Optimization of pulsed laser atom probe (PLAP) for the analysis of nanocomposite Ti–Si–N films

Laser-assisted atom probe tomography was used to investigate the nanostructure and composition of high-performance, ultra-hard Ti–Si–N nanocomposite films. However, the quality of data is heavily dependent on analysis conditions. In order to obtain reliable data from these, and other ‘less conducting’ specimens, the analysis parameter space was thoroughly investigated to optimize the mass resolution and hit multiplicity obtained in atom probe tomography. Geometric factors including tip radius and shank angle were found to play a significant role in mass resolution but had no apparent effect on the number of multiple hits observed. Increased laser energy led to a gradual increase in the number of single hits, but a modest improvement in mass resolution. The influence of other instrumental factors including detection rate and base temperature was investigated separately. Preliminary PLAP results are presented, and correlated with TEM analysis of the microstructure of the film.     

（Ti,Al,V）N薄膜抗氧化性能的研究

动脑筋热重法研究了多弧离子镀（Ti,Al,V)N、TiN镀层的氧化行为,在600-800℃内,各镀层的氧化行为均遵循抛物线规律。由于Al2O3保护膜的形成,推迟了（Ti,Al,V)N镀层的高温氧化,显示出良好的抗氧化性。     

A multi-technique characterization of ZDDP antiwear films formed on Al (Si) alloy (A383) under various conditions

The simulation of the lubrication of aluminum–silicon (Al–Si) alloy cylinder-bore conditions is an important goal in automotive tribology. This study describes the use of X-ray absorption near edge structure (XANES) to determine the macro-chemistry of zinc-dialkyl-dithiophosphates (ZDDPs) antiwear (AW) films formed on A383, an Al-Si alloy. The temperature dependence of the chemistry and mechanical properties were examined using X-ray photoelectron emission microscopy (X-PEEM), and imaging indentation techniques. Our findings suggest that ZDDPs break down to form polyphosphate glasses, which have different chemical natures and depend on the underlying substrate. Furthermore, the chemical nature of the films appears temperature dependent on both the macro- and micro-scale. Not only are the chemical species different, but the mechanical properties also differ, depending on the region upon which an AW pad is formed. Through the use of focused ion beam (FIB) milling, we can determine the film thickness, which was previously estimated from the P K-edge XANES areal density of samples with known thicknesses.     

FCVA沉积TiAlN薄膜的工艺研究

采用磁过滤阴极真空弧源(FCVA)沉积技术,在高速钢(HSS)基体上沉积TiAlN薄膜,用显微硬度计测定TiAlN薄膜的硬度和厚度,用X射线衍射(XRD)分析技术进行TiAlN薄膜的相分析并进行了摩擦磨损实验,为在刀具表面沉积TiAlN薄膜打下较好的工艺基础。     

Solid particle erosion behaviour of Ti6Al4V alloy

Abstract

The effects of particle impingement angle, impingement velocity and erodent particle size on the erosion rate and surface morphology of the Ti6Al4V alloy have been investigated comprehensively in order to evaluate solid particle erosion behaviour of Ti6Al4V alloy. Samples were eroded in a specially designed sandblasting system under various parameters using alumina (Al₂O₃) erodent particles. Surface morphology investigations were examined by scanning electron microscope using various analysis and modes (energy dispersive X-ray analysis, elemental mapping and compositional contrast). Ti6Al4V alloy showed ductile behaviour with a maximum erosion rate at 30° impingement angle. Erosion rate of Ti6Al4V alloy increased with increases in velocity and decreased with increases in erodent particle size. Scanning electron microscopy investigations of eroded surfaces of Ti6Al4V alloy samples reveal the dominant erosion mechanism such as microploughing, microcutting and plastic deformation. Embedded erodent particles on the surfaces of Ti6Al4V alloy nearly at all particle impingement angles and velocities were clearly detected.     

Effect of SiC particles on the friction and wear behavior of Ti3Si(Al)C2-based composites

The non-lubricated, sliding friction and wear behavior of Ti₃Si(Al)C₂ and SiC-reinforced Ti₃Si(Al)C₂ composites against AISI 52100 bearing steel ball were investigated using a ball-on-flat, reciprocating tribometer at room temperature. The contact load was varied from 5 to 20 N. For monolithic Ti₃Si(Al)C₂, high friction coefficients between 0.61 and 0.90 and wear rates between 1.79 × 10⁻³ and 2.68 × 10⁻³ mm³ (N m)⁻¹ were measured. With increasing SiC content in the composites, both the friction coefficients and the wear rates were significantly decreased. The friction coefficients reduced to a value between 0.38 and 0.50, and the wear rates to between 2.64 × 10⁻⁴ and 1.93 × 10⁻⁵ mm³ (N m)⁻¹ when the SiC content ranged from 10 to 30 vol.%. The enhanced wear resistance of Ti₃Si(Al)C₂ is mainly attributed to the facts that the hard SiC particles inhibit the plastic deformation and fracture of the soft matrix, the oxide debris lubricate the counterpair, and the wear mode converts from adhesive wear to abrasive wear during dry sliding.     

