Al Specimens Research Articles

Effect of Surface Condition on Tensile Properties of Fe-30Mn-0.2C-(1.5Al) High-Manganese Steels Hydrogen-Charged Under High Temperature and Pressure

In this study, two Fe-30Mn-0.2C-(1.5Al) high-manganese steels with different surface conditions were hydrogencharged under high temperature and pressure; then, tensile testing was performed at room temperature in air. The yield strength of the 30Mn-0.2C specimen increased with decreasing surface roughness(achieved via polishing), but that of the 30Mn-0.2C- 1.5Al specimen was hardly affected by the surface conditions. On the other hand, the tendency of hydrogen embrittlement of the two high-manganese steels was not sensitive to hydrogen charging or surface conditions from the standpoints of elongation and fracture behavior. Based on the EBSD analysis results, the small decrease in elongation of the charged specimens for the Fe-30Mn-0.2C-(1.5Al) high-manganese steels was attributed to the enhanced dislocation pile-up around grain boundaries, caused by hydrogen.

Effect of atmospheric control during MA-HIP process on mechanical properties of oxide dispersion-strengthened Cu alloy

In this study, mechanical properties of Dispersion Strengthened (DS)-Cu-Al (aluminum) and Zr (zirconium) alloys, which were fabricated by an MA-HIP method, were investigated for application to the heat sink materials of fusion reactors. The effect of air exposure before the HIP process was studied using a NIFS-Sealing Device. Cu–Al specimen with air exposure before HIP was broken during wire-electrical discharge formation. Cu–Al specimen without air exposure exhibited high fracture strength, but without yielding. Cu–Zr specimen, both with and without the exposure, yielded and exhibits elongation. An increase in yield and tensile strength by approximately 61% and 45%, respectively, were obtained for Cu–Zr specimen by avoiding air exposure. The results showed that Cu–Zr specimen is less susceptible to the atmosphere of the MA-HIP process than Cu–Al.

Energy absorption of bio-inspired multi-cell CFRP and aluminum square tubes

Abstract This paper aims to investigate the energy absorption of the bio-inspired multi-cell carbon fiber reinforced plastic (CFRP) and aluminum (Al) square tubes under the quasi-static axial crushing. Single-cell, double-cell and triple-cell CFRP and Al square tubes were bio-inspired designed and fabricated. The quasi-static compression tests were conducted to explore the force-displacement response, failure process, crashworthiness characteristics and the corresponding energy absorption mechanisms. The stable progressive folding with inextensional mode were found in Al tubes and progressive end crushing for CFRP tubes. The test results showed that the peak force, the mean crush force and the specific energy absorption (SEA) of CFRP tubes were higher than those of the Al tubes with the same cells. The cell number was sensitive to the crashworthiness characteristics for both CFRP and Al tubes. The specific energy absorption of the double-cell and the triple-cell CFRP tubes increased by approximately 17.0% and 2.4%, respectively, compared with that of the single-cell one, whilst 3.1% and 27.7%, respectively, for Al specimens. It was notable that the double-cell CFRP tubes exhibited the maximum SEA value of 66.31 J/g in the CFRP specimens, whereas the triple-cell Al tubes exhibited the maximum SEA value of 14.80 J/g in the Al specimens, which were attributable to the different interaction effect occurred in the connecting region.

Stress-strain Analysis of Premolars With Non-carious Cervical Lesions: Influence of Restorative Material, Loading Direction and Mechanical Fatigue.

Noncarious cervical lesions (NCCLs) are characterized by a loss of dental structure at the cementoenamel junction (CEJ) caused by stress, biocorrosion, and attrition. Variations in occlusal loading can promote different stress and strain patterns on the CEJ. Restoration of NCCLs is part of lesion management; however, there is still no conclusive restorative protocol for NCCLs. This study aimed to evaluate the stress and strain distribution of maxillary premolars with NCCLs according to three factors: 1) restorative technique; 2) direction of occlusal loading; and 3) mechanical fatigue. Three-dimensional (3D) finite element analysis (FEA) and strain gauge testing were used to assess stress and strain, respectively. 3D-FEA orthotropic, linear, and elastic models were generated: sound tooth (SO); unrestored NCCL; or NCCL restored with glass ionomer; flowable composite resin; nanofilled composite resin (CR); lithium disilicate ceramic; and nanofilled composite resin core associated with a lithium disilicate laminate (CL). A 150-N compressive static load was applied in two conditions: axially in both cusps (Al); and at a 45° angle to the long axis of the tooth applied to the palatine cusp (Ol). For the experimental tests, specimens were treated as described previously, and one strain gauge was attached to the buccal surface of each tooth to record tooth strains before and after cyclic loading (200,000 cycles, 50 N). FEA showed that the association of NCCL and Ol resulted in higher stress values. CR and CL restorations showed the closest biomechanical behavior to SO for both loading types. Loaded Al or Ol specimens showed higher strain values after mechanical fatigue. Lower stress and strain were observed with Al when compared with Ol. The restoration of NCCLs with composite resin only or associated with ceramic laminates seems to be the best approach because the results for those groups were similar in biomechanical behaviors to sound teeth.

