| In this study,the hybrid carbon nanotubes-aluminum reinforced ZA27 composites with core-shell structure was synthesized through high energy ball milling(HEM)and powder metallurgy(P/M)route using vacuum liquid phase sintering technique.The Al and CNTs are combined through a ball-milling process giving us a hybrid particle,which is then combined with pure Zn and Al to form the composite through HEM before P/M.The effect of preparation conditions,CNTs content and hot process parameter on the microstructural characterization and mechanical behavior of hybrid carbon nanotubes-aluminum reinforced ZA27 composites were determined based on microstructure observation and mechanics measurement.The hybrid carbon nanotubes-aluminum reinforced ZA27 composites with core-shell structure was synthesized through a ball-milling process(200 rpm/1h)and HEM(400 rpm/8 h),which effectively realized the homodispese of CNTs in matrix powder;The compaction density and sintered density reached to the maximum when the press pressure is 300 MPa;The hybrid carbon nanotubes-aluminum reinforced ZA27 composites were prepared using vacuum liquid phase sintering technique.According to the microstructure observations,the α-Al phase,η-Zn phase and β-ZnAl phase were found in the composites but the Al4C3 and other carbon compounds were not observed conspicuously,indicating that the CNTs didn’t react strongly with the matrix and which ensure the well combination of the reinforcements and matrix.Meanwhile,the influence of the sintering technique and CNTs content on the microsturcture and mechanical property of composites were investigated in this paper.The microstructure density,tensile strength and elongation of the composites have reached to their maximum under the sintering temperature of 480℃ and the holding time of 2 h.When the CNTs content was 0.4 wt.%,the grain was refined obviously and the tensile strength and elongation were improved simultaneously.The.strengthening of the composites mainly include grain refinement strengthening,geometrical dislocation strengthening caused by thermal mismatch,and the dislocation strengthening generated by hindering the dislocation movement of CNTs,etc.Using a controlled thermal-simulator system,the hybrid carbon nantube-aluminum reinforced ZA27 composites were subjected to hot compression testing in the temperature range of 473–623 K with strain rates of0.01–10 s-1.Based on experimental results,a comparison of predictions from an artificial neural network model and the constitutive equations to describe the hot compressive behavior was performed.Relative errors varied from-4.14 %to 6.75 % for the artificial neural network model and from-15.93 % to 17.29 %using the constitutive equations.The results indicate that the artificial neural network model was more accurate and efficient in predicting hot compressive behavior.The intrinsic workability was further investigated by constructing three-dimensional(3D)processing maps with the support of optical microstructure observations.The 3D processing maps were constructed on the basis of dynamic materials model to delineate variations of the efficiency of power dissipation and flow instability domains.The instability domains exhibited adiabatic shear band and flow localization which should be prevented during hot processing.The recommended domain is in the condition of the temperature range of 550–590 K and strain rate range of 0.01–0.35 s-1.And in this state the main soften mechanism is dynamic recrystallization.The microstructure observations are in a good agreement with the results from processing maps... |
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