表面机械研磨对H13钢表面性能的影响

使用表面机械研磨（SMA）方法处理H13钢表面使其表面获得一层变形层。采用SEM,TEM及硬度试验等检测方法对变形层的厚度、晶粒大小、截面硬度梯度和热稳定性等进行了分析;同时对H13钢在SMA处理前后的渗氮行为进行了比较。结果表明,经SMA处理后,H13钢表面形成了约10μm厚的变形层,变形层内的晶粒明显细化,并且这些晶粒具有较好的热稳定性;此外,可以大大提高H13钢渗氮的效率。     

表面机械研磨处理对N80套管钢低温渗铝层的影响

通过表面机械研磨处理(SMAT),采用低温渗铝剂在470℃的相对低温下对N80套管钢进行2h粉末包埋渗铝.分别采用金相显微镜、显微硬度仪、扫描电镜、能谱仪等分析了SMAT对N80套管钢金相组织、渗铝层微观结构和断面元素分布、渗铝套管钢的显微硬度及表面腐蚀形貌的影响.结果表明SMAT90min后,可以在N80套管钢表面形...     

纯铜表面的连续摩擦压扭处理

提出了一种在纯铜表面得到大面积亚微米细晶组织及晶表面硬化处理的新工艺。在T2紫铜表面，利用连续摩擦压扭过程中产生的剧烈的剪切塑性变形，使材料表面形成了一层厚为0．1－0．2mm，晶粒直径200－300nm的亚微米细晶组织，表面硬度比基材提高了1倍，压扭头行走速度和转速对变形区晶粒细化和硬化效果影响显著。理论分析结果表明，在垂直于行走方向上加热能量和变形程度基本均匀。     

表面机械研磨处理Fe-C合金腐蚀性能的研究

首先利用表面机械研磨技术(SMAT)使低碳钢实现了表面纳米化,然后通过金相显微镜、X射线衍射仪对SMAT后低碳钢的微观组织结构进行表征,最后通过CS350型电化学工作站测试系统对试样进行测试,分析及比较了低碳钢及其SMAT试样在0.05 mol/L H2SO4+0.05 mol/L Na2SO4介质中的腐蚀行为。实验表明,在SMAT之后,20号钢的耐腐蚀性能好于10号钢,而这恰恰与粗晶状态下10号钢的耐腐蚀性能好于20号钢的结果相反,其原因值得探究。     

表面机械研磨处理对Cu-10wt％Ni合金组织及性能的影响

对Cu-10％(质量分数)Ni合金进行表面机械研磨处理,采用X射线衍射仪、光学显微镜、显微硬度测试仪等对处理不同时间样品的组织及性能进行了分析.结果表明表面机械研磨处理后,Cu-10％(质量分数)Ni合金实现了表面纳米化.处理时间30min时,表面晶粒尺寸为42.92nm,随着处理时间的延长,晶粒逐渐细化,强烈变形层逐...     

Mo离子注入对纯铜表面纳米层稳定性的影响

采用表面机械研磨处理(SMAT)对纯铜进行表面改性,通过金属蒸汽真空弧离子注入技术在纳米表层注入Mo离子。利用光学显微镜(OM)、X射线衍射分析仪(XRD)和扫描电镜(SEM)观察SMAT处理效果,表面存在纳米层和变形层,通过原子力显微镜(AFM)表征纳米层的晶粒尺寸。结果表明:晶粒尺寸得到了显著的抑制,表面纳米层的晶粒在退火后长大到163nm,而注入了Mo离子的只长大到72nm。此外,SMAT并离子注入后材料表面的硬度仅达到SMAT试样的3.5倍,是纯Cu基体硬度的7倍左右。Mo离子的分散和由SMAT及离子注入引入晶体缺陷的反应促使了这些优化现象的产生。     

