Al Specimens Research Articles

Non-contact surface roughness evaluation of milled Al and Cu specimens by 1D and 2D wavelet transformation using histogram based linear regression model

Non-contact surface roughness evaluation of milled Al and Cu specimens by 1D and 2D wavelet transformation using histogram based linear regression model

Electromagnetic-mechanical response mechanism and microstructure evolution during Al-Mg electromagnetic pulse welding

Electromagnetic pulse welding technology can achieve effective bonding of different metals without intermetallic compounds and heat-affected zones. Current research primarily focuses on bonding interface and strength, neglecting the fact that the strength of the joint is also related to the performance of the plate itself. This study investigates the macro-microscopic responses, and relevant mechanisms of plates under electromagnetic-mechanical coupling effects are revealed by the integration of microscopic characterization, a finite element model, and mechanical tests. The results show that diverse crystal structures have different mechanical response behavior. The elongation of aluminum after pure pulsed electromagnetic field (EMF) treatment is 27% higher than the untreated specimen while the tensile strength remains the same. But magnesium alloys show an increase of 16%, and 23% for tensile strength, and elongation, respectively. Under a pure EMF, the movement and recombination of dislocations are promoted in aluminum alloy, which is beneficial to reducing the dislocation density of aluminum alloy. As for magnesium alloy, twinning and recrystallization are induced to realize grain refinement. Under the coupling of electromagnetic-mechanical, there is an interaction between the electromagnetic effect and strain rate hardening on dislocations. The tensile strength of the Al specimen increases first and then decreases with the discharge voltage rising. This is determined by the dislocation entanglement behavior. This paper can provide a reference for an in-depth understanding of the mechanism and welding process of electromagnetic pulse welding.

High bonding strength of polyphenylene sulfide-aluminum alloy composite structure achieved by constant current anodizing in tartaric acid

The high-strength and facile direct joining of metal to polymer has attracted increasing attention in adhesion. The aluminum alloy (Al) specimen was fabricated by constant current anodization and enlarging treatment. The influences of surface energy, porosity, and anodization time on the interface bonding strength of the injection molding polyphenylene sulfide (PPS)–Al composite structures were quantitatively discussed. Results showed that the bonding strength of the joints was significantly affected by the wettability, porosity, thickness, and pore diameter of the anodized aluminum oxide (AAO) films. When the current density and anodization time were 120 A/m2 and 30 min, the Al surface energy and the bonding strength reached the maximum of 74.8 mN/m and 11.7 MPa. With the enlargement treatment of the AAO film, when the etching duration was 45 min, the bonding strength increased to 25.0 MPa. In general, these results are of great importance to the further design and optimization of the polymer-metal hybrid with reliable interface adhesive strength.

Energy-absorption analyses of honeycomb-structured Al-alloy and nylon sheets using modified split Hopkinson pressure bar

Thin cylindrical honeycomb-structured aluminum alloy and mono-cast (MC) nylon were studied as superior energy-absorbing materials compared to metallic foams. Their energy-absorbing performance was assessed using a modified split Hopkinson pressure bar (SHPB). Key parameters included maximum impact acceleration (amax) and its reduction ratio (compared to the none-specimen case). The lowest amax reduction ratio was observed in bulk Al sheets without honeycomb cavities. As the cavity fraction increased up to 79% in honeycomb-structured Al specimens, the amax reduction ratio improved due to broadened stress–time curves with a shallow-plateau shape. This made high-cavity-fraction Al specimens preferable for higher-energy absorption and lighter-weight buffering materials. In nylon specimens, the amax reduction ratio increased until the fraction reached 52% due the softer and more deformable nature of the polymeric nylon. Thicker or rotated Al specimens also showed higher amax reduction ratios due to sufficient and continuous energy absorption. The modified SHPB demonstrated effective energy-buffering concepts and provided insightful amax interpretations, overcoming complexities in energy absorption analyses.

