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C. Carrasco C. Camurri J. García C. Montalba O. Prat D. Rojas 《Materialwissenschaft und Werkstofftechnik》2011,42(6):542-548
The influence of the semi‐solid solidification production parameters (shear rate and agitation time) and the concentration of reinforcing particles on the microstructure formation and mechanical properties of a 520 aluminum alloy reinforced with Al2O3 particles was investigated. Depending on the content of reinforcing particles and the stirring conditions different rosette structures were formed. The type of wear mechanism (delamination or adhesion) depends on the size of the rosettes and the distribution of Al2O3 reinforcements. Best mechanical properties were obtained for metal matrix composites reinforced with 12 wt% of Al2O3 stirred at a shear rate of 2100 s–1 for 1800 s. These samples showed tensile strength and yield stress similar to the commercial A520 alloy. The hardness and wear resistance were improved by the addition of Al2O3 particles, meanwhile the elongation to fracture was reduced. 相似文献
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The main aim of the present work is to experimentally evaluate the deep drawing behaviour of adhesive bonded sheets at different adhesive properties and predict the same using finite element simulations. The deep drawing quality steel and SS316L stainless steel are used as base materials for experiments and simulations. The deep drawing behaviour is also predicted using available analytical equations and proposed semi‐empirical equations. Such predictions are validated with experimental results. It is observed that due to increased plasticity of adhesive layer, the hardener rich formulation of adhesive improves the deep drawability of adhesive bonded blanks. The presence of carbon black in the adhesive has improved the drawability of bonded sheets up to a certain limit, say 2% by weight in the present work. The deep drawing behaviour predicted either by approach 1 (by giving experimentally evaluated adhesive properties as input) and by approach 2 (adhesive properties evaluated from rule of mixtures) are almost same, which indicates that both the methods can be used for forming behaviour prediction. The deep drawability predictions are moderately accurate with respect to experimental observation. The accuracy of analytical models for maximum load predictions is encouraging while comparing it with experimental results and numerical predictions. The proposed semi‐empirical equations show promising results to obtain initial estimate about the load‐progression behaviour of bonded sheets. 相似文献
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The formation of texture and its influence on some mechanical properties of retaining rings manufactured from stainless austenitic CrMnN steel were studied. It was found that different crystallite orientations prevail in tangential, radial and axial direction of the retaining ring as a result of plastic deformation by cold expansion. The change of texture from the inner to the outer diameter of the ring occurs because of a decreasing deformation. The formation of texture causes an anisotropy of mechanical properties. 相似文献
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Calcium phosphate cements (CPC), based on multicomponent powder mixtures of calcium orthophosphates with medium particle sizes in the region of 1 ‐ 20 μm, set isothermally in an aqueous environment to form hydroxyapatite (HA). HA cement reactants include tetracalcium phosphate (TTCP), tricalcium phosphate (TCP), dicalcium phosphate anhydrate (DCPA), dicalcium phosphate dihydrate (DCPD), monocalcium phosphate (MCPA) or octacalcium phosphate (OCP). The aim of this study was to improve the mechanical performance of TTCP / DCPA cement by adding several metal oxides to tetracalcium phosphate during the fabrication process. Cements based on tetracalcium phosphate mixed with silica or titanium oxide showed significant increases in compressive strength, approximately 80 ‐ 100 MPa, whilst no change in the mechanical behavior of CPC was observed if zirconia was added. X‐ray diffraction measurement confirmed the setting reaction of doped cements was similar to that of pure CPC. Low crystalline HA was found to be the main constituant of set cement; additional phases, such as calcium titanate or calcium zirconate, were not involved in the reaction. A mechanical reinforcement effect was thought to result from changes in the thermodynamic or kinetic solubilities of doped tetracalcium phosphates, this would lead to slower HA crystal formation and a more cross‐linked cement structure. 相似文献
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Tensile specimens of 1×6×25 mm in gauge dimension were cut from the surface and centre of 12.7 mm thick 2090 Al‐Li alloy plate, which were solution treated at 550 °C for 30 min, peak‐aged at 190 °C for 18 h, or reversion‐treated at 275 °C for 2 min. The flow stress of the centre layer was higher than that of the surface layer, regardless of the heat treatments. The textures of the surface and centre layers were approximated by the {001}<110> and {011}<211> orientations, respectively. The solution‐treated specimens gave rise to extensive serrations in their flow curves at a strain rate of 2×10‐4 s‐1. The serration amplitude was drastically reduced after the specimens were peak‐aged or reversion‐treated. However, for the peak‐aged alloy, the surface‐layer specimens underwent complex, serrated flows, whereas the flow curve of the centre‐layer specimen was almost devoid of serration. The serration, especially fine‐type serration in the peak‐aged and reversion‐treated specimens tended to disappear with increasing strain rate. The tensile behavior was explained in terms of the texture and strain rate. 相似文献