氮对Ti-6Al合金的铸态组织与性能的影响

采用熔铸工艺制备了w(N)=0.045~0.27%的原位自生氮化物增强钛铝基复合材料.分析测试了该材料的铸态组织和合金的力学性能.研究结果表明:在Ti-6A l的合金中,当w(N)=0.045~0.27%时,随着氮质量分数的增加,增强体的体积分数有所增加.Ti-6A l-xN中的氮化物较为细小.复合材料的硬度、抗压强度和弹性模量均高于Ti-6A l合金.随着氮质量分数增加材料的抗压强度、硬度和弹性模量增加.由压缩断口分析可知,基体为韧性断裂.随着氮质量分数增加,合金由韧窝 解理断口向具有解理特征的脆性断裂转变.     

原位自生成陶瓷相增强铝基复合材料的研究

采用粉末冶金法成功制备了原位生成陶瓷相增强AI基复合材料。应用X射线衍射仪进行了物相组成测试,发现含10％－20％（重量百分比） SiO2复合材料的最终物相均为MgAI2O4、MgO、Mg2Si、Si和AI。研究了SiO2含量对复合材料硬度、密度、电导率、抗压强度、磨擦磨损等性能的影响表明,随SiO2含量的增加,复合材料的硬度和密度增加,电导率、抗压强度和体积磨损量减小,而磨擦系数却增加。     

凝固偏析对氧化铝/铝-铜合金复合材料性能的影响

利用挤压铸造技术制备氧化铝／铝-铜合金复合材料，研究了凝固偏析对复合材料机械性能的影响．结果表明：复合材料在凝固过程中由于选择结晶，基体中的溶质元素偏聚在纤维／基体界面或晶界上；纤维加速了复合材料的时效强化过程，随着纤维体积分数的增加，复合材料的硬度、强度、弹性模量增大，而塑性下降；随着预制件预热温度的升高，冷却速度减慢，凝固偏析加剧，复合材料的机械性能下降．     

Effect of pressure on the solidification behavior and mechanical properties of SiCp/Al-Mg composites

SiCp/Al-Mg metal matrix composites were manufactured by semi-solid stirring technique. The composites were remelted and then solidified under different pressures to study the solidification behavior of composites by differential thermal analysis, scanning electron microscopy, and transmission electron microscopy. The experimental results show that SiCp reinforcements can not act as heterogeneous nucleation sites for α(Al), and an interfacial layer composed of MgAl2O4 spinel and Si-rich phase existed at Al/SiCp interface. The undercooling of the matrix alloy was improved by the pressure applied, resulting in the grain of matrix alloy refining. The X-ray diffraction pattern of composites testified that the matrix alloy exhibited a certain preferred orientation during solidification. In addition, with increasing the pressure for solidification, the pored defects in the composites decreased, while the relative density, hardness and compressive strength increased. Therefore, the microstructure and mechanical properties of the composites were improved by pressure placed during the solidification of SiCp/Al-Mg composites.     

Fabrication and compressive performance of plain carbon steel honeycomb sandwich panels

Plain carbon steel Q215 honeycomb sandwich panels were manufactured by brazing in a vacuum furnace.Their character- istic parameters,including equivalent density,equivalent elastic modulus,and equivalent compressive strength along out-of-plane (z-direction)and in-plane(x- and y-directions),were derived theoretically and then determined experimentally by an 810 material test system.On the basis of the experimental data,the compressive stress-strain curves were given.The results indicate that the meas- urements of equivalent Young's modulus and initial compressive strength are in good agreement with calculations,and that the maximum compressive strain near to solid can be up to 0.5-0.6 along out-of-plane,0.6-0.7 along in-plane.The strength-to-density ra- tio of plain carbon steel honeycomb panels is near to those of Al alloy hexagonal-honeycomb and 304L stainless steel square-honeycomb,but the compressive peak strength is greater than that of Al alloy hexagonal-honeycomb.     