The effect of thickness and surface roughness on the absorption coefficient (α) of Aluminum (Al)

Noise is an essential factor in determining various interior elements and machinery, especially those made of metal. The noise level generated by metal is caused by the low level of sound attenuation factor, known as the absorption coefficient (alpha, α) of the metal. Aluminum (Al) metal has the characteristics of corrosion resistance, lightweight, attractive color, and ease of form, so it is popular as a material for various households, machinery, and industrial machinery. This study explains the effect of surface roughness (0.05, 0.12, and 0.15 Ra) and thickness (2, 4, and 6 mm) of Al specimens on the measurement values of absorption coefficient (α). The measurements result show that the average value of α is relatively stable by variations in surface roughness and thickness within the low to medium frequency range (200-800 Hz). Although in general there are increased α values for the high-frequency ranges (1000-1200 Hz), the lowest average of α value occurs in the specimen with the highest surface roughness of Ra 25. Thus, even though the variation in thickness has no significant effect on the α value, the higher surface roughness of Al will reduce the value of the absorption coefficient (α) resulting in higher noise generated.

Microstructure evolution and tensile behaviour of fine-grained 6082 Al wire with high ultimate strength and high work hardening by friction stir extrusion of bulk Al sheet

Driven by the highly enhanced demand for metallic materials with excellent strength-ductility synergy, fine-grained alloy fabricated by severe plastic deformation (SPD) is a long-lasting research interest. In this study, a fine-grained aluminium (Al) alloy wire with high ultimate tensile strength (316.8 MPa) and high work hardening capability (n = 0.34) was developed via a novel bulk-consolidation friction stir extrusion (FSE) enabled by CoreFlow™ process based on FSE processed 6082-T6 Al sheet. Grain refinement of 200 times occurred in CoreFlowed Al alloy, which is rarely observed in FSEed Al alloy counterpart based on milling metal chips. The undesirable feature of coarse and preferred secondary phase particles in the initial 6082-T6 Al billet was well tailored during CoreFlow™ process, which led to an attractive characteristic of dispersed and refined particle phases in CoreFlowed Al alloy. Texture components of S (V = 8.24%) and Goss (V = 6.86%) were observed, however, the overall micro-texture intensity of CoreFlowed Al wire was significantly weakened. Due to the cooperative deformation modes consisting of dislocation slip and grain boundary sliding, as well as the positive compatibility effect of fine-grains on deformation, CoreFlowed Al specimens demonstrated an excellent ductility (EI = 19.3%) and acceptable yield strength (YS = 182 MPa) compared to initial 6082-T6 Al sheet (EL = 10.4%, and YS = 225 MPa). Benefiting from the higher work hardening capability, the final ultimate tensile strength (UTS) of CoreFlowed Al (316.8 MPa) reached almost the same level as the 6082-T6 Al sheet (324.6 MPa). Furthermore, after one simple post-processing one-step heat treatment (175 °C for 10 h), the wire's yield strength was improved to 250 MPa, although only maintaining 9% elongation. This low elongation could be attributed to micro-cracks induced by coarsening of the second phases, while high yield strength resulted from fine grain size and precipitate strengthening. The wide range of variations in the mechanical properties of CoreFlowed Al wire under different conditions provides significant freedom in tailoring the mechanical properties of alloy wire in applications.

Effect of porosity on shock propagation behaviour of single crystal aluminium: A molecular dynamics investigation

Materials' response to shock waves is largely affected not only by their inherent atomic structure but also by their physical structure. Current study involves analysis of shock propagation behaviour of single crystal aluminium (Al) specimens with different levels of porosities at nanoscale under a compressive shock loading using three dimensional molecular dynamics (MD) simulations. Solid, two dimensional array of pores, and three dimensional array of pores in the single crystal Al specimen were considered for detailed analysis of the shock response. It is observed that the porosity causes time delay in the travel of shock wave from front end of the surface to the rear end. The computational results indicate that the porosity results into increase in time of shock wave travel and it is found that the maximum porosity (47% in this simulation) causes 4 times the time of travel taken in solid Al specimen. The shock wave causes various sequential phenomenon in the Al specimen from compression to rarefaction which further leads to spalling of the material. The study also reveals that the pore walls act as a reflecting wall to the shock wave which causes secondary rarefactions and spalling phenomenon. Analyses show that the deformation in the material during shock loading is largely dominated by Shockley partial dislocations.

