《搅拌摩擦加工制备GNPs/Al复合材料的微观结构与力学性能》

本文以纯铝为基体，利用搅拌摩擦加工(FSP)制备GNPs/Al复合材料，研究了复合材料基体组织、增强相与界面等微观结构与力学性能，探讨了其增强机理。结果表明，添加GNPs并经FSP后复合材料基体晶粒得到明显细化且晶界由小角度为主转变为大角度为主；FSP制备过程致使GNPs片层一定程度剥离的同时，较大片径的GNPs被破碎而形成众多边缘缺陷，使其易发生Al-C原子扩散，结果在GNPs边缘与基体形成界面过渡；GNPs加入量约1.8vol%时，复合材料的屈服强度和抗拉强度达到72MPa和147MPa，较同等条件FSP的基体分别提高了89.5%和79.3%，理论计算界面载荷传递、Orowan和细晶强化依次是复合材料的主要增强机制；随着GNPs加入量的增加，复合材料屈服强度实验值与理论值的增长趋势一致，且偏差也略有提高，但可能因GNPs在复合材料中的杂乱排布，界面载荷传递强化不能充分发挥，实际的复合材料屈服强度与理论值尚有差距。     

等离子烧结Al35Ti15Cr20Mn20Cu10/6061Al复合材料的组织与性能

采用机械合金化与放电等离子烧结工艺制备了体积分数为5%的Al35Ti15Cr20Mn20Cu10增强6061Al复合材料,重点研究了烧结温度对轻质高熵合金增强铝基复合材料微观组织及力学性能的影响。当烧结温度为540℃时,复合材料的致密度最大为98.6%。此时复合材料基体与增强体之间产生明显过渡层,界面结合以扩散结合为主。随着烧结温度升高,复合材料的屈服强度出现先上升后下降的趋势。当烧结温度为540℃时,复合材料的屈服强度达到186MPa,相比基体的屈服强度提升了约75%,复合材料的屈服强度接近Iso-strain模型的计算值。     

Er、Zr及热处理对高锌铝合金组织和力学性能的影响

本文以Al-30Zn-3Cu-2.5Si高锌铝基合金为研究对象,探究稀土元素Er、Zr对铸态及热处理态合金组织和力学性能的影响,并分析和探讨了其作用机理。研究结果表明,当添加0.10 wt % Er和0.10 wt % Zr元素后能够明显的细化合金晶粒,平均晶粒尺寸由74.28 μm减小至60.01 μm,且α-Al晶粒转变为细小的等轴晶。稀土元素Er、Zr的添加会在合金内部形成Al3（Er,Zr）细小的粒子并能够起到钉扎位错的作用,从而提高合金的力学性能。添加Er、Zr后,铸态合金的抗拉强度由未添加稀土元素的323.01 MPa提高到了358.29 MPa,提升了10.93 %;屈服强度由309.33 MPa提高到了315.00 MPa,提升了1.83 %;延伸率基本未发生变化。合金经固溶时效热处理强化后,添加稀土元素合金的抗拉强度为449.48 MPa,屈服强度为408.51 MPa,比铸态合金分别提高了25.45 %、29.68 %。粗大的第二相存在于晶界处,导致合金的延伸率仍较差。     

碳纳米管-石墨烯增强AZ31镁基复合材料实验研究

采用粉末冶金法结合热挤压制备了不同质量分数的碳纳米管(CNTs)和石墨烯(GNPs)增强AZ31镁基复合材料。分析了CNTs和GNPs对AZ31镁合金及其复合材料组织、力学性能及物理性能的影响。结果表明:CNTs和GNPs的加入可以细化晶粒尺寸,并且可以提高材料的硬度、拉伸和压缩屈服强度。当同时添加0.5wt%CNTs和0.5wt%GNPs时,复合材料的抗拉强度和抗压强度分别可达到:309 MPa和399 MPa,复合材料的硬度相比基体提升了17.1%。但是复合材料的塑性和导电性相比基体材料降低。     

