Zhai Qijie

DSC study on the undercooling of droplet solidification of metal melt

In this paper, the influence of cooling rate on the undercooling of droplet solidification of metal melt has been investigated by employing the differential scanning calorimetry (DSC) method. The effect of cooling rate on the undercooling as well as its change tendency is analyzed theoretically. It is shown that the undercooling degree increases whereas the change rate of undercooling decreases with increasing cooling rate. Moreover, the change tendency approaches zero when the cooling rate exceedingly increased, indicating that an extremum of undercooling exists with increasing cooling rate.

Study on undercooling of metal droplet in rapid solidification

A mathematical model for the undercooling of the metal droplet during the rapid solidification is established, by which the factors that influence the undercooling of the metal droplet during the rapid solidification are analyzed, and the parameter \(\zeta = \sigma _{SL} ^3 /\left( {T_L \Delta H^2 } \right)\) is defined as the impact factor of the undercooling for the droplet solidification. Different undercoolings of droplets induced by various rapid solidification conditions are mainly ascribed to the change of the impact factor. Moreover, it is shown that the larger of ζ, the higher the relative undercooling can be gained. Meanwhile, the parameters such as solid-liquid interfacial energy σ SL and latent heat of solidification ΔH also vary with the rapid solidification conditions of droplets.AbstractA mathematical model for the undercooling of the metal droplet during the rapid solidification is established, by which the factors that influence the undercooling of the metal droplet during the rapid solidification are analyzed, and the parameter

Influence of ultrasonic vibration on mechanical properties and microstructure of 1Cr18Ni9Ti stainless steel

\zeta = \sigma _{SL} ^3 /\left( {T_L \Delta H^2 } \right)

Device capable of continuously measuring temperature of metal melt in pulse magnetic oscillation processing technology

is defined as the impact factor of the undercooling for the droplet solidification. Different undercoolings of droplets induced by various rapid solidification conditions are mainly ascribed to the change of the impact factor. Moreover, it is shown that the larger of ζ, the higher the relative undercooling can be gained. Meanwhile, the parameters such as solid-liquid interfacial energy σSL and latent heat of solidification ΔH also vary with the rapid solidification conditions of droplets.

Method for testing TTT (Time,Temperature,Transformation) curve

Abstract Single crystals of NiTi (with 50.0at% Ni) were prepared in a self-designed unidirectional solidification furnace with a graphite mold shell connected with a crystal selector. Both macrostructure and microstructure of the alloy were observed by OM and SEM with EDS, the grain orientation of single crystal was determined by XRD and pole figures, and shape memory effect was evaluated by an instrument developed by ourselves. The results show that dendritic features were presented in both cross section and longitudinal section; the direction of dendrites growth were close to solidified direction; there was no obvious grain boundary observed; the angle between normal direction of cross section and [111] orientation was 15°. Compared with normal NiTi polycrystals, the maximal recoverable strain and memory fatigue property of the alloy were improved because the bad effect of grain boundary on the martensite phase transformation was eliminated, and also [111] orientation was a preferred orientation of NiTi alloy which can provide larger recoverable strain.