Al Specimens Research Articles

Effect of Alloying Elements on the Consolidation and Mechanical Properties of Ti Compacts by SPS

In this study, we focused on the effect of alloying elements (Fe, Mo, and Al) on the consolidation and mechanical properties of Ti compacts. The elemental blended powders is manufactured by spark plasma sintering. The effects of amount of alloying elements and sintering temperature on the relative density and tensile properties of Ti compacts were investigated. The addition of β-stabilizing elements (Fe and Mo) was found significantly improve the densification of Ti compacts, where the sintered density ratio of Ti-5 wt.% Mo specimen was higher than 99.9 %, and Ti-5 wt.% Fe specimen was higher than 99.0 %. On the other hand, addition of Al as α-stabilizing element showed the sintered density rate of Ti-5 wt.% Al specimen was higher than 99.9 %. The tensile property for sintered Ti-5 wt.% Mo specimens had the highest elongation of 16 %. It will be discussed the microstructures and tensile property of the compacts.

Precipitation of nanosized nitrides in plasma nitrided Fe–M (M = Al, Cr, Ti, V) alloys

Nanosized alloy nitrides or alloying element (M)–Nitrogen(N) cluster formed in plasma nitriding of Fe–M binary alloys were investigated by means of high resolution TEM. Specimen surface of the Fe–Cr alloys was hardened by the formation of disk shaped CrN of NaCl structure, which is ∼2 nm thick and 10 nm in diameter. In nitrided Fe–Al specimen, two kinds of AlN nitrides of metastable NaCl type and stable wurtzite type were formed near the specimen surface. Both of these were much larger than CrN. Contrasting to these specimens, in nitrided Fe–Ti and Fe–V alloys, high density M–N clusters of few nanometres diameter, many of which were monolayered lying on {001}α, were formed, leading to larger hardness increase than that in Fe–Cr and Fe–Al alloys. The formation of M–N clusters in nitriding is explained by the thermodynamical analysis of phase separation between M/N poor and M/N rich bcc phases.

From micro- to nano-scale molding of metals: Size effect during molding of single crystal Al with rectangular strip punches

A single crystal Al specimen was molded at room temperature with long, rectangular, strip diamond punches. Quantitative molding response curves were obtained at a series of punch widths, ranging from 5 μm to 550 nm. A significant size effect was observed, manifesting itself in terms of significantly increasing characteristic molding pressure as the punch width decreases to 1.5 μm and below. A detailed comparison of the present strip punch molding results was made with Berkovich pyramidal indentation on the same single crystal Al specimen. The comparison reveals distinctly different dependence of the characteristic pressure on corresponding characteristic length. The present results show the feasibility of micro-/nano-scale compression molding as a micro-/nano-fabrication technique, and offer an experimental test case for size-dependent plasticity theories.

Simulation of Nanostructure Production by Electromigration Considering Specimen's Shape

Al nanowires have been successfully formed utilizing electromigration in the passivated Al thin film specimen. A numerical simulation of the nanostructure production method was recently developed based on the governing parameter for electromigration damage. The results of the simulation were verified through experiment. It was shown that this procedure predicted the nanostructure volume formed during lifetime of the specimen, though the nanostructure formation was influenced by the current density and substrate temperature. In this study, the method is applied to Al specimens with various shapes to devote to the theoretical discussion on the efficient production of nanostructure. It is found that volume of the formed nanostructure depends on shape of the specimen. The shape affects distributions of current density, temperature and atomic density in the specimen, so formation speed, lifetime and consequently nanostructure volume during the lifetime are changed. It is clarified that this simulation method will contribute to seeking the optimum specimen's shape for efficient NS production.