TiB2/Al-Si-Mg-Er复合材料的组织与性能

采用重熔稀释法制备了Al-7Si-0.5Mg-0.1Er和0.5TiB₂/Al-7Si-0.5Mg-0.1Er合金,研究了TiB₂颗粒增强Al-Si-Mg-Er复合材料的组织性能。结果表明,复合材料铸态组织主要由α-Al基体、共晶Si相和TiB₂颗粒组成。TiB₂粒子的加入使Al-7Si-0.5Mg-0.1Er合金二次枝晶间距减小了7.1 μm。抗拉强度达到217.53 MPa,较Al-7Si-0.5Mg-0.1Er合金提升了12.1 %。TiB₂/Al-Si-Mg-Er复合材料的最优T6热处理工艺为530 ℃×12 h固溶+160 ℃×7 h时效,经该工艺处理后,TiB₂/Al-Si-Mg-Er复合材料抗拉强度达到319.49 MPa,相比热处理前提高了46.9%,相比Al-7Si-0.5Mg-0.1Er合金提高了5.9%;屈服强度达到266.75 MPa,相比热处理前提高了106.4%,相比Al-7Si-0.5Mg-0.1Er合金提高了14.9%。复合材料抗拉强度的提升主要源于TiB₂颗粒加入后产生的晶粒细化、变质和热处理强化。     

机械搅拌制备SiC_p/AlSi7Mg2复合材料性能研究

采用机械搅拌制备SiC_p/Al Si7Mg2复合材料,对比不同体积分数(3.5vol.%、10vol.%、20vol.%和25vol.%)的Si C颗粒对复合材料力学性能的影响,当α-Si C颗粒的粒径为20μm时,20vol.%SiC_p/Al Si7Mg2复合材料铸态力学性能较高,其硬度达到HB 76.3。将20vol.%SiC_p/Al Si7Mg2复合材料做538℃/10 h+160℃/6 h热处理以后进行拉伸试验,复合材料抗拉强度311 MPa,屈服强度290 MPa,硬度HB 142,弹性模量90 GPa。进一步研究复合材料可重熔性,20vol.%SiC_p/Al Si7Mg2复合材料经过一次重熔后相比原铸态复合材料屈服强度提高了14.6%,硬度提高了8.8%,继续对熔体进行不同时间的静置和二次重熔,复合材料力学性能下降。     

两步烧结法制备SiCp/Al纳米复合材料

为了提高纳米SiC颗粒增强的Al基复合材料(MMC)的致密度,在传统粉末冶金热压烧结方法的基础上增加了一步中温(230℃)、高压(850 MPa)成型处理(以下称预烧结成型)工艺,经最终烧结处理后的5ψ/%,10ψ/%SiCp/Al MMC的致密度达到了99.9%,20ψ/%SiCp/Al MMC的致密度也达到了96.39%.20ψ/%SiCp/Al MMC的屈服强度达到了625MPa,硬度也有显著的提高.对SiCp/Al MMC的制粉、预烧结成型、烧结处理等制备过程进行了详细研究,从工艺原理上分析了其可行性,最后对其力学性能进行了简单讨论.     

聚碳硅烷原位自生增强钛基复合材料的组织及性能研究

以低氧氢化脱氢钛粉和陶瓷先驱体聚合物聚碳硅烷(PCS)为原料,通过粉末冶金工艺原位自生制备高强高塑钛基复合材料,探究了PCS的引入对钛基复合材料的控氧效果、烧结致密化过程、基体显微组织和力学性能的影响规律。研究表明：采用湿混包覆工艺可以将PCS包覆于Ti粉表面,有效控制材料制备过程中的氧增,其中制备的Ti-1.0 wt.% PCS复合材料的氧含量为0.21~0.24 wt.%,显著低于未经处理的CP-Ti样品(0.36~0.41 wt.%)。在烧结过程中,PCS受热分解并与Ti基体原位反应生成TiC颗粒,弥散分布在基体中,而Si元素则固溶于Ti基体。PCS的引入对Ti基体的性能具有明显的改善作用,经1200 °C/2 h烧结制备的Ti-1.0 wt.% PCS复合材料致密度达到98.4%,洛氏硬度为47.3 HRC,屈服强度为544 MPa,抗拉强度为650 MPa,延伸率为14.5%,其综合性能指标显著优于CP-Ti样品。     

单级固溶处理喷射沉积7090/SiCp的组织与性能

研究了固溶处理工艺对喷射沉积7090/SiCp铝基复合材料的显微组织和力学性能的影响.结果表明挤压态复合材料的基体合金中存在大量的第二相粒子;固溶处理后,晶粒发生不同程度的长大.在T6条件下,材料经470℃单级固溶处理后的布氏硬度值达到248 HB.对试样采用470℃×0.5 h(水淬)热处理,其抗拉强度可达到601.46 MPa,屈服强度为421.16 MPa.     

