The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and...The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.展开更多
The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),trans...The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-resolution transmission electron microscopy(HRTEM)images.The results show that the tensile strength of the Li-containing alloy can be significantly improved;however,the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture.The elasticity modulus of the Li-containing alloy increases by 11.6%compared with the base alloy.The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy,andδ′-Al_(3)Li phase becomes the main precipitates.Besides,β′′-Mg_(2)Si andδ′-Al_(3)Li dual phases precipitation can be visibly observed at 170℃ ageing for 100 h,although the quantity ofδ′-Al_(3)Li phase is more thanβ′′-Mg_(2)Si phase.The width of the precipitate-free zone(PFZ)of the Li-containing alloy is much wider at the over-ageing state than the base alloy,which has a negative impact on the ductile and results in the decrease of elongation.展开更多
The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles r...The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.展开更多
In Nb-Si based alloys with a two-phase Nbss/ intermetallic Nb5Si3 structure, the Nb5Si3 provides high-temperature strength, while the Nb solid-solution phase, Nbss, contributes to room-temperature ductility and toughn...In Nb-Si based alloys with a two-phase Nbss/ intermetallic Nb5Si3 structure, the Nb5Si3 provides high-temperature strength, while the Nb solid-solution phase, Nbss, contributes to room-temperature ductility and toughness. The results show that in Nb-15W-10Hf-xSi alloys (x= 0.5, 5 and 18, mole fraction, %), the volume fraction of the Nb5Si3 is 0 for the 0.5% Si sample, 15% for the 5% Si sample and the 50% for 18% Si sample. With increasing Si content, i.e., the Nb5Si3 fraction, the high-temperature strength is improved considerably, but room-temperature ductility and toughness are degraded. For the sample Nb-15W-10Hf-18Si with 50% Nb5Si3, the compressive strength at 1 500℃and the room-temperature fracture toughness are 500 MPa and 6.8 MPa·m1/2, respectively, those for the Nb5Si3 free sample, Nb-15W-10Hf-0.5Si, are 190 MPa and 13.6 MPa·m1/2.展开更多
The effect of adding 0.5mass% Cu on ductility and magnetic properties of Fe-6.5Si（mass%）alloy was investigated.The alloys with and without 0.5mass% Cu addition were warm rolled into thin sheets of thickness no more ...The effect of adding 0.5mass% Cu on ductility and magnetic properties of Fe-6.5Si（mass%）alloy was investigated.The alloys with and without 0.5mass% Cu addition were warm rolled into thin sheets of thickness no more than 0.3mm at temperature below 600 ℃.It was found that the alloy with 0.5mass% Cu addition was more easily warm rolled than Cu-free alloy.Tensile tests were carried out to further investigate this phenomenon,which confirmed that the ductility of the alloy with 0.5mass% Cu addition was significantly higher than that of Cu-free alloy at 550 ℃.Based on the results of transmission electron microscopy analysis,the ductility increase of the alloy with 0.5mass% Cu addition was attributed to the effect of Cu on the promotion of dynamic recovery and suppression of long-range order in the alloy during warm rolling process.It was also observed that the iron loss was lower and inductance was higher for the alloy with 0.5 mass% Cu addition.Thus,it can be concluded that adding a suitably small amount of Cu would not only increase the ductility of Fe-6.5Si alloy at warm rolling temperatures but also improve its magnetic properties.展开更多
Deformation behaviors and mechanisms under different temperatures for columnar-grained Fe 6.5Si （mass%） alloys fabricated by directional solidification and equiaxed grained Fe-6.5Si alloy fabricated by forging were ...Deformation behaviors and mechanisms under different temperatures for columnar-grained Fe 6.5Si （mass%） alloys fabricated by directional solidification and equiaxed grained Fe-6.5Si alloy fabricated by forging were comparatively investigated. The results showed that, with increasing the deformation temperature from 300℃ to 500℃, the elongation increased from 2.9% to 30.1% for the equiaxed-grained Fe-6.5Si alloy, while from 6.6% to about 51% for the columnar-grained Fe-6.5Si alloy. The deformation mode of equiaxed-grained Fe 6.5Si alloy trans ferred from nearly negligible plastic deformation to large plastic deformation dominated by dislocation slipping. Comparatively, the deformation mode of the columnar grained alloy transferred from nearly negligible plastic deformation to plastic deformation dominated by the twining, and finally to plastic deformation dominated by dislocation slipping. Meanwhile, compared with the alloy with equiaxed grains, it was found that ultimate tensile strength and elongation could be increased simultaneously, which was ascribed for the twinning deformation in columnar-grained Fe-6.5Si al loy. This work would assist us to further understand the plastic deformation mechanism of Fe-6.5Si alloy and pro vide more clues for high-efficiency production of the alloy.展开更多