Porous Ti–Al Intermetallic Based Alloys Fabricated by Pressure-Sintering Elemental Powders with a Space Holder Powder

ABSTRACTIn the present study, we have attempted to produce the porous Ti–Al intermetallic based alloys by pressure-sintering of the elemental powders of Ti and Al through a combustion reaction, with a NaCl space holder to achieve the development of a highly porous structure. The powders of Ti (particle size: <45 μm) and Al (particle size: <45 μm) were mixed to various total compositions of Ti–0-40 Al (at.%), and NaCl (particle size: 300-400 μm) was mixed with the Ti/Al powder to give a highly porous structure. The mixed powder was sintered at 700 oC under a constant pressure of 30 MPa to form cylindrical specimens with a diameter of 20 mm. The soaking of the specimens in pure water allows for the removal of NaCl (with a volume fraction of 60 %) and the formation of the pores to achieve a controlled relative density of 0.4. The present process can produce porous Ti–Al alloys with various compositions. In as-sintered Ti–Al specimens, an inhomogeneous microstructure consisting of Ti particles surrounded by the a Ti–Al alloy layer (various Ti–Al intermetallic phases) was observed. The as-sintered specimens exhibited the brittle behavior under compression, which is independent of their Al content. However, in a Ti–20Al alloy heat-treated at 1300 °C, a nearly Ti3Al single-phase microstructure appeared in the porous specimen. The heat-treated porous Ti–20Al alloy shows both a high plateau-strength level of approximately 100 MPa and a high plateau-end strain over 50%, resulting in a high absorption energy. The present results demonstrate that controlling the microstructure for the formation of the Ti3Al single-phase would be an effective method to achieve high energy absorption capacity of the porous Ti–Al alloy.

On the interpretation of the indentation size effect (ISE) through gradient theory for Vickers and Berkovich indenters

AbstractThe so-called indentation size effect (ISE) observed mainly in nanoindentation measurements with prismatic tips, is theoretically modeled in this article with the use of gradient theory. It is shown that the ISE, i.e. the dependence of the calculated hardness value on the indentation depth, is rather an artifact of the geometry of the tip used, than a phenomenon related to the material tested. The model predictions are compared with nanoindentation measurements of Al specimens.

A method to characterize the roughness of 2-D line features: recrystallization boundaries.

A method is presented, which allows quantification of the roughness of nonplanar boundaries of objects for which the neutral plane is not known. The method provides quantitative descriptions of both the local and global characteristics. How the method can be used to estimate the sizes of rough features and local curvatures is also presented. The potential of the method is illustrated by quantification of the roughness of two recrystallization boundaries in a pure Al specimen characterized by scanning electron microscopy.

Friction Stir Welding on Light-Weight Metal - Aluminum Alloy Al6061

Friction stir welding (FSW) is a solid state joining process in which metals are joined together using frictional heat and severe plastic deformation. The heating and the mixing of the metals is performed using a hardened tool with a shoulder and pin. FSW of lightweight metal alloy Al6061 has been carried out in the present study. For welding aluminum the parameters used were a constant tool rotation speed of 1600 rpm and varying tool translation speeds of 250, 500, 750 and 1000 mm/min. The welded coupons were characterized for microstructural observations and mechanical properties such as tensile and Charpy impact properties. The tensile and impact properties were studied at two different temperature namely, room temperature (RT) and 300°C. The FS welded aluminum specimens showed 86% – 98% tensile yield strength, in comparison to the base material at RT. At 300°C, the yield strength was observed to be 85% to 93% of the base material value. For the impact properties, the Al specimens showed 60% – 140% specific impact energy, in comparison to their respective base materials. Based on the mechanical properties and microstructural examination, the optimal weld parameter was identified as 1600 rpm and 250 mm/min which is dependent on the tool pin and shoulder design utilized in the study.