Role of alloyed Al on the microstructure and corrosion behavior of as-cast dilute Mg-2Zn-xAl-0.5Ca alloys

Effect of Al on microstructure and corrosion behaviors of cast Mg-2Zn-xAl-0.5Ca (x = 0, 0.5, 1.0, 2.0 wt%) alloys is investigated. The 0.5Al specimen shows the lowest corrosion rate (4 mm/y) because appropriate Al doping into Ca2Mg6Zn3 decreases cathodic activity of this phase and Al alloying significantly refines intermetallics, both of which contribute to reducing pitting corrosion. Moreover, finer grains enhance barrier effect of continuous net-like phases at grain boundaries, effectively confining the corrosion propagation. The formation of Al2O3 reinforces the surface film. Optimum Al content is determined as 0.5–1.0%, which endows alloy with admirable corrosion resistance and high ultimate tensile strength.

Microstructure and mechanical properties of SiCp/Al composite fabricated by concurrent wire-powder feeding laser deposition

In this study, the SiCp/Al matrix composites was fabricated by concurrent wire-powder feeding laser deposition (CWPLD). The microstructure and mechanical properties of the fabricated SiCp/Al composites were studied. The microstructure of fabricated composites consisted of Al matrix, SiC and reaction product Al4C3. The size of α-Al grain (mean area: 275.0 μm2) was much smaller than that of Al specimen fabricated by wire feeding laser deposition (WLD) (mean area: 1544.4 μm2). SiC and Flaky Al4C3 were non-uniformly distributed in the matrix. Al4C3 platelets distributed discontinuously at the interface between unmelted SiC and Al. Due to the inhomogeneous distribution of SiC and Al4C3, the Vickers hardness of the fabricated composites fluctuated violently, ranging from 85 HV to 120 HV. The ductility of the fabricated composites (3.75%) was lower than that of the Al specimen (8.94%) fabricated by WLD. The tensile strength of the fabricated composites (246.0 MPa) was higher than that of the Al specimen fabricated by WLD (230.8 MPa). In the tensile test, only SiC fracture were found in the fracture observation. The bonding strength of interface between SiC and Al was higher than strengths of SiC particle and Al matrix. The debonding between SiC and the Al matrix was not found on the fracture surface of tensile specimens.

Molecular dynamics simulation on creep-ratcheting behavior of columnar nanocrystalline aluminum

Creep-ratcheting deformation behavior of columnar nanocrystalline (NC) Al varying in grain sizes have been studied using molecular dynamics simulations at three different temperatures (300 K, 467 K, and 653 K). The underlying deformation mechanisms of columnar NC Al for two stress ratios of ratcheting are also evaluated in this study. The highest strain accumulation and rapid hysteresis loop proliferation are attained at 653 K. The dislocation density is low at 653 K in contrast to the other two deformation temperatures. The perfect dislocations support the creep-deformation process followed by Shockley partial dislocations. It is observed that the cyclic hardening phenomenon at 300 K and the cyclic softening phenomenon at 653 K dominate during creep-ratcheting loading. The specimen fails earlier at higher temperatures owing to the change in the shape of hysteresis loops. The predominant grain boundary-based deformation mechanisms of columnar NC Al specimens are grain boundary (GB) migration, GB diffusion, GB widening, GB sliding, and GBs merging for all the deformation temperatures. The variation in the extent of deformation with respect to temperatures depends on strain accumulation in the plastic region under creep-ratcheting loading.

Plastic Softening Induced by High-Frequency Vibrations Accompanying Uniaxial Tension in Aluminum.

We have investigated the influences of high-frequency vibration (HFV) superimposed onto the monotonic uniaxial tension in single-crystal aluminum (Al) specimens by molecular dynamics simulations. It was found that HFV induces softening, i.e., reduction in peak stress. Similar to previous experimental results, the softening increases with the increasing HFV amplitude. Dependences on lattice orientation, tensile strain rate, and a preset notch are considered. Lattice orientation plays an important role in peak stress and plasticity. The evolution of the atomic structure reveals that dislocations have enough time to annihilate under a lower tensile strain rate, resulting in strong ups and downs in the strain–stress curves. Under a higher strain rate, newly appearing dislocations interact with previous ones before the latter annihilate, densifying the dislocation network. As a result, further dislocation motions and annihilations are considerably impeded, leading to a relatively smooth flow stage. Furthermore, by modifying the propagation direction of shear bands, a preset notch can strengthen the peak tensile stress under low-level amplitude HFVs.

