2O_4晶格中促进了烧结致密化;CoO和Cr_2O_3复合掺杂有利于生成致密氧化层,有效抑制了氧气向材料内部侵蚀和金属Ni向外迁徙,提高了试样的抗高温氧化性能;当CoO和Cr_2O_3复合掺杂量为1%(质量分数)(m(CoO):m(Cr_2O_3)=2:1)时,抗高温氧化性最好,单位面积氧化增重量比未掺杂的试样降低了56.28%。     

原位生成Al2O3/Cu复合材料的新工艺

采用一种新型工艺制备了Al₂O₃/Cu复合材料。高能球磨制备亚稳态的Cu-0.8 wt% Al合金粉,再将Cu₂O粉与其一起进行高能球磨,然后将复合粉末压坯在真空炉中同时进行氧化和烧结。该工艺省略了还原剩余Cu₂O的环节,氧化和烧结时间仅为1 h。生成的Al₂O₃的粒径约250nm,颗粒间距约500 nm,均匀弥散分布;该材料冷加工后性能接近SCM制品性能。该配比的Al₂O₃/Cu复合材料的热稳定性良好,在800℃下循环冷淬20次无裂纹;软化温度为700℃。     

Preparation and mechanical properties of Al2O3 reinforced by submicrometer Co particles

Al2O3/Co composites were fabricated by vacuum hot-pressing a mixture of -Al2O3 powder and a fine cobalt powder. Submicron-sized cobalt particles were uniformly dispersed into the Al2O3 matrix, and the dispersed type was a more inter-/intragranular one with increases of cobalt content up to 40 wt% Co addition. The growth of cobalt particles occurred with increasing cobalt content. At 50 wt% Co addition, however, the growth as well as coalescence of cobalt particles occurred. The phases formed in the Al2O3/Co composites were f-Co(fcc), h-Co(hcp), -Al2O3, and a small amount of graphite. Significant improvements in bending strength (from 341 to 771 MPa) and fracture toughness (from 3.7 to 6.7 MPam1/2) of the Al2O3/40 wt% Co(23 vol% Co) composite compared to monolithic Al2O3 were achieved by dispersing submicron-sized Co particles into the Al2O3 matrix. The improvement in bending strength was attributed to the compressive thermal residual stress in the matrix Al2O3 induced by the mismatch of the coefficients of thermal expansion (CTE) between the matrix Al2O3 grains and cobalt particles during cooling from hot-pressing temperature. The fracture toughness of the composite was enhanced by crack bridging, crack deflection, and compressive thermal residual stress.     

陶瓷颗粒增强镍合金复合涂层冲蚀磨损的试验研究

以WC,ZrO₂,Cr₂O₃和Al₂O₃陶瓷颗粒为增强相,镍合金粉末为基体,运用等离子喷涂技术制备四种陶瓷/镍合金复合涂层。采用冲蚀磨损试验机和正交试验方法,进行陶瓷颗粒相浓度、磨粒粒度、冲蚀角和速度对陶瓷颗粒/镍合金复合涂层抗冲蚀磨损性能影响的试验研究。采用表面形状测量仪对陶瓷颗粒/镍合金复合涂层磨损表面形貌进行测量和分析。试验结果得到WC,ZrO₂,Cr₂O₃和Al₂O₃四种陶瓷颗粒/镍合金复合涂层冲蚀磨损率的经验关联式。     

Novel Ti based metal matrix composites reinforced with Al–Cr–Fe quasicrystals approximants

In this work, Ti/Al–Cr–Fe metal matrix composites were fabricated with Ti as matrix and Al–Cr–Fe quasicrystal approximants as reinforcements using spark plasma sintering. In all samples a Ti₃Al ring forms around each Al–Cr–Fe particle as a bonding layer between Ti and Al–Cr–Fe particles. In the sample sintered with a holding time of 5 min, there are only TiAl regions present at the Ti₃Al/Al–Cr–Fe interface. However, in the samples sintered with a holding time of 10, 15 or 20 min, TiAl, Ti(Al,Cr)₂ and L1₂ regions were detected at the Ti₃Al/Al–Cr–Fe interface. The addition of Al–Cr–Fe particles into the Ti matrix was found to improve the mircrohardness to 460 HV and increase the wear resistance by more than 50%.     