Microshear bond strength to dentin of self-adhesive flowable composite compared with total-etch and all-in-one adhesives

Background/purposeBecause of the lack of data on long-term survival of a flowable self-adhesive composite (SAC) restoration, the purpose of this study was to compare the microshear bond strengths (μSBSs) of flowable resin composites to dentin, either with self-adhesive ability or with the combined use of a total-etch adhesive and all-in-one adhesive, before and after thermocycling. Materials and methodsCoronal dentin specimens of 60 extracted sound third human molars were divided into three groups (n=20) as follows: Group 1, flowable SAC (VF); Group 2, total-etch adhesive+flowable composite (FL); Group 3, all-in-one adhesive+flowable composite (AL). For each adhesive, half of the specimens were subjected to μSBS testing after 24-hour water storage, and the other half of the specimens were subjected to 5000 thermocycles followed by μSBS testing. The morphologies of the adhesive interfaces were evaluated under a scanning electron microscope. Data were analyzed using one-way analysis of variance (ANOVA) and independent t test. ResultsOne-way ANOVA showed similar results for both 24-hour water storage and thermocycled groups. The FL group showed the highest μSBS values (P<0.001). The VF and AL groups were not statistically significantly different. Thermocycling had no effect on μSBS values (P=0.578). The interfacial observation revealed that VF had a gap at the resin–dentin interface. By contrast, both FL and AL specimens had distinct adhesive layers without any gap formation. ConclusionThe results from this study indicated that laboratory bonding effectiveness of flowable SAC was approximately that of all-in-one adhesive.

On the underlying micromechanisms in time-dependent anelasticity in Al-(1 wt%)Cu thin films

This paper reveals potential micro mechanisms underlying time-dependent anelasticity observed in Al-(1 wt%)Cu thin films. The analyzed deformation mechanisms involve dislocation motion and interaction with solute diffusion, grain boundaries and precipitates. In order to investigate the role of these mechanisms, Al-(1 wt%)Cu alloy thin films are heat treated to systematically change the precipitation state, while characterizing the grain boundary distribution with electron backscatter diffraction. Micromechanical characterization is performed by microbeam bending, nano-tensile creep testing and nano-indentation. Results in microbeam bending reveal, for all precipitate and grain boundary states considered, a similar time-dependent evolution of the anelastic strain after load release. The magnitude of the recovered strain is also observed to be independent of the precipitate or grain boundary configuration. The nano-tensile creep test also indicates the same time-dependent anelastic evolution, indicating that the loading state does not affect the underlying mechanisms. Analysis of strain bursts in nano-indentation shows that pinning of dislocations by Cu solutes is unaffected by the precipitation state. Based on uniaxial creep and time-dependent anelasticity measurements in pure Al specimens, it is made plausible that the time-dependent anelasticity originates from diffusion-limited glide or climb of dislocation segments that are pinned at Cu solutes or in dislocation structures, which provide an internal driving force.

Wear behavior of thermally sprayed Zn/15Al, Al and Inconel 625 coatings on carbon steel

Abstract In this study, Zn/15Al, Al and Inconel 625 coatings were applied on low carbon steel substrates by twin wire arc spray process as a corrosion and wear protection barrier against the marine atmosphere. The wear behavior of the coating layer was characterized by a pin-on-disk apparatus at a combination condition of three normal loads and two sliding speeds. The wear tests were conducted in a 3.5 wt.% NaCl solution to evaluate the wear resistance of the coatings in a corrosive environment. The results suggested that the Inconel 625 coating had a better wear resistance in a 3.5 wt.% NaCl solution as compared to the ZnAl and Al specimens. Zn/15Al coatings revealed less wear resistant in a corrosive environment due to the rupture of the oxide film on the coating surface during wear. For the sacrificial protection coatings of Zn/15Al and Al, the characteristics of surface oxide film play a vital role in the wear resistance of the coating materials.