Microstructure and tribological behavior of Ti–Si eutectic alloys with Al addition

The effect of Al element alloying on the microstructure and tribological behavior of Ti–Si eutectic alloys has been studied. The experimental results show that Al element changes the microstructure from large eutectic cells that consist of layered tablet phases Ti₅Si₃ and α-Ti (for the Al-free alloy) to near-equiaxed or rod-like Ti₅Si₃ particle reinforced continuous α-Ti (Al, Si) solid solutions. This microstructural change greatly improves the ductility and reduces brittle fracture of massive superficial materials during wear process. Microplough and local delamination are the main wear mechanisms of Al-added Ti–Si alloys. Therefore, the wear resistance and friction stability are simultaneously improved.     

Heteroepitaxy of AIIIBV films on vicinal Si(001) substrates

GaAs films on Si substrates miscut from the (001) plane by 6° in the [110] direction are grown by molecular beam epitaxy (MBE). GaAs films are grown both on the Si surface terminated by arsenic atoms and on thin pseudomorphic GaP/Si layers. The condition of formation of the As sublayer and the first monolayer of GaP on the Si surface is defined as the GaAs film orientation (001) or \((00\bar 1)\) . The processes of Si surface preparation and formation of the As sublayer and GaAs and GaP epitaxial layers are monitored by means of high-energy electron diffraction reflection (RHEED). The grown structures are investigated by methods of X-ray diffraction, atomic force microscopy (ATM), high-resolution transmission electron microscopy (HRTEM), and low-temperature luminescences. It is shown that the epitaxial film orientation affects both the surface morphology and its crystalline properties. Intense photoluminescence is obtained from the In_0.17Ga_0.83As quantum well structure grown on the GaAs/Si buffer layer.     

真空阴极电弧沉积（Ti,Al）N薄膜的应用研究

为了提高TiN涂层刀具的耐磨性,采用钛铝合金靶,以真空阴极电弧沉积法制备了（Ti,Al)N涂层,对膜层形貌成分,组织结构及硬度进行了测试及研究,并试验了（Ti,Al)N涂层高速钢钻头及YG6硬质合金刀具的使用寿命,结果表明：（Ti,Al)N涂层硬度高达HV0．1,15,3700,（Ti,Al)N涂层使高速钢钻头及YG6硬质合金刀具的使用寿命显著提高。     

硬质合金基体FCVA沉积TiAlN薄膜的试验研究

采用磁过滤阴极真空弧源(FCVA)沉积技术,通过改变氮气流量在硬质合金基体上沉积了TiAlN薄膜,用显微硬度计测定了TiAlN薄膜的硬度和厚度;采用X射线衍射(XRD)分析技术进行了TiAlN薄膜的相分析;并进行了摩擦磨损试验和对基体与薄膜的结合力进行定性的分析。结果表明:TiAlN薄膜厚度在450~520nm之间;最高硬度为2754Hv,对应氮气分压为N2分压在8.0×10-2Pa~1.1×10-1Pa;薄膜中主要存在Ti2AlN、Ti2N与TiN相。     

The influence of proteins on the fretting-corrosion behaviour of a Ti6Al4V alloy

The effects of collagen and albumin on the fretting-corrosion behaviour of a Ti6Al4V alloy contacting an Al₂O₃ counter-piece was investigated in pH buffered saline solutions at 37 °C using a tribo-electrochemical apparatus. Phosphate ion and hydroxyethyl-piperazinyl-ethanesulfonic acid (HEPES) were used as the pH buffer agents. Tests were conducted under two applied electrochemical potentials and two loads. Potentiodynamic polarisation curves were measured to assess the effect of proteins and pH buffer agents on the corrosion behaviour. Surfaces were characterised by XPS analysis, secondary electron spectroscopy and laser profilometry.Fretting wear of the Ti6Al4V alloy increased with increasing applied potential and load but was not significantly affected by the presence of collagen or albumin. Only a small lubricant effect of collagen could be observed at cathodic potentials. In phosphate buffer saline (PBS) solutions, those proteins were found to act as cathodic inhibitor by shifting the corrosion potential and the cathodic current towards more cathodic values. Phosphate ions were found to be incorporated on the Ti6Al4V alloy and to cause sedimentation of wear particles around the wear trace. In HEPES solutions wear particles were dispersed away from the wear trace.     