Digital spectrometer for coincidence measurement of Doppler broadening of positron annihilation radiation

High-resolution digital coincidence Doppler broadening spectrometer equipped with two high-purity Ge detectors and two-channel 12-bit fast digitizer was developed and tested in this work. Two configurations were compared: (i) semi-digital setup which uses active analogue shaping of detector pulses prior to digitization to improve signal-to-noise ratio, and (ii) pure-digital setup which samples detector pulses directly. Software procedure developed for analysis of sampled waveforms, i.e. precise determination of energy of detected photon and rejection of distorted pulses, is described. Performance of digital coincidence spectrometer was compared with traditional analogue setup connected to the same detectors. It was found that digital spectrometer enables to achieve better energy resolution than in traditional analogue setup. Moreover, in digital configuration one has better control over shape of the signal. This allows efficient elimination of undesired distorted or damaged waveforms and to obtain spectrum of better clarity. The superior parameters of new digital coincidence Doppler broadening spectrometer are demonstrated by benchmark measurements of well defined Fe and Al specimens and also by the detection of rare annihilation in flight events.

Evaluation of the planar inductive magnetic field sensors for metallic crack detections

The planar inductive magnetic field sensors were fabricated by photolithography process. The sensor was composed of the planar coils (42 turns and 120 turns) with magnetic thin film as a core. To evaluate the sensor for crack detection, the nonmagnetic Al and magnetic FeC specimens were prepared with the circular and slit shaped artificial surface cracks. The alternative current (0.1 A to 1.4 A) with frequency range of 1.0–2.0 MHz was generated by the straight shaped driving Cu coil. In the case of 120 turns of planar inductive magnetic field sensor, the induced signals on crack positions exhibited the high intensities and stable signal to ratio as varying the driving current and frequency in comparison with those of 42 turns of planar inductive sensor. The measured output signals on FeC specimen with the micro-sized surface crack by the non-contacted scanning were converted to the image which was compared with that of the optical image, respectively.

Formation and capacitance properties of Ti-Al composite oxide film on aluminum

Al specimens were covered with TiO 2 film by sol-gel dip-coating and then anodized in ammonium adipate solution. The structure, composition and capacitance properties of the anodic oxide film were investigated by transmission electron microscopy (TEM), Auger electron spectroscopy (AES), X-ray diffractometry (XRD) and electrochemical impedance spectroscopy (EIS). It was found that an anodic oxide film with a dual-layer structure formed between TiO 2 coating and Al substrate. The film consisted of an inner Al 2O 3 layer and an outer Ti-Al composite oxide layer. The thickness of layers varied with the number of times of sol-gel dip-coating. The capacitance of anodic oxide films formed on coated specimens was at most 80% higher than that without TiO 2. In film formation mechanism, it was claimed that the formation of composite oxide film was mainly affected by the structure of micro-pores network in TiO 2 coating which had an influence on Al 3+ and O 2− ions transport during the anodizing.

Investigation of bonding strength and sealing behavior of aluminum/stainless steel bonded at room temperature

This article reports the direct bonding of aluminum (Al) [99.999% (5N), 99% (2N)] and stainless steel SUS (304, 316) without heating for sealing in the ultra high vacuum (UHV) components. For bonding, the smooth surfaces of the Al and SUS specimens were activated using argon fast atom beam (Ar-FAB) for 1–60 and 60 min, respectively, in a background pressure of 6.0 × 10 −5 Pa followed by close contact under an external pressure of 960 N. High bonding strength resulted in the bonded mates of Al and SUS304 activated for 30 and 60 min, respectively, due to the adhesion forces of the surface atoms. Tensile pulling tests showed bulk fractures in Al with impurity dependent bonding strength. The bonding strengths for the Al5N/SUS304 and Al2N/SUS304 specimens were higher than 60 and 100 MPa, respectively. For the sealing test, the smooth surface of the SUS316 flange containing a hole was bonded with Al after surface activation 60 and 30 min, respectively. Leak rates for Al5N/SUS316 and Al2N/SUS316 specimens were 1.5 × 10 −11 and 2.0 × 10 −11 Pa m 3/s, respectively. These results satisfy the permissible leakage of a large-sized UHV chamber. Time dependence of the leak test behavior for both specimens shows a stable leak rate. Therefore, the sealing of Al/SUS316 may be utilized for the fabrication of corrosion free joints for fluid flow in the cooling of electron guns of small size equipment such as portable scanning electron microscopes in UHV pressure.

