The modification effect of a new type of Al-P master alloy on Al-24Si alloys was investigated. It is found that excellent modification effect can be obtained by the addition of this new type of Al-P master alloy into ...The modification effect of a new type of Al-P master alloy on Al-24Si alloys was investigated. It is found that excellent modification effect can be obtained by the addition of this new type of Al-P master alloy into Al-24Si melt and the average primary Si grain size is decreased below 47 μm from original 225 μm. It is also found that the TiC particles in the melt coming from Al8Ti2C can improve the modification effect of the Al-P master alloy. When the content of TiC particles in the Al-24Si melt is 0.03%, the improvement reaches the maximum and keeps steady with increasing content of TiC particles. Modification effect occurs at 50 min after the addition of the Al-P master alloy and TiC particles, and keeps stable with prolonging holding time.展开更多
Crystallization behavior of amorphous Zr 65 Cu 25 Al 10 alloy under isothermal annealing condition was investigated by DSC and XRD. It is found that two exothermic peaks appear in the DSC curve of amorphous Zr 65 Cu 2...Crystallization behavior of amorphous Zr 65 Cu 25 Al 10 alloy under isothermal annealing condition was investigated by DSC and XRD. It is found that two exothermic peaks appear in the DSC curve of amorphous Zr 65 Cu 25 Al 10 alloy, indicating that the crystallization proceeds through double stage mode. The crystallization process of amorphous Zr 65 Cu 25 Al 10 alloy under isothermal annealing condition is mainly controlled by nucleation and one dimensional growth with the crystallized volume fraction smaller than 70%. With the crystallized volume fraction ranging from 70% to 90%, crystallization process is mainly dominated by the growth of three dimensional pre existing quench in nuclei. And when the crystallized volume fraction reaches above 90%, transient nucleation becomes the master of the crystallization process.展开更多
The effect of minor additions of Sn on the as cast ageing behavior of Al 11Si 0.35Mg alloy was investigated. It is shown that precipitation has been retarded in Sn containing alloy and more time is needed to reach its...The effect of minor additions of Sn on the as cast ageing behavior of Al 11Si 0.35Mg alloy was investigated. It is shown that precipitation has been retarded in Sn containing alloy and more time is needed to reach its peak hardness,which is bigger than that of the base alloy. Analysis of the kinetic data shows that Sn addition does not change the growth dependent parameter n , but increases the nucleation density dependent parameter k . TEM results show that there are little precipitates in Sn containing alloy at the initial stage of as cast ageing. However, the Sn addition increases the net density of precipitates during as cast ageing, because there are many dislocation loops formed as ageing progresses and Sn segregated at the edges of dislocation loops, which acts as the nuclei of precipitates.展开更多
The fragility of Al Ni Ce alloy melts with three kinds of different compositions, Al85Ni10Ce5, Al85Ni8Ce7, Al85Ni5Ce10(mole fraction, %), was studied using oscillating vessel viscometer and differential scanning calor...The fragility of Al Ni Ce alloy melts with three kinds of different compositions, Al85Ni10Ce5, Al85Ni8Ce7, Al85Ni5Ce10(mole fraction, %), was studied using oscillating vessel viscometer and differential scanning calorimetry. Their fragility parameters obtained from experiments and theoretic calculation are: 238, 228 and 335 respectively. The results indicate that these three kinds of Al Ni Ce alloy melts are very fragile liquids, which kinetically show strong non Arrhenius behaviour in the Angell plot, so they have poor glass forming ability (GFA). The alloy melt Al85Ni5Ce10 has the largest fragility parameter among the three alloy melts. In the preparation of rapidly quenched amorphous ribbons, Al85Ni10Ce5 and Al85Ni8Ce7 can gain amorphous ribbons when the rotate speed of the roller reaches 800 r/min, while for Al85Ni5Ce10 it must exceed 1 000 r/min.展开更多
Crystallization behavior of amorphous Zr 70 Cu 20 Ni 10 alloy isothermally annealed at 380 ℃ was first investigated by employing the differential scanning calorimetry (DSC) and transmission electron microscopy (TEM)....Crystallization behavior of amorphous Zr 70 Cu 20 Ni 10 alloy isothermally annealed at 380 ℃ was first investigated by employing the differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). It has been found that an exothermic peak appears in the DSC trace when the annealing time is about 17～18 min, indicating a certain phase transformation occurs in the matrix of amorphous Zr 70 Cu 20 Ni 10 alloy. Meanwhile, isothermal annealing experiments for amorphous Zr 70 Cu 20 Ni 10 alloy ranging from 360 ℃ to 400 ℃ with a temperature interval of 10 ℃ were also carried out, from which no exothermic reaction can be observed except for the case of 380 ℃. This behavior indicates that the phase transformation during isothermal annealing of amorphous Zr 70 Cu 20 Ni 10 alloy is strongly temperature and time dependent. Further investigations are required to reveal the nature of such phenomenon.展开更多
By means of constant temperature and constant pressure molecular dynamic simulation technique, a series of simulations of the glass transition and crystallization processes of Ag 50Au 50 were performed. The atoms inte...By means of constant temperature and constant pressure molecular dynamic simulation technique, a series of simulations of the glass transition and crystallization processes of Ag 50Au 50 were performed. The atoms interact via EAM potential function. Pair correlation functions of liquid Ag 50Au 50 during different cooling rates and temperatures were simulated to reveal the structural features of liquid, super-cooled liquid, glass state and crystal. The thermodynamics and kinetics of structure transition of Ag 50Au 50 during cooling processes were performed.展开更多
文摘The modification effect of a new type of Al-P master alloy on Al-24Si alloys was investigated. It is found that excellent modification effect can be obtained by the addition of this new type of Al-P master alloy into Al-24Si melt and the average primary Si grain size is decreased below 47 μm from original 225 μm. It is also found that the TiC particles in the melt coming from Al8Ti2C can improve the modification effect of the Al-P master alloy. When the content of TiC particles in the Al-24Si melt is 0.03%, the improvement reaches the maximum and keeps steady with increasing content of TiC particles. Modification effect occurs at 50 min after the addition of the Al-P master alloy and TiC particles, and keeps stable with prolonging holding time.
