Microstructure, mechanical and corrosion properties of magnesium alloy bone plate treated by high-energy shot peening

To enhance the mechanical properties and corrosion resistance of magnesium alloys,high-energy shot peening(HESP)was used.According to the results,the in-situ surface nanocrystallization(ISNC)microstructure was fabricated on the magnesium alloy surface,and its formation mechanism was the coordination among twins,dislocations,subgrain boundary formation and dynamic recrystallization.Under the released surface stress of sample,the residual compressive stress and microhardness rose,thus enhancing compactness of the surface passivation film Mg(OH)2.Besides,the corrosion rate dropped by 29.2% in maximum.In the polarization curve,the maximum positive shift of the corrosion potential of sample was 203 mV, and the corrosion current density decreased by 31.25% in maximum.Moreover,the compression resistance and bending resistance of the bone plate were enhanced,and the maximum improvement rates were 18.2% and 23.1%,respectively.Accordingly,HESP significantly enhanced mechanical properties and corrosion resistance of magnesium alloys.

Microstructure evolution of AZ91D induced by high energy shot peening

A nanostructured surface layer was fabricated on a AZ91D magnesium alloy by using a high-energy shot peening(HESP).HESP induced structure along the depth of the treated sample surface layer was characterized by means of X-ray diffractometer (XRD),transmission electron microscope(TEM) and high resolution transmission electron microscope(HRTEM).The experimental results show that a deformed layer of about 50 μm has formed after HESP treatment and the average grain size increases from about 40 nm in the surface layer to about 200 nm at the depth of 40 μm.The surface nanocrystallization can realize intercoordination of the dislocations slipping and dynamic recrystallization.The nanocrystalline grains have stacking faults and dislocation in their interiors.The microhardness of the top surface is about triplicate that of the coarse-grained matrix.

Prediction model for surface layer microhardness of processed TC17 via high energy shot peening

The bulk TC17was subjected to the high energy shot peening(HESP)at the air pressures ranging from0.35to0.55MPa and processing durations ranging from15to60min.The microhardness(HV0.02)from topmost surface to matrix of the HESP processed TC17was measured,which generally decreases with the increase of depth from topmost surface to matrix and presents different variation with air pressure and processing duration at different depths.A fuzzy neural network(FNN)model was established to predict the surface layer microhardness of the HESP processed TC17,where the maximum and average difference between the measured and the predicted microhardness were respectively8.5%and3.2%.Applying the FNN model,the effects of the air pressure and processing duration on the microhardness at different depths were analyzed,revealing the significant interaction between the refined layer shelling and the continuous grain refinement.

Internal Friction and Elastic Study on Surface Nanocrystallized 304 Stainless Steel Induced by High-energy Shot Peening

The 304 stainless steel with nanostructured surface layer was successfully obtained by using the high-energy shot peening (HESP) method. The internal friction and Young's modulus of this kind of surface nanocrystallized material were dynamically measured by means of the vibrating reed apparatus. The results implied that different treatment time could induce different microstructure and distribution characteristic of defects in this kind of materials. It is also demonstrated that there is a transition layer between the nano-layer on surface and the coarse grain region inside. The transition layer obviously has certain influence on the overall mechanical properties.

Microstructure characteristics of as-surface nanocrystallized 1420 aluminum alloy by high-energy shot peening

A nanostructured surface layer was fabricated on 1420 aluminum alloy by high-energy shot peening.Microstructures were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and high-resolution electron microscope(HRTEM), and microhardness measurement was conducted along the depth from top surface layer to matrix of the sample peened for 30 min. The results show that a nanocrystalline layer about 20 μm in thickness is formed on the surface of the sample after high-energy shot peening, in which the grain size is changed from about 20 nm to 100 nm. In the surface layer of 20 -50 μm in depth, the microstructure consists of submicron grains. The surface nanocrystallization is accomplished by dislocation slip. The microhardness of the top surface nanostructured layer is enhanced obviously after high-energy shot peening(HESP) compared with that of the coarse-grained matrix.

