The microstructures of an Mg-4Y-3Nd-0.5Zr alloy by differential pressure casting were investigated using scanning electron microscopy(SEM) and transmission electron microscopy(TEM), and its tensile deformation behavio...The microstructures of an Mg-4Y-3Nd-0.5Zr alloy by differential pressure casting were investigated using scanning electron microscopy(SEM) and transmission electron microscopy(TEM), and its tensile deformation behavior was measured using a Gleeble1500 D themo-simulation machine in the temperature range of 200 to 400 °C at initial strain rates of 5×10-4 to 10-1 s-1. Results show that the as-cast microstructure consists of primary α-Mg phase and bone-shaped Mg5 RE eutectic phase distributed along the grain boundary. The eutectic phase is dissolved into the matrix after solution treatment and subsequently precipitates during peak aging. Tensile deformation tests show that the strain rate has little effect on stress under 300 °C. Tensile stress decreases with an increase in temperature and the higher strain rate leads to an increase in stress above 300 °C. The fracture mechanism exhibits a mixed quasi-cleavage fracture at 200 °C, while the fracture above 300 °C is a ductile fracture. The dimples are melted at 400 °C with the lowest strain rate of 10-4 s-1.展开更多
Bi-metal material consisting of spray-formed Al-22 Si and ZL104 is a suitable candidate for applications in internal combustion engines. This research investigated the effects of surface treatment and appropriate gati...Bi-metal material consisting of spray-formed Al-22 Si and ZL104 is a suitable candidate for applications in internal combustion engines. This research investigated the effects of surface treatment and appropriate gating system on the microstructures and mechanical properties in evaluating the optimal strategy for producing high quality bi-metal materials. The bi-metal materials were prepared using ZL104 gravity casting by different pouring types around the spray-formed Al-22 Si with varied surface treatments. The wettability between Al-22 Si and ZL104 was significantly improved when Zn coating was used to remove the natural oxide layer. This research also obtained the improved interfacial microstructures and interfacial bonding strength for materials when applying the appropriate pouring method. The hardness profiles of Al-22Si/ZL104 bi-metal were consistent with the observed microstructures. The average tensile strength of the bi-metal material with zinc coating is ~42.3 MPa, which is much higher than that with oxide film at ~10 MPa. The process presented is a promising and effective approach for developing materials in the automotive industry.展开更多
Four Zn-rich Al-Zn-Mg-Cu alloys with different Mg and Cu contents were fabricated by spray deposition.The effects of Mg and Cu contents on the aging behaviors of the whole precipitation process of the alloys were syst...Four Zn-rich Al-Zn-Mg-Cu alloys with different Mg and Cu contents were fabricated by spray deposition.The effects of Mg and Cu contents on the aging behaviors of the whole precipitation process of the alloys were systematically investigated.The results show that the primary precipitates in the under-aged and peak-aged alloys are GPⅡ and η'phases;no GPⅠ zones were observed.During aging,the dissolution driving force of the precipitates increases with increasing Mg content;therefore,the volume fraction of precipitates in the grain interior and the area fraction of precipitates at the grain boundary increase obviously,which contributes to a considerable improvement in yield strength and decrease in plasticity of the high Mg content alloys.Cu content has no apparent effect on the size and volume fraction of precipitates.However,a higher Cu content can effectively prevent coarsening and transformation of precipitates,which is beneficial to maintain the peak aging state of the alloys.This research provides a basis for the composition optimization of the rapid-solidified highly alloying Al-Zn-Mg-Cu alloys.展开更多
The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperat...The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperature range of 1323-1473 Kand strain rate range of 0.001-0.5s^(-1).The calculated activation energy in the above variational ranges of temperature and strain rate possesses a low activation energy value of approximately 365.6kJ/mol based on the constitutive relationship models developed with the Arrhenius-type constitutive model respectively considering the strain rate and deformation temperature.The hot working flow behavior during the deformation process was analyzed combined with the microstructural evolution.Meanwhile,the processing maps during the deformation process were established based on the dynamic material model and Prasad instability criterion under different deformation conditions.Finally,the optimal hot processing window of this alloy corresponding to the wide temperature range of 1353-1453 Kand the low strain rate of 0.001-0.1s^(-1) was obtained.展开更多
The Al22Si/ZL102 bimetal was designed and prepared by extrusion at near-eutectic temperature.The properties and fracture behaviors of different surface treatments between oxide film and zinc coating were compared betw...The Al22Si/ZL102 bimetal was designed and prepared by extrusion at near-eutectic temperature.The properties and fracture behaviors of different surface treatments between oxide film and zinc coating were compared between the Al22 Si and ZL102 bimetal.The average bonding strength of bimetal with intermittent oxide film interface was about 89.3MPa,which is higher than that of the bimetal fabricated by zinc coating method(about 76.3MPa).During the process of extrusion,the oxidation film was extruded to crush and the metal was extruded through the micro-cracks of the oxidation film,then the two surfaces were joined together.Altogether,the results showed that extrusion at near-eutectic temperature is favorable for achieving a high-quality metallurgical bonded interface.展开更多