不同Al含量的Ti/Al合金靶对磁控溅射离子镀TiAlN薄膜力学性能的影响

采用不同Al含量的Ti/Al合金靶材在硬质合金刀具上沉积TiAlN薄膜,研究靶材中不同的Al含量对TiAlN薄膜表面粗糙度、硬度以及膜基结合力等性能的影响,通过显微硬度仪、划痕仪、金相显微镜和XRD等仪器分别对薄膜的硬度、结合力、组织结构等主要性能进行测试分析。实验结果表明:随着Ti/Al合金靶中Al含量的增加,TiAlN薄膜的硬度先增加后减小,膜基结合力逐渐增加;当Al在Ti/Al合金靶材中所占的比值为2:3时,TiAlN薄膜的硬度、耐磨性等综合力学性能最佳。     

混杂增强AZ91复合材料的制备及其显微组织和性能

采用挤压铸造方法制备了以AZ91镁合金为基体、Al2O3短纤维(Al2O3f)和石墨颗粒(Grp)混杂为增强体的复合材料。观察了不同复合材料的显微组织,测试了其力学性能,并对其摩擦磨损性能进行了研究。结果表明:用此法制备的镁基复合材料增强相分布均匀,与基体结合紧密。硬度随Grp体积分数的增加而降低,Al2O3f的加入能提高复合材料的硬度。抗拉强度和伸长率都随Grp体积分数的增加而减小。Grp体积分数增加,磨损质量损失和摩擦系数都降低。随着摩擦过程的进行,在试样表面逐渐形成一层黑色连续的润滑膜。     

原位合成Al_2O_3/FeAl复合材料的组织与性能

利用Fe-Al-Fe2O3体系的放热反应,原位热压合成了Al2O3/FeAl复合材料.借助XRD和SEM等研究了复合材料的物相组成和显微结构,以及Al2O3生成量对复合材料显微结构和力学性能的影响.结果表明:经1 250℃保温1.5h热压烧结的块体材料主要由FeAl及少量Al2O3相构成,FeAl基体为片层结构,增强相Al2O3分散在基体和晶界处.随着Al2O3含量的增加,基体晶粒尺寸明显减小,同时对材料起增强增韧作用.在Al2O3含量为1.2wt%时,试样的抗弯强度达到最大值1 329.22MPa;在Al2O3含量为0.8wt%时,试样的断裂韧性达到最大值29.95MPa·m1/2.此值正好处于金属与陶瓷材料性能链的断缺处.因此,本研究结果对于完善材料性能体系具有重要意义.     

Effect of Cold-rolling on Hardness of SiC_w/Al Composite

1　IntroductionDiscontinuouslyreinforcedaluminummetalmatrixcomposites (AMCs)arenowrecognizedasimportantstructuralmaterials[1,2 ] .Oneoftheprimeadvantagesofthesematerialsisthattheycanbeprocessedandshapedbyconventionalmetalworkingtechniques ,suchasextru sio…     

基于RFPA的砾石对砂砾岩破裂影响规律研究

为研究砾石尺寸及强度特征对砂砾岩裂纹扩展模式和力学参数的影响。采用岩石破裂过程模拟系统RFPA,建立了非均质的砂砾岩岩心模型,研究了砾石尺寸及力学性质变化对砂砾岩岩心抗压强度、杨氏模量、泊松比等弹性力学参数的变化规律。结果表明,随砾石尺寸的增加,岩心模型的泊松比与杨氏模量逐渐增加,强度先减小后增大,且不同砾石尺寸的岩心裂纹形态基本一致;随砾石强度的增大,岩石单轴抗压强度逐渐增大,而后基本保持不变,主要由基质强度决定。研究结果真实再现了砂砾岩裂纹萌生、扩展过程,得到了砾石尺寸及强度对岩心破裂的影响规律。     

Effect of Cold-rolling on Hardness of SiCw／Al Composite

A SiCw|A| compostie was fabricated through a squeeze cast route and cold rolled to about 30%,50% and 70% reduction in thickness.respectively.The length of whiskers in the composite before and after rolling was examined using SEM.Some of the rolled composites were annealed by recrystallizing to remove the work hardening of the matrix alloy.The hardness of the rolled and annealed SiC A SiCw|A| composites was examined and then associated with the change of the whisker length and the work hardening of the matrix alloy.It was found that the hardness was a function of the degree of cold rolling .For the cold rolled composites .with the increase in the degree of cold rolling .the hardness increases at first,and decreases when the degree of cold rolling excecds 50%.For the annealed ones .however,the hardness monotonously with the increase in rolling degree.The different changes in hardness beticeen the rolled and annealed composites coukl be attributed to a result of the competition benceen the work hardening of the matrix resulting from the cold rolling and the work softening arising from the change of whisker length.     

