IF钢晶界的微观力学性能及其对宏观力学性能的影响

利用纳米压痕技术对不同晶粒尺寸无间隙原子钢(IF钢)晶界的微观力学性能进行表征,并测试了IF钢的维氏硬度和拉伸性能,分析了晶界微观力学性能对宏观力学性能的影响。结果表明:不同尺寸晶粒内的纳米压痕硬度和弹性模量基本一致,但晶粒尺寸较小试样的平均纳米压痕硬度约为3.12GPa,比晶粒尺寸较大试样的(2.36GPa)更高,平均模量约为205GPa,低于晶粒尺寸较大试样的(210GPa),晶粒尺寸较小试样的维氏硬度和抗拉强度明显高于晶粒尺寸较大试样的;晶界的纳米压痕硬度(3.25GPa以上)比晶粒内的(2.61GPa)更高而弹性模量略低是导致宏观力学性能差异的主要原因。     

用纳米压痕法研究拉伸变形对电沉积镍镀层力学性能的影响

用纳米压痕法对受不同程度拉伸变形后的电沉积镍镀层试样的硬度、弹性模量和蠕变性能进行了研究.结果表明:随着变形量从零增加到28.3%,镍镀层的硬度及其弹性模量都有明显降低,硬度从9.37 GPa下降到6.13 GPa,弹性模量从242.51 GPa下降到116.23 GPa;而蠕变位移随变形量的增加而增加,从未拉伸试样的1.25 mm增加到伸长率为28.3%试样的4.52 mm.     

纳米压痕技术表征Al2O3/3%TiO2爆炸喷涂涂层的各向异性

利用纳米压痕技术研究了爆炸喷涂涂层的微观结构特征和力学性能的关系。结果表明:相对于涂层表面,涂层横截面存在着尺度分布较宽的孔洞和微裂纹等缺陷;涂层微观结构的各向异性使得涂层的弹性、塑性、硬度和弹性模量等出现各向异性;与涂层横截面相比,涂层表面具有较好的抵抗外加载荷的能力和卸栽后良好的弹性恢复能力;涂层表面的硬度和弹性模量分别为10．3 GPa和170．7 GPa,而涂层横截面的分别为2．9 GPa和234．5 GPa。     

磁控溅射微纳米梯度镀层对45钢及40Cr钢弹性变形性能的影响

利用磁控溅射离子镀技术在屈强比不同的45钢及40Cr钢基体上制备Cr、类石墨碳(Graphite-like-carbon,GLC)及CrTiAlN微纳米梯度镀层,通过考察镀层/金属复合体系弹性模量和屈服强度的变化来研究镀层对基体弹性变形行为的影响。研究结果表明:磁控溅射离子镀层可以改善金属基体的弹性变形性能,但镀层对不同金属基体力学参量的影响不同;屈强比低的45钢,镀层可同时提高弹性模量和屈服强度,在v=0.1mm/min的低速拉伸时,45钢试样的屈服强度可提高20%左右;屈强比高的40Cr钢,镀层对其屈服强度基本无影响,但对弹性模量提高的程度更显著,当拉伸速度为0.7mm/min时,40Cr钢试样的弹性模量可提高60%,而45钢仅为22%;镀层/基体复合体系的弹性模量随拉伸速度的增加表现为先增大后减小的特点,其变化规律不同于金属基体;镀层的高硬度和良好的膜基匹配能力有助于阻碍工件表面及亚表面微塑性形变区的扩展,从而提高试样的力学性能。     

铝合金5083焊接试样微观力学测试分析

焊接接头是零件强度最薄弱的地方,为研究焊接试样的微观力学性能,利用纳米压痕测试技术对5083铝合金焊接试样进行微观力学测试,通过纳米压痕玻式压头测得焊接接口的弹性模量与硬度分布,同时利用纳米压痕球形压头分析了焊接接口基体区与焊缝区的应力-应变曲线。     

镁合金磁控溅射镀铝耐蚀防护层研究

在AZ31镁合金表面进行了磁控溅射铝防护层的镀覆,并研究了镀层的成分分布、形貌、显微力学性能、防腐蚀性能及工艺条件对镀层的影响。结果表明：直径为1～2μm的细小晶粒均匀在镁合金基体表面沉积形成致密铝镀层,镀层和基体之间存在混融的过渡层;镀层表面粗糙度在2μm以下并与基体结合良好,其硬度、弹性模量等高于镁合金基体并具有一定韧性和弹塑性能;适当降低氩气压力,提高溅射电流,可改善镀层质量。镀层提高了镁合金基体的自腐蚀电位并降低了腐蚀电流,从而抑制了腐蚀倾向,但自腐蚀电位低于热喷涂铝电位且腐蚀电流高于微弧氧化处理电流。     