基于SPS-热轧法钨颗粒增强铝基复合材料微观组织及力学性能研究

本文采用放电等离子烧结→热轧制方法制备了颗粒含量为1～7%的钨颗粒增强铝基复合材料,研究钨颗粒含量对复合材料的微观组织、机械性能和导电性能的影响。研究结果表明：钨颗粒均匀的分布在基体铝合金当中,W/Al界面之间达到了冶金结合,在界面处存在元素扩散和WAl12金属间化合物的生成。在复合材料中,随着钨颗粒含量的增加,复合材料的致密度和韧性降低而拉伸强度呈现先升高后降低的趋势。其中,1和3 vol.% W/Al复合材料的拉伸强度和断裂韧性分别为192.85 MPa (16.84%) 和315.18 MPa (11.93%)。此外,W/Al复合材料具有良好的电导率,W颗粒的含量对复合材料的影响较小。     

石墨烯纳米片增强铝基复合材料的制备与性能

采用高能球磨、放电等离子烧结以及热挤压工艺制备含量为5.0％(体积分数)的石墨烯增强铝基复合材料.分别采用X射线光电子能谱、透射电镜及拉伸试验研究挤压态复合材料的显微组织与力学性能,发现5.0％(体积分数)的石墨烯分散在铝晶界上,并且未与铝基体发生界面反应.最终,挤压态复合材料的屈服强度和抗拉强度高达462 MPa和4...     

Copper-Coated Graphene Nanoplatelets-Reinforced Al–Si Alloy Matrix Composites Fabricated by Stir Casting Method

In this study,Cu nanoparticles-coated graphene nanoplatelets(Cu-NPs@GNPs) were synthesized by a simple in situ method with the assistance of Na Cl templates and used for reinforcing Al–10 Si composites through stir casting process.The experimental results showed that the coating of Cu-NPs on the GNPs could compromise the density mismatch between GNPs and metal matrix and eff ectively hinder the float of GNPs during stirring.The reaction of Cu-NPs and Al matrix could protect the structural integrity of GNPs as well as improve the interfacial wettability between GNPs and the matrix,thus promoting the uniform dispersion of GNPs in the composites.As a result,the as-prepared 0.5 wt% Cu-NPs@GNPs/Al–10 Si composite exhibited a tensile strength of 251 MPa(45% higher than the Al–10 Si) with a total elongation of 15%.The strengthening eff ects were mainly attributed to the following three reasons:Firstly,the Cu-NPs coating improved the interfacial bonding between GNPs and Al matrix which promoted the load transfer from the matrix to the GNPs.Secondly,the nanoscale Al 2 Cu formed by the reaction of Cu-NPs and Al matrix played a role in precipitation strengthening.Thirdly,GNPs refined the silicon phases and improved the monolithic performances of the composites.     

Effect of Spark-Plasma-Sintering Conditions on Tensile Properties of Aluminum Matrix Composites Reinforced with Multiwalled Carbon Nanotubes (MWCNTs)

In this study, aluminum (Al) matrix composites containing 2 wt.% multiwalled carbon nanotubes (CNTs) were fabricated by powder metallurgy using high-energy ball milling (HEBM), spark plasma sintering (SPS), and subsequent hot extrusion. The effect of SPS conditions on the tensile properties of CNT/Al composites was investigated. The results showed that composites with well-dispersed CNTs and nearly full-density CNT/Al can be obtained. During HEBM, CNTs were shortened, inserted into welded Al powder particles, bonded to Al, and still stable without CNT-Al reaction. After consolidation, Al₄C₃ phases formed in composites under different sintering conditions. With the increase of sintering temperature and holding time, the strength decreased. Conversely, the ductility and toughness noticeably increased. As a result, a good balance between strength (367 MPa in ultimate tensile strength) and ductility (13% in elongation) was achieved in the as-extruded CNT/Al composite sintered at 630°C with a holding time of 300 min.     

