Alloy Thin Plate Research Articles

圧縮せん断法により作製したCu-Zn合金薄板の機械特性に与えるせん断ひずみの影響

圧縮せん断法により作製したCu-Zn合金薄板の機械特性に与えるせん断ひずみの影響

Metamagnetic Shape Memory Alloy Thin Plates Consolidated by Compression Shearing Method at Room Temperature for Thermal Energy Harvesting Device

Metamagnetic Shape Memory Alloy Thin Plates Consolidated by Compression Shearing Method at Room Temperature for Thermal Energy Harvesting Device

Ultrasonic Infrared Thermography of Aluminium Thin Plates for Crack Inspection in Friction Stir Welded Joints

Ultrasonic infrared thermography, thanks to its defect selective, dark-field damage detection capability, is a powerful tool for the inspection of cracks, but the ultrasound coupling is difficult for thin-walled or low-rigidity specimens if an external stimulation is employed, and the crack signature is poor for metals with high thermal conductivities. In order to detect cracks in friction stir welded joints of aluminium alloy thin plates, the constraint-excitation schemes and post image processing methods were investigated. A base excitation combined with unsymmetrical constraint condition of the thin plate were proposed and analyzed by using experiment and vibration modal analysis; a wavelet image enhancement based on symlets or biorthogonal wavelets was presented. The base excitation skill with unsymmetrical support condition and the post image processing with wavelet image enhancement were high-lighted. The results showed that the new constraint-excitation scheme was a feasible approach to detect kissing cracks in friction stir welded joints of thin plates; the wavelet image enhancement method was effective. The presented measures can greatly improve the detectability of ultrasonic thermography for thin plates.

Microstructure Characteristic and Fatigue Damage Behaviors of 2060 Al-Li Alloy Thin Plate

The microstructure characteristic, fatigue damage behaviours and evolution of microstructure during the fatigue testing of 2060 Al-Li alloy thin plate were studied by fatigue tester equipped with in-situ observation device, OM, EBSD, SEM and TEM. The results show that recrystallized grains with irregularity shape and large size are observed, the Goss and Cube texture are the mainly types, abundant of T1 with size of 50~60nm are found in grains. During axial loaded fatigue testing, a crack initiates from the edge of sample and extend into grain along the direction with maximum Schmid factor. When the crack reaches and crosses the first grain boundary, the extending direction deflects from 45° degree to perpendicular with loading direction, and propagates along this direction till the sample quickly fracture. A large size deformation region contains numerous slip strips around the crack tip during the initiation and extending process is observed. The dislocations cut across the T1 precipitates located in grains during deformation, and release the stress concentration on the crack tip. The fatigue crack extends across the grains with serrated shape can result from the big orientation difference of grains and easy screwed T1 precipitates.

Local deformation and macro distortion of TC4 titanium alloy during laser shock processing

Experimental investigation has been carried out to understand the local deformation, macro distortion, and residual stress distribution of TC4 titanium alloy thin plate with different thickness during laser peening processing. The results show that the geometry distortions generate different profile directions depending on the laser shock processing condition. The deformation coefficient λ based on laser power density and sheet thickness is used to predict the macro deformation mode. When λ < 0.212, no macro distortion is produced; when 0.212 < λ < 0.58, volume is transferred along the top surface, the geometric distortion direction is away the laser beam, compressive residual stress is induced on the surface, and convex deformation is produced; when 0.65 < λ, volume is transferred along the bottom surface, the macro distortion direction is toward the laser beam, tensile residual stress is induced on the surface, and concave deformation is produced; the threshold of concave and convex deformation is about 0.62. The deformation coefficient λ and the threshold of concave and convex deformation can be adopted to predict and control the geometry distortion of TC4 titanium alloy thin plate during laser shock processing.

Four-point bending tests to reveal tension-compression flow stress asymmetry in NiTi shape memory alloy thin plate

A Nickel Titanium (NiTi) shape memory alloy band plate (strip) of less than 0.8 mm thickness was strained by four-point bending at various temperatures. When the bending stress was beyond the elastic range, the inelastic strain on the top surface deviated from that on the bottom surface, which resulted in two different bending curves. The bending strain in tension under a given load was always larger than that in compression in both cubic and martensite phases. The crystallographic theory of martensite was applied to calculate the strains of a variant (Bain correspondence variant), a variant pair (correspondent variant pair), and the reorientation of martensite variants (detwinning). It is concluded that the asymmetry observed in the band plate may due to [111] texture in the rolling direction, as has been pointed out in former studies of bulk alloys.