超级双相不锈钢中σ相力学性能的纳米压痕表征

为了预测金属间化合物σ相的析出对00Cr25Ni7Mo4N超级双相不锈钢力学性能的影响,采用纳米压痕技术对加热缓冷后该钢的σ相进行了表征,并对其显微组织进行了观察。结果表明:钢中σ相的体积分数为36.7%,其纳米压痕硬度范围为14.0～17.1GPa,平均值为15.7GPa,弹性模量范围为262～380GPa,平均值为317GPa;测试结果基本排除了基体效应的影响。     

纯钛表面等离子渗钼梯度改性层的微尺度准静态接触力学性能

采用双层辉光等离子表面合金化技术,在TA2纯钛基体表面制备钼梯度改性层,对改性层截面形貌和元素分布进行分析,并研究改性层的微尺度准静态接触力学性能。结果表明:钼梯度改性层均匀致密,厚度约为12.0μm,由厚度2.7μm的沉积层与厚度9.3μm的扩散层组成;钼、钛元素含量沿厚度方向呈梯度变化,改性层与基体形成良好的冶金结合;改性层的硬度和弹性模量分别为13.82,264.00GPa,比基体的分别增大了10.87,142.38GPa,改性层具有较高的强度和良好的塑性;当试验载荷为15N时,微米压入深度接近15μm,复合硬度和弹性模量与基体的相近,改性层的强化作用完全失效。     

TC4合金超声振动滚压表面质量的纳米压痕测试

传统滚压容易在工件表层形成加工硬化层,与内部基体材料有明显的分层现象,易造成表层脱落。本文采用超声振动滚压方式对TC4合金表面进行滚压加工,并通过纳米压痕技术测试了超声滚压后的表面质量。实验结果表明:滚压表面的材料弹性模量、硬度都有所提高;随着测点距离滚压表面深度的增加,材料的弹性模量和硬度都呈现下降趋势;相比于普通滚压,超声滚压具有更深的作用范围,试样表层晶粒明显细化,且材料的弹性模量、硬度等变化更为均匀,有利于减小滚压分层。     

AZ31B镁合金超声滚压表层力学性能的纳米压痕测试

超声滚压可以使镁合金表面纳米化,从而影响表层的力学性能。研究多道次超声滚压AZ31B镁合金表层力学性能,可以为镁合金超声滚压仿真分析提供依据。本文通过车削和多道次超声滚压对AZ31B镁合金棒进行表面处理,采用白光干涉ZeGageTM Plus光学轮廓仪对车削和超声滚压后试样的表面形貌进行观测,通过纳米压痕仪测定试样表层的纳米硬度和弹性模量,并获得载荷-位移曲线。结果表明,经3道次超声滚压加工后,AZ31B镁合金表面粗糙度由车削后的0.568um降低至0.192um,下降了66.2%;相同的加载方式下,越接近超声滚压表面,纳米压痕深度越浅;在距离表面300μm深度内,纳米硬度得到明显提升,且越接近超声滚压表面,纳米硬度越大;在距离表面200μm深度内,弹性模量明显增大,说明3道次超声滚压对AZ31B镁合金表层纳米力学性能的显著影响层深度达到200μm。多道次超声滚压提高了材料表层的纳米硬度和弹性模量,起到了表面强化的作用。     

Tribological and physical-mechanical properties of protective coatings from Ni-Cr-B-Si-Fe/WC-Co-Cr before and after fission with a plasma jet

A new type of coating is developed, which is a mechanical mixture of two different powders, namely, Ni-Cr-B-Si-Fe (PG-19N-01) and WC-Co (hard alloy). After the coatings from this mixture are deposited, their surface layer is fused with a plasma jet using an eroding electrode made of W. The additional treatment of the coatings with the plasma jet yields new phases and causes the redistribution of elements in the layer 45–60 μm deep; the percentage ratio of the phases WC, α-CoCr, Co, and Ni, as well as Cr₃Ni₂ + γ-(Fe, Ni) appearing during coating deposition also changes. The redistribution of elements occurs in the upper coating layer owing to fusion with the plasma jet. These processes yield variations in the physical-mechanical properties of the coatings, such as the hardness and elastic modulus; the coating wear rate decreases severalfold. It is found that with increasing load applied to the Berkovich pyramid the elastic modulus of the coating drops from 240 (at an indentation depth of 50 nm) to 175 GPa (at 150 nm). The elastic modulus of the substrate rises from 25 to 42 GPa. The coating hardness calculated from the loading-unloading curves is 15.3 to 10.6 GPa under increased load applied to the indentor. Specimens covered with the coating fused with the plasma jet in three passes demonstrate the lowest material wear.     

