The phase equilibria and compositions in Mg-rich side at 300 ℃ were investigated in Mg-Zn-Ca ternary system through the equilibrated alloy method by using scanning electron microscopy,electron probe microanalysis,X-r...The phase equilibria and compositions in Mg-rich side at 300 ℃ were investigated in Mg-Zn-Ca ternary system through the equilibrated alloy method by using scanning electron microscopy,electron probe microanalysis,X-ray diffraction and transmission electron microscopy.The results show that two ternary compounds T1 and T2 can be in equilibrium with the Mg-based solid solution in Mg-Zn-Ca system.T1 phase is a linear compound with the composition region（molar fraction） of 15% Ca,20.5%-48.9% Zn and balanced Mg at 300 ℃.Its hexagonal structure parameters decrease with increasing Zn content,i.e.a=0.992-0.945 nm,c=1.034-1.003 nm.T2 phase has hexagonal structure with the composition region of 26.4%-28.4% Mg,63.2%-65.5% Zn and 7.1%-8.4% Ca.At 300 ℃,the solubility of Zn in the Mg-based solid solution increases for the addition of Ca,the maximum solubility of Zn is 3.7%.Three-phase fields consisting of--Mg＋Mg2Ca＋T1,--Mg＋T1＋T2,--Mg＋T2＋MgZn and MgZn＋T2＋Mg2Zn3 exist in the Mg-Zn-Ca system at 300 ℃.展开更多
Magnesium alloys with homogeneous degradation and controlled degradation rate are desirable for biodegradable materials.In the present work,Mg-3 wt.%Zn-0.2 wt.%Ca alloys with different columnar structures were fabrica...Magnesium alloys with homogeneous degradation and controlled degradation rate are desirable for biodegradable materials.In the present work,Mg-3 wt.%Zn-0.2 wt.%Ca alloys with different columnar structures were fabricated and the degradation in 0.9 wt.%NaCl were investigated.With the increase of the growth rate for the directional solidification,the microstructure of the directionally solidified(DSed)alloy evolved from cellular to dendritic coupled with the change of the spacing of the primary trunks(λ_(1))and the volume fraction(fv)of Ca_(2)Mg_(6)Zn_(3) phase.The results of the corrosion test suggested that the alloy with cellular structure experienced homogeneous corrosion and exhibited the lowest corrosion rate.The good corrosion resistance of the alloy with cellular structure was attributed to the protective corrosion products film(CPF),which was closely related to the fv of Ca_(2)Mg_(6)Zn_(3) phase andλ_(1).To evaluate the corrosion rates(CR)of the DSed Mg-Zn-Ca alloys with different microstructures,a parameterαwas proposed in this work,which was calculated byλ_(1) and the fv of Ca_(2)Mg_(6)Zn_(3) phase.The fitting result showed that there was a linear relationship between CR andα,which was CR=4.1899+0.00432α.This means that the CR of the DSed Mg-Zn-Ca alloy can be evaluated if the microstructure had been characterized.展开更多
Mg69Zn27Ca4 alloys with diameters of 1.5, 2 and 3 mm were fabricated using copper mold injection casting method. Microstructural analysis reveals that the alloy with a diameter of 1.5 mm is almost completely composed ...Mg69Zn27Ca4 alloys with diameters of 1.5, 2 and 3 mm were fabricated using copper mold injection casting method. Microstructural analysis reveals that the alloy with a diameter of 1.5 mm is almost completely composed of amorphous phase. However, with the cooling rate decline, a little α-Mg and MgZn dendrites can be found in the amorphous matrix. Based on the microstructural and tensile results, the ductile dendrites are conceived to be highly responsible for the enhanced compressive strain from 1.3% to 3.1% by increasing the sample diameter from 1.5 mm to 3 mm. In addition, the Mg69Zn27Ca4 alloy with 1.5 mm diameter has the best corrosion properties. The current Mg-based alloys show much better corrosion resistance than the traditionally commercial wrought magnesium alloy ZK60 in simulated sea-water.展开更多
基金Project(50731002) supported by the National Natural Science Foundation of ChinaProject(20082030) supported by the Natural Science Foundation of Liaoning Province,China