Effect of corrosion rates of preheated Schinzochytrium sp. microalgae biodiesel on metallic components of a diesel engine

Hitherto, the myriad of researches conducted on biofuels coupled with their poor oxidative stabilities, show that none of these studies has considered monitoring the corrosive effects of Schinzochytrium sp. microalgae biodiesel on diesel engines. In this study, corrosion behaviors of mild steel (MS), aluminum (Al) and copper (Cu) were compared via immersion tests in preheated schinzochytrium sp. microalgae biodiesel and its blends at room temperature and 60 °C for 1200 h. Property-variation of the individual/blended fuels, corrosion rates/products of the metals, and their morphologies were examined. For the metals, the corrosion rates are in the order of Al < MS < Cu at room temperature and 60 °C. The degraded properties and corrosion rates of the metals in the diesel fuel (B-100) and biodiesel fuel-blends, were seen to be minimal relative to those of neat biodiesel (D-100). The morphologies of the metals in contact with the fuels, showed substantial variation in surface properties for the Al, MS and Cu specimens. Furthermore, of all the three metals, copper was most prone to biodiesel corrosion. Hence, the results suggest the need to anticipate a future where the use of corrosion inhibitors for preventing engine-part degradation induced by biofuels becomes a reality.

Significant Bauschinger effect and back stress strengthening in an ultrafine grained pure aluminum fabricated by severe plastic deformation process

Bauschinger test in uniaxial tension-compression mode was carried out for the first time on the pure Al specimens having homogeneous ultra-fine grained (UFG) microstructures fabricated by equal-channel angular pressing (ECAP) and subsequent annealing processes. Significant Bauschinger stress (transient softening), Bauschinger energy parameter and their strong dependences on the tensile plastic pre-strain at the very early stage of the tensile deformation were measured in the UFG specimens, in sharp contrast to their coarse-grained (CG) counterpart. The grain size dependence of the Bauschinger effect in pure Al was qualitatively discussed in terms of the back stress arising from the formation of dislocation pile-up against the grain boundary during plastic deformation.

Особенности окисления медно-никелевых сплавов, синтезированных искровым плазменным спеканием

Data on high-temperature tests for heat resistance of copper-nickel-based powder materials synthesized by spark plasma sintering (SPS) are presents. The features of oxidation of copper-nickel alloys with various alloying elements at temperatures above 1000 °C have been studied. Based on the research results, the dependence of the growth rate of the oxide film on the high-temperature oxidation temperature was established, and the influence of alloying elements in the composition of sintered copper-nickel alloys on their heat resistance was considered. It is shown that the highest heat resistance is provided by alloying copper-nickel alloys with aluminum and chromium. For all considered compositions of copper-nickel alloys synthesized by spark plasma sintering, the temperature point of 1100 °C during a 20-hour heat resistance test is the limiting one, since most of the samples are completely destroyed. The scale growth rate for composition Cu – Ni – Cr – Al 1.49·10–3 g/cm3 is lower than the oxidation rate of pure nickel 3.78·10–3 g/cm3 at 1000 °C and these two samples demonstrate the lowest weight gain after testing at 1000 °С. For compositions Cu – Ni, Cu – Ni – Cr – C(graphite) and Cu – Ni – Al the oxidation rate increases by two orders of magnitude, for compositions Cu – Ni – Cr and Cu – Ni – Cr – Si — by three orders of magnitude. Despite increase of test temperature up to 1100 °C, the rate of scale growth on the surface of Cu – Ni – Cr and Cu – Ni – Al specimens remain practically unchanged: 124.01·10–3 and 210.43·10–3 g/cm3 at 1000 °C; 153.44·10–3 and 203.87·10–3 g/cm3 at 1100 °C. Deceleration of the oxidation kinetics of these samples with temperature increase is ensured by formation of oxide film on the surface, which has a dense structure with good adhesion to the basic material.