Evaluating local elasticity of the metal nano-films quantitatively based on referencing approach of atomic force acoustic microscopy

Traditional technique such nanoindenter(NI) can’t measure the local elastic modulus at nano-scale(lateral). Atomic force acoustic microscopy (AFAM) is a dynamic method, which can quantitatively determine indentation modulus by measuring the contact resonance spectra for high order modes of the cantilever. But there are few reports on the effect of experimental factors, such length of cantilever, contact stiffness on measured value. For three different samples, including copper(Cu) film with 110 nm thickness, zinc(Zn) film of 90 nm thickness and glass slides, are prepared and tested, using referencing approach in which measurements are performed on the test and reference samples (it’s elastic modulus is known), and their contact resonance spectra are measured used the AFAM system experimentally. According to the vibration theory, from the lowest two contact resonance frequencies, the tip-sample contact stiffness is calculated, and then the values for the elastic properties of test sample, such as the indentation modulus, are determined. Using AFAM system, the measured indentation modulus of copper nano-film, zinc nano-film and glass slides are 113.53 GPa, 87.92 GPa and 57.04 GPa, which are agreement with literature values MCu=105-130 GPa, MZn=88.44 GPa and MGlass=50-90 GPa. Furthermore, the sensitivity of contact resonance frequency to contact stiffness is analyzed theoretically. The results show that for the cantilevers with the length 160μm, 225μm and 520μm respectively, when contact stiffness increases from 400 N/m to 600 N/m, the increments of first contact resonance frequency are 126 kHz, 93 kHz and 0.6 kHz, which show that the sensitivity of the contact resonance frequency to the contact stiffness reduces with the length of cantilever increasing. The novel method presented can characterize elastic modulus of near surface for nano-film and bulk material, and local elasticity of near surface can be evaluated by optimizing the experimental parameters using the AFAM system.     

MoS2/Ti复合固体润滑膜的力学性能与摩擦特性

采用非平衡磁控溅射法在9Cr18轴承钢基底上制备了厚度约3μm的MoS2/Ti复合固体润滑膜,基于球形压头纳米压痕试验,采用连续刚度法对MoS2/Ti复合固体润滑膜的力学性能进行研究,探究MoS2/Ti复合固体润滑膜力学性能随压痕深度的变化规律;根据压痕试验载荷-位移曲线,采用Hertz接触理论计算MoS2/Ti复合固体润滑膜的弹性模量并与试验结果进行对比;利用CSM摩擦试验机对低速、低载下MoS2/Ti复合固体润滑膜的摩擦特性进行研究;基于压痕试验提出了一种能够更准确计算钢球加载时MoS2/Ti复合固体润滑膜接触应力的方法,并计算了摩擦试验不同载荷下的接触应力。结果表明:MoS2/Ti复合固体润滑膜的力学性能和摩擦特性都会受到表面形貌的影响;除表面初始压入阶段外,MoS2/Ti复合固体润滑膜的弹性模量和接触刚度都随着压痕深度的增大而增大;滑动速度和载荷共同影响MoS2/Ti复合固体润滑膜的摩擦特性。     

两步压入法--薄膜力学性能的可靠测量方法

提出了采用力学探针测量薄膜力学性能的两步压入法.该方法通过大载荷压入展示基体变形对薄膜硬度的影响,从而选择不影响基体变形的小载荷测出薄膜的硬度和弹性模量.对高速钢基片上的TiN硬质薄膜,单晶硅片上的金属Ni薄膜和(Ti,Al)N/VN纳米多层膜的测量表明,两步压入法能够测出各种性质薄膜的力学性能,并且具有准确可靠的特点.此外,两步法对(Ti,Al)N/VN纳米多层膜的力学性能的测量表明,该体系的纳米多层膜存在硬度和弹性模量异常升高的超硬、超模量效应.     

