首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
A pulsed action of an electron beam on a Zr-1% Nb zirconium alloy is studied. Alloy samples are irradiated by three 50-μs pulses at an energy density of 15–25 J/cm2, a power of (3–6) × 104 W/cm2, a current density of 10–50 A/cm2, and an electron energy of 18 keV. This method of processing is found to modify the surface layer of the alloy without changing the structure-phase state of its volume. This surface modification increases the hydrogen saturation resistance of the alloy.  相似文献   

2.
The influence of hydrogen and a pulsed electron beam on the properties of Zr-1%Nb alloy is studied. It is shown that electron beam processing results in the formation of martensite with an intricate morphology in the subsurface layer of the alloy. It is found that the amount of hydrogen penetrating into the modified alloy is twice as low as in the as-prepared material. In addition, the modified alloy is more stable against the hydrogen action.  相似文献   

3.
 用含Cn+和H+、加速电压250 kV、脉冲宽度70 ns、束流密度160 A/cm2的强流脉冲离子束辐照DZ4合金,辐照次数分别为2,5,10,15。实验结果表明:辐照后样品的表面出现了熔坑,多次脉冲辐照后样品的表面熔坑边缘模糊甚至消失。近表面存在厚1~2 mm的重熔层,晶粒较细,晶界模糊;熔坑周围富集Cr和Mo等元素;强流脉冲离子束辐照处理后DZ4合金的耐腐蚀性能明显提高,腐蚀速率下降,这是由于辐照减弱了由于晶界和晶粒本体的成分差异而引起的晶界腐蚀;同时离子束辐照后的DZ4合金在高温氧化时更容易形成一层连续的保护性氧化物,其主要成分是致密的Al2O3,使得DZ4合金的耐高温氧化性能也有所改善。  相似文献   

4.
利用原子力显微术的轻敲模式(TM-AFM),并采用形貌与相位同时成像技术对强流脉冲离子束(IPIB)辐照前后试样表面进行了系统标征,得到了试样表面的高度像及相位像的衬度.分析结果表明:在高流强密度、多次脉冲条件下,IPIB辐照可使试样表面变得光滑化,从相位像中可以定性分析出辐照后表面硬度也得到一定程度的提高.  相似文献   

5.
Supersaturated surface alloys produced by very high dose (0.8–2.6×1017cm–2) implantation of As-ions into silicon and subsequent pulsed electron-beam annealing have been investigated by means of the channeling technique. The maximum solubility limit of 7×1021 As/cm3 has been determined. It exceeds the equilibrium solubility limit by more than a factor of 4. Angular scan measurements indicated that for doses above 1×1017cm–2 As atoms are displaced by about 0.12 Å from the regular lattice sites.  相似文献   

6.
The dry sliding tribological behavior of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at energy density of 3.4 J/cm2 with 10 shots is investigated by dry sliding wear tests in order to explore the effect of HIPIB irradiation on tribological property of magnesium alloy. Surface morphologies, composition and structure of the irradiated AZ31 magnesium alloys are examined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results indicated that HIPIB irradiation led to the increase in surface microhardness and the reduction in friction coefficient and wear rate. Wear rate for both the original and the irradiated samples increased with increasing sliding load from 0.1 to 0.5 N. The transition from severe metallic wear to mild oxidative wear induced by HIPIB irradiation was observed by a combined analysis in surface morphology and chemical composition of wear tracks, mechanically mixed materials and wear debris, which is mainly attributed to the significant increase in microhardness resulting from grain refinement on the irradiated surface. In addition, defects induced by HIPIB irradiation promoted the diffusion of oxygen during sliding wear and therefore led to the formation of compact mixed materials and protective films on the wear tracks surface, which also contributes to the transition in wear mechanism of AZ31 magnesium alloy induced by HIPIB irradiation.  相似文献   

7.
Droplet behavior from the surfaces of pure metals Ti and Al ablated by high-intensity pulsed ion beam (HIPIB) with an ion current density from 30 to 200 A/cm2 has been investigated to explore the mechanism of mass transfer on HIPIB-irradiated materials. Droplet ejection on the ablated metal surface is studied by scanning electron microscope observation, energy dispersive X-ray spectroscopy analysis and profilometer measurement. The presence of ejected droplets from the irradiated surfaces is detected on both the surfaces of irradiated metals and substrates locating adjacent to the ablated surfaces. Moreover, the number density of droplets observed on both the surfaces tends to increase with increasing the ion current density. This phenomenon correlates to the fact that higher ion-beam intensity led to a more intense ablation, i.e. a severer droplet ejection. In addition, surface roughness (Ra) for the respective metals is continuously increased with increasing the ion current density, indicating a more significant disturbance on the melted surfaces caused by the correspondingly severer droplet ejection. Combined with the previous finding of selective ablation on titanium, it is concluded that the droplet ejection is the efficient cause of cratering and disturbance on HIPIB-ablated surfaces.  相似文献   

8.
9.
论述了离子束作用下固体表面次级电子产生的机制,介绍了特种真空器件中次级电子抑制的各种方法及其优缺点,提出了脉冲离子束作用下靶面次级电子抑制的自偏势法和曲面靶法等设计思路,并在实验上进行了初步验证。实验结果表明,自偏势电压大于80 V后,次级电子得到很好的抑制。在相同束流情况下,曲面靶较平面靶的次级电子产额少。利用实验结果进行估算得到了近似的次级电子产额约为0.67,比文献中的结果(0.58)偏大。对实验中自偏势法抑制反峰电子电流的效果进行了分析和讨论,结果表明:自偏势法不但能够有效抑制离子打靶产生的次级电子,还能抑制由功率源不稳定带来的入射反峰电子流。  相似文献   

