1,721,146 research outputs found
Effect of welding parameters on mechanical and microstructural properties of dissimilar AA6082-AA2024 joints produced by Friction Stir Welding
No full textCNTs reinforced Al-based composites produced via modified flake powder metallurgy
No full textThe bimodal Al–Mg alloy structure reinforced with carbon nanotubes was evaluated after the composites production through a modified flake metallurgy technique followed by hot extrusion. The obtained bimodal microstructure of the matrix allowed to identify the microstructural mechanisms, leading to high strength, uniform elongation and strain hardening ability of the produced composites. The effect of the reinforcing phases percentages on the dislocations mechanisms evolution was evaluated through stress relaxation tests, leading to the underlying of the effect of reinforcing phases on the modification of the interphase influence zone. The results revealed that the deformation mechanism for unreinforced Al–Mg materials was forest dislocation cutting, whereas for CNT reinforcing Al–Mg composite was grain boundary and interface mediated straining. In fact, for Al–Mg/CNT composite, a task allocation occurred during the deformation process, namely at the early deformation stage by forest dislocation cutting and afterward at later deformation stage by dislocation/grain boundary/interface interaction
High temperature deformation of friction stir processed 7075 aluminium alloy
No full texthe mechanical and microstructural properties of 7075 aluminium alloy resulting from Friction Stir Processing (FSP), into sheets of 7 mm thickness, were analysed in the present study. The sheets were processed perpendicularly to the rolling direction; the tensile mechanical properties were evaluated at room temperature in the transverse and longitudinal directions with respect to the processing one. Tensile tests were also performed at higher temperatures and different strain rates in the nugget zone, in order to analyse the superplastic properties of the recrystallized material and to observe the differences from the parent material as a function of the strong grain refinement due to the Friction Stir Process. The high temperature behaviour of the material was studied, in the parallel direction, by means of tensile tests in the temperature and strain rate ranges of 150-500 °C and 10-2-10-4 s-1 respectively, electron microscopy (FEGSEM) observations were carried out to investigate more closely the fracture surfaces of the specimens tested at different temperatures and strain rates
Making ultra-high strengthening and toughening efficiency in hybrid reinforcing of aluminum laminated composites via dispersion engineering
Full text linkTo overcome the strength-ductility trade-off dilemma, herein we propose a hybrid in-situ/ex-situ reinforced aluminum matrix composite to achieve a uniform dispersion of reinforcements and strong reinforcement-matrix interfacial bonding. To exploit the pros of inter/intra granular dispersion of reinforcements, nano- Al3BC particles have been in-situ synthesized into ultrafine-grained (UFG) Al grain interior reinforced by carbon nanotubes (CNTs) via an elemental powder mixture, mechanical activation and subsequent annealing process. The in-situ nano-scaled Al3BC were uniformly distributed inside the elongated ultrafine Al grains, enabling stronger dislocation pinning and retention, providing stronger effective stress which consequently helps to enhance strength and strain hardening. The as-fabricated (Al3BC, CNT)/UFG Al exhibits simultaneous enhancement in strength (394 MPa) and total elongation (19.7 %) compared with its counterpart without the nano-Al3BC, suggesting the promising strengthening effects of in-situ/ex-situ reinforcing benefitting from the uniform dispersion and the strong semicoherent interface with the matrix
Progress of flake powder metallurgy research
No full textThis paper reviewed several recent progresses of the new powder metallurgy technology known as flake powder metallurgy (FPM) including different processing routes, conventional FPM (C-FPM), slurry blending (SB), shift-speed ball milling (SSBM), and high-shear pre-dispersion and SSBM (HSPD/SSBM). The name of FPM was derived from the use of flake metal powders obtained by low-speed ball milling (LSBM) from spherical powder. In this case, the uniformity of reinforcement distribution leads to increased strength and ductility. Powder is the basic unit in PM, especially advanced PM, and its control is key to various new PM technologies. The FPM is a typical method for finely controlling the powder shape through low-energy ball milling (LEBM) to realize the preparation of advanced material structures. The present paper represents a review of the main results of research on FPM and indicates the potential for future studies devoted to the optimization of this processing route
Effect of bimodal grain structure on the microstructural and mechanical evolution of al-mg/cnts composite
No full textThe Al-Mg alloy structure reinforced with carbon nanotubes was evaluated after the composites production through a modified flake metallurgy technique followed by hot extrusion. The obtained bimodal microstructure of the matrix allowed to identify the microstructural mechanisms leading to high strength; uniform elongation and strain hardening ability of the produced composites. The presence of Mg transformed the native Al2O3 layer into spinel MgAl2O4 nano-phases dispersed both inside CG and UFGs and on the interfaces, improving the interfacial bonding of Al-Al as well as Al-CNT. The effect of the reinforcing phases percentages on the dislocations mechanisms evolution was evaluated through stress relaxation tests leading to the underlying of the effect of reinforcing phases on the modification of the interphase influence zone
Regularity and exhaustivity for finitely additive functions. The Dieudonné's convergence theorem.
No full textRegularity and exhaustivity for finitely additive functions. The Dieudonné's convergence theorem.
No full textDynamic loading behaviour of CrMnFeCoNi cold spray coatings
No full textFeCoCrNiMn high entropy alloy powders were employed to produce coatings on carbon steel through high pressure cold spray. The microstructure of the sprayed coatings, characterized through optical and electron microscopy as well as through X-ray diffraction revealed a low porosity compact aspect of the cross sections as well as the retention of the body centered cubic crystallographic structure after particles splat. A high flattening ratio of the particles, measured by the scanning electron microscope observations, indicated an excellent adhesion of the coating to the substrate. Residual stresses of the coatings were measured through X-ray diffraction at different levels of the coating thickness; the hardness profile was revealed through nanoindentation. The cyclic behavior of the coatings was evaluated through 3 point bending tests. Cyclic tests were performed by increasing the maximum stroke from 0.3 to 2.4 mm with steps of 0.3 mm each 200 bending cycles. Other 3-point bending tests were conducted at fixed maximum stroke at the same deformation levels indicated for the previous test. Each 100 cycles the test is stopped and the coating surface is observed in order to monitor the superficial fracture behavior. The fracture surface of the coatings after rupture were observed through scanning electron microscopy in order to describe the rupture features related to the different loading conditions imposed to the coatings
- …
