Microstructure and properties of Al-0.30Zr and Al-0.30Zr-0.08Y （mass fraction, %） alloys were investigated by electrical conductivity measurements, microhardness tests, scanning electron microscopy （SEM） and trans...Microstructure and properties of Al-0.30Zr and Al-0.30Zr-0.08Y （mass fraction, %） alloys were investigated by electrical conductivity measurements, microhardness tests, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Micron-sized primary Al3Y phases form within grains and at grain boundaries simultaneously as product of eutectic reaction in as-cast Al-Zr--Y alloys. The addition of Y obviously accelerates the precipitation kinetics of Al3Zr （Ll2） in Al-Zr-Y alloys. The Al-Zr-Y alloys exhibit greater electrical conductivity during aging due to formation of increased volume fractions of Al3（Zr, Y） precipitates. In ternary Al-Zr-Y alloys, spheroidal L l2-structured Al3（Zr, Y） precipitates with increased number density and smaller mean radius were observed. The Al-0.30Zr-0.08Y alloys show improved recrystallization resistance compared with Al-0.30Zr alloys展开更多
In order to increase the processability and process window of the selective laser melting(SLM)-fabricated Al−Mn−Mg−Er−Zr alloy,a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed.The effect of Si alloying on the sur...In order to increase the processability and process window of the selective laser melting(SLM)-fabricated Al−Mn−Mg−Er−Zr alloy,a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed.The effect of Si alloying on the surface quality,processability,microstructure,and mechanical properties of the SLM-fabricated alloy was studied.The results showed that introducing Si into the Al−Mn−Mg−Er−Zr alloy prevented balling and keyhole formation,refined the grain size,and reduced the solidification temperature,which eliminated cracks and increased the processability and process window of the alloy.The maximum relative density of the SLM-fabricated Si/Al−Mn−Mg−Er−Zr alloy reached 99.6%.The yield strength and ultimate tensile strength of the alloy were(371±7)MPa and(518±6)MPa,respectively.These values were higher than those of the SLM-fabricated Al−Mn−Mg−Er−Zr and other Sc-free Al−Mg-based alloys.展开更多
The electrical conductivity of NaF-AlF3-CaF2-Al2O3-ZrO2 system was studied by a tube-type cell with fixed cell constant. The results show that the electrical conductivity of NaF-AlF3-3%Al2O3-3%CaF2-ZrO2 molten salt sy...The electrical conductivity of NaF-AlF3-CaF2-Al2O3-ZrO2 system was studied by a tube-type cell with fixed cell constant. The results show that the electrical conductivity of NaF-AlF3-3%Al2O3-3%CaF2-ZrO2 molten salt system decreases with increase of ZrO2 content in an interval of 0-5%. The increase of 1%ZrO2 results in a corresponding electrical conductivity decrease of 0.02 S/cm, and the equivalent conductivity increases with the increase of molar ratio of NaF to AlF3. When the temperature increases by 1 °C, the electrical conductivity increases by 0.004 S/cm. At last, the regression equations of electrical conductivity relative to temperature and ZrO2 are obtained by quadratic regression analysis.展开更多
The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting （DCC）.The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogeniz...The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting （DCC）.The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogenization conditions were studied.The results show that the grain morphology is large dendritic structure and the grain size increases obviously by the addition of 0.5% Er.Moreover,most of Er element in the alloy segregates at grain boundary during solidification,resulting in ternary Al8Cu4Er phase.After homogenization,most of the MgZn2 phase at grain boundary has dissolved back to Al matrix in the two alloys.In the Er-containing alloy,the dissolution temperature of Al8Cu4Er phase is about 575 °C.Therefore,the homogenization treatment cannot eliminate Al8Cu4Er phase validity.展开更多
In order to study the welding process,microstructure and properties of Al-Mg-Mn-Sc-Zr alloy,comparative methods of friction stir welding（FSW） and tungsten inert gas（TIG） were applied to the two conditions of this ...In order to study the welding process,microstructure and properties of Al-Mg-Mn-Sc-Zr alloy,comparative methods of friction stir welding（FSW） and tungsten inert gas（TIG） were applied to the two conditions of this alloy,namely hot rolled plate and cold rolled-annealed plate.The relationships between microstructures and properties of the welded joints were investigated by means of optical microscopy and transmission electron microscopy.Compared with the base metal,the strength of FSW and TIG welded joints decreased,and the FSW welding coefficients were higher than the TIG welding coefficients.The loss of substructure strengthening and a very little loss of precipitation strengthening of Al3（Sc,Zr） cause the decreased strength of FSW welded joint.But for the TIG welded joint,the disappearance of both the strain hardening and most precipitation strengthening effect of Al3（Sc,Zr） particles contributed to its softening.At the same time,the grains in weld nugget zone of FSW welded joints were finer than those in the molten zone of TIG welded joints.展开更多
基金Project(2012CB619505)supported by the Basic Research Program of ChinaProject(51274141)supported by the National Natural Science Foundation of China
文摘Microstructure and properties of Al-0.30Zr and Al-0.30Zr-0.08Y （mass fraction, %） alloys were investigated by electrical conductivity measurements, microhardness tests, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Micron-sized primary Al3Y phases form within grains and at grain boundaries simultaneously as product of eutectic reaction in as-cast Al-Zr--Y alloys. The addition of Y obviously accelerates the precipitation kinetics of Al3Zr （Ll2） in Al-Zr-Y alloys. The Al-Zr-Y alloys exhibit greater electrical conductivity during aging due to formation of increased volume fractions of Al3（Zr, Y） precipitates. In ternary Al-Zr-Y alloys, spheroidal L l2-structured Al3（Zr, Y） precipitates with increased number density and smaller mean radius were observed. The Al-0.30Zr-0.08Y alloys show improved recrystallization resistance compared with Al-0.30Zr alloys
基金the National Natural Science Foundation of China(Nos.51801079,52001140)the Portugal National Funds through FCT Project(No.2021.04115).