Micro-scale abrasive wear testing of duplex and non-duplex (single-layered) PVD (Ti,Al)N, TiN and Cr–N coatings

A micro-scale abrasive wear test, based on ball-cratering, has been used to evaluate the wear resistance of duplex and non-duplex (Ti,Al)N, TiN and Cr–N coatings. The term duplex is used here when plasma nitriding is followed by PVD coating. Coatings without the plasma nitriding stage are termed single-layered. Coating properties were evaluated by surface profilometry, hardness and scratch testing. All duplex coatings showed higher micro-abrasive wear resistance than their single-layered counterparts, with the duplex (Ti,Al)N coating achieving the best performance. After a certain number of ball revolutions, the coating material became worn through, exposing the substrate material. After this point, the presence of a hard nitrided case diminished the scratching action of the SiC abrasive particles. The experimental results also indicate that the choice of the PVD coating plays an important role in improving the micro-abrasive wear resistance. Apart from single-layered and duplex Cr–N coatings, all the other coating systems provided a higher micro-abrasive wear resistance than the uncoated substrate (hardened AISI H13 steel). The poor abrasive wear resistance recorded for the single-layered and duplex Cr–N coatings could be attributed to the hardness of the Cr–N being much lower than that of the SiC abrasive particles, which caused tearing of the coating with subsequent delamination. The wear pattern observed was found to change from surfaces characterised by grooves (uncoated substrate, single-layered TiN and Cr–N systems and duplex Cr–N system) to surfaces which exhibited multiply indented surfaces (single-layered and duplex (Ti,Al)N systems), indicating a transition between wear mechanisms. This transition was found to be dependent on the ratio between the hardness of the SiC abrasive particles and surface (coating) or subsurface hardness. By decreasing this ratio, the ability of the SiC abrasive particles to scratch the composite surface was reduced and the resistance to micro-scale abrasion was improved.     

(Ti,Al)N+TiN涂层硬质合金刀具加工铁基高温合金正交切削试验研究

采用正交试验方案,应用(Ti,Al)N+TiN涂层硬质合金刀具对GH2132铁基高温合金进行外圆干切削,测量了切削力、切削温度、表面粗糙度和刀具寿命。利用最小二乘法对试验数据进行了多元回归分析,分别建立其经验公式,并分析了切削用量三要素分别对切削力、切削温度、表面粗糙度和刀具寿命的影响规律及其原因。通过试验得出了切削用量三要素分别对其影响的主次顺序。切削力:a_p>f>v_c,切削温度:v_c>a_p>f,表面粗糙度:f>v_c>a_p,刀具寿命:v_c>f>a_p。     

反应生成Al3Ti、Al2O3/Al复合材料的力学性能研究

讨论了不同的TiO2/Al摩尔比对Al-TiO2系热扩散反应法（XD）合成铝基复合材料的力学性能的影响。反应产物Al3Ti呈棒状，Al2O3呈细小颗粒状；随着TiO2/Al摩尔比的增加，增强相（Al3Ti、Al2O3）体积分数提高，材料的拉伸强度明显增强，伸长率逐渐减小。棒状物Al3Ti强底低，阻碍Al3Ti、Al2O3／Al的拉伸性能进一步提高。     

Structure determination of the hexagonal quasicrystal approximant micro'-(Al,Si)4Cr by the strong reflections approach

A number of different crystalline phases have been found in Al-rich Al-Cr-Si alloys by transmission electron microscopy (TEM). Among these, the new hexagonal phase micro'-(Al,Si)(4)Cr (a=2.01 and c=1.24 nm) often found coexisting with the hexagonal micro-(Al,Si)(4)Cr (a=1.998 and c=2.4673 nm, isostructural with micro-Al(4)Mn) and also with the hexagonal lambda-(Al,Si)(4)Cr (a=2.839 and c=1.239 nm, isostructural with lambda-Al(4)Mn). It is evident from their electron diffraction patterns that the structures of these three phases are related. The strong reflections in all three are distributed in a similar way. They all exhibit a pseudo-icosahedral symmetry. The structure factor amplitudes and phases for the strong reflections of the micro' phase could therefore be adopted from those of the lambda phase, according to the strong reflections approach. A structure model of the micro' phase is thus deduced from the known lambda-Al(4)Mn. micro' consists of chains of 3+3 or 4+2 interpenetrated icosahedra along the 100 directions. Similar to the lambda phase, there are two flat layers (F) and four puckered layers (P) in each unit cell of micro', stacked along the c-axis in a sequence of PFP(PFP)' where the (PFP)' block is related to the PFP block by a 6(3) screw.     