Al-Si-Fe-Cu-Mg alloy was prepared by spray deposition and was further processed by hot extrusion as well as T6heat-treatment.The results indicate that the microstructure of the deposited alloy is composed of primary S...Al-Si-Fe-Cu-Mg alloy was prepared by spray deposition and was further processed by hot extrusion as well as T6heat-treatment.The results indicate that the microstructure of the deposited alloy is composed of primary Si particles with average size of less than 5μm,α-Al,Al_2CuMg,β-Al_5FeSi andδ-Al_4FeSi_2(rectangular shape),and no eutectic silicon is found due to the special solidification behavior.The age hardening curves reveal two peaks.The uniform ultimate tensile strength(UTS)and the elongation of the peak-aged Al-Si-Fe-Cu-Mg alloy are 468.3 MPa,0.61% at 298 Kand 267.4MPa,6.42% at 573 K,respectively.The fracture surfaces display brittle fracture morphology at 298 K,whereas it varies to mixture of brittle and ductile failure with increasing the temperature.展开更多
The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al (C95800) alloy were investigated in this study. Plane castings were produced with two types ...The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al (C95800) alloy were investigated in this study. Plane castings were produced with two types of pouting systems, and their tensile properties were measured and then analyzed by means of Weibull statistics method. The fracture surfaces of the tensile specimens were examined using scanning electron microscopy equipped with energy-dispersive spectroscopy. A large amount of double oxide film defects were observed on the tensile fractured specimens of the topfilled plane castings, and their chemical composition is identified to be Al2O3. Weibull statistics analyses showed that the double oxide film defects significantly reduce mechanical properties of the castings investigated. Furthermore, the ultimate tensile strength is more obviously deteriorated by double oxide film defects than elongation.展开更多
Mciro-arc oxidation(MAO)was used to coat porous films on the surface of a Zr-based bulk metallic glass sample.The compressive test results indicated that,compared with the as-cast sample,the MAO treated one exhibite...Mciro-arc oxidation(MAO)was used to coat porous films on the surface of a Zr-based bulk metallic glass sample.The compressive test results indicated that,compared with the as-cast sample,the MAO treated one exhibited higher deformation capacity,associated with multiple shear bands with higher density on the side surface and well-developed vein patterns with smaller size on the fractured surface.The pore in the MAOed film and the matrix/coating interface initiated the shear bands and impeded the rapid propagation of shear bands,thus favoring the enhanced plasticity of the MAO treated sample.The obtained results demonstrated that MAO can be considered as an effective method to finely tune the mechanical performance of monolithic bulk metallic glasses.展开更多
基金supported by the Ministry of Science and Technology of China through Grant 2009GJB 2001.1
文摘The microstructures of an Mg-4Y-3Nd-0.5Zr alloy by differential pressure casting were investigated using scanning electron microscopy(SEM) and transmission electron microscopy(TEM), and its tensile deformation behavior was measured using a Gleeble1500 D themo-simulation machine in the temperature range of 200 to 400 °C at initial strain rates of 5×10-4 to 10-1 s-1. Results show that the as-cast microstructure consists of primary α-Mg phase and bone-shaped Mg5 RE eutectic phase distributed along the grain boundary. The eutectic phase is dissolved into the matrix after solution treatment and subsequently precipitates during peak aging. Tensile deformation tests show that the strain rate has little effect on stress under 300 °C. Tensile stress decreases with an increase in temperature and the higher strain rate leads to an increase in stress above 300 °C. The fracture mechanism exhibits a mixed quasi-cleavage fracture at 200 °C, while the fracture above 300 °C is a ductile fracture. The dimples are melted at 400 °C with the lowest strain rate of 10-4 s-1.
基金financially supported by the National Natural Science Foundation of China(No.51375110)
文摘Bi-metal material consisting of spray-formed Al-22 Si and ZL104 is a suitable candidate for applications in internal combustion engines. This research investigated the effects of surface treatment and appropriate gating system on the microstructures and mechanical properties in evaluating the optimal strategy for producing high quality bi-metal materials. The bi-metal materials were prepared using ZL104 gravity casting by different pouring types around the spray-formed Al-22 Si with varied surface treatments. The wettability between Al-22 Si and ZL104 was significantly improved when Zn coating was used to remove the natural oxide layer. This research also obtained the improved interfacial microstructures and interfacial bonding strength for materials when applying the appropriate pouring method. The hardness profiles of Al-22Si/ZL104 bi-metal were consistent with the observed microstructures. The average tensile strength of the bi-metal material with zinc coating is ~42.3 MPa, which is much higher than that with oxide film at ~10 MPa. The process presented is a promising and effective approach for developing materials in the automotive industry.
基金supported by the National Defense Pre-Research Foundation of China(Grant No.9140C500108140C50225)Shanghai Science and Technology Committee Innovation(Grant Nos.17JC1400600 and 17JC1400601)Open Foundation of Jiangsu Province Key Laboratory of High-end Structure Materials(Grant No.hsm1905).