机械研磨金属表面纳米化的研究进展

在表面机械处理(SMAT)方式下,材料表面可以通过强烈塑性变形而实现纳米化,获得表面为纳米晶、晶粒尺寸沿厚度方向逐渐增大的梯度结构。表面纳米化可以使材料表面硬度提高且整体力学性能得到改善。同时材料表面活性得到极大地提高,为进一步化学处理提供良好的条件。从SMAT的基本原理、制备技术、纳米化机理、结构性能和化学处理等方面介绍了表面机械纳米化研究工作已取得的进展。     

表面机械研磨法制备Ni+WC复合涂层的耐磨性研究

为强化TA1钛合金的组织结构并提高其耐磨损性能,采用行星式机械球磨装置,在Ni与WC 2种粉末配比分别为1∶1、2∶1、3∶1、4∶1及5∶1的5种混合型增强介质下对TA1合金进行表面机械复合强化处理,在0.05 MPa氮气气氛下,设定转速为350 r/min,时间为8 h,对TA1钛合金进行表面机械变形+固相涂层复合强化处理,这种一步法表面复合强化技术具有工艺简单、能耗少、涂层选材灵活等优势。结果显示：TA1钛合金表面形成由Ni+WC涂层+形变细晶区组成的复合强化层,涂层区厚度在40μm以上,其中Ni∶WC为3∶1时所得复合涂层内部缺陷最少,且连续均匀。在5 N、10 N载荷下Ni∶WC为3∶1摩擦系数相较于其他比例低,摩擦区间更加稳定且持续时间更长。2种载荷下磨损量均较TA1原样少,其中Ni∶WC为3∶1的强化样磨痕深度、磨损量均优异于其他4种配比,因此减摩效果最为优异。此种Ni、WC混合增强介质下表层机械复合强化工艺可大幅提升TA1钛合金表层耐磨损性。混合增强颗粒涂层具有较强的减摩效果,其磨损机制主要是磨粒磨损与氧化磨损。     

表面机械处理制备金属涂层的研究进展

表面机械处理(SMAT)是一种前景良好的金属材料表面改性方法,本文综述了其发展与应用。首先介绍了SMAT的不同试验方法与装置,如振动喷丸、旋转球磨、球磨辅助电镀等方法;然后分类说明SMAT制备的金属基体上的各种涂层,介绍了各类涂层的结构与性能,特别是纳米晶、非晶涂层的研究进展。最后对SMAT的发展方向及应用前景进行了展望。     

石油矿场机械中表面处理技术的应用分析

石油矿场机械表面处理常用的方法主要有化学化学镀镍和热喷涂技术,伴随石油勘探技术的进步,这两种常用的技术也随之不断改进。两种表面处理技术的应用,有效地降低了石油矿场机械的磨损,延长了机械寿命,提高了石油采掘的效率,为石油工业的发展节省了成本。本文将结合石油机械表面处理技术的发展趋势对两种主要表面处理技术进行简要的分析。     

Effect of surface mechanical attrition treatment of titanium using alumina balls: surface roughness,contact angle and apatite forming ability

The effect of surface mechanical attrition treatment (SMAT) of commercially pure titanium (CP-Ti) using 8 mm ? alumina balls was studied. SMAT induced plastic deformation, increased the surface roughness, reduced the grain size and decreased the contact angle (from 64° to 43°) with a corresponding increase in surface energy (from 32 to 53 mJ/m²). Untreated CP-Ti and those treated using alumina balls for 900 s reveals no apatite growth until the 28th day of immersion whereas those treated for 1800 and 2700 s exhibit apatite growth in selective areas and the extent of growth is increased with increase in immersion time in SBF. The study reveals that SMAT using alumina balls is beneficial in imparting the desired surface characteristics, provided the surface contamination is limited, which would otherwise decrease the apatite forming ability.     

Improving mechanical properties for pure irons by local surface mechanical attrition treatment

After a short-time surface mechanical attrition treatment process, a planar uneven structure was obtained on the surface of irons. The yield strength of the sample subjected to surface mechanical attrition treatment for 60?s is almost twice than that of the annealed sample, but the ductility is still well retained. The good combination of strength and ductility is mainly due to the extra strain hardening and the coexistence of soft and hard phases. The extra strain hardening delays the annihilation of dislocations and reduces the plastic instability, while the hard phase in the planar uneven structure suppresses the crack initiation, and the soft phase delays the crack propagation.     

