The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at ca...The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope.During the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient.The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed.Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.展开更多
In view of the problem that crystalline particles cause wall vibration at a low temperature,based on two-phase flow model,computational fuid dynamics is used to conduct the numerical simulation of internal flows when ...In view of the problem that crystalline particles cause wall vibration at a low temperature,based on two-phase flow model,computational fuid dynamics is used to conduct the numerical simulation of internal flows when the valve openings are 20%,60%and 100%respectively.The molten salt fow may be changed under strict conditions and produce forced vibration of the inner parts of molten salt particle shock valve body.Euler two-phase flow model is used for different molten salt sizes to extract temporal pressure pulse information and conduct statistical data processing analysis.The influence of the molten salt crystallization of molten salt particles on the fow and pressure pulse strength is analyzed.The results show that the crystallization of molten salt has a serious impact on the vibration of the valve body,especially in the throttle rate.The valve oscillation caused by the pressure pulsation mostly occurs from the small opening rate.As the opening increases,the pressure pulse threshold and its change trend decrease.展开更多
基金the National Natural Science Foundation of China(No.U1703131,No.51674027,No.51974027 and No.52004028)Guangdong Basic and Applied Basic Research Foundation(2019A1515111126)the Fundamental Research Funds for the Central Universities(FRF-TP-18-005C1 and FRF-TP-18-041A1).
文摘The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope.During the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient.The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed.Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.
基金the National Natural Science Foundation of China(No.51569012)。
文摘In view of the problem that crystalline particles cause wall vibration at a low temperature,based on two-phase flow model,computational fuid dynamics is used to conduct the numerical simulation of internal flows when the valve openings are 20%,60%and 100%respectively.The molten salt fow may be changed under strict conditions and produce forced vibration of the inner parts of molten salt particle shock valve body.Euler two-phase flow model is used for different molten salt sizes to extract temporal pressure pulse information and conduct statistical data processing analysis.The influence of the molten salt crystallization of molten salt particles on the fow and pressure pulse strength is analyzed.The results show that the crystallization of molten salt has a serious impact on the vibration of the valve body,especially in the throttle rate.The valve oscillation caused by the pressure pulsation mostly occurs from the small opening rate.As the opening increases,the pressure pulse threshold and its change trend decrease.