A novel approach for microscale dry contact stiction and friction assessment: Experimentation and analysis

Accurate and quantitative evaluation of friction is of fundamental interest for materials science and manufacturing. Driven by the trend towards miniaturization, micro metal forming techniques with characteristic forming dimensions approaching a few microns have developed rapidly over the past two decades. In contrast, the assessment of microscale friction is lagging. Here, we present a novel test, compression molding and demolding test (CMDT), to assess stiction and friction at the microscale. CMDT was conducted via in-situ instrumented molding and demolding of an Al specimen with cylindrical tool steel and Ti alloy punches. High-rate data acquisition enabled direct measurements, for the first time, of microscale stiction and friction forces during disengagement between the punches and the molded Al under dry contact conditions. Stiction and friction stresses were then deduced and analyzed. The average friction coefficient was estimated by combining the cavity expansion model and finite element method analysis. Examinations suggest that punch geometry and surface finish, together with the accuracy of estimating the sidewall contact pressure, influence the obtained friction coefficient values. CMDT exhibits merits such as high operation simplicity and measurement accuracy and offers an alternative approach to providing new experimental evidence for a range of microscale friction problems.

Selective laser melting of SiCp/Al composites: Densification, microstructure, and mechanical and tribological properties

In this paper, SiCp/Al composites were successfully fabricated by selective laser melting (SLM), and the dependence of phase composition, densification behavior, and mechanical properties of the composites on laser power was researched and discussed. The results showed that the density, microhardness and friction resistance of the SLM formed SiCp/Al composites were enhanced with increasing the laser power density, which may be caused by the higher molten pool temperature at higher laser power density. When SiCp/Al composites were prepared at 400 W with a scanning speed of 300 mm/s, the highest relative density of approximately 91.1 % and microhardness of approximately 191 HV0.1 (more than six times higher than that of the selective laser melted pure Al specimens, 191 HV0.1vs 31 HV0.1) were obtained, and the minimum wear rate and friction coefficient were 1.31 × ×10−5 mm3 N−1 m−1 and 0.38, respectively.

Atomistic simulation of crack propagation in CNT reinforced nanocrystalline aluminum under uniaxial tensile loading

ABSTRACT A molecular dynamics simulation-based study has been performed to examine the deformation behaviour of the predetermined parallel and perpendicular centreline cracks in CNTs embedded nanocrystalline aluminum (CNTs-NC Al) composite specimens under uniaxial loading. The hybrid potential (i.e. EAM, AIREBO, and LJ) method is adopted for carrying out the tensile deformation at three different temperatures (such as 10 K, 300 K, and 653 K). The mechanical properties are evaluated for both cases of parallel and perpendicular cracks of NC Al and CNTs-NC Al specimens. (30,30) CNT-NC Al specimen has shown superior fracture strain and ultimate tensile strength (UTS) at low temperature, whereas, higher fracture strain and lower UTS at high temperature than NC Al specimen. The mechanical properties of CNTs-NC Al nanocomposites are affected by the pre-existing crack and loading direction. The CNTs-NC Al nanocomposite specimens have exhibited the highest dislocation density compared to the NC Al specimen. The Shockley partial dislocations are a major driving factor for the parallel and perpendicular cracks of both (NC Al and CNTs-NC Al) specimens. The structural evolution and defect variation (such as stacking faults interaction with various dislocations, twin boundary, and grain boundary widening) has been elucidated during the tensile deformation of NC Al and CNT-NC Al nanocomposites.

Evaluation of Vibration Amplitude Stepping and Welding Performance of 20 kHz and 40 kHz Ultrasonic Power of Metal Welding