Prediction of hardness minimum locations during natural aging in an aluminum alloy 6061-T6 friction stir weld

This study describes a method that can predict the hardness minimum location as a function of natural aging time in a heat-treatable 6061-T6 Al alloy plate subjected to friction stir welding (FSW). First, temperature distributions were simulated in the FSW plate by finite element modeling. Second, to determine the natural aging kinetics, hardness changes were measured as a function of natural aging time from a number of Al specimens that had been isothermally heat treated at different peak temperatures. Finally, the simulated temperature profiles and the natural aging kinetics were correlated to predict the hardness profiles in the FSW plate. The predicted hardness minimum locations are consistent with the measured hardness profiles in that the hardness moves away from the weld centerline as the aging time increases. Moreover, the predicted hardness minimum is located at the similar position of failure in cross-weld tensile samples.

Structure, microhardness and damping characteristics of Al matrix composite reinforced with AlCuFe or Ti using ultrasonic impact peening

Abstract Ultrasonic impact peening (UIP) is used to modify the near-surface layers of cp aluminum. The effects of icosahedral quasicrystalline (QC) AlCuFe or hcp Ti fine powders added to the zone of severe plastic deformation at the UIP process on microstructure, phase composition, microhardness of near-surface layers and damping properties of aluminum are studied. The results show that composite layers, which are characterized by relatively uniform distribution of reinforcing particulates with similar volume fraction of about 0.17 are formed. While semi-coherent particulate/matrix interface is observed for QC reinforcements, the Ti particulates seem to be strongly adhered to the aluminum matrix due to formation of Ti 3 Al interlayer. While a dislocation-cell structure is formed after the UIP only, highly-misoriented fine grain structure with mean grain size of 0.1–0.5 μm is observed in the AlCuFe reinforced composite layer, and the Ti reinforced layer is characterized by mean grain size of 0.5–2 μm. Observed microsructural features predetermine significant enhancement of microhardness and damping properties of as-treated aluminum specimens. Much higher magnitudes of microhardness (about 1.3 GPa) and logarithmic decrement (about 12 × 10 − 4 ) are observed in Al specimens covered with the QC reinforced composite layer in comparison to those for specimens contained the Ti reinforced layer (about 1 GPa and 3.6 × 10 − 4 ) and to the as-peened aluminum specimen (0.58 GPa and 1.4 × 10 − 4 ). It is due to (i) the smallest grain size, (ii) semi-coherent particulate/matrix interface and (iii) high hardness and specific stiffness of the AlCuFe QC phase. Relatively high level of microhardness (about 1.1 GPa and 0.8 GPa) and logarithmic decrement (about 5 × 10 − 4 and 2 × 10 − 4 ) are conserved for Al specimens covered with the QC and Ti reinforced composite layers even after heating to 623 K.

Semi-Fixed Abrasive Machining for Plane Aluminium

Aluminum is a non-ferrous metal material which has excellent comprehensive performance. It has been widely used in many sectors. In this paper, plane abrasive machining is carried out for the aluminum. The quality of the Al specimen’s surface is compared after the semi-fixed and loose abrasive processing. The experiment proved that semi-fixed abrasive machining is better than loose abrasive in reducing surface roughness of Al-blocks. In the semi-fixed abrasive machining, the surface roughness of Al-block continued to drop and become stable after 40 minutes. It can prevent deep scratches on Al-blocks’ surface effectively and can get a mirror effect. The surface roughness can reach to Ra 22nm, Rmax 490nm, Rv 130nm. Its removal efficiency is also higher than loose abrasive machining. It is proved that semi-fixed abrasive machining can take the place of rough polishing processing.

A Numerical Simulation of Nanostructure Formation Utilizing Electromigration

A numerical method to simulate nanostructure formation due to electromigration in passivated Al specimens is developed based on the governing parameter for electromigration damage, \( {\hbox{AFD}}^{\ast}_{\rm gen}. \) The nanostructure formation is influenced by conditions such as the current density and substrate temperature. The results of the simulations are verified through experiments, and good agreement between the simulations and experiments is found for changes in nanostructure volume. The simulation is expected to be useful for identifying effective conditions for nanostructure formation.

