Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) a...Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) alloy.The liquid Ti_(85)Ni_(10)Al_(5) alloy was substantially undercooled up to 335 K(0.18T_(L)).As undercooling increased,the potential energy of the liquid alloy decreased and the alloy entered into a high metastable state.At this state,the atoms tended to bond with each other and the clusters were inclined to convert into high-coordinated clusters,as confirmed by the fraction of the high-coordinated clusters variation.The enlarged clusters and enhanced local structure stability contributed to the increase of the thermophysical parameters and crystal growth velocity,and eventually dendrite refinement.The density,the specific heat and the surface tension of liquid alloy exhibited a linear relation with temperature and the shear viscosity of liquid alloy showed exponential variation which showed good agreement with the calculation results by molecular dynamics simulation.The growth velocity first increased slowly and then dramatically once the undercooling exceeded the threshold.The achieved maximum crystal growth velocity was 12.4 m s^(−1) and it was up to 326 times of the value at 94 K undercooling.展开更多
Based on the short-range order,it is found that the abundance of the P-centered P-transition-metal clusters are the common feature among the liquid Pd-Cu-Ni-P alloys,and hence this feature alone could not uncover the ...Based on the short-range order,it is found that the abundance of the P-centered P-transition-metal clusters are the common feature among the liquid Pd-Cu-Ni-P alloys,and hence this feature alone could not uncover the underlying mechanisms of the variation of glass forming ability among the liquid alloys.For the so called similar elements such as Cu and Ni,their behaviors are significantly different when interacting with Pd or P atoms.Cu has weak bonding with both Pd and P while Ni has very strong bonding with P but nearly no bonding with Pd.The different bonding characters thus underlie the phenomenon that in the best glass formers the ratio of the two similar elements often deviates from 1:1.Only if the parameters of chemical short-range order of Cu and Ni around P become closest to each other the best glass forming ability is reached.It is also illustrated that the calculated dynamic properties are very helpful to locate the composition of the best glass former.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.U1806219,52073232,52088101 and U1660108)the Science Fund for Distinguished Young Scholars of Shaanxi Province(Grant No.2020JC-11)the Science Fund for Scientific and Technological Innovation Team of Shaanxi Province(Grant No.2021TD-14)。
文摘Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) alloy.The liquid Ti_(85)Ni_(10)Al_(5) alloy was substantially undercooled up to 335 K(0.18T_(L)).As undercooling increased,the potential energy of the liquid alloy decreased and the alloy entered into a high metastable state.At this state,the atoms tended to bond with each other and the clusters were inclined to convert into high-coordinated clusters,as confirmed by the fraction of the high-coordinated clusters variation.The enlarged clusters and enhanced local structure stability contributed to the increase of the thermophysical parameters and crystal growth velocity,and eventually dendrite refinement.The density,the specific heat and the surface tension of liquid alloy exhibited a linear relation with temperature and the shear viscosity of liquid alloy showed exponential variation which showed good agreement with the calculation results by molecular dynamics simulation.The growth velocity first increased slowly and then dramatically once the undercooling exceeded the threshold.The achieved maximum crystal growth velocity was 12.4 m s^(−1) and it was up to 326 times of the value at 94 K undercooling.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50971082 and 50831003)
文摘Based on the short-range order,it is found that the abundance of the P-centered P-transition-metal clusters are the common feature among the liquid Pd-Cu-Ni-P alloys,and hence this feature alone could not uncover the underlying mechanisms of the variation of glass forming ability among the liquid alloys.For the so called similar elements such as Cu and Ni,their behaviors are significantly different when interacting with Pd or P atoms.Cu has weak bonding with both Pd and P while Ni has very strong bonding with P but nearly no bonding with Pd.The different bonding characters thus underlie the phenomenon that in the best glass formers the ratio of the two similar elements often deviates from 1:1.Only if the parameters of chemical short-range order of Cu and Ni around P become closest to each other the best glass forming ability is reached.It is also illustrated that the calculated dynamic properties are very helpful to locate the composition of the best glass former.