FeNiMnCuC0．2Alx高熵合金结构及性能研究

通过高频感应加热在真空下制备FeNiMnCuC0．2Alx（x=0、0．1、0．2、0．5mol）高熵合金,对固溶处理后的试样进行结构及性能研究。结果表明,FeNiMnCuC0．2Alx高熵合金具有简单的面心立方结构;添加少量Al（x=0．1、0．2mol）能细化FeNiMnCuC0．2Alx高熵合金晶粒,但x=0．5mol时,晶粒又变得粗大;初生树枝状晶富含Fe、Ni元素,Mn、Cu在枝晶间相内有所聚集,C、Al大体上均匀分布于两相中;x=0时,FeNiMnCuC0．2Alx高熵合金具有高的抗压强度（5218MPa）,x=0．1mol时,舍金抗压强度（4037MPa）和压缩率（〉75％）均较佳,随Al添加量的继续增加,合金压缩性能有所下降,x=0．5mol时,合金表现为脆性断裂。     

Fabrication of in situ Ti2AlN/TiAl composites by reaction hot pressing and their properties

Ti2AIN/TiAI composites with different volume fractions of reinforcement were successfully fabricated by hot-pressing sintering method （reaction hot pressing） using Ti, Al and TiN powders as starting materials. The synthesis process includes four stages： first, the reactions between Al and Ti powers and between Al and TiN powders respectively occur and result in TiAl3 phase; secondly, AI powders in the sample are exhausted; the remaining Ti cores react with TiAl3 layer to form Ti-Al intermetallics; moreover, a few Ti2AlN particles precipitate from the TiAl3 phase; thirdly, Ti-Al intermetallics react with the remaining Ti cores to form Ti3Al and TiAl phases. TiAl phase and original TiN powers are in direct contact each other; finally, the residual TiN powers react with TiAl phase and result in a plenty of TizAIN phase. Compared with TiAl matrix, the hardness, elastic modulus and high-temperature compressive strength of Ti2AlN/TiAl composite are improved obviously and they are all enhanced with increasing the volume fraction of Ti2AlN phase.     

碳纳米管增强铝基复合材料制备及性能研究

采用真空热压烧结法制备碳纳米管与 SiO2多相增强铝基复合材料,测量复合材料的体积密度,根据其理论密度计算其致密度;再对制得的复合材料进行硬度、抗压强度、抗剪强度等力学性能测试,并观察样品的剪切断口微观形貌,研究 CNTs 对复合材料力学性能的影响。低含量的碳纳米管由于其在铝基体中的分散性及弥散度较好,作为第二相增强相,所制备的铝基复合材料的致密度、硬度、抗压强度与剪切强度均优于高含量碳纳米管增强铝基复合材料。 CNTs 的含量、以及其在铝基体中的弥散度是影响铝基复合材料力学性能的关键因素。     

风积沙混凝土轴心受压力学性能研究

试验设计风积沙和粉煤灰内掺替代等质量的河砂及水泥,制备了10组风积沙-粉煤灰混凝土,进行60d风积沙-粉煤灰混凝土轴心抗压试验,开展风积沙-粉煤灰混凝土轴心受压破坏形貌、微观结构、应力-应变关系、轴心抗压强度、峰值应变、弹性模量、泊松比等内容的试验研究。结果表明：弹性阶段各掺量风积沙混凝土应力-应变曲线基本趋于一致,进入弹塑性阶段后,风积沙混凝土较基准混凝土应力增长较快,混凝土脆性增加。轴心抗压强度、弹性模量及泊松比随风积沙掺量增加呈现先增大后减小的变化趋势,随粉煤灰掺量增加在降低。最后,对过镇海经典模型上升段本构参数A进行二次演化,建立了本构参数与轴心抗压强度和风积沙掺量之间的演化模型,得出风积沙混凝土应力-应变上升段本构方程。     

脉冲N离子束轰击对TiAlN膜层显微硬度影响的研究

采用俄罗斯UVN 0.5D2I脉冲离子束辅助电弧离子镀沉积设备,在高速钢W18Cr4V基材上沉积TiAlN膜层。研究了膜层沉积之前N离子束轰击基材以及膜层沉积过程中N离子束辅助轰击对TiAlN膜层显微硬度的影响。结果表明:膜层沉积之前,N离子轰击得到高度洁净的表面,使基材的显微硬度由原来的900HV0.01提高到1230HV0.01。膜层沉积过程中,脉冲N离子束轰击,消除了膜层中的硬度"软点"及阴影效应,增加(Ti,Al)N相的含量,膜层的内部产生了压应力,这些因素显著提高了膜层的硬度,膜层的最高硬度为2530HV0.01。但轰击能量不能过高,否则会降低膜层的显微硬度。     