文摘In order to increase the processability and process window of the selective laser melting(SLM)-fabricated Al−Mn−Mg−Er−Zr alloy,a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed.The effect of Si alloying on the surface quality,processability,microstructure,and mechanical properties of the SLM-fabricated alloy was studied.The results showed that introducing Si into the Al−Mn−Mg−Er−Zr alloy prevented balling and keyhole formation,refined the grain size,and reduced the solidification temperature,which eliminated cracks and increased the processability and process window of the alloy.The maximum relative density of the SLM-fabricated Si/Al−Mn−Mg−Er−Zr alloy reached 99.6%.The yield strength and ultimate tensile strength of the alloy were(371±7)MPa and(518±6)MPa,respectively.These values were higher than those of the SLM-fabricated Al−Mn−Mg−Er−Zr and other Sc-free Al−Mg-based alloys.
基金Project (2007CB210305) supported by the National Basic Research Program of ChinaProject (51074045) supported by the National Natural Science Foundation of China
文摘The electrical conductivity of NaF-AlF3-CaF2-Al2O3-ZrO2 system was studied by a tube-type cell with fixed cell constant. The results show that the electrical conductivity of NaF-AlF3-3%Al2O3-3%CaF2-ZrO2 molten salt system decreases with increase of ZrO2 content in an interval of 0-5%. The increase of 1%ZrO2 results in a corresponding electrical conductivity decrease of 0.02 S/cm, and the equivalent conductivity increases with the increase of molar ratio of NaF to AlF3. When the temperature increases by 1 °C, the electrical conductivity increases by 0.004 S/cm. At last, the regression equations of electrical conductivity relative to temperature and ZrO2 are obtained by quadratic regression analysis.
基金Project(50875031) supported by the National Natural Science Foundation of ChinaProject(2005CB623705) supported by National Basic Research Program of China
文摘The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting （DCC）.The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogenization conditions were studied.The results show that the grain morphology is large dendritic structure and the grain size increases obviously by the addition of 0.5% Er.Moreover,most of Er element in the alloy segregates at grain boundary during solidification,resulting in ternary Al8Cu4Er phase.After homogenization,most of the MgZn2 phase at grain boundary has dissolved back to Al matrix in the two alloys.In the Er-containing alloy,the dissolution temperature of Al8Cu4Er phase is about 575 °C.Therefore,the homogenization treatment cannot eliminate Al8Cu4Er phase validity.
基金Project (MKPT-2005-16ZD) supported by the National Key Scientific and Technological Project of ChinaProject supported by the Postdoctoral Science Foundation of Central South University,China
文摘In order to study the welding process,microstructure and properties of Al-Mg-Mn-Sc-Zr alloy,comparative methods of friction stir welding（FSW） and tungsten inert gas（TIG） were applied to the two conditions of this alloy,namely hot rolled plate and cold rolled-annealed plate.The relationships between microstructures and properties of the welded joints were investigated by means of optical microscopy and transmission electron microscopy.Compared with the base metal,the strength of FSW and TIG welded joints decreased,and the FSW welding coefficients were higher than the TIG welding coefficients.The loss of substructure strengthening and a very little loss of precipitation strengthening of Al3（Sc,Zr） cause the decreased strength of FSW welded joint.But for the TIG welded joint,the disappearance of both the strain hardening and most precipitation strengthening effect of Al3（Sc,Zr） particles contributed to its softening.At the same time,the grains in weld nugget zone of FSW welded joints were finer than those in the molten zone of TIG welded joints.
