The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous stud...The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the alloys.In this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%Sc.The results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc addition.The ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.展开更多
W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator.The densification,microstructure and their dependence on sintering mode and Fe addition were investigated in detail.Owing to the volumetric heat...W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator.The densification,microstructure and their dependence on sintering mode and Fe addition were investigated in detail.Owing to the volumetric heating intrinsic in microwave processing,a microstructure with larger W grain size in center regions was observed as against larger grain size in edge regions for conventional sintering.Microwave sintering demonstrates its intrinsic advantages such as rapid heating rate,densification enhancement and microstructural homogeneity;but it undesirably promotes W grain growth.Under microwave sintering,the role of Fe addition on compact consolidation is not so substantial as under conventional sintering.Moreover Fe degrades the microstructural quality,generating worse uniformity and coarser W grains.展开更多
In this study, Cu was added as the third additive to lower the sintering temperature of W-Ni-Fe alloy. By adding 2 wt pct Cu, a dense 93W-3.5Ni-l.5Fe-2.0Cu tungsten alloy was obtained by hot-pressing at a low temperat...In this study, Cu was added as the third additive to lower the sintering temperature of W-Ni-Fe alloy. By adding 2 wt pct Cu, a dense 93W-3.5Ni-l.5Fe-2.0Cu tungsten alloy was obtained by hot-pressing at a low temperature of 1573 K which is a process of liquid-phase sintering. As a result, the morphology of W-Ni-Fe alloy changed obviously after the addition of Cu and the alloy had-higher relative density and rupture strength. The mechanism of the densification of W-Ni-Fe-Cu alloy at the low temperature.was then mainly investigated. It was found that, part sintering activators Ni and Fe could exist in liquid form at 1573 K due to the addition of Cu, which made it easy for Ni and Fe to dissolve W and thus the full densification of W-Ni-Fe-Cu alloy at the low temperature was realized.展开更多
The properties and microstructure of microwave and conventional sintered Fe-2Cu-0.6C powder metallurgy （PM） alloys were investigated. The experimental results show that microwave sintered alloy has the better proper...The properties and microstructure of microwave and conventional sintered Fe-2Cu-0.6C powder metallurgy （PM） alloys were investigated. The experimental results show that microwave sintered alloy has the better properties （sintered density 7.20 g/cm3, Rockwell hardness 75 HRB, tensile strength 413.90 MPa and elongation 6.0%）, compared with the conventional sintered counterpart. Detailed analyses by using optical microscopy and scanning electron microscopy （SEM） reveal that microwave sintered sample has finer microstructure with small, rounded and uniformly distributed pores, and also demonstrate the presence of more flaky and granular pearlite in the mi- crowave sintered body, both of which account for the property improvement. SEM images on the fracture morphology indicate that a mixed mode containing ductile and brittle fracture is presented in microwave sintered alloy, in contrast with the brittle fracture in conventional sintered counterpart.展开更多
2024 Aluminum alloy powder( 60wt%) and Fe-based amorphous powder( 40 wt%) were adopted. They were mechanical machined for 48hours after being mixed. Bulk material was gained after Spark Plasma Sintering. The sintering...2024 Aluminum alloy powder( 60wt%) and Fe-based amorphous powder( 40 wt%) were adopted. They were mechanical machined for 48hours after being mixed. Bulk material was gained after Spark Plasma Sintering. The sintering parameters included sintering temperature,heating or cooling rates,pressure and holding time. 300 ℃- 800 ℃ were adopted while the heating or cooling rate was 100 ℃ / min and with the pressure of 50 MPa in the experiments. The holding time was 10 min or 20 min at different temperatures, respectively. Bulk materials after sintering were examined by Scanning Electron Microscopy and X-Ray Diffraction. The micro-hardness and relative density also were tested. The sintering temperature had the most significant influence on the microstructure and property of the bulk material. The influence of holding time came second while the heating or cooling rates and pressure were fixed. The density became larger with the increase of the temperature. The compactness was best at 500℃. The pressure and generation of high-temperature phases were the factors which affected the density and the compactness.展开更多