Complex surface modification of carbide tool by Nb + Hf + Ti alloying followed by hardfacing (Ti + Al)N

The surface of the WC/Co carbide tool was modified by an electron beam with the magnetron sputtering of Nb + Hf + Ti alloy to obtain a gradient interlayer before hardfacing with (Ti + Al)N. The results of investigations of the composite using a scanning electron microscope equipped with a device for X-ray energy dispersion spectroscopy are given. The results of the comparative mechanical tests show reduced wear rate.     

Al2 O3/Cr3C2/(W,Ti)C陶瓷抗弯强度的研究

热压烧结制备了Al2O3／Cr3C2／（W,Ti）C复合陶瓷材料,对其抗弯强度及组织形貌进行了研究,分析了Cr3C2与（W,Ti）C对抗弯强度的影响。结果表明：添加（W,Ti）C与Cr3C2有利于阻止晶界迁移,延缓晶粒长大,提高材料强度,但每一相的添加量以10％内为宜,两者添加总量在20％左右时Al2O3／Cr3C2／（W,Ti）C复合材料抗弯强度较佳。铬、钨、钛离子在Al2O3基体晶粒中的固溶起强化作用,网状结构是降低材料抗弯强度的重要原因。     

Influence of particle content and porosity on the wear behaviour of cast in situ Al(Mn)–Al2O3(MnO2) composite

Aluminium-based tribological materials may reduce the weight of components, leading to significant fuel economy. The aim of the present study is to investigate the wear and friction in cast in situ Al(Mn)–Al₂O₃(MnO₂) composites synthesized by dispersing MnO₂ particles in molten aluminium, which get reduced to form Al₂O₃ particles. Wear tests have been conducted at four normal loads of 9.8, 19.6, 29.4 and 39.2 N and at a constant sliding speed of 1.05 m/s using a pin-on-disc wear testing machine, under dry sliding conditions. The results of the investigation indicate that the cumulative volume loss and wear rate of in situ composites are significantly lower than those observed in either the commercial aluminium or Al–Mn base alloy, under similar loading and sliding conditions. The influences of both reinforcing particle and porosity contents on the tribological behaviour of in situ composites were evaluated. It has been found that at a given particle content, the wear rate increases with increasing porosity content due to its combined effect on real area of contact and subsurface cracking. The wear rate of in situ composites with relatively lower porosity decreases with increasing particle content, but does not appear to change significantly or even increases a little with increasing particle content when the composites have relatively higher porosity. In view of large fluctuations in coefficient of friction during sliding, no effect of particle or porosity contents on the coefficient of friction could be determined unambiguously for different in situ composites.     

[Si(Al)O_4]四面体聚合度对Na~+固化性能的影响

运用核磁共振分析手段(NMR),采用结构分析的方法研究了赤泥基胶凝材料的水化过程,探讨了[Si(Al)O4]四面体聚合度对Na+固化性能的影响.结果表明:当原料中硅以SiQ0、SiQ1等低聚合度形式存在时,由于低聚合度的[Si(Al)O4]四面体易在早期发生解聚,并在富含Ca2+的溶液中发生反应生成钙硅比较高的C-S-H凝胶,这不利于Na+的固化;当硅主要以SiQ2、SiQ3等中聚合度形式存在时,由于水化后期[Si(Al)O4]四面体的逐渐解聚和铝对硅的取代作用,促进了低钙硅比的(Na,Al)-C-S-H凝胶的生成,改善了Na+的固化性能;而在硅主要以SiQ4高聚合度形式存在时,又不利于Na+固化.     

Structural studies of pulsed-laser deposited nanocomposite metal-oxide films

Pulsed laser deposition in vacuum has been used to develop metal-oxide nanocomposite films with well controlled structural quality. Results for the copper–aluminium oxide (Cu:Al₂O₃) system are used to illustrate the main morphological and structural features of these films. High resolution transmission electron microscopy (TEM) analysis shows that the films consist of Cu nanocrystals with average dimensions that can be controlled between 2 nm and 10 nm embedded in an amorphous Al₂O₃ matrix. It is observed that the in-plane shape of the nanocrystals evolves from circular to elongated, and the number of nanocrystals per unit area decreases as their size increases. This evolution is explained in terms of nucleation at the substrate surface and coalescence during the later stages of growth. The thermal stability of the films has been studied by in situ TEM annealing and no transformation could be observed up to about 800 °C when partial crystallization of the Al₂O₃ starts.