文摘Crystallization behavior of amorphous Zr 65 Cu 25 Al 10 alloy under isothermal annealing condition was investigated by DSC and XRD. It is found that two exothermic peaks appear in the DSC curve of amorphous Zr 65 Cu 25 Al 10 alloy, indicating that the crystallization proceeds through double stage mode. The crystallization process of amorphous Zr 65 Cu 25 Al 10 alloy under isothermal annealing condition is mainly controlled by nucleation and one dimensional growth with the crystallized volume fraction smaller than 70%. With the crystallized volume fraction ranging from 70% to 90%, crystallization process is mainly dominated by the growth of three dimensional pre existing quench in nuclei. And when the crystallized volume fraction reaches above 90%, transient nucleation becomes the master of the crystallization process.
文摘The effect of minor additions of Sn on the as cast ageing behavior of Al 11Si 0.35Mg alloy was investigated. It is shown that precipitation has been retarded in Sn containing alloy and more time is needed to reach its peak hardness,which is bigger than that of the base alloy. Analysis of the kinetic data shows that Sn addition does not change the growth dependent parameter n , but increases the nucleation density dependent parameter k . TEM results show that there are little precipitates in Sn containing alloy at the initial stage of as cast ageing. However, the Sn addition increases the net density of precipitates during as cast ageing, because there are many dislocation loops formed as ageing progresses and Sn segregated at the edges of dislocation loops, which acts as the nuclei of precipitates.
文摘The fragility of Al Ni Ce alloy melts with three kinds of different compositions, Al85Ni10Ce5, Al85Ni8Ce7, Al85Ni5Ce10(mole fraction, %), was studied using oscillating vessel viscometer and differential scanning calorimetry. Their fragility parameters obtained from experiments and theoretic calculation are: 238, 228 and 335 respectively. The results indicate that these three kinds of Al Ni Ce alloy melts are very fragile liquids, which kinetically show strong non Arrhenius behaviour in the Angell plot, so they have poor glass forming ability (GFA). The alloy melt Al85Ni5Ce10 has the largest fragility parameter among the three alloy melts. In the preparation of rapidly quenched amorphous ribbons, Al85Ni10Ce5 and Al85Ni8Ce7 can gain amorphous ribbons when the rotate speed of the roller reaches 800 r/min, while for Al85Ni5Ce10 it must exceed 1 000 r/min.
文摘Crystallization behavior of amorphous Zr 70 Cu 20 Ni 10 alloy isothermally annealed at 380 ℃ was first investigated by employing the differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). It has been found that an exothermic peak appears in the DSC trace when the annealing time is about 17～18 min, indicating a certain phase transformation occurs in the matrix of amorphous Zr 70 Cu 20 Ni 10 alloy. Meanwhile, isothermal annealing experiments for amorphous Zr 70 Cu 20 Ni 10 alloy ranging from 360 ℃ to 400 ℃ with a temperature interval of 10 ℃ were also carried out, from which no exothermic reaction can be observed except for the case of 380 ℃. This behavior indicates that the phase transformation during isothermal annealing of amorphous Zr 70 Cu 20 Ni 10 alloy is strongly temperature and time dependent. Further investigations are required to reveal the nature of such phenomenon.
文摘By means of constant temperature and constant pressure molecular dynamic simulation technique, a series of simulations of the glass transition and crystallization processes of Ag 50Au 50 were performed. The atoms interact via EAM potential function. Pair correlation functions of liquid Ag 50Au 50 during different cooling rates and temperatures were simulated to reveal the structural features of liquid, super-cooled liquid, glass state and crystal. The thermodynamics and kinetics of structure transition of Ag 50Au 50 during cooling processes were performed.