10.
The results of examination of the GaAs-target erosion under irradiation by a high-power pulsed ion beam are reported. In the experiments, use was made of a high-power pulsed ion source with the following parameters: ion energy — 250 keV, target current density — 350 A/cm2, pulse duration — 80 ns, target energy density — up to 7 J/cm2. The target erosion coefficient and its dependence on the number of successive pulses are measured. It is found that the surface roughness parameter is increased with the number of successive beam pulses. A regular structure of surface relief is observed to form in the case where the number of pulses > 20–40. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–70, January, 2007.  相似文献   

11.
论述了离子束作用下固体表面次级电子产生的机制,介绍了特种真空器件中次级电子抑制的各种方法及其优缺点,提出了脉冲离子束作用下靶面次级电子抑制的自偏势法和曲面靶法等设计思路,并在实验上进行了初步验证。实验结果表明,自偏势电压大于80 V后,次级电子得到很好的抑制。在相同束流情况下,曲面靶较平面靶的次级电子产额少。利用实验结果进行估算得到了近似的次级电子产额约为0.67,比文献中的结果(0.58)偏大。对实验中自偏势法抑制反峰电子电流的效果进行了分析和讨论,结果表明:自偏势法不但能够有效抑制离子打靶产生的次级电子,还能抑制由功率源不稳定带来的入射反峰电子流。  相似文献   

12.
In order to predict the glass forming ability of binary alloys produced by ion beam mixing, a two dimensional map is constructed. The two coordinates of this map are the ratio of atomic radii rA/rB, and the heat of formation ΔH of an equiatomic compound, calculated using Miedema's model. In this map, binary systems which form in the amorphous phase are clearly separated from the others. The same map is valid both for metal-metal and metal-semiconductor binaries.  相似文献   

13.
Nonlinear processes involved in oxygen diffusion from the adsorption layer into the bulk of an alloy exposed to a low-energy high-current pulsed electron beam are investigated in the framework of a mathematical model accounting for nonequilibrium activation and melting of the irradiated material. An example is a TiNi alloy. The model includes heat, diffusion, and kinetic equations, with initial and boundary conditions corresponding to electron-beam treatment of the alloy. Kinetic parameters are estimated. The time and space distributions of the TiNi temperature and oxygen concentration for a varying maximum pulse power density and pulse duration are calculated. The heating and diffusion depths are determined. The results obtained with and without regard to the activation effect are compared. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 8–15, March 2007.  相似文献   

14.
A film/substrate system has been treated with a submillisecond high-intensity electron beam. Examinations have shown that the electron-beam treatment of the film/substrate system resulted in alloying of the surface layer of the material throughout the melt which was accompanied by the formation of nanodimensional phases.  相似文献   

15.
The results from secondary ion mass spectrometry (SIMS) investigations of the surface of Zr50V50 intermetallic getter alloy under residual and elevated partial pressures of hydrogen at different temperatures are reported.  相似文献   

16.
The surface morphology of aluminum alloys under irradiation by a high-power nanosecond ion beam with a low current density is investigated. The possible factors responsible for the change in the surface relief are considered.  相似文献   

17.
The pulsed intense ion beam, emitted from a dense plasma focus (DPF) discharges performed with hydrogen gas, has been used to ablate the graphite target depositing diamond-like carbon (DLC) films on Si substrates. The substrates were mounted on a holder, which allowed for deposition at positions between normal and 20° off-normal to the target. The samples were removed for analysis after 10 and 20 shots. Nano-particles were observed in the films by a field-emission scanning electron microscope. Raman spectra indicate that sample deposited at 20° off-normal with 20 shots possesses the highest sp3 content among the samples. The film deposited at this position was also found has the highest hardness.  相似文献   

18.
对强流脉冲离子束(IPIB)辐照Ti靶的烧蚀效应进行了二维数值研究.得到了表面烧蚀物质随脉冲时间的变化关系.得出TEMP Ⅱ 型加速器产生的脉冲束流辐照靶材时引起的汽、液化均是从表面开始、并且汽化过程中表面物质被层层烧蚀的结论.同时,得到中心区的平均烧蚀速度为10m/s 数量级,它远小于产生的烧蚀等离子体的喷发速度.得到脉冲期间靶材内部不同位置烧蚀斑痕形状的时间演化过程,以及束流中含有的离子种类分额不同时IPIB辐照过程产生的不同效果. 关键词: 强流脉冲离子束 靶 烧蚀过程 二维数值模拟  相似文献   

19.
采用一维无碰撞的动力学鞘层模型计算了脉冲等离子体在恒压引出时的等离子体鞘层厚度变化,分别对短脉冲和长脉冲放电时的离子源发射面演变进行了分析。结果表明:对于短脉冲放电,发射面位置的变化相对等离子体密度的变化存在一定时间的延迟;对于长脉冲的上升沿和直流放电的开启阶段,鞘层厚度变化的速度与离子初始速度相关,稳定后发射面的位置与离子初始速度和等离子体密度的乘积相关。  相似文献   

20.
Intense pulse metallic ion beams (Al+, Cu+, and Pb+) were produced by a magnetically insulated ion diode having a metal anode. Metal ion plasmas on the anode could be generated through enhanced electron bombardment by using a radial cathode. The energy, current density, and duration time of the lead ion beam were 30~140 keV, ~7.5 A/cm2 (total ion current ⩾0.5 kA), and 800 ns, respectively. The ion current density exceeded the space-charge-limited current by a factor of 50. The lead ions in the first-to-sixth states of ionization were detected by a Thomson-parabola ion-spectrometer together with light loss, such as C+ and O +. The ratio of the ion current of heavy metals to the total ion current was measured using a magnetic mass analyzer with a charge collector. The ratio was about 90% for a lead ion beam and 20~50% for Al and Cu ion beams  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号