Deformation mechanism and dynamic precipitation in a Mg-7Al-2Sn alloy processed by surface mechanical attrition treatment

The effect of second phases on the deformation mechanism of as-cast, solution-treated and aged Mg-7Al-2Sn (AT72) alloys during surface mechanical attrition treatment (SMAT) was investigated. Twinning was suppressed in the alloys containing second phases, which can provide nonuniform microstructures and phase boundaries as dislocation sources. Dynamic precipitation in AT72 alloys was studied during SMAT deformation as well. Mg₂Sn particles can dynamically precipitate on the surface of all AT72 alloys during SMAT process. The quantity of Mg₂Sn particles in the as-cast alloy, which is determined by the initial quantity of second phases, is larger than that of T4 and T6 alloys after the SMAT process.     

水平机械研磨酸性镀铜工艺研究

为研究不同研磨珠直径对镀层细化及性能的影响,在硫酸盐酸性镀铜溶液中添加玻璃珠,玻璃珠的运动对A3钢表面产生机械研磨作用(MA),并采用扫描电镜、显微硬度测试仪、电化学工作站等方法对其进行观察和分析.结果表明:与传统硫酸盐酸性镀铜层相比,机械研磨镀铜层的膜厚和孔隙率降低,硬度、耐蚀性、防渗碳性能提高;机械研磨镀铜层的晶粒尺寸大小随着研磨直径的增大先减小后增大;当研磨珠直径为8 mm时,镀层的晶粒尺寸小于2μm,硬度达到168.3 HV,孔隙率为0.6个/cm~2,渗碳层的厚度为40μm.     

高压扭转致纯铜晶粒细化及与应变的关系

设计并加工了在材料试验机上使用的高压扭转夹持装置,并用装置获得了不同扭转变形量的纯铜试样.使用电子背散射衍射技术测量了处理后试样晶粒尺寸沿径向的分布.对比分析了晶粒细化程度和应变量的关系,提出了一个描述晶粒细化的简单剪切球模型.结果表明,晶粒细化程度随着应变量的增大而增强,平均晶粒尺寸为原始平均尺寸的1/50.当剪切应变小于10时,晶粒尺寸随着剪切应变的增大迅速变小;当剪切应变大于10时,晶粒尺寸的变化趋于缓慢,晶粒细化程度与Stuwe等效应变之间有幂函数关系.依据简单剪切球形晶粒的模型,得到了晶粒细化程度随剪切应变增大而增强的规律,并与实验数据的变化趋势一致.     

Pack boronizing of AISI H11 tool steel: Role of surface mechanical attrition treatment

The role of surface mechanical attrition treatment (SMAT) on pack boronizing of AISI H11 type tool steel is addressed. SMAT induced plastic deformation, enabled nanocrystallization at the surface, reduced the grain size and increased the volume fraction of non-equilibrium gain boundaries, increased the accumulation of defects and dislocations at the grain boundaries and within the grains. These features helped to promote the diffusion of boron during boronizing and increased the case depth and hardness of the borided layer. Duplex treatment on SMATed H11 steel samples helps to achieve a higher case depth when compared to the single stage treatment. The findings of the study suggest that SMAT can be used as a pre-treatment for boronizing of H11 tool steel.     