The thermal stability of milling Fe86Zr11-xNbxB3（x=5.5, 6） melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray ...The thermal stability of milling Fe86Zr11-xNbxB3（x=5.5, 6） melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray diffractometry（XRD）, differential scanning calorimetry（DSC） and scanning electron microscopy（SEM）. The results show that milling melt-spun powder remains in the amorphous state, and the crystallization temperature of which is 480530℃, the apparent activation energy Ep of crystallization process is 294.1219.5kJ/mol. The increasing Nb content can increase crystallization temperature and decrease Ep. Under the sintering conditions of 5.5GPa/3min, when Pw is 1150W, single phase α-Fe nanocrystalline （20.626.7nm） bulk alloy with relative density higher than 99.0% can be obtained. Under the sintering conditions of 5.5GPa/1150W/3min, the magnetic properties of these nanocrystalline bulk alloys are Fe86Zr5.5Nb5.5B3 alloy, Bs=1.15T, Hc=5.08kA·m-1; Fe86Zr5Nb6B3 alloy, Bs=1.26T, Hc=4.27kA·m-1.展开更多
MA W-Ni-Fe alloyed powder compact was sintered by microwave technology, and the influence of microwave sintering on consolidation of W-Ni-Fe alloy was studied. The fracture morphology and microstructure of alloys were...MA W-Ni-Fe alloyed powder compact was sintered by microwave technology, and the influence of microwave sintering on consolidation of W-Ni-Fe alloy was studied. The fracture morphology and microstructure of alloys were measured by SEM and metallurgical microscope. The experimental results showed that microwave sintering promoted the densification of MA W-Ni-Fe alloyed powder quickly with the higher heating rate. The density of the sintered samples increased with the increase of sintering temperature, and significant densification shrinkage occured at 1300 ~ 1400°C. The tungsten grain grew rapidly at 1450°C. When the alloy was microwave sintered at 1550°C, the inner structure of alloy is more homogeneous, the average W grain size is about 15 μm, and the relative density of sintered specimen is 99%.展开更多
Fe3Al alloys with nearly full density were fabricated by plasma activated sintering（PAS） and hot pressing（HP） from mechanical alloyed Fe-28%Al（mole fraction） powders,respectively.It is found that A2-type Fe3Al a...Fe3Al alloys with nearly full density were fabricated by plasma activated sintering（PAS） and hot pressing（HP） from mechanical alloyed Fe-28%Al（mole fraction） powders,respectively.It is found that A2-type Fe3Al alloys were obtained by PAS,and they had a heterogeneous grain size distribution,most areas had a grain size smaller than 500 nm,and other areas had a grain size of about 1 μm.Different to PAS,D03-type Fe3Al alloys with a grain size of of 1-2 μm were obtained by HP.The compression testing results show that yield strength values of Fe3Al alloys fabricated by PAS and HP are almost equal at an elevated temperature,and the compression yield strength was about 100 MPa for all at 800 ℃.The room temperature compression ductility of Fe3Al alloys by PAS was about 20%,which was superior to that of Fe3Al alloys prepared by HP and casting.展开更多
基金supported by the Key Research&Development Program of Yunnan Province(Grant numbers 202103AA080017,202203AE140011).
文摘The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the alloys.In this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%Sc.The results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc addition.The ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.
基金Funded by China Postdoctoral Science Foundation (No. 20060400882) Postdoctoral Science Foundation of Central South University
文摘W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator.The densification,microstructure and their dependence on sintering mode and Fe addition were investigated in detail.Owing to the volumetric heating intrinsic in microwave processing,a microstructure with larger W grain size in center regions was observed as against larger grain size in edge regions for conventional sintering.Microwave sintering demonstrates its intrinsic advantages such as rapid heating rate,densification enhancement and microstructural homogeneity;but it undesirably promotes W grain growth.Under microwave sintering,the role of Fe addition on compact consolidation is not so substantial as under conventional sintering.Moreover Fe degrades the microstructural quality,generating worse uniformity and coarser W grains.
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.2020CDJDPT001)the Chongqing Natural Science Foundation,China(No.cstc2021jcyj-msxm X0699)。
基金supported by the National Natural Science Foundation,China (No.52074131)the National Key R&D Project,China (No.2022YFC3900500)+2 种基金the International Technology Cooperation Program of Guangdong Academy of Sciences,China (No.2020GDASYL-20200504001)the Open Competition to Select the Best Candidate of Shangrao,China (No.2021A005)the BL13HB beamline of Shanghai Synchrotron Radiation Facility (SSRF)for providing synchrotron radiation beamtime (Nos.2020-SSRF-PT-011937,2021-SSRF-PT-017645).
文摘In this study, Cu was added as the third additive to lower the sintering temperature of W-Ni-Fe alloy. By adding 2 wt pct Cu, a dense 93W-3.5Ni-l.5Fe-2.0Cu tungsten alloy was obtained by hot-pressing at a low temperature of 1573 K which is a process of liquid-phase sintering. As a result, the morphology of W-Ni-Fe alloy changed obviously after the addition of Cu and the alloy had-higher relative density and rupture strength. The mechanism of the densification of W-Ni-Fe-Cu alloy at the low temperature.was then mainly investigated. It was found that, part sintering activators Ni and Fe could exist in liquid form at 1573 K due to the addition of Cu, which made it easy for Ni and Fe to dissolve W and thus the full densification of W-Ni-Fe-Cu alloy at the low temperature was realized.