Fe-6. 5 mass% Si alloy is an excellent soft magnetic material with good application prospects. After rolling,the structure of the sheet is likely to be heterogeneous along the normal direction. The microstructure and ...Fe-6. 5 mass% Si alloy is an excellent soft magnetic material with good application prospects. After rolling,the structure of the sheet is likely to be heterogeneous along the normal direction. The microstructure and ordering evolution in the thickness range of the sheets during hot-warm rolling process was studied by means of optical microscope and transmission electron microscope. The results show that dynamic recrystallization occurs in the surface parts during the hot and warm rolling processes,where the grains are equiaxed but have high density of dislocations due to the large deformation. The grains in the center part are elongated along the rolling direction. It is also found that in the hot rolled sheet,the center part has lower density of dislocations because of dynamic recovery. Meanwhile,this part has higher ordering content compared with the surface part,indicating that the high density of dislocations can inhibit the formation of ordering in the air cooling process after hot rolling. In the warm rolling process,both of the parts are deformed heavily. Large deformation destroys ordered phases and induces disordering. The ordering content is low in the whole warm rolled sheet.展开更多
Morphology and distribution of precipitates in the Fe-6.5Si-0.02B alloy were characterized, and these effects on room- temperature compression cracks were investigated. The results showed that the precipitate in the F...Morphology and distribution of precipitates in the Fe-6.5Si-0.02B alloy were characterized, and these effects on room- temperature compression cracks were investigated. The results showed that the precipitate in the Fe-6.5Si-0.02B alloy is FezB with body-centered tetragonal structure, and its nano-hardness is 15.0 GPa which is higher than that of the matrix （- 8.5 GPa）. In the as-cast alloys, most of the intragranular precipitates are coarse lath-like with the length of 5-15 μm and width of 2-5 μm, and the precipitates formed at the grain boundaries are of about 2-3 μm in width. After oil quenching followed by heat treatment at 1100 ℃ for more than 30 min, the precipitates inside grains are refined with a size of several hundred nanometers and the precipitates at the grain boundaries are refined with a size of 〈 1 μm. After compression test, transgranular and intergranular cracks occur in the as-cast alloys with coarse precipitates. For the quenched alloys with fine precipitates, the number of cracks decreases significantly, and no transgranular cracks happen because some cracks are blocked or the propagation direction is changed by grain boundary.展开更多
Because of the effect of silicon on the formation of oxide scale, black strip defect is common on the surface of compact strip production （CSP） hot-rolled silicon steel, which leads to difficulty in pickling process...Because of the effect of silicon on the formation of oxide scale, black strip defect is common on the surface of compact strip production （CSP） hot-rolled silicon steel, which leads to difficulty in pickling process compared with plain carbon steels. Although high-temperature oxidation of Fe-Si alloy has been discussed a lot, few studies have explained the mechanism of black strip defect generated on the surface of hot-rolled silicon steel and proposed means to prevent it effectively. Thermogravimetric analyzer （TGA） is used to simulate oxidation of Fe-2.2Si alloy for 30 min under air condition, and temperature range is from 1000 to 1150 ℃. Effect of rolling deformation on scale morphology is also discussed. Electron probe microanalysis （EPMA） is used to analyze cross-sectional morphology and elemental distribution of the oxide scale. Schematic diagram of formation of black strip defect is obtained, which helps to provide theoretic basis for proposing of solutions for the Problem. It is proposed that lowering furnace tem-perature and shortening time to stay at high teniperature condition after rolling will be helpful tO relieve the black strip problem.展开更多
基金Project(51274245) supported by the National Natural Science Foundation of China
文摘The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.
