Nitrogen-PBII modification of ultra-high molecular weight polyethylene: Composition, structure and nanomechanical properties

Plasma based ion implantation of nitrogen was performed on mechanically polished UHMWPE model samples by applying 27.13 MHz RF energized low pressure N₂ plasma with 15-30 kV pulses and fluences up to 5 · 10¹⁷ ions/cm². Surface compositional and structural alterations and nanomechanical property changes were investigated by XPS, Raman and by nano-indentation and nano-scratch techniques. The implanted N amounted up to 13-20 at.% (N/C = 0.18-0.30), while a significant amount of oxygen could also be detected on the surface. Three types of chemical states of the incorporated nitrogen were detected, related to linear sp² CN-C and to planar and non-planar sp³ type C-N bonds. The applied PBII treatment led to severe dehydrogenation of the polyethylene resulting in conversion of the surface into a nitrogen-containing DLC type structure. Up to four-fold increase of the hardness at 50-100 nm depth was measured compared to the untreated samples. The scratch volume, characterising the wear resistance, decreased also significantly down to 25-35% of the original value.     

热处理对G50超高强度钢力学性能的影响

通过调整热处理过程的主要工艺参数,研究了840～900℃淬火以及200～500℃回火温度范围内G50钢硬度、强度、塑性以及冲击性能的演变规律。结果表明:在相同回火温度下,随着淬火温度的升高,G50钢的硬度和强度总体呈降低趋势,而塑性和冲击性能则得到提高;在相同淬火温度下,随着回火温度的升高,G50钢的硬度、强度和冲击性能在总体上呈降低趋势,而塑性则先降低后增加。"高温淬火+低温回火"将有助于G50钢获取较优的力学性能。      

Effect of chromium additions on the mechanical and physical properties and microstructure of Fe-Co-Ni-Cr-Mo-C ultra-high strength steel: Part I

The effect of chromium additions to an Fe-14Co-10Ni-0.1Mo-0.16C (AF1410 based) secondary hardening steel was evaluated by mechanical and physical properties and by microstructural examination. This unique behavior was extended to encompass a large range of aging temperatures and times that may be encountered during commercial thermal treatment and/or welding. In the aging range of 482 to 550 °C, an increase in chromium from 2 to 3% in the AF1410 based steel resulted in a substantial strength decrease concomitant with an increase in toughness. This behavior is related to a peak hardening shift, early M₂C carbide coarsening, and an increase in reverted austenite for the 1 wt% Cr increase. The increased aging kinetics resulting from the 3Cr steel caused a faster dissolution of Fe₃C and rapid changes in chromium partitioning in the (Mo,Cr)₂C carbide resulting in a coherency loss with a corresponding decrease in lattice parameter. The kinetics of the secondary hardening reaction, for the two steels, was determined by resistivity data for changes in aging parameters (time/temperature).     

淬火温度对GE1014超高强度钢组织及性能的影响

采用力学性能测试、透射电镜(TEM)、X射线衍射(XRD)仪和电子背散射衍射(EBSD)等分析方法,研究了淬火温度对GE1014超高强度钢组织及性能的影响。结果表明,试验钢的抗拉强度随淬火温度的升高先逐渐升高,随后降低,并且在925 ℃达到峰值2112 MPa,规定塑性延伸强度则呈现随淬火温度的升高小幅降低的趋势,试验钢的断面收缩率和U型冲击性能均随淬火温度的升高缓慢升高,在950 ℃附近出现降低趋势;试验钢的原始奥氏体晶粒和马氏体块的尺寸都随着淬火温度的升高而长大,当淬火温度超过925 ℃时,原始奥氏体晶粒尺寸快速粗化,而马氏体块尺寸则全程长大缓慢;850~925 ℃范围内,基体中的残留奥氏体含量随着淬火温度的升高而显著降低;淬火温度低于900 ℃时,试验钢中存在球状富Mo型M₆C碳化物,淬火温度升高至900 ℃未观察到未溶相。     

Effect of small concentrations of oxygen and nitrogen on the structure and mechanical properties of sputtered titanium films

The results of a study of small additions of oxygen and nitrogen on the structure and mechanical properties of nanocrystalline titanium films obtained by magnetron sputtering are presented.     