铝合金表面激光熔敷铜基复合材料涂层的工艺和组织

在ＺＬ１０４铝合金表面激光熔敷铜基混合粉末（ｗ（Ｂ）／％：２０Ｎｉ,８．０Ｃｏ５．０Ｆｅ,６．８Ｍｏ,１．５Ｃｒ,３．５Ｓｉ,０．２ＲＥ,其余为Ｃｕ）,制备了高硬度铜基复合材料涂层。研究发现,熔敷层稀释率随光宽度和扫描速度增大而减小,随激光束产大而显著增大;     

Cu对粉末冶金Fe3Al基复合材料性能的影响

研究了Cu含量对粉末冶金Fe3Al基复合材料的烧结性能和力学性能的影响,分析了施加载荷和改变转速对加入不同量铜粉末冶金Fe3Al基复合材料的摩擦磨损性能的影响,并借助电子显微镜和能谱分析了不同铜含量Fe3Al基复合材料的磨损机理.结果表明:加入12%的Gu可使Fe3Al基复合材料具有良好的烧结性能和力学性能;载荷和转速对复合材料的磨损形式受铜的加入量的影响;铜的加入影响复合材料的磨损形式和磨损机理,当含铜量较少时,复合材料以磨粒磨损为主,随加入铜的量的增多,其磨损形式变为磨粒磨损和轻微的粘着磨损形式,加入大量铜时,则以粘着磨损为主.     

Al2O3/6-6-3青铜复合材料的制备及性能

采用粉末冶金法制备出Al₂O₃/青铜复合材料, 研究了烧结温度、Al₂O₃颗粒尺寸、含量及表面状态对复合材料性能的影响。结果表明, 采用二次压制与烧结工艺制备的复合材料的组织致密,Al₂O₃颗粒分布均匀, 综合性能优于6-6-3青铜材料。Al₂O₃颗粒的化学包覆处理可以使复合材料的性能进一步提高。      

Processing of Ceramic Based Nanocomposite Using α-Al2O3 Powder and FeCl2 Solution as Starting Materials

Alumina-iron nanocomposite powders were prepared by a two-step process. In the first step, α-Al2O3-FeCl2 powder mixture was formed by mixing α-Al2O3 powders with FeCl2 solution followed by drying. In the second step, the FeCl2 in the dry power mixture was selectively reduced to iron particles. A reduction temperature of 750℃ for 15 min in dry H2 was chosen based on the thermodynamic calculations. The concentration of iron in FeCl2 solution was calculated to be 20 vol. pct in the final composite. Two techniques were used to produce composite bulk materials. The Al2O3 nanocomposite powders were divided to two batches. The first batch of the produced mixture was hot pressed at 1400℃ and 27 MPa for 30 min in a graphite die. To study the effect of oxygen on the Al2O3/Fe interface bonding and mechanical properties of the composite,the second batch was heat treated in air at 700℃ for 20 min to partially oxidize the iron particles before hot pressing. Characterization of the composites was undertaken by conventional density measurements, X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe micro analysis (EPMA). The suggested processing route (mixing, reduction and hot pressing)produces ceramic-metal nanocomposite much tougher than the pure Al2O3. The fracture strength of the produced Al2O3/Fe nanocomposite is nearly twice that of the pure Al2O3. The presence of spinel phase,FeAl2O4, as thick layer around the Fe particles in the Al2O3 matrix has a detrimental effect on interfacial bonding between Fe and Al2O3 and the fracture properties of the composite.     

Processing of Ceramic Based Nanocomposite Using α-Al2O3 Powder and FeCl2 Solution as Starting Materials

Alumina-iron nanocomposite powders were prepared by a two-step process. In the first step, α-Al2O3-FeCl2 powder mixture was formed by mixing α-Al2O3 powders with FeCl2 solution followed by drying. In the second step, the FeCl2 in the dry power mixture was selectively reduced to iron particles. A reduction temperature of 750℃ for 15 min in dry H2 was chosen based on the thermodynamic calculations. The concentration of iron in FeCl2 solution was calculated to be 20 vol. pct in the final composite. Two techniques were used to produce composite bulk materials. The Al2O3 nanocomposite powders were divided to two batches. The first batch of the produced mixture was hot pressed at 1400℃ and 27 MPa for 30 min in a graphite die. To study the effect of oxygen on the Al2O3/Fe interface bonding and mechanical properties of the composite, the second batch was heat treated in air at 700℃ for 20 min to partially oxidize the iron particles before hot pressing. Characterization of the composites was undertaken by conventional density measurements, X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electron probe micro analysis （EPMA）. The suggested processing route （mixing, reduction and hot pressing） produces ceramic-metal nanocomposite much tougher than the pure Al2O3. The fracture strength of the produced Al2O3/Fe nanocomposite is nearly twice that of the pure Al2O3. The presence of spinel phase, FeAl204, as thick layer around the Fe particles in the Al2O3 matrix has a detrimental effect on interfacial bonding between Fe and AI203 and the fracture properties of the composite.