基金Project(2016YFB0300802)supported by the National Key Research and Development Program of China。
文摘The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-resolution transmission electron microscopy(HRTEM)images.The results show that the tensile strength of the Li-containing alloy can be significantly improved;however,the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture.The elasticity modulus of the Li-containing alloy increases by 11.6%compared with the base alloy.The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy,andδ′-Al_(3)Li phase becomes the main precipitates.Besides,β′′-Mg_(2)Si andδ′-Al_(3)Li dual phases precipitation can be visibly observed at 170℃ ageing for 100 h,although the quantity ofδ′-Al_(3)Li phase is more thanβ′′-Mg_(2)Si phase.The width of the precipitate-free zone(PFZ)of the Li-containing alloy is much wider at the over-ageing state than the base alloy,which has a negative impact on the ductile and results in the decrease of elongation.
文摘The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.
基金Project(50671002) supported by the National Natural Science Foundation of China
文摘In Nb-Si based alloys with a two-phase Nbss/ intermetallic Nb5Si3 structure, the Nb5Si3 provides high-temperature strength, while the Nb solid-solution phase, Nbss, contributes to room-temperature ductility and toughness. The results show that in Nb-15W-10Hf-xSi alloys (x= 0.5, 5 and 18, mole fraction, %), the volume fraction of the Nb5Si3 is 0 for the 0.5% Si sample, 15% for the 5% Si sample and the 50% for 18% Si sample. With increasing Si content, i.e., the Nb5Si3 fraction, the high-temperature strength is improved considerably, but room-temperature ductility and toughness are degraded. For the sample Nb-15W-10Hf-18Si with 50% Nb5Si3, the compressive strength at 1 500℃and the room-temperature fracture toughness are 500 MPa and 6.8 MPa·m1/2, respectively, those for the Nb5Si3 free sample, Nb-15W-10Hf-0.5Si, are 190 MPa and 13.6 MPa·m1/2.
基金Item Sponsored by Natural Science Foundation of Hubei Province of China(2008CDA040)
文摘The effect of adding 0.5mass% Cu on ductility and magnetic properties of Fe-6.5Si（mass%）alloy was investigated.The alloys with and without 0.5mass% Cu addition were warm rolled into thin sheets of thickness no more than 0.3mm at temperature below 600 ℃.It was found that the alloy with 0.5mass% Cu addition was more easily warm rolled than Cu-free alloy.Tensile tests were carried out to further investigate this phenomenon,which confirmed that the ductility of the alloy with 0.5mass% Cu addition was significantly higher than that of Cu-free alloy at 550 ℃.Based on the results of transmission electron microscopy analysis,the ductility increase of the alloy with 0.5mass% Cu addition was attributed to the effect of Cu on the promotion of dynamic recovery and suppression of long-range order in the alloy during warm rolling process.It was also observed that the iron loss was lower and inductance was higher for the alloy with 0.5 mass% Cu addition.Thus,it can be concluded that adding a suitably small amount of Cu would not only increase the ductility of Fe-6.5Si alloy at warm rolling temperatures but also improve its magnetic properties.
基金Item Sponsored by Major States Basic Research Development Program of China(2011CB606300)National Natural Science Foundation of China(51504023)+1 种基金Fundamental Research Funds for the Central Universities of China(FRF-TP-15-051A2)State Key Laboratory of Advanced Metals and Materials Foundation of China(2014-Z06)
文摘Deformation behaviors and mechanisms under different temperatures for columnar-grained Fe 6.5Si （mass%） alloys fabricated by directional solidification and equiaxed grained Fe-6.5Si alloy fabricated by forging were comparatively investigated. The results showed that, with increasing the deformation temperature from 300℃ to 500℃, the elongation increased from 2.9% to 30.1% for the equiaxed-grained Fe-6.5Si alloy, while from 6.6% to about 51% for the columnar-grained Fe-6.5Si alloy. The deformation mode of equiaxed-grained Fe 6.5Si alloy trans ferred from nearly negligible plastic deformation to large plastic deformation dominated by dislocation slipping. Comparatively, the deformation mode of the columnar grained alloy transferred from nearly negligible plastic deformation to plastic deformation dominated by the twining, and finally to plastic deformation dominated by dislocation slipping. Meanwhile, compared with the alloy with equiaxed grains, it was found that ultimate tensile strength and elongation could be increased simultaneously, which was ascribed for the twinning deformation in columnar-grained Fe-6.5Si al loy. This work would assist us to further understand the plastic deformation mechanism of Fe-6.5Si alloy and pro vide more clues for high-efficiency production of the alloy.