Surface modification of ultra-high molecular weight polyethylene for joint prosthesis and sports applications

The recent progresses in the surfaee modification of ultra high molecular weight polyethylene (UHMWPE) using such advanced surface modification technologies as conventional ion implantation (CⅡ), new plasma immersion ion implantation (PⅢ) and novel active screen plasma (ASP), were all reported. Significantly improved wear resistance was achieved, which has great potential for extending the life-span of joint replacement prostheses and enhancing the performance of such sports equipment as skis and snowboards.     

Friction and wear properties of ultra-high molecular mass polyethylene reinforced with Al2O3 nano-particle

The ultra-high molecular mass polyethylene (UHMMPE) as an artificial joint acetabular material was filled with nano-powder of Al2O3 of various mass fractions. The effect of Al2O3 mass fraction on the hardness, wetting property and tribological properties of the Al2O3-UHMMPE composites under dry friction sliding against both stainless steel and Ti-6Al-4V alloy was investigated. The morphologies of the worn surfaces of composites were observed with optical microscope. The results show that, wetting property and wear resistance of the composites are improved by filling Al2O3, while the friction coefficient is decreased largely under dry friction as compared with that of the unfilled UHMMPE. This is attributed to the reinforcing function of the nano-powder of Al2O3 in the composites. The wear of UHMMPE is dominated by plowing, plastic deformation and fatigue wear; while the Al2O3-UHMMPE composites are characterized by the mild fatigue wear.     

The correlation between surface acoustic wave velocity and mechanical properties of TiN and TiNx coatings

Surface Brillouin scattering is used to study a variety of acoustic excitations in TiN films on high speed and mild steel. The dispersion relation is measured and calculated using surface Green's functions. Reduced elastic constants of the thinner films are necessary to produce agreement between theory and experiment. This is considered to be the result of an interface layer consisting mainly of titanium oxide (TiO) as identified by XPS measurements. In TiN_x films the residual stress and critical load are well correlated with the surface acoustic wave velocity.     

固溶温度对G33超高强度钢微观组织和力学性能的影响

采用光学显微镜、扫描电镜和物理化学相分析技术等方法研究了固溶温度对G33新型超高强度钢组织和性能的影响.结果表明:G33钢在860℃固溶时板条马氏体基体上存在M6 C、VC和NbN未溶相并且以M6 C碳化物为主;随着固溶温度升高,未溶相快速溶解,VC和M6 C相分别在940℃和980℃完全溶解;M6 C、VC未溶相的溶...     

淬火温度对2200 MPa级超高强度钢力学性能与微观组织的影响

采用力学性能测试、光学显微镜(OM)、透射电镜(TEM)、X射线衍射(XRD)等材料分析方法研究了淬火温度对2200 MPa级超高强度钢的力学性能及微观组织的影响。结果表明,试验钢最佳淬火温度为1025 ℃,再经后续热处理能获得最佳的强韧性匹配,此时抗拉强度为2244 MPa,屈服强度为1836 MPa,U型缺口冲击吸收能量为59 J,断裂韧性为57.7 MPa·m^1/2。淬火温度较低时,出现粗大一次碳化物富Mo型M₆C碳化物,严重影响强度和韧性。随着淬火温度升高,一次碳化物逐渐减少,直至1000 ℃完全消失,当淬火温度高于1025 ℃时晶粒显著粗化,晶粒尺寸成为主要的负面影响因素。     

