Cu-Ag filamentary microcomposites with different Ag contents were prepared by cold drawing and intermediate heat treatments. The microstructure characterization and filamentary distribution were observed for two-phase...Cu-Ag filamentary microcomposites with different Ag contents were prepared by cold drawing and intermediate heat treatments. The microstructure characterization and filamentary distribution were observed for two-phase alloys under different conditions. The effect of heavy drawing strain on the microstructure evolution of Cu-Ag alloys was investigated. The results show that the microstructure components consist of Cu dendrites, eutectic colonies and secondary Ag precipitates in the alloys containing 6%-24% （mass fraction） Ag. With the increase in Ag content, the eutectic colonies in the microstructure increase and gradually change into a continuous net-like distribution. The Cu dendrites, eutectic colonies and secondary Ag precipitates are elongated in an axial direction and developed into the composite filamentary structure during cold drawing deformation. The eutectic colonies tend to evolve into filamentary bundles. The filamentary diameters decrease with the increase in drawing strain degree for the two-phase alloys, in particular for the alloys with low Ag content. The reduction in filamentary diameters becomes slow once the drawing strain has exceeded a certain level.展开更多
The iron aluminides show anomalous stress peaks at temperatures of the order of 400～600 ℃, irrespective of whether the crystal structure is B2 type or DO 3 type. Such features will be examined on the basis of therma...The iron aluminides show anomalous stress peaks at temperatures of the order of 400～600 ℃, irrespective of whether the crystal structure is B2 type or DO 3 type. Such features will be examined on the basis of thermally activated dislocation processes, considering the influence of test parameters such as temperature and strain rate, and material parameters such as crystal composition and orientation. Detailed analyses of deformation modes by slip step studies, transmission electron microscopy examinations of dislocation structures, and texture studies will also be considered. Observations of dislocation structures are clearly of great interest for suggesting the possible models of deformation, but suffer from two major weaknesses: the post mortem structures in samples deformed at high temperature may not be the same as those producing plasticity; almost all possible hypotheses for strengthening can find support from such observations, since almost all imaginable dislocation configurations can be found with sufficient diligence by the researcher. Strengthening at intermediate temperatures in DO 3 and B2 ordered iron aluminides will be analysed here, making combined use of observations of deformation structures and examinations of the influence of varying the deformation parameters.展开更多
Inoculation can reduce the chill depth of a chilled iron,and therefore influence the microstructure and properties of the iron.In this paper,the effect of rare earth Lanthanun (La) on the microstructure and properties...Inoculation can reduce the chill depth of a chilled iron,and therefore influence the microstructure and properties of the iron.In this paper,the effect of rare earth Lanthanun (La) on the microstructure and properties of a chilled iron camshaft was studied.The results show that the La addition efficiently enhances the mechanical properties,yet with the unfavorable effect of decreasing the chilled depth and hardness.Moreover,La promotes graphite concentration and results in large graphite size,as well as A-type graphite.It is also found that excessive La destroys the interconnection and directivity of ledeburite.According to the experimental results,the optimum adding content of La should be no more than 0.02wt.%.展开更多
基金Project (No. 50671092) supported by the National Natural Science Foundation of China
文摘Cu-Ag filamentary microcomposites with different Ag contents were prepared by cold drawing and intermediate heat treatments. The microstructure characterization and filamentary distribution were observed for two-phase alloys under different conditions. The effect of heavy drawing strain on the microstructure evolution of Cu-Ag alloys was investigated. The results show that the microstructure components consist of Cu dendrites, eutectic colonies and secondary Ag precipitates in the alloys containing 6%-24% （mass fraction） Ag. With the increase in Ag content, the eutectic colonies in the microstructure increase and gradually change into a continuous net-like distribution. The Cu dendrites, eutectic colonies and secondary Ag precipitates are elongated in an axial direction and developed into the composite filamentary structure during cold drawing deformation. The eutectic colonies tend to evolve into filamentary bundles. The filamentary diameters decrease with the increase in drawing strain degree for the two-phase alloys, in particular for the alloys with low Ag content. The reduction in filamentary diameters becomes slow once the drawing strain has exceeded a certain level.
文摘The iron aluminides show anomalous stress peaks at temperatures of the order of 400～600 ℃, irrespective of whether the crystal structure is B2 type or DO 3 type. Such features will be examined on the basis of thermally activated dislocation processes, considering the influence of test parameters such as temperature and strain rate, and material parameters such as crystal composition and orientation. Detailed analyses of deformation modes by slip step studies, transmission electron microscopy examinations of dislocation structures, and texture studies will also be considered. Observations of dislocation structures are clearly of great interest for suggesting the possible models of deformation, but suffer from two major weaknesses: the post mortem structures in samples deformed at high temperature may not be the same as those producing plasticity; almost all possible hypotheses for strengthening can find support from such observations, since almost all imaginable dislocation configurations can be found with sufficient diligence by the researcher. Strengthening at intermediate temperatures in DO 3 and B2 ordered iron aluminides will be analysed here, making combined use of observations of deformation structures and examinations of the influence of varying the deformation parameters.
基金supported by the Science and Technology Project of Xi’an,China (grant No.CXY1134WL18)
文摘Inoculation can reduce the chill depth of a chilled iron,and therefore influence the microstructure and properties of the iron.In this paper,the effect of rare earth Lanthanun (La) on the microstructure and properties of a chilled iron camshaft was studied.The results show that the La addition efficiently enhances the mechanical properties,yet with the unfavorable effect of decreasing the chilled depth and hardness.Moreover,La promotes graphite concentration and results in large graphite size,as well as A-type graphite.It is also found that excessive La destroys the interconnection and directivity of ledeburite.According to the experimental results,the optimum adding content of La should be no more than 0.02wt.%.