Effect of shot peening on hydrogen embrittlement of high strength steel

The effect of shot peening（SP） on hydrogen embrittlement of high strength steel was investigated by electrochemical hydrogen charging, slow strain rate tensile tests, and hydrogen permeation tests. Microstructure observation, microhardness, and X-ray diffraction residual stress studies were also conducted on the steel. The results show that the shot peening specimens exhibit a higher resistance to hydrogen embrittlement in comparison with the no shot peening（NSP） specimens under the same hydrogen-charging current density. In addition, SP treatment sharply decreases the apparent hydrogen diffusivity and increases the subsurface hydrogen concentration. These findings are attributed to the changes in microstructure and compressive residual stress in the surface layer by SP. Scanning electron microscope fractographs reveal that the fracture surface of the NSP specimen exhibits the intergranular and quasi-cleavage mixed fracture modes, whereas the SP specimen shows only the quasi-cleavage fractures under the same hydrogen charging conditions, implying that the SP treatment delays the onset of intergranular fracture.

High-precision simulation and experimental verification of residual stress and surface topography of cylindrical surface shot peening

Shot peening is commonly employed for surface deformation strengthening of cylindrical surface part.Therefore,it is critical to understand the effects of shot peening on residual stress and surface topography.Compared to flat surface,cylindrical surface shot peening has two significant features:(i)the curvature of the cylindrical surface and the scattering of the shot stream cause dis-tributed impact velocities;(i)the rotation of the part results in a periodic variation of the impact velocity component.Therefore,it is a challenge to quickly and accurately predict the shot peening residual stress and surface topography of cylindrical surface.This paper developed a high-precision model which considers the more realistic shot peening process.Firstly,a kinematic analysis model was developed to simulate the relative movement of numerous shots and cylindrical surface.Then,the spatial distribution and time-varying impact information was calculated.Subsequently,the impact information was used for finite element modeling to predict residual stress and surface topography.The proposed kinematic analysis method was validated by comparison with the dis-crete element method.Meanwhile,9310 high strength steel rollers shot peening test verified the effectiveness of the model in predicting the residual stress and surface topography.In addition,the effects of air pressure and attack angle on the residual stress and surface topography were investigated.This work could provide a functional package for efficient prediction of the surface integrity and guide industrial application in cylindrical surface shot peening.

喷丸对CoCrFeMnNi高熵合金疲劳性能的影响

愈发严苛的服役环境对高熵合金未来在航空航天领域的应用提出更高要求,喷丸强化技术能够细化晶粒,改善材料表面完整性及疲劳性能,研究了喷丸强化对CoCrFeMnNi高熵合金疲劳性能的影响。选用陶瓷丸进行喷丸强化处理,采用X射线衍射技术测量了表面残余应力,并对试样进行了旋转弯曲疲劳试验。结果表明,喷丸强化在CoCrFeMnNi高熵合金表面引入了残余压应力,最大值为437 MPa。450 MPa下,CoCrFeMnNi高熵合金寿命延长至原始试样寿命12倍左右,疲劳极限从245 MPa提升至400 MPa,疲劳寿命得到显著提升。此外,喷丸强化处理改变了高熵合金试样的裂纹萌生位置,喷丸试样的疲劳裂纹萌生于材料表面的下表层,原始试样的疲劳裂纹则起始于材料表面。

医用钛合金表面纳米化组织与性能研究

针对近β型TLM钛合金试样表面进行了不同时间的高能喷丸处理,采用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)以及显微硬度仪等对不同喷丸处理后的试样进行了组织观察和性能测试。研究发现,在喷丸的近表层发生了纳米化,形成了一定厚度的纳米晶层。喷丸处理时间越长,最表层的平均晶粒尺寸越小,晶粒尺寸沿着厚度方向有梯度变化,距喷丸表面越远,晶粒尺寸就会越大。同时纳米晶层的显微硬度相对于基体组织有大幅提高,显微硬度距表面距离越远,显微硬度越低,硬度的提升主要是由于表面晶粒细晶强化的作用所致。

喷丸对4Cr5Mo2V钢高温摩擦磨损性能的影响

对4Cr5Mo2V钢试样进行3道次复合喷丸,通过与未喷丸试样对比,研究了喷丸对试验钢表面形貌、显微组织、硬度、残余应力以及高温(100,300,500℃)摩擦磨损性能和机制的影响。结果表明:喷丸处理显著提高了试验钢表面粗糙度,使试验钢表面形成了明显的塑性变形层、硬化层与残余压应力层;在100,300,500℃下,与喷丸前相比,喷丸后试验钢的磨损率分别降低了41.8%,17.1%,63.3%,耐磨性能的提高与喷丸产生的硬化层和残余压应力层有关。在100,300℃下,喷丸前后试验钢的磨损机制均主要为黏着磨损和磨粒磨损,而当温度升高至500℃时,磨损机制为氧化磨损,喷丸试验钢仍能保持较高的硬度与残余压应力,同时表面氧化层更致密稳定,仅发生轻微氧化磨损。