热处理温度对超高强海工钢组织性能的影响

针对超高强海工钢的研发,采用低碳和较高Ni含量设计了实验钢化学成分,通过力学性能分析及显微组织观察,对比研究了热轧钢板、以及不同热处理温度实验钢板的组织性能,明确了不同热处理温度对超高强海工钢板力学性能的影响规律。结果表明：热轧钢板组织基本为全马氏体组织,经热处理后开始析出碳化物,在热处理温度为650℃时界面处存在一定量的新鲜马氏体或残余奥氏体;经400、500、600℃热处理后,虽然可将实验钢板屈服强度提高至1 000 MPa以上,且断后伸长率大于14%,但由于存在时效脆性,使得钢板在-80℃时发生脆性断裂。经650℃热处理后,尽管实验钢板的屈服强度下降,但仍保持超高屈服强度,为786 MPa;另外,实验钢板的低温冲击韧性得到了显著改善,-80℃冲击吸收功大于125 J,具有最佳的综合力学性能。     

氮含量对HPD-1双相不锈钢组织及力学性能的影响

通过显微组织观察与力学性能测试研究了氮含量(0.08%～0.22%,质量分数)对HPD-1双相不锈钢硬度、拉伸性能、低温冲击性能及疲劳性能的影响。结果表明,氮含量变化可显著影响试验钢γ/α相比例,当氮含量由0.08%升高到0.22%,γ相含量由38.1%提高至56.5%。α相的硬度由273 HV10提高到343 HV10,γ相的硬度由238 HV10提高到299 HV10,试验钢强度明显提升。氮元素对两相比例和奥氏体相韧性的双重影响导致试验钢低温冲击性能呈先上升后下降的趋势;更高的氮含量抑制疲劳裂纹萌生与拓展,是影响HPD-1双相不锈钢室温疲劳性能的主要因素。撕裂棱是疲劳断口的显著特征。     

回火对含钒超高强度管线钢组织与性能的影响

利用光学显微镜、扫描电镜和透射电镜等分析方法,研究了回火工艺对含V超高强度管线钢组织与力学性能的影响。结果表明,随着回火温度的升高和回火时间的延长,试验钢的强度先上升再降低,伸长率和屈强比增加,冲击性能降低。这主要是由于回火后位错密度降低、M/A岛(martensite-austenite)分解、NbC/Nb(CN)与VC/V(CN)等析出相的形成及聚合长大等因素造成。在600 ℃´60 min的回火条件下,试验钢综合力学性能优良,其屈服强度、抗拉强度和－20 ℃冲击吸收能量分别是671 MPa、755 MPa和177 J,均达到超高强度管线钢X100的要求。     

Polarization sensitive THz absorption spectroscopy for the evaluation of uniaxially deformed ultra-high molecular weight polyethylene

Mechanically extensional–deformation of ultra-high molecular weight polyethylene (UHMWPE) was examined by using polarization terahertz (THz) spectroscopy as well as X-ray diffraction (XRD) analysis. Due to the B_1u lattice translational mode, a THz absorption band was observed around 2.2 THz. The band intensity of the non-deformed UHMWPE is isotropic. For deformed UHMWPE, the dichroism appeared in the 2.2 THz band. The absorption intensity was smaller in spectra in which the THz wave electric polarization direction was parallel to the deformation direction than that in which the polarization was perpendicular. The intensities in each polarization direction are dependent on the amount of elongation strain. Based on the influences drawn from the THz and XRD results, THz non-destructive diagnosis of the tensile strain in deformed UHMWPE is proposed based on the dichroism of B_1u band intensities observed in polarization THz spectroscopy.     

氮元素对CrFeMnVTi6高熵合金显微组织和力学性能的影响

为了评估氮元素的间隙固溶强化机制对高熵合金性能的影响,采用机械冶金化和放电等离子体烧结工艺制备N掺杂CrFeMnVTi6高熵合金,并利用XRD、SEM、TEM和FIB检测手段对合金的相组成及显微组织进行表征.实验结果显示,CrMnFeVTi6合金组织由TiNx、BCC、Laves相和B2有序相组成.因此,合金在低温区域...     