Visualisation and numerical simulation of material flow behaviour during high-speed FSW process of 2024 aluminium alloy thin plate

Material flow during friction stir welding of ultra-thin 2024 aluminium alloy plates was investigated by using copper powder as marker material. Based on the visualised experiment and numerical computation of material flow produced in the research, the effect of rotational speed on material flow was revealed. In high rotational speed FSW process, flow distance along welding direction of plastic metal on both sides and transverse flow distance to the weld centre line on the retreating side were shorter; however, a larger flow velocity was shown. The flow velocity of plastic metal decreased with the increasing of distance from the weld centre, while it increased with the increasing of rotational speed under a constant rotational speed/welding speed ratio. Maximum and minimum values of the flow velocity of plastic metal were located at the intersection of triple spiral groove of shoulder and both sides of its outer diameter edge, respectively.

Projectile impact on fabric-metal assemblies – Influence of fabric-metal sequence

Fabrics woven from high-strength fibres are increasingly employed for protection against projectile impact, because of superior mechanical properties. In some applications, high-strength fabrics are combined with metallic components to provide sufficient structural rigidity and strength – e.g. for vehicle bodies, turbine engine fragment barriers, building doors, etc. An understanding of how the fabric-metal layer sequence affects the resulting ballistic resistance, is essential for effective design of such fabric-metal assemblies. This motivates the current study, whereby multiple plies (1, 2 or 4) of Twaron (T) aramid fabric were combined with an aluminium alloy (A) thin plate to form a lightweight protective panel. The projectile impact penetration resistance of three types of fabric-metal arrangements were examined – i) the aluminium alloy plate as the impact face; ii) the Twaron fabric as the impacted layer; iii) the aluminium alloy plate sandwiched between fabric layers. For assemblies with a smaller number of fabric plies (i.e. 1 or 2), siting the aluminium alloy plate as the rearmost layer results in a significantly higher impact energy absorption capacity, compared to having the aluminium alloy plate as the impact face – e.g. for (A+1T) assemblies, i.e. Al plate+1 ply of Twaron, 1T/A (impact face layer appears first in this nomenclature) performs much better than A/1T. For (A+2T) assemblies, 2T/A provides the highest impact resistance, A/2T is the weakest, and 1T/A/1T lies in between. However, when the number of fabric plies is increased to 4, a variety of responses was observed. An A/4T configuration absorbs significantly higher energy than a 4T/A arrangement, while a symmetrical 2T/A/2T sequence absorbs less energy than either an A/4T or 4T/A configuration. High-speed optical photography images and post-test specimens were analysed, to examine the deformation and failure modes of the fabric plies and Al plate in the fabric-metal targets, and how they are affected by the fabric-metal sequence. These help identify the interaction between the fabric plies and Al plate for various fabric-metal sequences, in order to account for the phenomena observed in experiments.

Ballistic performance and energy absorption characteristics of thin nickel-based alloy plates at elevated temperatures

To study the aeroengine containment capability at high temperatures, experimental and numerical investigations have been carried out to determine the ballistic performance and energy absorption characteristics of GH4169 alloy thin plates at temperatures ranging from 25–600 °C. First, experiments were conducted using a gas gun. Target plates were impacted by projectiles with various initial velocities. The effects of the temperature and initial velocity on the deformation, failure pattern and energy absorption of the plate were correspondingly obtained. The experimental results showed that at higher temperature, the deformation of the target plates is greater, the energy absorbed by the target plates is smaller and the ballistic limit velocities are lower. The petal deformation of the target plate caused by bending is severe at the temperature of 600 °C. Second, numerical simulations of the impact were conducted by an explicit dynamics FE code (LS-DYNA). The Johnson-Cook constitutive model with parameters obtained from split Hopkinson pressure bar (SHPB) experiments was used to describe the materials properties of the plates at various temperatures and strain rates. It was found that the numerical results are consistent with those obtained by the ballistic experiments. In addition, the results of the numerical simulations also showed that the ballistic limit velocity of the target plate exhibits an approximately linear relationship with the temperature of the target plate. The energy absorbed by the target plate is decreased by 18% and 9% at 600 °C and 300 °C, respectively, compared with that at 25 °C.