Microstructure and mechanical properties of ADC12 composites reinforced with graphene nanoplates prepared by ultrasonic assisted casting

Microstructure and mechanical properties of ADC12 composites reinforced with graphene nanoplates (GNPs) prepared by high-intensity ultrasonic assisted casting were investigated. The results indicated that high-intensity ultrasound can promote the uniform distribution of GNPs in the melt, resulting in refining the α(Al) phase and Si phase. The optimal addition of GNPs was 0.9 wt.%, and the optimal ultrasonic time was 12 min. The tensile strength, the yield strength and the hardness of the composite produced under the optimal parameters were 256.8 MPa, 210.6 MPa and HV 126.0, respectively, which increased by 30.5%, 42.7%, and 34.8% compared with those of the matrix, respectively. After adding the GNPs, the fracture mechanism gradually turned from a brittle fracture to a ductile fracture. The good interface and distribution allowed GNPs to play the role in fine grain strengthening, dislocation strengthening and load transfer strengthening effectively.     

低压压制和真空烧结制备银-石墨烯复合材料的致密化行为

为阐明低压压制成形和真空烧结制备的银-石墨烯复合材料的致密化行为,通过24 h机械球磨制得石墨烯含量0.5wt.%至2.0wt.%的银-石墨烯复合粉末,随后进行低压双向压制和真空烧结。通过测量复合材料压制后和烧结后的密度,研究了不同成形压力和不同烧结温度工艺条件下复合材料的成形能力和烧结能力。试验结果表明：银-石墨烯粉末的压制数据符合川北公夫方程。致密化系数(K)值随石墨烯含量的增加而增大,表明复合粉末抗塑性变形能力增大。银-0.5wt.%石墨烯复合材料具有最佳的烧结性能。石墨烯含量1.5wt.%的复合材料具有较好增强效果的力学性能,其抗拉强度达到252 MPa。     

Microstructural and mechanical evaluation of Al-TiB2 nanostructured composite fabricated by mechanical alloying

Production of bulk Al-TiB₂ nanocomposite from mechanically alloyed powder was studied. Al-20 wt.% TiB₂ metal matrix nanocomposite powder was obtained by mechanical alloying (MA) of pure Ti, B and Al powder mixture. A double step process was used to prevent the formation of undesirable phases like Al₃Ti intermetallic compound, which has been described in our previous papers. The resultant powder was consolidated by spark plasma sintering (SPS) followed up by hot extrusion. The structural characteristics of powder particles and sintered samples were studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hardness measurements were conducted on the cross section of powder particles and sintered sample and the tensile behavior of extruded samples was evaluated. The results showed that the prepared Al-20 wt.% TiB₂ nanocomposite has good thermal stability against grain growth and particle coarsening. Extruded Al-20 wt.% TiB₂ showed a hardness value of 180 VHN and yield and tensile strength of 480 and 540 MPa, respectively, which are much higher than those reported for similar composites made by other processes.     

Sintering Behavior of Elemental Powders with FeB Addition in the Composition of Martensitic Stainless steel

The effect of sintering additive for the development of high-strength martensitic stainless steel from elemental powders was studied. The sintering parameters investigated were: sintering temperature, sintering time, and wt.% of FeB. In vacuum sintering, effective sintering took place between 1300 and 1350 °C with 1-1.5 wt.% FeB addition. The maximum sintered density and ultimate tensile strength (UTS) were achieved after sintering at 1350°C for 60 min with 1 wt.% FeB. Secondary pores were observed in samples containing more than 1.5 wt.% FeB sintered at 1350 °C for 60 min. More than 1.5 wt.% FeB content and temperature above 1350°C caused slumping of the specimens. Maximum UTS of 505 MPa was achieved with 1 wt.% FeB content. Above 0.5 wt.% FeB content, maximum increase in density was observed. Fracture morphologies of the sintered samples are reported.     

金属注射成形Ti-6Al-4V烧结坯的力学性能与烧结时间关系

研究了在1260℃烧结时,烧结时间对Ti-6Al-4V烧结坯力学性能的影响.结果表明平均晶粒尺寸为45 μm的氢化-脱氢粉末样品在1 260C烧结3 h～6 h,其相对密度为95.6%～96.7%、拉伸强度648 MPa～686 MPa、屈服强度526 MPa～615 MPa,但延伸率仅小于4%.90%气雾化(晶粒尺寸为32.5 μm)和10%氢化-脱氢混合粉末样品在1 260℃烧结2 h～6 h,其相对密度大于95%、拉伸强度800 MPa～848 MPa、屈服强度712 MPa～762 MPa、延伸率7.4%～9.5%.混合粉末样品的力学性能几乎达到美国ASTM粉末冶金的标准.