热浸铝钢等离子体电解氧化陶瓷层的微观力学特性

采用纳米压入方法表征了热浸镀铝钢表面由Al2O3层、Al层和FeAl层组成的复合涂层的纳米硬度、弹性模量及断裂韧性等微观力学性能,采用扫描电镜(SEM)观察了纳米压痕形貌,并分析了孔洞对陶瓷层的纳米压入行为和压痕裂纹扩展的影响.结果表明:等离子体电解氧化(PEO)陶瓷层中包含许多微米和亚微米尺度的细小孔洞,陶瓷层弹性模量约为226.4 Gpa,纳米硬度约为19.6 Gpa.当纳米压入深度为250 nm时,所测得陶瓷层的力学参数分散性较大.与FeAl层比较,PEO陶瓷层具有较高的裂纹扩展阻力. FeAl层纳米压痕顶端产生了沿直线扩展的径向裂纹;而陶瓷层纳米压痕中除径向裂纹外出现了侧边裂纹.     

核电主管道铸造不锈钢的热老化脆化

为了研究中国核电主管道铸造不锈钢Z3CN20-09M的热老化,在300、350和400℃下,对Z3CN20-09M进行了长达30000h的加速热老化实验.对不同热老化时间下的样品进行了冲击性能和铁素体纳米硬度测定.以夏比冲击功作为热老化脆化参量,利用拟合的方法得出该材料的热老化激活能为51.962kJ·mol^-1.通过热老化因子P得出了用夏比冲击功表示的热老化脆化动力学公式.利用热老化激活能和热老化动力学公式预测了Z3CN20-09M在实际运行温度下服役40a内的夏比冲击功和铁素体显微硬度变化.预测结果表明在运行5a内是该材料韧性迅速下降的时期,随后的运行过程中下降过程趋缓.     

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采用MEVVA离子源技术对由磁过滤阴极真空电弧沉积的TiN薄膜注入不同剂量的Si元素,利用XPS和纳米硬度仪表征Si离子注入后化学成分、元素键合状态以及硬度的变化。结果表明,Si离子注入后,薄膜表面硬度得到提高,5×1016 ions/cm2的样品硬度峰值从27.18GPa增加到39.85GPa,随着注入剂量的增加,纳米硬度峰值有下降的趋势,1×1017 ions/cm2的样品硬度峰值为33.27GPa,但表面改性层的深度增加,纳米硬度在一定的深度范围内得到了整体的提高。离子注入使薄膜表面层的弹性模量显著提高,表层弹性模量随注入剂量的增加而提高。并且由于Si元素的注入,形成了新的微结构相Si3N4,新相的含量与注入剂量有关。     

45钢/锡基合金摩擦磨损后表层组织及纳米硬度的表征

采用销盘式摩擦试验机,对45钢/锡基合金摩擦副进行干摩擦试验.经扫描电镜（SEM）对摩擦磨损试验后45钢盘试样、锡基合金销试样的磨损表面及截面形貌进行观察,用原子力显微镜（AFM）对摩擦磨损试验后45钢盘试样截面距磨损表面10μm处纳米晶颗粒进行观察,通过纳米压痕技术对45钢磨损表面纳米硬度和Young＇s模量进行测量.结果显示,磨损表层组织明显细化,晶粒尺寸接近纳米级;45钢磨损表面的纳米硬度和弹性模量分别为8.53 GPa和164.12 GPa,是基体硬度和弹性模量的687％和261％,且随摩擦影响层深度增加而降低.     

Effect of nitrogen on mechanical properties of thin films of the Ta-B-N system

Amorphous-crystalline thin films of the Ta-B-N system on steel substrates have been produced by high-frequency magnetron reaction sputtering of a TaB₂ target in a nitrogen-argon gas mixture. The effect of the nitrogen content of the mixture on the film mechanical properties has been studied. It has been found that the formation of an amorphous-crystalline structure causes the Ta-B-N film nanohardness and elastic modulus to decrease and the plasticity to increase as compared to TaB₂ nanocrystalline films. The amorphous boron formation results in the viscoelastic mechanical behavior of thin films of the Ta-B-N system.     

Hardness and wear behaviour of electroless Ni–B coatings

Depth-dependent hardness variation of dimethylamine borane-reduced electroless Ni–5?wt-%B deposits has been examined using the nanoindentation technique. The deposits were characterised using ICP-OES, FESEM, XRD and DSC for evaluating the composition, morphology, structure and phase transformation behaviour, respectively. Coatings were also analysed for hardness and wear resistance. The surface of the as-plated deposit exhibits a typical nodular morphology. DSC traces show the presence of a single exothermic peak at 313°C conforming to its phase transformation. X-ray diffraction pattern of as-prepared deposit contains a mixture of amorphous and sharp microcrystalline nickel peaks. Heat-treated coating exhibits improved hardness and wear resistance. Depth-dependent nanohardness profile of as-deposited film neither obeys Nix–Gao nor the Lam–Chong model of indentation.     

Load Dependence of Nanohardness in Nitrogen Ion Implanted Ti6AI4V Alloy and Fractal Characterization

Three different nitrogen ion doses were implanted into a Ti6A14V alloy to improve its mechanical surface properties for the application of artificial joints. The titanium nitride phase and nitrogen element distribution profile were characterized with X-ray photoelectron spectroscopy （XPS）. Nano-indentation tests were carried out on the surface of the Ti6A14V alloy and implanted samples on a large scale of applied loads. The XPS analysis results indicate that nitrogen diffuses into the titanium alloy and forms a hard TiN layer on the Ti6A14V alloy. The nanohardness results reveal that nitrogen ion implantation effectively enhances the surface hardness of Ti6A14V. In addition, the nanohardness clearly reveals load dependence over a large segment of the applied loads. Thus a concept of nanohardness fractal dimension is first proposed and the dual fractal model can effectively describe nonlinear deformation in indentation areas on the Ti6A14V surface. The fractal dimension shows a decreased trend in two regions of applied loads, indicating a decrease of the self-similarity complexity in surface indentation owing to an increase in nanohardness after nitrogen ion implantation.     

AFM的纳米硬度测试与分析

基于原子力显微镜(AFM)和金刚石针尖建立了一套纳米压痕测量系统。通过向系统发送控制电压使金刚石针尖在完成加载和卸载全过程的同时进行实时的数据采集并直接绘出载荷-压深曲线。利用该系统,对单晶铝和单晶铜薄膜材料进行了单点压痕实验,用美国Hysitron公司的纳米原位测量仪(TriboIndenter)做了验证试验。实验结果表明,该系统适合测量较软材料的纳米硬度。分析了基体材料对薄膜硬度和弹性模量的影响,在薄膜厚度低于5~10倍压入深度时,基体对薄膜材料的力学性能影响很大;并根据获得的载荷－压深曲线分析得出由于尺度效应的影响,随着压痕深度的减小,薄膜的硬度值呈明显的上升趋势,弹性模量没有这个趋势。     

基于AFM纳米硬度测量系统的实验

为了解决用AFM自身压痕软件进行纳米硬度测量时无法直接获得载荷-压深曲线和由于受到扫描陶管扫描范围的限制而进行多点压痕实验范围有限的问题,建立了三维微动工作台和原子力显微镜相结合的纳米压痕硬度测量系统.基于该系统,对单晶薄膜材料进行了单点压痕实验,得出该系统适合进行纳米硬度测量的结论;并对薄膜材料的纳米硬度和弹性模量进行了分析,讨论了尺寸效应对两者的影响.另外,进行了40×40的点阵压痕实验,得到了材料整个压痕面的三维形貌图和三维硬度图.