Joining of CFRTP and aluminum alloy thin plates using ultrasonic vibrations

Joining of CFRTP and aluminum alloy thin plates using ultrasonic vibrations

Global analysis of crises in shape memory thin plate system

The unique global properties of shape memory alloy are mainly derived from the martensite phase transition and its inverse, which result from the change of temperature and external load. In this paper, the global characteristics of shape memory alloy thin plate system are analyzed with the temperature and harmonic excitation amplitude as control parameters. Based on the method of Poincare map, the complex crisis phenomenon of the system including the sudden change in number, size and type of attractors can be observed through the global multivalued bifurcation diagram. However, the specific crisis type is not clear, it is necessary to be analyzed from the global viewpoint. By computing the global diagram with the composite cell coordinate system method which constructs a composite cell state space by multistage division of the continuous phase space, the attractors, saddles and basins of attraction of the system can be obtained more accurately. The vivid evolutionary processes of the crisis phenomena of the system are illustrated, and it can be found that the system presents a complex global structure with amplitude and temperature changing. There exist two kinds of crises: one is the boundary crisis resulting from the collision between a chaotic/periodic attractor and a chaotic saddle within the basin boundary, which causes the attractor to vanish, and the other is the merging crisis caused by the collision of two or more attractors with the chaotic saddle within the basin boundary where a new chaotic attractor appears. When multiple attractors coexist in the system, the basin boundary may be smooth or fractal, and for any point at boundary, its small open neighborhood always has a nonempty intersection with three or more basins, which is known as Wada basin boundary. It is difficult to predict the dynamic behavior of the system accurately due to the fractal, the Wada-Wada, Wada-fractal and fractal-Wada basin boundary metamorphoses which can be observed along with the variation of temperature and amplitude through the composite cell coordinate system method, which owns a unique advantage in depicting basin boundary. Furthermore, the Wada property is displayed more clearly by refining specified region. The results of this paper provide a theoretical analysis tool for adjusting the dynamic response of shape memory alloy thin plate system and optimizing the deformation and vibration control of mechanical equipment through controlling temperature and excitation intensity.

Microstructure Evolution and Mechanical Properties of High-Speed Friction Stir Welded Aluminum Alloy Thin Plate Joints

Sound friction stir welded (FSW) joints of 6061-T6 aluminum alloy sheets with an 0.8 mm thickness were obtained at conventional speed (2000 rpm, 300 mm/min) and high speed (11,000 rpm, 1500 mm/min). The recrystallization mechanism, precipitate evolution, mechanical properties and fracture behavior were investigated in detail. Microstructure analyses revealed that the grain structure evolution in the nugget zone (NZ) was dominated by continuous dynamic recrystallization. In the process of FSW, high speed facilitates the formation of finer equiaxed recrystallized grains, higher density of dislocations and substructures, and a larger number of precipitates in the NZ compared to the conventional speed, which further significantly improves the hardness and tensile strength of the joints. The maximum tensile strength was obtained with 292.6 MPa, 83.2% for the 6061-T6 aluminum alloy and 122.6% for the conventional-speed FSW joints. This work provides an effective method for preparing FSW aluminum alloy thin plate joints with excellent mechanical properties.

Effect of high rotational speed on temperature distribution, microstructure evolution, and mechanical properties of friction stir welded 6061-T6 thin plate joints

High rotational speed friction stir welding (FSW) was successfully employed to weld 6061-T6 aluminum alloy thin plates. The effect of high rotational speed and fast transverse speed on temperature distribution, microstructure evolution, and tensile properties of friction stir welded 6061-T6 joints was investigated in detail. The high rotational speed with fast transverse speed had a significant influence on the peak temperature in the nugget zone (NZ). Increasing the rotational speed and decreasing the transverse speed could obviously improve the peak temperature in the NZ, but exhibit little effect on the heat-affected zone under high rotational speed FSW. The NZ was characterized as a significant refinement of the equiaxed grain. The number of precipitates, subgrains, and low angle grain boundaries in the NZ of high rotational speed FSW joint increased significantly due to moderate heat input and strain rate. The weld zone was seriously softened at low rotational speed, whereas it was alleviated at high rotational speed and was affected slightly by rotational speed and transverse speed. The excellent mechanical properties of the friction stir welded 6061-T6 joints were obtained at a combination of high rotational speed and fast transverse speed. The maximum tensile strength reached 301.8 MPa, 85.8% of the base material.

Enhanced stress corrosion cracking resistance and electrical conductivity of a T761 treated Al-Zn-Mg-Cu alloy thin plate

The stress corrosion cracking (SCC) behavior, electrical conductivity and mechanical properties of an Al-Zn-Mg-Cu alloy pre-stretched thin plate for wing skin were researched in this paper. The microstructures and SCC fracture surfaces of the alloy treated at different conditions were characterized by transmission electron microscopy, optical microscopy and scanning electron microscopy. Results indicated that with the increasing of aging temperature, the electrical conductivity and the elongation increased greatly, while the strength decreased gradually which were closely associated with the type and morphology of the precipitates. Compared with the T6 treated alloy, the SCC resistance of the T761 treated Al-Zn-Mg-Cu alloy was improved greatly. The SCC behavior of the T6 treated alloy was dominated by anodic dissolution theory, whereas the hydrogen induced cracking controlled the fracture behavior of the T761 treated alloy which was influenced by the morphology of grain boundary precipitates in this investigated alloy.