基金Funded by the National Science and Technology Development Program (No.2004-09ZD)
文摘The properties and microstructure of microwave and conventional sintered Fe-2Cu-0.6C powder metallurgy （PM） alloys were investigated. The experimental results show that microwave sintered alloy has the better properties （sintered density 7.20 g/cm3, Rockwell hardness 75 HRB, tensile strength 413.90 MPa and elongation 6.0%）, compared with the conventional sintered counterpart. Detailed analyses by using optical microscopy and scanning electron microscopy （SEM） reveal that microwave sintered sample has finer microstructure with small, rounded and uniformly distributed pores, and also demonstrate the presence of more flaky and granular pearlite in the mi- crowave sintered body, both of which account for the property improvement. SEM images on the fracture morphology indicate that a mixed mode containing ductile and brittle fracture is presented in microwave sintered alloy, in contrast with the brittle fracture in conventional sintered counterpart.
基金Sponsored by the National Basic Research Development Program of China(973 Program)(Grant No.2012CB619503)National High Technology Research and Development Program of China(863 Program)(Grant No.2013AA031001)International S&T Cooperation Program of China(Grant No.2012DFA50630)
文摘2024 Aluminum alloy powder( 60wt%) and Fe-based amorphous powder( 40 wt%) were adopted. They were mechanical machined for 48hours after being mixed. Bulk material was gained after Spark Plasma Sintering. The sintering parameters included sintering temperature,heating or cooling rates,pressure and holding time. 300 ℃- 800 ℃ were adopted while the heating or cooling rate was 100 ℃ / min and with the pressure of 50 MPa in the experiments. The holding time was 10 min or 20 min at different temperatures, respectively. Bulk materials after sintering were examined by Scanning Electron Microscopy and X-Ray Diffraction. The micro-hardness and relative density also were tested. The sintering temperature had the most significant influence on the microstructure and property of the bulk material. The influence of holding time came second while the heating or cooling rates and pressure were fixed. The density became larger with the increase of the temperature. The compactness was best at 500℃. The pressure and generation of high-temperature phases were the factors which affected the density and the compactness.
基金Project(0452NM086) supported by the Tackling Key Science and Technology Programof Shanghai , China
文摘The thermal stability of milling Fe86Zr11-xNbxB3（x=5.5, 6） melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray diffractometry（XRD）, differential scanning calorimetry（DSC） and scanning electron microscopy（SEM）. The results show that milling melt-spun powder remains in the amorphous state, and the crystallization temperature of which is 480530℃, the apparent activation energy Ep of crystallization process is 294.1219.5kJ/mol. The increasing Nb content can increase crystallization temperature and decrease Ep. Under the sintering conditions of 5.5GPa/3min, when Pw is 1150W, single phase α-Fe nanocrystalline （20.626.7nm） bulk alloy with relative density higher than 99.0% can be obtained. Under the sintering conditions of 5.5GPa/1150W/3min, the magnetic properties of these nanocrystalline bulk alloys are Fe86Zr5.5Nb5.5B3 alloy, Bs=1.15T, Hc=5.08kA·m-1; Fe86Zr5Nb6B3 alloy, Bs=1.26T, Hc=4.27kA·m-1.
文摘MA W-Ni-Fe alloyed powder compact was sintered by microwave technology, and the influence of microwave sintering on consolidation of W-Ni-Fe alloy was studied. The fracture morphology and microstructure of alloys were measured by SEM and metallurgical microscope. The experimental results showed that microwave sintering promoted the densification of MA W-Ni-Fe alloyed powder quickly with the higher heating rate. The density of the sintered samples increased with the increase of sintering temperature, and significant densification shrinkage occured at 1300 ~ 1400°C. The tungsten grain grew rapidly at 1450°C. When the alloy was microwave sintered at 1550°C, the inner structure of alloy is more homogeneous, the average W grain size is about 15 μm, and the relative density of sintered specimen is 99%.
基金Project (50871084) supported by the National Natural Science Foundation of ChinaProject (2009AA032601) supported by the National High Technology Research and Development Program of China
文摘Fe3Al alloys with nearly full density were fabricated by plasma activated sintering（PAS） and hot pressing（HP） from mechanical alloyed Fe-28%Al（mole fraction） powders,respectively.It is found that A2-type Fe3Al alloys were obtained by PAS,and they had a heterogeneous grain size distribution,most areas had a grain size smaller than 500 nm,and other areas had a grain size of about 1 μm.Different to PAS,D03-type Fe3Al alloys with a grain size of of 1-2 μm were obtained by HP.The compression testing results show that yield strength values of Fe3Al alloys fabricated by PAS and HP are almost equal at an elevated temperature,and the compression yield strength was about 100 MPa for all at 800 ℃.The room temperature compression ductility of Fe3Al alloys by PAS was about 20%,which was superior to that of Fe3Al alloys prepared by HP and casting.
