The stray crystals seriously affect the properties of metals which fabricated by directional solidification(DS). In order to observe the formation of the stray crystals, the growth behavior of Sn-10 wt.%Bi alloy was o...The stray crystals seriously affect the properties of metals which fabricated by directional solidification(DS). In order to observe the formation of the stray crystals, the growth behavior of Sn-10 wt.%Bi alloy was observed by synchrotron X-ray imaging technique using self-developed directional solidification(DS) apparatus. The experimental results show that Sn–10 wt.%Bi alloy is oriented with the form of dendrites to grow into the liquid phase during the DS process, and dendrites are arranged neatly to form columnar crystal microstructures. It is also found that parts of the dendrite arms begin to crack. These cracked dendrites drift upward to grow up in front of the solid-liquid interface and form stray crystals.展开更多
Microstructures of Cu-4.7Sn(%) alloys prepared by two-phase zone continuous casting(TZCC)technology contain large columnar grains and small grains.A compound grain structure,composed of a large columnar grain and at l...Microstructures of Cu-4.7Sn(%) alloys prepared by two-phase zone continuous casting(TZCC)technology contain large columnar grains and small grains.A compound grain structure,composed of a large columnar grain and at least one small grain within it,is observed and called as grain-covered grains(GCGs).Distribution of small grains,their numbers and sizes as well as numbers and sizes of columnar grains were characterized quantitatively by metallographic microscope.Back propagation(BP) artificial neural network was employed to build a model to predict microstructures produced by different processing parameters.Inputs of the model are five processing parameters,which are temperatures of melt,mold and cooling water,speed of TZCC,and cooling distance.Outputs of the model are nine microstructure quantities,which are numbers of small grains within columnar grains,at the boundaries of the columnar grains,or at the surface of the alloy,the maximum and the minimum numbers of small grains within a columnar grain,numbers of columnar grains with or without small grains,and sizes of small grains and columnar grains.The model yields precise prediction,which lays foundation for controlling microstructures of alloys prepared by TZCC.展开更多
基金financially supported by the project of Yangtze Normal University under grant No.2017KYQD130 and No.2017XJQN08
文摘The stray crystals seriously affect the properties of metals which fabricated by directional solidification(DS). In order to observe the formation of the stray crystals, the growth behavior of Sn-10 wt.%Bi alloy was observed by synchrotron X-ray imaging technique using self-developed directional solidification(DS) apparatus. The experimental results show that Sn–10 wt.%Bi alloy is oriented with the form of dendrites to grow into the liquid phase during the DS process, and dendrites are arranged neatly to form columnar crystal microstructures. It is also found that parts of the dendrite arms begin to crack. These cracked dendrites drift upward to grow up in front of the solid-liquid interface and form stray crystals.
基金financially supported by the National Key Research and Development Plan of China (No.2016YFB0301300)the National Natural Science Foundation of China (Nos.51374025,51674027 and U1703131)the Beijing Municipal Natural Science Foundation (No.2152020)
文摘Microstructures of Cu-4.7Sn(%) alloys prepared by two-phase zone continuous casting(TZCC)technology contain large columnar grains and small grains.A compound grain structure,composed of a large columnar grain and at least one small grain within it,is observed and called as grain-covered grains(GCGs).Distribution of small grains,their numbers and sizes as well as numbers and sizes of columnar grains were characterized quantitatively by metallographic microscope.Back propagation(BP) artificial neural network was employed to build a model to predict microstructures produced by different processing parameters.Inputs of the model are five processing parameters,which are temperatures of melt,mold and cooling water,speed of TZCC,and cooling distance.Outputs of the model are nine microstructure quantities,which are numbers of small grains within columnar grains,at the boundaries of the columnar grains,or at the surface of the alloy,the maximum and the minimum numbers of small grains within a columnar grain,numbers of columnar grains with or without small grains,and sizes of small grains and columnar grains.The model yields precise prediction,which lays foundation for controlling microstructures of alloys prepared by TZCC.