基金Item Sponsored by Major State Basic Research Development Program of China(2011CB606304)High-tech Research and Development Program of China(2012AA03A505)National Natural Science Foundation of China(51301019,51471031)
文摘Fe-6. 5 mass% Si alloy is an excellent soft magnetic material with good application prospects. After rolling,the structure of the sheet is likely to be heterogeneous along the normal direction. The microstructure and ordering evolution in the thickness range of the sheets during hot-warm rolling process was studied by means of optical microscope and transmission electron microscope. The results show that dynamic recrystallization occurs in the surface parts during the hot and warm rolling processes,where the grains are equiaxed but have high density of dislocations due to the large deformation. The grains in the center part are elongated along the rolling direction. It is also found that in the hot rolled sheet,the center part has lower density of dislocations because of dynamic recovery. Meanwhile,this part has higher ordering content compared with the surface part,indicating that the high density of dislocations can inhibit the formation of ordering in the air cooling process after hot rolling. In the warm rolling process,both of the parts are deformed heavily. Large deformation destroys ordered phases and induces disordering. The ordering content is low in the whole warm rolled sheet.
基金This research was funded by the Major States Basic Research Development Program of China （973 Program, No. 2011CB606300） and China Postdoctoral Science Foundation （Nos. 2012M520263 and 2013T60110）.
文摘Morphology and distribution of precipitates in the Fe-6.5Si-0.02B alloy were characterized, and these effects on room- temperature compression cracks were investigated. The results showed that the precipitate in the Fe-6.5Si-0.02B alloy is FezB with body-centered tetragonal structure, and its nano-hardness is 15.0 GPa which is higher than that of the matrix （- 8.5 GPa）. In the as-cast alloys, most of the intragranular precipitates are coarse lath-like with the length of 5-15 μm and width of 2-5 μm, and the precipitates formed at the grain boundaries are of about 2-3 μm in width. After oil quenching followed by heat treatment at 1100 ℃ for more than 30 min, the precipitates inside grains are refined with a size of several hundred nanometers and the precipitates at the grain boundaries are refined with a size of 〈 1 μm. After compression test, transgranular and intergranular cracks occur in the as-cast alloys with coarse precipitates. For the quenched alloys with fine precipitates, the number of cracks decreases significantly, and no transgranular cracks happen because some cracks are blocked or the propagation direction is changed by grain boundary.
基金Item Sponsored by National High-Tech Research and Development Program(863Program)of China(2011BAE13B04)Fundamental Research Funds for Central Universities of China(N100307006)
文摘Because of the effect of silicon on the formation of oxide scale, black strip defect is common on the surface of compact strip production （CSP） hot-rolled silicon steel, which leads to difficulty in pickling process compared with plain carbon steels. Although high-temperature oxidation of Fe-Si alloy has been discussed a lot, few studies have explained the mechanism of black strip defect generated on the surface of hot-rolled silicon steel and proposed means to prevent it effectively. Thermogravimetric analyzer （TGA） is used to simulate oxidation of Fe-2.2Si alloy for 30 min under air condition, and temperature range is from 1000 to 1150 ℃. Effect of rolling deformation on scale morphology is also discussed. Electron probe microanalysis （EPMA） is used to analyze cross-sectional morphology and elemental distribution of the oxide scale. Schematic diagram of formation of black strip defect is obtained, which helps to provide theoretic basis for proposing of solutions for the Problem. It is proposed that lowering furnace tem-perature and shortening time to stay at high teniperature condition after rolling will be helpful tO relieve the black strip problem.