冷变形对含氮028合金微观组织和力学性能的影响

通过对含氮028合金进行不同变形量的冷轧,采用光学显微镜(OM)、透射电镜(TEM)和拉伸试验研究了冷变形量对其组织和力学性能的影响。结果表明,当冷变形量相同时,随着氮含量的增加,屈服强度增加明显。当冷变形量从0%增加到70%时,0.25%N 试验合金的抗拉强度从764 MPa提高到1405 MPa,屈服强度从390 MP提高到1249 MPa。在低变形量时,试验合金中存在大量位错和平面滑移结构。随着冷变形量的增加,试验合金中形变孪晶的数量逐渐增加,位错不断增殖。当冷变形量继续增加时,形变孪晶被割裂破碎。     

磁场对25CrMo48V超高强度钢回火组织与力学性能的影响

为研究磁场作用下热处理工艺对超高强度钢组织调控及碳化物种类、形态、尺寸和演变规律的影响,采用OM、SEM、TEM、EBSD和力学性能测试等技术手段研究了磁场作用对含有Nb、V、Ti等微合金元素的25CrMo48V超高强度钢中组织演变与力学性能的影响。试样均在1000 ℃下进行30 min奥氏体化处理,水淬之后在1 T磁场作用下,在200~600 ℃温度范围内回火1 h。结果表明,磁场的施加会抑制马氏体板条合并,促进M₂₃C₆和M₇C₃型碳化物的析出。经外加1 T磁场不同温度回火后,试样的硬度均高于未加磁场的常规回火处理试样,而其强度低于常规回火处理。     

淬火工艺对BR1500HS超高强度硼钢板组织与性能的影响

研究了淬火加热温度和保温时间对BR1500HS超高强度硼钢板的抗拉强度、硬度等力学性能和显微组织的影响。结果表明,随着淬火温度的升高,抗拉强度和硬度逐渐增加,当保温时间大于8 min时,淬火温度越高,组织越粗大,试验钢的抗拉强度和硬度降低。试验钢合理的淬火工艺为：淬火温度900~950 ℃、保温时间4~8 min,在此工艺下淬火的BR1500HS超高强度硼钢板马氏体转变完全,具有较好的综合力学性能。     

Elastic moduli and mechanical properties of bulk metallic glasses after quasi-static compression

The effect of quasi-static compressive stress on the elastic moduli and mechanical properties of a Cu₄₆Zr₄₆Al₈ bulk metallic glass (BMG) was investigated. When the applied quasi-static stress is below 2 GPa (equivalent to 1.4 times the yield strength of the BMG), the elastic moduli of the deformed BMGs are found to decrease with the applied stress, revealing the softening or dilatation of the bulk metallic glass. The Poisson ratio is relatively stable when the stress is below 1000 MPa, but it decreases significantly afterwards. Both the plasticity and strength of the BMG are found to increase at low applied stress, and achieve a maximum value before decreasing at higher applied stress. The applied stress is shown to enhance the mechanical properties of the BMG and the properties can be controlled by quasi-static compressive stress. The results demonstrate that an applied stress far below the macroscopic yield strength can still result in microscopic yielding and microstructure change in metallic glass systems.     

First principles study on the phase stability and mechanical properties of MoSi2 alloyed with Al,Mg and Ge

The phase stability, mechanical properties and electronic structure of C11_b and C40 MoSi₂ with alloying elements Al, Mg and Ge were systematically investigated using first principles methods. The calculated lattice constants and elastic constants of C11_b and C40 MoSi₂ are in good agreement with the previous results. It is found that there is a phase transition from C11_b to C40 when the concentrations of Al and Mg reach ∼7 at.% and ∼6 at.%, respectively. Based on the elastic constants, the anisotropy, ductility, hardness and melting temperatures are presented for MoSi₂ with alloying elements. For C11_b, the ductility will be enhanced by increasing the concentrations of Al or Mg. Simultaneously, hardness will be reduced by the increasing of Al or Mg. Ge have a reverse effects. For C40, the ductility is reduced weakly by Al or Mg. In addition, the effects of substitution of Mo by Nb with Si substitution of Si by Al, Mg and Ge are also investigated. Nb and Mg codoping can improve the ductility of MoSi₂. Finally, the density of states is used to analysis the effects of alloying elements on the mechanical properties, and the results are in consistent with the predictions based on elastic constants.