3,3,3-Trifluoropropyltrimethoxysilane (TFPTMS) sol-gel-coated aluminum specimens: influence of sol-gel preparation medium on coating properties

Coating a component/structure is, arguably, the most common corrosion protection method, with organic barrier coatings being the most widely used variant. Many concerns have been raised about these coatings; for example, they are not biodegradable and emit volatile organic compounds. Thus, there is interest in a new generation of organic barrier coatings. This type of coating is the subject of the present study, which involved 1) application of coatings prepared from 3,3,3-trifluoropropyltrimethoxysilane (TFPTMS) sol-gel, using both an organic solvent (ethanol solution) and an aqueous solution, to Al specimens; and 2) characterization of the coatings. The influence of sol-gel preparation medium (ethanol solution versus aqueous solution) and post-coating treatment method (drying versus curing) on an assortment of coating properties, such as corrosion resistance in NaCl solution and contact angle in water, was determined. The most corrosion-resistant coating was obtained using an aqueous TFPTMS sol-gel and curing of the coated specimen at 105°C for 24 h.

A filtering method to reveal crystalline patterns from atom probe microscopy desorption maps

A filtering method to reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. The method filters atoms based on the time difference between their evaporation and the evaporation of the previous atom. Since this time difference correlates with the location and the local structure of the evaporating atoms on the surface, it can be used to reveal any crystallographic information contained within APM data. The demonstration of this method is illustrated on:•A pure Al specimen for which crystallographic poles are clearly visible on the desorption patterns easily indexed.•Three Fe-15at.% Cr datasets where crystallographic patterns are less obvious and require this filtering method.

Mechanical properties and microstructure of Al/Al laminated structure produced via ultrasonic consolidation process

Mechanical properties of a 2024 aluminium alloy laminated structure produced by the ultrasonic consolidation were investigated. In comparison with the monolithic aluminium alloy, the existence of laminated structure gave different fatigue and fracture mechanisms that associated with the layer interfaces. The Al/Al laminated specimens had the lower tensile strength but much higher fracture toughness than the monolithic Al specimens due to the exit of interface delaminations around the crack tip. The fatigue life of the laminated specimens was comparable to that of the monolithic Al specimens, though the initiation and propagation of the crack in the laminated specimens depended strongly on the microstructure of each material. The interface between layers could arrest the fatigue crack and impede the further propagation.

Determination of Mechanical Properties on Aluminium with 5% Copper Powder Metallurgy Route Compacts through Equal Channel Angular Pressing

The need for super-plasticity and high strength leads to the development of Severe Plastic Deformation technique. The strength of the material is directly dependent upon the grain size of the material. So, there is a need for producing Ultra-Fine Grain microstructure (UFG). UFG material is the material with very small grain size in the range of sub-micrometre. Application of severe plastic deformation, imparts extremely high strain. Equal channel angular pressing (ECAP) is a severe plastic deformation process in which the metal specimen is pressed through an angular channel of equal cross section. The material is subjected to shear deformation and strain is imparted in the specimen. Geometric parameters such as channel angle and corner angle play a major role in grain refinement. Aluminium (Al) specimens are subjected to undergo severe plastic deformation. Since, the strength of Al is not high, other materials are added in order to enhance its mechanical properties by matrix work hardening. Copper (Cu) along with Al shows increase in its strength and also in hardness. An attempt is made with Aluminium and copper, blended in the ratio 95:5 by weight with the main objective to study the Tensile strength, Hardness and Percentage Elongation properties of the specimen.

On the thermal stability of ultrafine-grained Al stabilized by in-situ amorphous Al2O3 network

Bulk Al materials with average grain sizes of 0.47 and 2.4µm, were fabricated by quasi-isostatic forging consolidation of two types of Al powders with average particle sizes of 1.3 and 8.9μm, respectively. By utilizing the native amorphous Al2O3 (am-Al2O3) film on the Al powders surfaces, a continuous, ∼7nm thick, am-Al2O3 network was formed in situ in the Al specimens. Systematic investigation of the changes to the am-Al2O3 network embedded in the Al matrix upon heating and annealing up to 600°C was performed by transmission electron microscopy (TEM). At the same time, the stability of the Al grain structure was studied by transmission Kikuchi diffraction (TKD), electron back-scatter diffraction (EBSD), and TEM. The am-Al2O3 network remained stable after annealing at 400°C for 24h. In-situ TEM studies revealed that at temperatures ≥450°C, phase transformation of the am-Al2O3 network to crystalline γ-Al2O3 particles occurred. After annealing at 600°C for 24h the transformation was completed, whereby only nanometric γ-Al2O3 particles with an average size of 28nm resided on the high angle grain boundaries of Al. Due to the pinning effect of γ-Al2O3, the Al grain and subgrain structures remained unchanged during annealing up to 600°C for 24h. The effect of the am-Al2O3→γ-Al2O3 transformation on the mechanical properties of ultrafine- and fine-grained Al is discussed from the standpoint of the underlying mechanisms.