文摘The phase equilibria and compositions in Mg-rich side at 300 ℃ were investigated in Mg-Zn-Ca ternary system through the equilibrated alloy method by using scanning electron microscopy,electron probe microanalysis,X-ray diffraction and transmission electron microscopy.The results show that two ternary compounds T1 and T2 can be in equilibrium with the Mg-based solid solution in Mg-Zn-Ca system.T1 phase is a linear compound with the composition region（molar fraction） of 15% Ca,20.5%-48.9% Zn and balanced Mg at 300 ℃.Its hexagonal structure parameters decrease with increasing Zn content,i.e.a=0.992-0.945 nm,c=1.034-1.003 nm.T2 phase has hexagonal structure with the composition region of 26.4%-28.4% Mg,63.2%-65.5% Zn and 7.1%-8.4% Ca.At 300 ℃,the solubility of Zn in the Mg-based solid solution increases for the addition of Ca,the maximum solubility of Zn is 3.7%.Three-phase fields consisting of--Mg＋Mg2Ca＋T1,--Mg＋T1＋T2,--Mg＋T2＋MgZn and MgZn＋T2＋Mg2Zn3 exist in the Mg-Zn-Ca system at 300 ℃.
基金This work was supported by the Key Research and Development Plan of Shandong Province(2019JZZY020329)the National Key Research and Development Program of China(grant number.2017YFB0103904)+1 种基金the National Natural Science Foundation of China(No.51701211)DongGuan Innovative Research Team Program(2020607234007).
文摘Magnesium alloys with homogeneous degradation and controlled degradation rate are desirable for biodegradable materials.In the present work,Mg-3 wt.%Zn-0.2 wt.%Ca alloys with different columnar structures were fabricated and the degradation in 0.9 wt.%NaCl were investigated.With the increase of the growth rate for the directional solidification,the microstructure of the directionally solidified(DSed)alloy evolved from cellular to dendritic coupled with the change of the spacing of the primary trunks(λ_(1))and the volume fraction(fv)of Ca_(2)Mg_(6)Zn_(3) phase.The results of the corrosion test suggested that the alloy with cellular structure experienced homogeneous corrosion and exhibited the lowest corrosion rate.The good corrosion resistance of the alloy with cellular structure was attributed to the protective corrosion products film(CPF),which was closely related to the fv of Ca_(2)Mg_(6)Zn_(3) phase andλ_(1).To evaluate the corrosion rates(CR)of the DSed Mg-Zn-Ca alloys with different microstructures,a parameterαwas proposed in this work,which was calculated byλ_(1) and the fv of Ca_(2)Mg_(6)Zn_(3) phase.The fitting result showed that there was a linear relationship between CR andα,which was CR=4.1899+0.00432α.This means that the CR of the DSed Mg-Zn-Ca alloy can be evaluated if the microstructure had been characterized.
基金the financial support for this work from the National Natural Science Foundation of China(Nos.U1764254,51871166)the Tianjin Natural Science Foundation,China(No.20JCYBJC00620)。
基金Project(NCET-11-0554)supported by the Program for New Century Excellent Talents in UniversityProject(2011BAE22B04)supportedby the National Key Technology R&D Program of ChinaProject(51271206)supported by the National Natural Science Foundation of China
文摘Mg69Zn27Ca4 alloys with diameters of 1.5, 2 and 3 mm were fabricated using copper mold injection casting method. Microstructural analysis reveals that the alloy with a diameter of 1.5 mm is almost completely composed of amorphous phase. However, with the cooling rate decline, a little α-Mg and MgZn dendrites can be found in the amorphous matrix. Based on the microstructural and tensile results, the ductile dendrites are conceived to be highly responsible for the enhanced compressive strain from 1.3% to 3.1% by increasing the sample diameter from 1.5 mm to 3 mm. In addition, the Mg69Zn27Ca4 alloy with 1.5 mm diameter has the best corrosion properties. The current Mg-based alloys show much better corrosion resistance than the traditionally commercial wrought magnesium alloy ZK60 in simulated sea-water.