Today ultrasonic power technique is consider a mandatory technique which is always entered in many processes such as in metal and plastic welding to overcomes many issues, with aided of applying force (pressure) and supplied high frequency vibration, a solid-state weld can be generated by ultrasonic metal welding technique. That give a technique the ability to join not only a small components, whereas also to join thicker specimens, depend on a proper control of matching welding conditions. Therefore a welding performance can be study and compared after designed welding horn to resonance at frequencies of 20 kHz and 40 kHz. The analyses of the designed horn are completed through use a vibration mathematical expressions, modal and harmonic analyses to ensure the weldability due to applying ultrasonic power to the working area and also to compare the performance of joint at using two resonance frequencies of 20 kHz and 40 kHz. The dimensions of the horns were determined to match the selected resonance frequencies, which the lengths were calculated as 132 mm and 66 mm respectively. The analysis of the exciting modal indicates that the axial vibration modes of 19,584Hz and 39,794Hz are obtained in 10th mode, while the two frequency values are recorded 19,600 Hz and 39,800 Hz from the frequency response of the two horns. The weld strength between Al and Cu specimens with a thickness 0.5 mm were evaluated using tensile test, which the analyses were obtained under using different welding pressure and varied amplitudes. The results were recorded within exciting a horn with two different resonance frequencies, show the enhancement of weld strength and quality through control of stepping amplitude, the enhancement means obtain good strength of the weld, reduce sticking horn to specimen, and lower specimen marking

Evaluation of Vibration Amplitude Stepping and Welding Performance of 20 kHz and 40 kHz Ultrasonic Power of Metal Welding

Today ultrasonic power technique is consider a mandatory technique which is always entered in many processes such as in metal and plastic welding to overcomes many issues, with aided of applying force (pressure) and supplied high frequency vibration, a solid-state weld can be generated by ultrasonic metal welding technique. That give a technique the ability to join not only a small components, whereas also to join thicker specimens, depend on a proper control of matching welding conditions. Therefore a welding performance can be study and compared after designed welding horn to resonance at frequencies of 20 kHz and 40 kHz. The analyses of the designed horn are completed through use a vibration mathematical expressions, modal and harmonic analyses to ensure the weldability due to applying ultrasonic power to the working area and also to compare the performance of joint at using two resonance frequencies of 20 kHz and 40 kHz. The dimensions of the horns were determined to match the selected resonance frequencies, which the lengths were calculated as 132 mm and 66 mm respectively. The analysis of the exciting modal indicates that the axial vibration modes of 19,584Hz and 39,794Hz are obtained in 10th mode, while the two frequency values are recorded 19,600 Hz and 39,800 Hz from the frequency response of the two horns. The weld strength between Al and Cu specimens with a thickness 0.5 mm were evaluated using tensile test, which the analyses were obtained under using different welding pressure and varied amplitudes. The results were recorded within exciting a horn with two different resonance frequencies, show the enhancement of weld strength and quality through control of stepping amplitude, the enhancement means obtain good strength of the weld, reduce sticking horn to specimen, and lower specimen marking.

Evaluation of Vibration Amplitude Stepping and Welding Performance of 20 kHz and 40 kHz Ultrasonic Power of Metal Welding

Today ultrasonic power technique is consider a mandatory technique which is always entered in many processes such as in metal and plastic welding to overcomes many issues, with aided of applying force (pressure) and supplied high frequency vibration, a solid-state weld can be generated by ultrasonic metal welding technique. That give a technique the ability to join not only a small components, whereas also to join thicker specimens, depend on a proper control of matching welding conditions. Therefore a welding performance can be study and compared after designed welding horn to resonance at frequencies of 20 kHz and 40 kHz. The analyses of the designed horn are completed through use a vibration mathematical expressions, modal and harmonic analyses to ensure the weldability due to applying ultrasonic power to the working area and also to compare the performance of joint at using two resonance frequencies of 20 kHz and 40 kHz. The dimensions of the horns were determined to match the selected resonance frequencies, which the lengths were calculated as 132 mm and 66 mm respectively. The analysis of the exciting modal indicates that the axial vibration modes of 19,584Hz and 39,794Hz are obtained in 10th mode, while the two frequency values are recorded 19,600 Hz and 39,800 Hz from the frequency response of the two horns. The weld strength between Al and Cu specimens with a thickness 0.5 mm were evaluated using tensile test, which the analyses were obtained under using different welding pressure and varied amplitudes. The results were recorded within exciting a horn with two different resonance frequencies, show the enhancement of weld strength and quality through control of stepping amplitude, the enhancement means obtain good strength of the weld, reduce sticking horn to specimen, and lower specimen marking.