文摘Four Zn-rich Al-Zn-Mg-Cu alloys with different Mg and Cu contents were fabricated by spray deposition.The effects of Mg and Cu contents on the aging behaviors of the whole precipitation process of the alloys were systematically investigated.The results show that the primary precipitates in the under-aged and peak-aged alloys are GPⅡ and η'phases;no GPⅠ zones were observed.During aging,the dissolution driving force of the precipitates increases with increasing Mg content;therefore,the volume fraction of precipitates in the grain interior and the area fraction of precipitates at the grain boundary increase obviously,which contributes to a considerable improvement in yield strength and decrease in plasticity of the high Mg content alloys.Cu content has no apparent effect on the size and volume fraction of precipitates.However,a higher Cu content can effectively prevent coarsening and transformation of precipitates,which is beneficial to maintain the peak aging state of the alloys.This research provides a basis for the composition optimization of the rapid-solidified highly alloying Al-Zn-Mg-Cu alloys.
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.51301157 and 51434007)the National High Technology Research and Development Program of China 863 Program(Grant No.2013AA031103)
文摘The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperature range of 1323-1473 Kand strain rate range of 0.001-0.5s^(-1).The calculated activation energy in the above variational ranges of temperature and strain rate possesses a low activation energy value of approximately 365.6kJ/mol based on the constitutive relationship models developed with the Arrhenius-type constitutive model respectively considering the strain rate and deformation temperature.The hot working flow behavior during the deformation process was analyzed combined with the microstructural evolution.Meanwhile,the processing maps during the deformation process were established based on the dynamic material model and Prasad instability criterion under different deformation conditions.Finally,the optimal hot processing window of this alloy corresponding to the wide temperature range of 1353-1453 Kand the low strain rate of 0.001-0.1s^(-1) was obtained.
文摘The Al22Si/ZL102 bimetal was designed and prepared by extrusion at near-eutectic temperature.The properties and fracture behaviors of different surface treatments between oxide film and zinc coating were compared between the Al22 Si and ZL102 bimetal.The average bonding strength of bimetal with intermittent oxide film interface was about 89.3MPa,which is higher than that of the bimetal fabricated by zinc coating method(about 76.3MPa).During the process of extrusion,the oxidation film was extruded to crush and the metal was extruded through the micro-cracks of the oxidation film,then the two surfaces were joined together.Altogether,the results showed that extrusion at near-eutectic temperature is favorable for achieving a high-quality metallurgical bonded interface.
基金Item Sponsored by National Natural Science Foundation of China(51375110)Scientific Research Foundation of Inner Mongolia University of Technology of China(ZD201405)
文摘Al-Si-Fe-Cu-Mg alloy was prepared by spray deposition and was further processed by hot extrusion as well as T6heat-treatment.The results indicate that the microstructure of the deposited alloy is composed of primary Si particles with average size of less than 5μm,α-Al,Al_2CuMg,β-Al_5FeSi andδ-Al_4FeSi_2(rectangular shape),and no eutectic silicon is found due to the special solidification behavior.The age hardening curves reveal two peaks.The uniform ultimate tensile strength(UTS)and the elongation of the peak-aged Al-Si-Fe-Cu-Mg alloy are 468.3 MPa,0.61% at 298 Kand 267.4MPa,6.42% at 573 K,respectively.The fracture surfaces display brittle fracture morphology at 298 K,whereas it varies to mixture of brittle and ductile failure with increasing the temperature.
文摘The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al (C95800) alloy were investigated in this study. Plane castings were produced with two types of pouting systems, and their tensile properties were measured and then analyzed by means of Weibull statistics method. The fracture surfaces of the tensile specimens were examined using scanning electron microscopy equipped with energy-dispersive spectroscopy. A large amount of double oxide film defects were observed on the tensile fractured specimens of the topfilled plane castings, and their chemical composition is identified to be Al2O3. Weibull statistics analyses showed that the double oxide film defects significantly reduce mechanical properties of the castings investigated. Furthermore, the ultimate tensile strength is more obviously deteriorated by double oxide film defects than elongation.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.51371065,51671070,51671067,51671071)the Opening Funding of AWJ-16-Z02 in the State Key Laboratory of Advanced Welding and Joining,China
文摘Mciro-arc oxidation(MAO)was used to coat porous films on the surface of a Zr-based bulk metallic glass sample.The compressive test results indicated that,compared with the as-cast sample,the MAO treated one exhibited higher deformation capacity,associated with multiple shear bands with higher density on the side surface and well-developed vein patterns with smaller size on the fractured surface.The pore in the MAOed film and the matrix/coating interface initiated the shear bands and impeded the rapid propagation of shear bands,thus favoring the enhanced plasticity of the MAO treated sample.The obtained results demonstrated that MAO can be considered as an effective method to finely tune the mechanical performance of monolithic bulk metallic glasses.