Young's moduli of cold and vacuum plasma sprayed metallic coatings

Monolithic metallic copper alloy and NiCrAlY coatings were fabricated by either the cold spray (CS) or the vacuum plasma spray (VPS) deposition processes. Dynamic elastic modulus property measurements were conducted on these monolithic coating specimens between 300 and 1273 K using the impulse excitation technique. The Young's moduli decreased almost linearly with increasing temperature at all temperatures except in the case of the CS Cu–23%Cr–5%Al and VPS NiCrAlY, where deviations from linearity were observed above a critical temperature. It was observed that the Young's moduli for VPS Cu–8%Cr were larger than the literature data compiled for Cu. The addition of 1%Al to Cu–8%Cr significantly increased its Young's modulus by 12–17% presumably due to a solid solution effect. Comparisons of the Young's moduli data between two different measurements on the same CS Cu–23%Cr–5%Al specimen revealed that the values measured in the first run were about 10% higher than those in the second run. It is suggested that this observation is due to annealing of the initial cold work microstructure resulting form the cold spray deposition process.

ポリピロール／金の２層構造を有する３次元マイクロアクチュエーターの作製

Three-dimensional micro-actuators consisting of a polypyrrole (PPy)/Au bi-layer, were fabricated by Al anodizing, laser irradiation, and electrochemical techniques. Aluminum specimens covered with porous type oxide films were irradiated with a pulsed Nd-YAG laser to remove the oxide films locally. Then an Au layer and a PPy layer were deposited at the area where the film had been removed. Finally, the specimens were immersed in a NaOH solution after connection with or without a Pt plate to separate PPy/Au actuators from the Al substrate and anodic oxide film. The PPy layer did not lose its electroconductivity when the specimen was immersed in NaOH solution after connection with a Pt plate, although the conductivity was lost after immersion of the specimen alone. Immersion with the Pt connection suppressed the PPy reduction and enabled the fabrication of PPy/Au actuators. Three-dimensional PPy/Au bi-layer micro-actuators were fabricated using column Al specimens. They are much more flexible than PPy/Au/resin three-layer actuators described in a previous paper.

TEXTURE DEVELOPMENT AND DRAWABILITY OF FRICTIONALLY ROLLED AA 5052 AL ALLOY SHEET

The microstructure, pole figure and r -value of the frictionally rolled and subsequently heat treated AA 5052 Al sheets were investigated by optical microscopy, x-ray diffractometer and tensile tester, respectively. Frictionally rolled AA 5052 Al specimens showed a fine grain size. After subsequently heat treated specimens, the ND//<111> texture component was increased. The r -values of the frictionally rolled and subsequently heat treated Al alloy sheets were about two times higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through frictional rolling in and subsequent heat treatment of AA 5052 Al sheet.

Study of high-pressure sintering behavior of cBN composites starting with cBN–Al mixtures

Cubic boron nitride (cBN) composites starting with cBN–Al mixtures were sintered on WC-16 wt% Co substrates under static high pressure of 5.0 GPa and at temperatures of 800–1400 °C for 30 min. Vickers hardness of the sintered samples increased with increasing cBN content, and the highest hardness of 32.7 GPa was achieved for the cBN–5 wt% Al specimens sintered at 1400 °C. The reactions between cBN and Al started to occur at about 900 °C, and the reaction products strongly depended on the Al content, sintering temperature, and Co diffusion from the substrates according to the x-ray diffraction (XRD) observations. The high pressure and high temperature in situ resistance measurement indicated that the reactions between cBN and Al could be completed in about 90 s when the temperature was higher than ∼1200 °C at high pressure. The cBN composite sintered at 1200 °C from a cBN–15 wt% Al mixture showed the best cutting performance.