喷丸对TNM-TiAl合金组织以及450℃下高周疲劳性能的影响

目的针对TNM-TiAl合金(Ti-43.5Al-4Nb-1Mo-0.1B)服役时受高周疲劳影响的问题,揭示喷丸处理技术对TNM-TiAl合金疲劳性能的影响规律。方法通过扫描电镜和透射电镜分析喷丸前后的组织演变,测量喷丸前后合金表面残余应力、表面粗糙度和显微硬度分布规律,采用梯度法测量喷丸前后的高周疲劳极限,并分析断口形貌和断口附近组织。结果喷丸后合金表面粗糙并且存在烧蚀坑,表面附近的片层团发生弯曲,在组织内部引入大量位错、位错缠结以及位错胞等缺陷。喷丸后表面粗糙度明显提高,显微硬度提高了209HV0.05,从表面到内部形成深度为260μm的硬度梯度。喷丸后试样表面的残余压应力为446 MPa,深度约为85μm。喷丸后在450℃下保温30 h后合金表面最大硬度仍比喷丸前的硬度高166HV0.05,硬化深度约为150μm。未喷丸光滑试样、喷丸光滑试样、未喷丸缺口试样和喷丸缺口试样的疲劳极限分别为615、637、385、455 MPa,光滑试样断裂类型为穿晶解理型脆性断裂,而缺口试样为穿晶脆性断裂。结论喷丸能够显著提高最大残余压应力和引入应力的深度,且喷丸引入的组织具有一定的热稳定性,喷丸明显提高了TNM-TiAl合金的疲劳极限。

医用钛合金表面喷丸后微米压痕研究

采用高能喷丸强化(HESP)对医用钛合金进行了表面处理,并采用SEM、AFM、TEM和微米压痕对处理过程的微观组织演变及其微观力学性能进行了研究。结果表明,经过HESP处理,在材料表面形成了梯度组织,并且材料表面粗糙度随着冲击时间的增加而先增加后降低,逐渐趋于稳定;TEM分析显示材料表面经过处理形成了纳米晶。通过微米压痕分析发现,强化后的样品弹性模量随加工时间的增加而减小,最小值出现在处理60 min的表面位置,约为59.026 GPa,相对于未处理样品下降了15.78%,且随着喷丸时间的增加,屈服强度和应变硬化指数逐渐增加。

高压柱塞泵关键部件超声空化水喷丸表面强化工艺研究

高压柱塞泵是高端液压装备的核心元件,但由于其工作环境恶劣且内部几何结构复杂,国内缺乏良好的关键部件强化手段,导致国产高压柱塞泵寿命较低。该文利用超声波诱导水体产生空化泡,空泡溃灭产生射流冲击待强化表面,可获得良好的强化效果。为能够多维度分析不同参数对表面完整性的影响,以加工时间、靶向距离、超声振幅(声压强度)为试验因素,试件表面粗糙度和残余应力为评价指标,设计三因素三水平正交试验。结果表明,超声空化水喷丸工艺可以提高其表面性能,是一种十分有研究前景的强化方式。

复合喷丸工艺对A100钢表面完整性和疲劳性能的影响研究

A100超高强度钢是航空领域中广泛用于关键承力部位的材料,其疲劳特性对零部件的使用性能有着重要影响。对A100超高强度钢在复合喷丸强化后的表面完整性和疲劳性能进行了研究,探究了复合喷丸工艺参数对A100超高强度钢零部件表面粗糙度、显微硬度、表面残余应力、疲劳性能等的影响。结果表明:合理的复合喷丸强化能使零部件获得良好的表面完整性,显著提升其抗疲劳性能。