하스텔로이 박판의 레이저 절단 후 단면분석을 통한 공정조건 선정에 관한 연구

To evaluate the quality of the cross section of Ni alloy thin plate cut by laser, we have proposed an analysis method using SEM image to measure surface roughness of cross section. The surface roughness of the cut area of the thin plate is considerably difficult to analyze using conventional measurement technique such as profile measurement with a probe. When the SEM image is used, the roughness value can be collected quantitatively while judging the surface status qualitatively. A Hastelloy C-276 thin plate with a thickness of 50 μm coated with HTS was cut by Nd:YAG laser, and the state of the cross section was analyzed by applying the proposed method in this research. The optimum laser cutting process condition could be found for the lowest surface roughness.

Investigation of fatigue crack propagation mechanisms of branching crack in 2324-T39 aluminum alloy thin plates under cyclic loading spectrum

Significant macroscopic crack branching has been observed in the crack growth paths of 2324-T39 aluminum alloy under spectrum loading, the mechanisms of which was investigated in this paper. The relationships between microscopic fracture surface characteristics and macroscopic fatigue crack growth paths and the relationship between plastic zone size and fracture surface characteristics were revealed. The change in fracture mode, which relates to the changes in the plastic zone in the thickness direction, and the growth of secondary cracks led to the appearance of branched cracks. A high level of σx, σz leads to mixed-mode growth of the subsurface secondary cracks.

Modelling of Zircaloy-4 accelerated degradation kinetics in nitrogen–oxygen mixtures at 850 °C

Zirconium-based alloys used in PWR cladding show an acceleration of their oxidation kinetics in air at high temperature compared to their behaviour under oxygen or steam alone. This paper presents an analysis of the oxidation kinetics in order to explain the role of nitrogen during the accelerated corrosion. Isothermal thermogravimetry on alloy thin plates was used to collect kinetic data during the reaction of Zircaloy-4 at 850°C in oxygen and nitrogen mixtures. The influence of oxygen and nitrogen partial pressure on the degradation kinetics was studied by a jump method. The presence of nitrogen in the reacting gas enables the formation of zirconium nitride near the oxide–metal interface which acts as a catalytic phase. A three steps reaction path composed of nitride oxidation, α-Zr(O) nitridation and oxidation is proposed. A detailed mechanism and the rate-determining step of the overall process are proposed that account for the experimentally observed dependence of the kinetic rate with the oxygen and nitrogen partial pressures; a kinetic model based on surface nucleation and growth of regions attacked by nitrogen was successful in describing the mass variations with time of exposure at 850°C.

Perforation of aluminium alloy thin plates

Low velocity perforation of aeronautical aluminium alloy sheets 2024 T3 is studied in this paper. After a literature review on recent experiments and models of plate's perforation, experimental results for 2 thicknesses (2 mm and 4 mm) of plates are presented. Perforation tests are performed with an instrumented drop test. The striker has a large diameter and a conical shape nose. Two models for perforation are presented and calibrated to bring a better understanding of the experiments. The first one is an analytical model based on an energetic approach. The second one is a numerical shell Finite Element FE model. A Johnson Cook phenomenological behaviour law of the plate's material is implemented in the finite element code Abaqus/Explicit. The velocity, the evolution of the impact force, the absorbed energy and the cracks' propagation are analysed.

Numerical Study on Bending Behavior of Copper Alloy Thin Plate by Single Pulse Laser

To study the bending characteristics of copper alloy thin plate by single pulse laser, the thermal mechanical coupling model of pulsed laser forming (PLF) was established; the dynamic change and steady distribution for the fields of temperature, stress&amp; strain and displacement were analyzed. The results show n that during the pulse laser heating stage, the temperature gradient along the thickness direction is far less than that of the heat affected zone; due to the constraints of materials around the heating field, the compressive stress and negative strain are appeared, the cantilever end of sample produces warping deformations; in the cooling stage, the temperature of top and bottom surface material drops rapidly, the sample is with a negative bending and reduced deformation. This is related to the transferring of the stress change and the recovery of part of the elastic deformation in heating area.

Effects of Biaxial Pre-Stretching on Microstructures and Mechanical Properties of 2024 Aluminum Alloy Thin Plates

Biaxial pre-stretching is implemented by bulge forming model. After engraved circular grids on new quenching blank, the specimen is biaxially pre-stretching formed. We use JGX-2 Engineering Microscope to measure principal pre-stretching points with 1.5%-3.1% elongation, which are in plane strain state. Hardness is measured by GYZJ 934-1 type Barcol Hardness and microstructures are observed by JEM-200CX Transmission Electron Microscope. The result shows that the influence on tensile strength of biaxial pre-stretching for new quenching state specimen is not big; however, it is the principal pre-stretching quantity 1.75% that improves microstructure and hardness.