In vitro apatite formation on nano-crystalline titania layer aligned parallel to Ti6Al4V alloy substrates with sub-millimeter gap.

Pure titanium substrates were chemically oxidized with H2O2 and subsequent thermally oxidized at 400°C in air to form anatase-type titania layer on their surface. The chemically and thermally oxidized titanium substrate (CHT) was aligned parallel to the counter specimen such as commercially pure titanium (cpTi), titanium alloy (Ti6Al4V) popularly used as implant materials or Al substrate with 0.3-mm gap. Then, they were soaked in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5°C) for 7days. XRD and SEM analysis showed that the in vitro apatite-forming ability of the contact surface of the CHT specimen decreased in the order: cpTi>Ti6Al4V>Al. EDX and XPS surface analysis showed that aluminum species were present on the contact surface of the CHT specimen aligned parallel to the counter specimen such as Ti6Al4V and Al. This result indicated that Ti6Al4V or Al specimens released the aluminum species into the SBF under the spatial gap. The released aluminum species might be positively or negatively charged in the SBF and thus can interact with calcium or phosphate species as well as titania layer, causing the suppression of the primary heterogeneous nucleation and growth of apatite on the contact surface of the CHT specimen under the spatial gap. The diffusion and adsorption of aluminum species derived from the half-sized counter specimen under the spatial gap resulted in two dimensionally area-selective deposition of apatite particles on the contact surfaces of the CHT specimen.

Microstructural characterization of aluminum alloys using Weck's reagent, part II: Coloring mechanism

This paper is the second part of the study focusing on the color metallography using Weck's reagent for Al alloys. Following the first part of the study which demonstrated a wide application of Weck's reagent, this paper investigates the coloring mechanism of color etching with Weck's reagent in detail by various characterizations of the specimen surface after etching. The results show that after the Al specimen is etched with Weck's reagent, a thin film consisting of Mn oxide is formed on the surface with different morphologies and thicknesses from location to location, which causes different colors observed by optical microscopy correspondingly. Further investigations show that the film is characterized by a relatively smooth surface but a rough interface with the substrate. Such structure may cause interference of light reflected from different sites. The growth of film is strongly influenced by the solute micro-segregation in the Al phase. Film starts to form first on the area with higher solute (Ti) concentration. As the etching time increases, film also grows on other areas. 12s etching yields to the best color contrast because the difference in the film morphology and thickness is the most obvious at this time.

Al 소재의 방열특성 향상을 위한 미세조직 제어 연구

【In this study, the control of microstructure for increasing surface roughness of Al with an electro-chemical reaction and a post treatment is systematically investigated. The Al specimen is electro-chemically treated in an electrolyte. In condition of the post treatment at $100^{\circ}C$ for 10 min, a change of the surface microstructure occur at 50V (5 min), and a oxidized layer is at 400V, to which lead a decreasing surface roughness. The minimum temperature of the post treatment for a change of microstructure is $80^{\circ}C$ . Moreover, in the condition of 300V (5 min), the electro-chemical reaction is followed by the post treatment at $100^{\circ}C$ , the critical enduring time for the change of microstructure is 3 min. The longer post treatment time leads to the rougher surface. The treated Al specimen demonstrate better heat release ability owing to the higher surface roughness than the non-treated Al.】

Experimental analysis on metallic foams-a response surface methodology approach

This study aimed to fabricate metallic porous materials using powder metallurgy (PM) space-holder technique. In the PM route, Al powder was mixed with different ratios (7%, 10%, and 20%) and sizes (500 and 1000 μm) of sodium chloride granules as space-holder agent. The mixture was then compacted at different compacting pressures (150, 200, and 250 MPa) and then heated to 280 °C for sintering. Subsequently, sodium chloride granules were removed by dissolving in water to obtain the porous structure. Tests were performed on all porous Al specimens, and characteristics such as density and porosity were measured. A statistical approach was used to optimize processing parameters. ANOVA statistical tool was used to obtain the final evaluation of the most significant features, namely, relative density and porosity fraction.