Ti3SiC2/TiB2复合材料的制备及其组织和力学性能

以2TiC／Ti／Si／0．2Al／TiB2粉为原料，采用热压烧结工艺成功制备了Ti3SiC2／TiB2复合材料。结果表明：不同TiB2含量的试样中主晶相为Ti3siC2与TiB2两相，没有发现其它杂质相；当复合材料中TiB2的体积分数为10％时，其硬度、抗压强度、弯曲强度、断裂韧性都有显著的提高。经热处理后，Ti3SiC2／10％TiB2复合材料的弯曲强度由367．5MPa     

Processing technique and sliding friction and wear behavior of TiB2／ZA27 composite

In-situ TiB2 particles reinforced ZA27 composite was prepared by the stir-casting technique and a twostep method. TiB2/Al composite was produced by incorporating K2 TiF6, KBF4 salts and other agents into Al melt. As a master alloy, TiB2/Al composite was used to manufacture TiB2/ZA27 composite, which results in the generation of well-distributed reinforcing TiB2 phase. The hardness, friction and wear behavior of TiB2/ZA27 composite were investigated. The results show that the hardness of the composite is enhanced with increasing the content of TiB2 particles, the incorporation of TiB2 reduces the wear rate of TiB2/ZA27 composite and improves the friction property under lubricated and dry sliding friction conditions. The worn track width of ZA27 alloy is 1.6 and 2.5 times as long as that of 2.1%TiB2/ZA27 composite at 150 N and 700 N load under lubricated conditions, which indicates that TiB2/ZA27 composite possesses higher bearing ability.     

碱激发下粉煤灰-市政污泥固废基混凝土抗冻融性能

为改善市政污泥对混凝土抗冻融性能的劣化效果,在氢氧化钠及水玻璃的复合激发下,用经生石灰改性后的市政污泥取代10%细骨料,粉煤灰分别取代10%、20%与30%水泥,制备了混凝土。分析了不同冻融循环次数下,混凝土的表观现象、相对质量、相对动弹性模量、相对抗压强度及微观结构随粉煤灰掺量与碱当量的变化规律,分别以相对动弹性模量与相对抗压强度为损伤变量建立了不同的冻融损伤模型。研究结果表明：随冻融循环次数增加,混凝土表观损伤愈发严重,内部孔隙增多,相对动弹性模量及相对抗压强度显著降低;与对照组相比,粉煤灰及碱激发剂的加入可以改善市政污泥对混凝土冻融耐久性的劣化效果,降低混凝土在冻融循环作用下的质量损失、动弹性模量损失及抗压强度损失;当粉煤灰掺量10%、碱当量4%时,粉煤灰可在碱激发剂及改性污泥中残余碱的联合作用下被较充分地激发,可消纳改性污泥中的残余碱,减弱市政污泥对混凝土抗冻融性能的劣化效果,此时混凝土水化程度最高,在冻融循环作用下的质量损失、动弹性模量损失及抗压强度损失最小,且服役寿命最长,约为16a以上;相对动弹性模量与相对抗压强度相关性良好,分别以两者为损伤变量的冻融损伤模型与试验结果均吻合良好。     

Effects of cryogenic treatment on mechanical properties and microstructure of Fe-Cr-Mo-Ni-C-Co alloy

Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h. Hardness tester, OM, XRD, SEM were used to investigate the mechanical properties and microstructures of the alloy. The results show that the hardness increases by 1-2 （HRC） and the compressive strength decreases slightly after cryogenic treatment. The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbide η-Fe2C. The decrease in compressive strength is caused by residual stress. The great amount of carbides, such as Cr7C3 and Fe2MoC, in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress. The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite. The cryogenic martensite is long and fine; while the non-cryogenic martensite is short and coarse. There is obvious surface relief of the cryogenic martensite transformation. It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly. The surface relief in the non-cryogenic martensite is wide and arranged in parallel, and the boundary of surface relief is not smooth. These characteristics may imply different growth ways of the two kinds of martensite.