航空发动机制造表面完整性技术在特种工艺的研究与应用

本文研究喷丸覆盖率对GH4698高温合金转子部件表面完整性的影响。通过对不同覆盖率的喷丸处理试样进行显微硬度测试和金相观察,分析喷丸处理对高温合金表面硬度和微观结构的影响。结果显示,喷丸处理可以提高高温合金的表面硬度,并形成细小晶粒结构,改善其完整性。此外,随喷丸覆盖率的增加,高温合金硬度和完整性也呈现增加趋势。这些研究结果对于航空发动机制造中表面完整性技术的应用具有重要意义。

机械喷丸成形对试片的影响

本研究围绕机械喷丸成形对试片的影响进行了深入探讨。研究的主要目的是评估机械喷丸成形如何改变预应力钢材试片的物理和机械性能。实验方法包括对不同预应力水平的高强度钢试片进行机械喷丸处理,并进行硬度测试、拉伸强度测试、微观结构分析以及疲劳寿命测试。研究结果表明,机械喷丸成形显著提高了试片的硬度和拉伸强度,改善了微观结构,并延长了疲劳寿命。这些发现对于理解和优化高性能材料的加工工艺具有重要意义。然而,研究也存在局限性,未来工作应包括探索不同材料的响应和优化喷丸参数。

先进喷丸表面改性技术研究进展

综述了先进喷丸表面改性技术研究现状及应用,阐述了微粒子喷丸、激光喷丸、超声/高能喷丸、高压水射流喷丸的基本原理,与传统喷丸对比发现,微粒子喷丸可提高材料的耐磨性,激光喷丸可精确控制定位,超声/高能喷丸可实现材料表面纳米化,高压水射流喷丸可承受半柔性冲击并减少应力集中.此外,对各种喷丸技术综合分析并进行对比,认为超声喷丸、复合喷丸(高能-微粒喷丸,激光-机械喷丸)综合性能最佳,并展望了未来应重点开展的工作.

SS400钢焊接接头表层组织纳米均一化及硬度均一化处理

采用高能喷丸技术对 ＳＳ４００钢焊接接头的表面层进行处理 利用 ＸＲＤ，ＴＥＭ，ＳＥＭ对处理后的表面层进行结构表征，同时测量了高能喷丸引起的硬度变化 结果表明，高能喷丸处理可使焊接接头的表面层形成尺寸均匀、取向随机分布的纳米晶；焊接接头三个区域的纳米层硬度一致，且远高于高能喷丸处理前样品的硬度，实现了 ＳＳ４００钢焊接接头区表层组织纳米均一化和硬度均一化 表面纳米化对材料表面的强化有着重要的贡献。

铝合金表面纳米化处理及显微结构特征

采用高能喷丸技术在 14 2 0铝合金上制备出纳米晶结构表层 ,利用X射线衍射仪、透射电子显微镜及高分辨电子显微镜研究由表层沿厚度方向的结构变化特征 ,并对硬度沿厚度方向的变化进行分析。结果表明 :经过表面高能喷丸处理 ,样品表面形成了厚度约为 2 0 μm的纳米晶层 ,平均晶粒尺寸由约 2 0nm逐渐增加到约 10 0nm ;距表层约 2 0～ 5 0 μm为亚微细晶层 ;表面纳米化的程度与塑性变形量有关 ;表面纳米化是通过位错滑移的塑性变形方式实现的 ;与样品的内部相比 。

喷丸表面覆盖率对Ti60高温钛合金疲劳性能的影响

采用新型的陶瓷弹丸,对Ti60钛合金进行相同喷丸强度和不同表面覆盖率(100%,200%,400%)的喷丸强化,研究了喷丸前后的表面形貌、表面粗糙度、残余应力场、X射线衍射峰半高宽等表面完整性特征参数以及其对高温疲劳寿命的影响。结果表明,喷丸覆盖率对表面完整性具有重大影响,因此不同覆盖率喷丸Ti60钛合金试样具有显著差异的疲劳寿命。采用200%覆盖率喷丸,可以使钛合金Ti60保持较小的表面粗糙度(Ra=1.2μm),较大的尖端圆角曲率半径(相对磨削加工),较好的残余应力分布和稳定的强化层微观组织,这些较好的表面完整性状态使Ti60钛合金的高温旋转弯曲疲劳寿命提高了4倍左右;而采用其他表面覆盖率(100%,400%)喷丸时,Ti60钛合金的高温疲劳寿命提高了2倍左右。