This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility...This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications. On the process front, vacuumassisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications. Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications. Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams. Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.展开更多
The effects of different Zn addition(0,0.2,0.5,1.0 wt%)on the microstructure and mechanical properties of cast Mg-1Nd-1Ce-Zr alloy in as-cast,solution-treated and 200℃peak-aged conditions were studied.Precipitates in...The effects of different Zn addition(0,0.2,0.5,1.0 wt%)on the microstructure and mechanical properties of cast Mg-1Nd-1Ce-Zr alloy in as-cast,solution-treated and 200℃peak-aged conditions were studied.Precipitates in cast Mg-1Nd-1Ce-Zr alloy are significantly modified by the Zn addition.In the Zn-free alloy,the disk-shaped prismatic precipitates and the point-like precipitates are the main strengthening phases.When 0.2 Zn is added,the disk-shaped precipitates are refined and very fine basal precipitates form additionally.When 0.5 Zn is added,the basal precipitates become the main strengthening phase.Further increasing the Zn addition to 1.0%,only spare basal precipitates and point-like precipitates exist.The 0.5 Zn addition alloy has the highest strength at room temperature,whose yield strength,ultimate tensile strength and elongation in T6 condition are 136 MPa,237 MPa and 9%,respectively.展开更多
Based on the hot tearing index|△T/△(fs)^(0.5)|recently proposed by Kou and the thermodynamic calculations of Pandat software,Al,Cu,and Mn elements were picked up and their influence on hot tearing susceptibility of ...Based on the hot tearing index|△T/△(fs)^(0.5)|recently proposed by Kou and the thermodynamic calculations of Pandat software,Al,Cu,and Mn elements were picked up and their influence on hot tearing susceptibility of Mg-x Zn(x=6,8,10,wt%)alloys was studied by experiments.The results indicate that Al addition can significantly reduce the hot tearing susceptibility of Mg-Zn alloys.Either 0.5Cu or 0.3Mn addition individually can reduce the HTS of the Mg-6Zn-(1,4)Al alloys,while adding together increases the susceptibility.The addition of 0.5Cu and 0.3Mn both individually and together increases the HTS of Mg-8/10Zn-1Al alloys.Based on the experimental and calculation results,the index can be modified to|△T/△(fs)^(0.5)|(d)^(2)for more accurate prediction on the hot tearing resistance of Mg-Zn based alloys.Grain refinement significantly improves the hot tearing resistance of Mg-Zn based alloys.展开更多
Few studies were reported on the phases'relationships of AE44(Mg-4.0Al-4.1RE-0.3Mn,wt.%)and its composites.In this work,AE44 alloy and Saffil(6-Al2O3)/AE44 Metal matrix composite(MMC)were both prepared by slow sho...Few studies were reported on the phases'relationships of AE44(Mg-4.0Al-4.1RE-0.3Mn,wt.%)and its composites.In this work,AE44 alloy and Saffil(6-Al2O3)/AE44 Metal matrix composite(MMC)were both prepared by slow shot high pressure die casting(SS-HPDC)technology and their phase constitutions were all studied in detail using experimental techniques combined with CALPHAD(Calculation of Phase Diagram)modeling.The results revealed that the alloy consists of the a-Mg matrix,A1hRE3 intermetallic phase,and one trace phase AI3RE,while the composite contains five major phases:a-Mg,5-AI2O3,AI3RE,MgO and Mg2Si.and two trace phases of A12RE and AI11RE3,respectively.A1hRE3 is partly derived from ALRE,while A13RE is a product of the peritectoid reaction between the two precipitates.The presence of MgO and Mg2Si is due to the interfacial reaction between the SiO2 binder in the fiber preforms and the molten magnesium during infiltration.The use of SiO2 binder in the preform manufacturing was limited/minimized to reduce the MgO formation in the MMC casting process,which can be detrimental to the fatigue performance of the MMC materials.展开更多
The nucleation and propagation of h011]superdislocations in intermetallic TiAl were investigated using molecular dynamics simulations and static energetics calculation,as part of our systematic effort to understand th...The nucleation and propagation of h011]superdislocations in intermetallic TiAl were investigated using molecular dynamics simulations and static energetics calculation,as part of our systematic effort to understand the twining and dislocation behavior of alloys based on c-TiAl.It was found that compared to ordinary dislocations in disordered crystals,superdislocations in ordered TiAl lattice behave differently when sheared in the two opposite senses along[0"11]direction.This difference is due to the lower L10lattice symmetry compared with the face-centered cubic(fcc)lattice that it based on,with different yield stress and strain,and dislocation core dissociation and motion.Superdislocations nucleated in the form of loops dissociated in a planar manner into four Shockley partials separated by three kinds of faults:superlattice intrinsic stacking fault(SISF),anti-phase domain boundary(APB)and complex stacking fault(CSF),with partial separations depending on the sense of shearing and dislocation character.During loop expansion,the dislocation core changes both in width and dissociation manner depending on the character of the segment in the loop.The core contains four partials close to edge orientation,gradually changing to three fold near 60°,and finally into twofold dissociationaround 30°character.Superdislocations may have multiple critical resolved shear stresses(CRSS)for motion depending on dissociation and shearing sense even for the same slip system,with lower critical stress for the motion when SISF is in leading position.展开更多
文摘This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications. On the process front, vacuumassisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications. Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications. Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams. Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.