Effect of surface mechanical attrition treatment (SMAT) on microhardness,surface roughness and wettability of AISI 316L

Surface roughness and wettability are among the surface properties which determine the service lifetime of materials. Mechanical treatments subjected to the surface layer of materials are often performed to obtain the desired surface properties and to enhance the mechanical strength of materials. In this paper, the surface microhardness, roughness and wettability of AISI 316L stainless steel resulting from surface mechanical attrition treatment (SMAT) are discussed. The SMAT was conducted with various processing parameters, including the duration of treatment, the number and diameter of milling ball, and the motor speed of the SMAT machine. The result indicates an increasing surface microhardness due to the SMAT. A harder surface is yielded by the SMAT with a longer duration, a bigger and a larger number of milling balls, and a higher vibration frequency. The SMAT also creates craters on the steel surfaces which correspond to the increasing roughness from 0.046 μm to the values in ranging from 0.681 to 0.909 μm. The change on the surface roughness by the SMAT does not only depend on the duration of treatment, but also the other processing parameters. In addition, the wettability of AISI 316L surface slightly increases by the SMAT as seen on the decreasing droplet contact angle from 88.6° to the values ranging from 74.4° to 87.0°. Such a droplet contact angle reduction is related to the increasing surface roughness after the SMAT. In conclusion, this study reveals the possibility of the SMAT to be used for surface properties optimization in addition to the strength enhancement of stainless steel.     

一维单体纳米材料弹塑性变形机理的原位研究进展EI北大核心CSCD

近年来,随着研究技术手段的发展,纳米线表现出了大量具有潜在应用价值的新现象。清晰描绘纳米线结构与力学性能的构效关系对纳米器件的设计、服役以及性能优化具有重要的指导意义。本文首先归纳了纳米线力学性能几种常用的原位测试方法,其次介绍了各类纳米线在拉伸实验中的弹性和强度等力学性能,阐述了纳米线与尺寸相关的塑性变形,此外简述了纳米线在原位测试中所表现出的奇特力学行为。今后,系统地研究原位电镜表征过程中电子束辐照对纳米线变形行为的影响,探究纳米线在复杂外场环境下所展现的力学性能,从而建立一套完备的理论指导体系,是纳米材料性能原位表征领域的重要发展方向。     

Size effect on deformation behavior and ductile fracture in microforming of pure copper sheets considering free surface roughening

In meso/micro-scaled plastic deformation, material deformation and ductile fracture are quite different from those in macro-scale. The roughness of the free surfaces of workpiece increases with deformation and the decrease of grain number in the sample thickness direction, leading to the nonuniformity of specimen thickness. The so-called size effect and free surface roughening may in turn affect the deformation behavior, ductility and fracture morphology of the samples. To explore the coupled effect of workpiece geometry and grain size on material flow behavior in meso/micro-scaled plastic deformation, uniaxial tensile test of pure copper sheets with different thicknesses and comparable microstructure was performed. The experimental results reveal that the material flow stress, fracture stress and strain, and the number of microvoids on fracture surface are getting smaller with the decreasing ratio of specimen thickness to grain size. In addition, the modified Swift’s equation and the corrected uniform strain are closer to the experimental ones considering the thickness nonuniform coefficient induced by the free surface roughening. Furthermore, the observation of fracture morphologies confirms that the local deformation caused by the free surface roughening leads to strain localization and a decreased fracture strain when there are only a few grains involved in plastic deformation.     

Dislocation distributions in monocrystalline nickel‐based superalloys subjected to thermo‐mechanical fatigue with and without hold times

The characteristics of dislocation configurations under thermo‐mechanical fatigue cycling were investigated in [001] oriented nickel‐based single‐crystal superalloys. Thermo‐mechanical fatigue tests were performed on TMS‐75 (without hold time) and TMS‐82 (with hold time) superalloys. The specimens were subsequently studied by transmission electron microscopy under two‐beam conditions. In TMS‐75 superalloy, cross‐slipping is the main characteristic for the low number of dislocations. In TMS‐82 superalloy, more complex process of dislocation configurations has been demonstrated in detail, involving five stages: after the first stress relaxation, after the first tensile plastic deformation, after the second stress relaxation, after 30 cycles and after rupture. In addition, for TMS‐82 superalloy, there is a reversible movement behaviour of stacking faults that occur in compression and disappear in tension. After rupture, the number of dislocation is related to the hold time. Longer hold time could generate a higher degree of stress relaxation and produce more dislocations with climbing characteristic.