The microstructure and microhardness of ADC12 alloy that was mixed with 0,0.3,0.6,and 0.9 wt.% rare earth praseodymium/cerium (Pr/Ce) were studied.The addition of Pr/Ce improved the microhardness of the alloys.The ADC...The microstructure and microhardness of ADC12 alloy that was mixed with 0,0.3,0.6,and 0.9 wt.% rare earth praseodymium/cerium (Pr/Ce) were studied.The addition of Pr/Ce improved the microhardness of the alloys.The ADC12+0.6 wt% Pr/Ce alloy displayed the smallest grain size and maximal microhardness.The tribological behavior of the alloys was tested by the pin-on-disc dry sliding friction pair with a sliding velocity of 0.21 m/s under various loads (20,40,60,80 N).The wear morphology was observed by a scanning electron microscope (SEM) and the wear mechanism was discussed.The result indicated that the wear resistance of ADC12+0.6 wt% Pr/Ce alloy was the most optimal.The wear rate relative to the matrix is reduced by 67.5% under a load of 20 N.The wear mechanism is adhesive wear.展开更多
Effects of （Pr＋Ce） addition on the Al-7Si-0.7Mg alloy were investigated by optical microscope （OM）, energy diffraction spectrum （EDS）, X-ray diffraction （XRD） and tensile tests. The results showed that the Al...Effects of （Pr＋Ce） addition on the Al-7Si-0.7Mg alloy were investigated by optical microscope （OM）, energy diffraction spectrum （EDS）, X-ray diffraction （XRD） and tensile tests. The results showed that the Al-7Si-0.7Mg alloy was modified with （Pr＋Ce） addition. The needle-like eutectic silicon phase developed into rose form and the crystalline grains decreased in size and showed a high degree of spheroidization. When the amount of the （Pr＋Ce） addition reached 0.6 wt.%, the mean diameter was 31.8μm （refined by 50%）. The aspect ratio decreased to 1.35, and the tensile strength and ductility reached 192.4 MPa and 2.18%, respectively At higher levels of addition, over-modification occurred, as indicated by increased grain size and reduced mechanical properties. The poisoning effect of the （Pr＋Ce） addition on eutectic silicon and the constitutional supercooling caused by the （Pr＋Ce） addition were the major causes of alloy modification, grain refinement, and the improvement of mechanical properties.展开更多
The rare earth elements contents (La, Ce, Pr, Nd, Sm) in 150 Pu er tea samples were analyzed by using inductively coupled plasma atomic emission spectroscopy (ICP-AES), to evaluate the safety of Pu er tea. Among the i...The rare earth elements contents (La, Ce, Pr, Nd, Sm) in 150 Pu er tea samples were analyzed by using inductively coupled plasma atomic emission spectroscopy (ICP-AES), to evaluate the safety of Pu er tea. Among the investigated rare earth elements (REEs), Ce was the highest (35% of the total REEs content) whose concentrations were found to be in the range of 0.11–1.39 mg/kg, whereas that of Sm in the range 0.01–0.21 mg/kg, showing minimum levels (5.2%). La was the second highest element (28%) found in Pu e...展开更多
基金Funded by the National Natural Science Foundation of China(No.51965040)Natural Science Foundation of Jiangxi Province(No.20181BAB206026)。
文摘The microstructure and microhardness of ADC12 alloy that was mixed with 0,0.3,0.6,and 0.9 wt.% rare earth praseodymium/cerium (Pr/Ce) were studied.The addition of Pr/Ce improved the microhardness of the alloys.The ADC12+0.6 wt% Pr/Ce alloy displayed the smallest grain size and maximal microhardness.The tribological behavior of the alloys was tested by the pin-on-disc dry sliding friction pair with a sliding velocity of 0.21 m/s under various loads (20,40,60,80 N).The wear morphology was observed by a scanning electron microscope (SEM) and the wear mechanism was discussed.The result indicated that the wear resistance of ADC12+0.6 wt% Pr/Ce alloy was the most optimal.The wear rate relative to the matrix is reduced by 67.5% under a load of 20 N.The wear mechanism is adhesive wear.
基金Project supported by the National Natural Science Foundation of China(51364035)Ministry of Education tied up with the Special Research Fund for the Doctoral Program for Higher School(20133601110001)+1 种基金Loading Program of Science and Technology of College of Jiangxi Province(KJLD14003)Open Project Program of Jiangxi Engineering Research Center of Process and Equipment for New Energy,East China Institute of Technology(JXNE2015-09)
文摘Effects of （Pr＋Ce） addition on the Al-7Si-0.7Mg alloy were investigated by optical microscope （OM）, energy diffraction spectrum （EDS）, X-ray diffraction （XRD） and tensile tests. The results showed that the Al-7Si-0.7Mg alloy was modified with （Pr＋Ce） addition. The needle-like eutectic silicon phase developed into rose form and the crystalline grains decreased in size and showed a high degree of spheroidization. When the amount of the （Pr＋Ce） addition reached 0.6 wt.%, the mean diameter was 31.8μm （refined by 50%）. The aspect ratio decreased to 1.35, and the tensile strength and ductility reached 192.4 MPa and 2.18%, respectively At higher levels of addition, over-modification occurred, as indicated by increased grain size and reduced mechanical properties. The poisoning effect of the （Pr＋Ce） addition on eutectic silicon and the constitutional supercooling caused by the （Pr＋Ce） addition were the major causes of alloy modification, grain refinement, and the improvement of mechanical properties.
基金Project supported by the Foundation of National Key Technology R & D Program (2007BAD58B05-3)
文摘The rare earth elements contents (La, Ce, Pr, Nd, Sm) in 150 Pu er tea samples were analyzed by using inductively coupled plasma atomic emission spectroscopy (ICP-AES), to evaluate the safety of Pu er tea. Among the investigated rare earth elements (REEs), Ce was the highest (35% of the total REEs content) whose concentrations were found to be in the range of 0.11–1.39 mg/kg, whereas that of Sm in the range 0.01–0.21 mg/kg, showing minimum levels (5.2%). La was the second highest element (28%) found in Pu e...