Investigation of metal‐induced crystallization in amorphous Ge/crystalline Al bilayers by Auger microanalysis and selected‐area depth profiling

AbstractThe diffusion processes and accompanying microstructural changes occurring in amorphous Ge (a‐Ge)/crystalline Al bilayers upon annealing have been investigated by using a combined approach of Auger microanalysis, selected‐area depth profiling (SA‐DPR), scanning electron microscopy (SEM) and X‐ray diffraction. Upon annealing at 150 °C for 10 min, the partially crystallized Al/a‐Ge (with the Al layer at the top) and a‐Ge/Al (with the a‐Ge layer at the top) specimens show reacted and unreacted regions with a lateral size of ∼1–2 µm at their surfaces. SA‐DPR at the location of unreacted regions at the surface shows that at such locations the original Al/a‐Ge (or a‐Ge/Al) bilayer structure is almost preserved. On the other hand, depth profiling at the location of reacted regions shows that at such locations the original a‐Ge sublayer had fully crystallized and contains 10–20 at.% Al, and that in the original Al sublayer, crystalline Ge (c‐Ge) had formed at the Al grain boundaries (GBs). These observations could be explained in consequence of the initiation of crystallization of a‐Ge at the Al GBs followed by the nucleation of crystallization at the a‐Ge/Al interface, as supported by thermodynamic calculations of interface energetics. Copyright © 2008 John Wiley & Sons, Ltd.

440 試験片形状の異なるエレクトロマイグレーション・ナノストラクチャー創製の数値シミュレーション(T08-1 金属ナノ材料の創製と展開(1) 金属ナノ材料の創製,大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

A technique of generating metallic nanostructure by utilizing electromigration has been proposed. Electromigration is the phenomenon that the metallic atoms are transported by electron wind due to high current density. A numerical simulation method of nanostructure formation utilizing electromigration in the passivated Al specimen was recently developed based on the governing parameter for electromigration damage, AFD^*_<gen>. In the present study, the numerical simulation method of the nanostructure-generation technique was applied to Al specimens with various two-dimensional shapes, and the effect of specimen's shapes on nanostructure formation was discussed.

Microstructure and the wear mechanism of grain-refined aluminum during dry sliding against steel disc

This article discusses on the influence of grain refinement on the wear mechanism of commercially pure Al. In this work, commercially pure Al, grain refined using Al–Ti, Al–Ti–B grain refiner master alloys, prior to casting. These castings after machining have been subjected to dry-sliding wear against high-chromium hardened steel disc at a constant load of 50 N and speed of 1 m s −1. The effect of grain refinement of aluminum on its wear behavior has been investigated. The sub-surface and the worn surfaces of the specimens were characterized in order to understand the wear behavior of aluminum against steel disc. Although it has been found that wear mechanism of aluminum is same for both untreated and grain refined, untreated aluminum exhibits higher wear loss than that of grain-refined aluminum. The results also show that grain refinement has a significant effect on the transfer of Fe from the steel disc to the worn surface and sub-surface of Al specimens.

Effect of Ceramic Powders on the Reaction Sintering of Ceramic/Metal Mixed Powders

The reaction-sintered alumina and zirconia-alumina ceramics with low firing shrinkage were prepared from Al 2 O 3 /Al and ZrO 2 (C a -PSZ)/Al powder mixture by attrition milling and the effect of the characteristics of used ceramic powders was investigated. Flaky Al powders mixed with coarse alumina powders could be effectively pulverized due to high hardness of alumina powders. On the contrary fused Ca-PSZ/Al powder mixture could not be effectively comminuted due to lower hardness than alumina powders. So by using hard alumina ball media or coarse Al 2 O 3 powders rather than Al, the milling efficiency could be much more increased. After attrition milling the Al 2 O 3 /Al specimens were oxidized at 1200°C for 8 hours and followed by sintering at 1550°C for 3 hours. Because mixed powders of Al with alumina were much more effectively comminuted, more than 97% theoretical density of sintered body could be achieved. In the case of fused Ca-PSZ powder reaction-sintered with Al at 1550°C for 3 hours, the reaction-sintering and densification were a little more difficult than Al 2 O 3 /Al specimens because of the insufficient milling. And the unstabilization of Ca-PSZ body which caused the cracks in the specimens was brought by the diffusion of Ca ion from Ca-PSZ grains to alumina.