基金This work was supported by National Key Research and Development Program of China(2016YFB0301000&2016YFB0701204)Shanghai Rising-Star Program(15QB1402700)+1 种基金National Natural Science Foundation of China(NSFC)(51671128&51771113)Special Fund of Jiangsu Province for the Transformation of Scientific and Technological Achievements(BA2016039).
文摘The effects of different Zn addition(0,0.2,0.5,1.0 wt%)on the microstructure and mechanical properties of cast Mg-1Nd-1Ce-Zr alloy in as-cast,solution-treated and 200℃peak-aged conditions were studied.Precipitates in cast Mg-1Nd-1Ce-Zr alloy are significantly modified by the Zn addition.In the Zn-free alloy,the disk-shaped prismatic precipitates and the point-like precipitates are the main strengthening phases.When 0.2 Zn is added,the disk-shaped precipitates are refined and very fine basal precipitates form additionally.When 0.5 Zn is added,the basal precipitates become the main strengthening phase.Further increasing the Zn addition to 1.0%,only spare basal precipitates and point-like precipitates exist.The 0.5 Zn addition alloy has the highest strength at room temperature,whose yield strength,ultimate tensile strength and elongation in T6 condition are 136 MPa,237 MPa and 9%,respectively.
基金supported by the National Key Research and Development Program of China(2016YFB0701204)Shang-hai Rising-Star Program(15QB1402700)Special Fund of Jiangsu Province for the Transformation of Scientific and Technological Achievements(BA2016039).
文摘Based on the hot tearing index|△T/△(fs)^(0.5)|recently proposed by Kou and the thermodynamic calculations of Pandat software,Al,Cu,and Mn elements were picked up and their influence on hot tearing susceptibility of Mg-x Zn(x=6,8,10,wt%)alloys was studied by experiments.The results indicate that Al addition can significantly reduce the hot tearing susceptibility of Mg-Zn alloys.Either 0.5Cu or 0.3Mn addition individually can reduce the HTS of the Mg-6Zn-(1,4)Al alloys,while adding together increases the susceptibility.The addition of 0.5Cu and 0.3Mn both individually and together increases the HTS of Mg-8/10Zn-1Al alloys.Based on the experimental and calculation results,the index can be modified to|△T/△(fs)^(0.5)|(d)^(2)for more accurate prediction on the hot tearing resistance of Mg-Zn based alloys.Grain refinement significantly improves the hot tearing resistance of Mg-Zn based alloys.
基金This work was co-funded by,The National Key Research and Development Program of China(NO.2016YFB0301002)and General Motors Global Research and Development.
文摘Few studies were reported on the phases'relationships of AE44(Mg-4.0Al-4.1RE-0.3Mn,wt.%)and its composites.In this work,AE44 alloy and Saffil(6-Al2O3)/AE44 Metal matrix composite(MMC)were both prepared by slow shot high pressure die casting(SS-HPDC)technology and their phase constitutions were all studied in detail using experimental techniques combined with CALPHAD(Calculation of Phase Diagram)modeling.The results revealed that the alloy consists of the a-Mg matrix,A1hRE3 intermetallic phase,and one trace phase AI3RE,while the composite contains five major phases:a-Mg,5-AI2O3,AI3RE,MgO and Mg2Si.and two trace phases of A12RE and AI11RE3,respectively.A1hRE3 is partly derived from ALRE,while A13RE is a product of the peritectoid reaction between the two precipitates.The presence of MgO and Mg2Si is due to the interfacial reaction between the SiO2 binder in the fiber preforms and the molten magnesium during infiltration.The use of SiO2 binder in the preform manufacturing was limited/minimized to reduce the MgO formation in the MMC casting process,which can be detrimental to the fatigue performance of the MMC materials.
基金supported by the National Basic Research Program of China (2011CB606404)the National Natural Science Foundation of China (51171195)GM Research Project
文摘The nucleation and propagation of h011]superdislocations in intermetallic TiAl were investigated using molecular dynamics simulations and static energetics calculation,as part of our systematic effort to understand the twining and dislocation behavior of alloys based on c-TiAl.It was found that compared to ordinary dislocations in disordered crystals,superdislocations in ordered TiAl lattice behave differently when sheared in the two opposite senses along[0"11]direction.This difference is due to the lower L10lattice symmetry compared with the face-centered cubic(fcc)lattice that it based on,with different yield stress and strain,and dislocation core dissociation and motion.Superdislocations nucleated in the form of loops dissociated in a planar manner into four Shockley partials separated by three kinds of faults:superlattice intrinsic stacking fault(SISF),anti-phase domain boundary(APB)and complex stacking fault(CSF),with partial separations depending on the sense of shearing and dislocation character.During loop expansion,the dislocation core changes both in width and dissociation manner depending on the character of the segment in the loop.The core contains four partials close to edge orientation,gradually changing to three fold near 60°,and finally into twofold dissociationaround 30°character.Superdislocations may have multiple critical resolved shear stresses(CRSS)for motion depending on dissociation and shearing sense even for the same slip system,with lower critical stress for the motion when SISF is in leading position.