Quantitative measurement of indentation hardness and modulus of compliant materials by atomic force microscopy

An atomic force microscopy (AFM) based technique is proposed for the characterization of both indentation modulus and hardness of compliant materials. A standard AFM tip is used as an indenter to record force versus indentation curves analogous to those obtained in standard indentation tests. In order to overcome the lack of information about the apex geometry, the proposed technique requires calibration using a set of reference samples whose mechanical properties have been previously characterized by means of an independent technique, such as standard indentation. Due to the selected reference samples, the technique has been demonstrated to allow reliable measurements of indentation modulus and hardness in the range of 0.3-4.0 GPa and 15-250 MPa, respectively.     

Scratch tests to contribute designing performance maps of multilayer polymeric coatings

The scratching technique has gained interest in recent times because of the numerous inherent properties implied (adherence, hardness, elasticity, visco-elasticity, cohesion, etc.) during tests. Some singular mechanical responses have been noticed (cyclical slips and unsticking, degradation modes, etc.) and valued on multilayers polymeric coatings. The results allow differentiating them and illustrating the mare resistance for part. Scratch test is identified as one of the most efficient to build coating performance maps. The main purpose of our work related to the characterization of multilayers polymeric coatings, is to determine a set of experiments in order to compare their mar resistance. Experiments are made by indentation (hardness, creep, stress relaxation), scratch test (determination of the critical load), glossy reflection and wear. In this paper we describe the scratch experiments used to compare the mar resistance of the coatings. The parameters recorded are used to build a performance map relative to a specimen and this performance map is used to compare all characteristics of different multilayers coatings. Two organic systems are taken as samples to illustrate it. They are composed of three layers with a common steel sheet substrate and a common PET topcoat. The intermediary layer is soft and thick for the first product while it is hard and thin for the second one. The scratch results combined with other test results in performances maps underline the role of an intermediary layer in order finally to better design multilayer polymeric coatings.     

甘油润滑下CrCN涂层的超低摩擦特性

为开发与CrCN涂层具有良好配伍润滑性能的绿色润滑剂,使用磁控溅射技术在304不锈钢表面沉积CrCN涂层,利用场发射扫描电子显微镜、原子力显微镜、纳米压痕仪、维氏硬度计、X射线衍射仪、X射线光电子能谱仪分别对其表面形貌、涂层厚度、力学性能、物相组成以及元素化学价态进行分析,并借助多功能摩擦磨损试验机评价在甘油润滑下CrCN涂层的摩擦学性能,并与PAO6润滑下结果进行比较。利用磁控溅射技术在不锈钢表面构筑的CrCN涂层表面光滑致密,粗糙度仅为1.01 nm,硬度可达14.39 GPa。对比钢-钢和钢-CrCN体系的摩擦学性能发现,钢-CrCN体系在甘油润滑下展现出优异的润滑性能;当负载为0.5 N时,钢-CrCN体系在甘油润滑下的摩擦因数可低至0.01,大大低于PAO6润滑下的摩擦因数。对磨痕的XPS分析表明,在摩擦过程中,甘油发生摩擦化学反应,在CrCN涂层的接触表面生成一层FeOOH层,甘油分子及其降解产物可能进一步吸附在FeOOH层,形成流体润滑层,有效降低了摩擦和磨损。     

薄膜的力学测试技术

对薄膜力学性能的测试方法、技术以及所取得的主要成果进行简要的综合介绍。     

Substrate Effects on the Micro/Nanomechanical Properties of TiN Coatings

Nanoindentation and nanoscratch tests were performed for titanium nitride (TiN) coatings on different tool steel substrates to investigate the indentation/scratch induced deformation behavior of the coatings and the adhesion of the coating–substrate interfaces and their tribological property. In this work, TiN coatings with a thickness of about 500 nm were grown on GT35, 9Cr18 and 40CrNiMo steels using vacuum magnetic-filtering arc plasma deposition. In the nanoindentation tests, the hardness and modulus curves for TiN/GT35 reduced the slowest around the film thickness 500 nm with the increase of indentation depth, followed by TiN/9Cr18 and TiN/40CrNiMo. Improving adhesion properties of coating and substrate can decrease the differences of internal stress field. The scratch tests showed that the scratch response was controlled by plastic deformation in the substrate. The substrate plays an important role in determining the mechanical properties and wear resistance of such coatings. TiN/GT35 exhibited the best load-carrying capacity and scratch/wear resistance. As a consequence, GT35 is the best substrate for TiN coatings of the substrate materials tested.