Hot tearing susceptibility(HTS)of Mg-2Zn-(3+0.5 x)Y-x Al(x=0,2 and 3 at%)alloys is predicted by using modified Clyne-Davies’model(CSC^(∗)).The solidification path,solidification characteristic temperatures and dendri...Hot tearing susceptibility(HTS)of Mg-2Zn-(3+0.5 x)Y-x Al(x=0,2 and 3 at%)alloys is predicted by using modified Clyne-Davies’model(CSC^(∗)).The solidification path,solidification characteristic temperatures and dendritic coherency solid fraction have been studied by double-thermocouple thermal analysis.The solidification contraction stress vs.temperature(and time)curves are measured by using a“T”type hot tearing permanent-mold.The results reveal that the CSC^(∗)prediction values are in good agreement with the experimental results.Moreover,Al_(2)Y phase acts as the heterogeneous nucleation core ofα-Mg and significantly influences the grain size.It has been observed that minimum grain size,optimal dendritic coherency and minimum HTS are exhibited by Mg-2Zn-(3+0.5 x)Y-x Al alloy(x=2).Furthermore,when Al content was increased to 3 at%,Al_(2)Y phase exhibited a peritectic reaction and transformed into a mixed structure of Al_(2)Y and Al+Al_(3)Y phases,which increased the HTS of the alloy due to reduced fine-grained Al_(2)Y content.展开更多
The hot-tearing susceptibility(HTS)of Mg-6Zn-xGd(x=0.5,1,2,3,4,6)alloys was evaluated using a constrained rod casting(CRC)method.The results show that the HTS curve follows a typical"Λ"shape with the increa...The hot-tearing susceptibility(HTS)of Mg-6Zn-xGd(x=0.5,1,2,3,4,6)alloys was evaluated using a constrained rod casting(CRC)method.The results show that the HTS curve follows a typical"Λ"shape with the increase of Gd content.The Mg-6Zn-2Gd alloy has the highest while Mg-6Zn-6Gd alloy has the lowest HTS value.The hot-tearing behavior characteristics of Mg-6Zn-xGd alloys were further studied through a multifunctional hot-tearing test device.According to the dendrite contact point inferred from the stress curve,the Clyne-Davies criterion was modified and found to be accurate in predicting the HTS of Mg-6Zn-xGd alloys.Microstructure observation reveals that the grain size and the volume of eutectic liquid are the two key factors affecting HTS of Mg-6Zn-xGd alloys.The large grain with columnar structure can easily promote initiation and propagation of hot-tearing due to the poor feeding and coordinating deformation capability,which have a harmful effect on HTS.A higher volume fraction of eutectic phase can refill the cracking and provide continuous feeding channels by dendrite bridge and thicker liquid film,thus increase the hot-tearing resistance.展开更多
基金The authors would like to acknowledge the financial support from the National Natural Science Foundation of China(Nos.51571145 and 51504153)Innovation Talent Pro-gram in Sciences and Technologies for Young and Middle-aged Scientists of Shenyang(No.RC180111)+2 种基金Doctoral Scientific Research Foundation of Liaoning Province(No.20170520033)Youth Project of Liaoning Education Depart-ment(No.LQGD20170328)Natural Science Foundation of Liaoning Province(No.201602548).In addition,the authors would also like to thank Zhenglai Zhang from Zhejiang Hua Shuo Technology Co.,Ltd.and Ningbo City“Science and Technology Innovation 2025”major special project(new en-ergy vehicle lightweight magnesium alloy material precision forming technology research)funding support.
文摘Hot tearing susceptibility(HTS)of Mg-2Zn-(3+0.5 x)Y-x Al(x=0,2 and 3 at%)alloys is predicted by using modified Clyne-Davies’model(CSC^(∗)).The solidification path,solidification characteristic temperatures and dendritic coherency solid fraction have been studied by double-thermocouple thermal analysis.The solidification contraction stress vs.temperature(and time)curves are measured by using a“T”type hot tearing permanent-mold.The results reveal that the CSC^(∗)prediction values are in good agreement with the experimental results.Moreover,Al_(2)Y phase acts as the heterogeneous nucleation core ofα-Mg and significantly influences the grain size.It has been observed that minimum grain size,optimal dendritic coherency and minimum HTS are exhibited by Mg-2Zn-(3+0.5 x)Y-x Al alloy(x=2).Furthermore,when Al content was increased to 3 at%,Al_(2)Y phase exhibited a peritectic reaction and transformed into a mixed structure of Al_(2)Y and Al+Al_(3)Y phases,which increased the HTS of the alloy due to reduced fine-grained Al_(2)Y content.
基金supported by the National Key R&D Program of China(Grant No.2018YFB1106800)the National Natural Science Foundation of China(Grant No.51771152).
文摘The hot-tearing susceptibility(HTS)of Mg-6Zn-xGd(x=0.5,1,2,3,4,6)alloys was evaluated using a constrained rod casting(CRC)method.The results show that the HTS curve follows a typical"Λ"shape with the increase of Gd content.The Mg-6Zn-2Gd alloy has the highest while Mg-6Zn-6Gd alloy has the lowest HTS value.The hot-tearing behavior characteristics of Mg-6Zn-xGd alloys were further studied through a multifunctional hot-tearing test device.According to the dendrite contact point inferred from the stress curve,the Clyne-Davies criterion was modified and found to be accurate in predicting the HTS of Mg-6Zn-xGd alloys.Microstructure observation reveals that the grain size and the volume of eutectic liquid are the two key factors affecting HTS of Mg-6Zn-xGd alloys.The large grain with columnar structure can easily promote initiation and propagation of hot-tearing due to the poor feeding and coordinating deformation capability,which have a harmful effect on HTS.A higher volume fraction of eutectic phase can refill the cracking and provide continuous feeding channels by dendrite bridge and thicker liquid film,thus increase the hot-tearing resistance.
