This research explores the prospect of fabricating a face-centered cubic(fcc) Ni-base alloy cladding(Inconel 690) on an fcc Fe-base alloy(316 L stainless-steel) having improved mechanical properties and reduced sensit...This research explores the prospect of fabricating a face-centered cubic(fcc) Ni-base alloy cladding(Inconel 690) on an fcc Fe-base alloy(316 L stainless-steel) having improved mechanical properties and reduced sensitivity to corrosion through grain boundary and microstructure engineering concepts enabled by additive manufacturing(AM) utilizing electron-beam powder bed fusion(EPBF). The unique solidification and associated constitutional supercooling phenomena characteristic of EPBF promotes[100] textured and extended columnar grains having lower energy grain boundaries as opposed to random, high-angle grain boundaries, but no coherent {111} twin boundaries characteristic of conventional thermo-mechanically processed fcc metals and alloys, including Inconel 690 and 316 L stainless-steel.In addition to [100] textured grains, columnar grains were produced by EPBF fabrication of Inconel 690 claddings on 316 L stainless-steel substrates. Also, irregular 2–3 μm diameter, low energy subgrains were formed along with dislocation densities varying from 108 to 109 cm^2, and a homogeneous distribution of Cr_(23)C_6 precipitates. Precipitates were formed within the grains(with ~3 μm interparticle spacing),but not in the subgrain or columnar grain boundaries. These inclusive, hierarchical microstructures produced a tensile yield strength of 0.527 GPa, elongation of 21%, and Vickers microindentation hardness of 2.33 GPa for the Inconel 690 cladding in contrast to a tensile yield strength of 0.327 GPa, elongation of 53%, and Vickers microindentation hardness of 1.78 GPa, respectively for the wrought 316 L stainlesssteel substrate. Aging of both the Inconel 690 cladding and the 316 L stainless-steel substrate at 685?C for50 h precipitated Cr_(23)C_6 carbides in the Inconel 690 columnar grain boundaries, but not in the low-angle(and low energy) subgrain boundaries. In contrast, Cr_(23)C_6 carbides precipitated in the 316 L stainless-steel grain boundaries, but not in the low energy coherent {111} twin boundaries. Consequently, the Inconel690 subgrain boundaries essentially serve as surrogates for coherent twin boundaries with regard to avoiding carbide precipitation and corrosion sensitization.展开更多
This work aims to elucidate the impact of aluminum-content on microstructure and deformation mechanisms of transformation-induced plasticity（TRIP） steels through macroscale and nanoscale deformation experiments comb...This work aims to elucidate the impact of aluminum-content on microstructure and deformation mechanisms of transformation-induced plasticity（TRIP） steels through macroscale and nanoscale deformation experiments combined with post-mortem electron microscopy of the deformed region.The solid-state transformation-induced mechanical deformation varied with the Al contents,and influenced tensile strength-ductility combination.Steels with 2–4 wt% Al were characterized by TRIP effect.In contrast to 2 Al-TRIP and 4 Al-TRIP steels,twinning-induced plasticity（TWIP） was also observed in conjunction with strain-induced martensite in 6 Al-TRIP steel.This behavior is attributed to the increase in stacking fault energy with the increase of Al content and stability of austenite,which depends on the local chemical variation.The study addresses the knowledge gap with regard to the effect of Al content on austenite stability in medium-Mn TRIP steels.This combination is expected to potentially enable cost-effective alloy design with high strength-high ductility condition.展开更多
Mechanical properties were tested for in situ TiB2/A357 composite fabricated by LSM (mixed salts reaction) method. Micro structures of as cast and plastic deformed TiB2/A357 were investigated. The results show that th...Mechanical properties were tested for in situ TiB2/A357 composite fabricated by LSM (mixed salts reaction) method. Micro structures of as cast and plastic deformed TiB2/A357 were investigated. The results show that there is a low misfit between (200) Al and (101)TiB2 with [011]//Al [101]TiB2. There is a change from fully dendritic structure of the α-Al of A357 to a rosette-type structure of TiB2/A357. Significant increases in proof stress and Young's modulus can be obtained at low TiB2 additions. There exist dislocation loops around neighboring TiB2 particles with about 0.1μm in diameter and dislocation multiplication near TiB2 particles.展开更多
Purpose of the study was to demonstrate the ability of Pleurotus eryngii(PE)extracts to stimulate the production of nitric oxide(NO)and TNF-αas well as to evaluate the cell viability by the use of chicken peripheral ...Purpose of the study was to demonstrate the ability of Pleurotus eryngii(PE)extracts to stimulate the production of nitric oxide(NO)and TNF-αas well as to evaluate the cell viability by the use of chicken peripheral blood mononuclear cells(PBMCs)and RAW 264.7 macrophages in vitro.The PE contained 341.0±14.5 mg/g DW,78,2±4.1 Bg/g DW and 38.4+3.3 mg/g DW of crude polysaccharide,adenosine and crude triterpenoid contents,respectively.The results of cell viability assay showed that 95,0%of chicken PBMCs and RAW 264.7 macrophages were survived under the treatment of 9.6 mg/mL of PE extracts by microculture tetrazolium assays(MTAs).Moreover,the cell inhibitory activity did not show the 50%cyto-toxicity effect(ICs0).In addition,no production by stimulated chicken PBMCs and RAW 264.7 macrophages exhibited individually the linear relations with the concentration of PE extracts,and they were approximately 65μM and 45 p.M in 1600μg/mL,respectively.The tendency with the release of TNF-αby RAW 264.7 maerophages also corresponded with concentration of PE extracts.It is concluded,PE extracts act as an immunostimulant for both tested cells but have no serious effect on inhibiting chicken PBMCs viability,and therefore it may be suggested as immune supplements for broilers.展开更多
基金Support for this project was provided by US Department of Energy grant DE-SC0011826
文摘This research explores the prospect of fabricating a face-centered cubic(fcc) Ni-base alloy cladding(Inconel 690) on an fcc Fe-base alloy(316 L stainless-steel) having improved mechanical properties and reduced sensitivity to corrosion through grain boundary and microstructure engineering concepts enabled by additive manufacturing(AM) utilizing electron-beam powder bed fusion(EPBF). The unique solidification and associated constitutional supercooling phenomena characteristic of EPBF promotes[100] textured and extended columnar grains having lower energy grain boundaries as opposed to random, high-angle grain boundaries, but no coherent {111} twin boundaries characteristic of conventional thermo-mechanically processed fcc metals and alloys, including Inconel 690 and 316 L stainless-steel.In addition to [100] textured grains, columnar grains were produced by EPBF fabrication of Inconel 690 claddings on 316 L stainless-steel substrates. Also, irregular 2–3 μm diameter, low energy subgrains were formed along with dislocation densities varying from 108 to 109 cm^2, and a homogeneous distribution of Cr_(23)C_6 precipitates. Precipitates were formed within the grains(with ~3 μm interparticle spacing),but not in the subgrain or columnar grain boundaries. These inclusive, hierarchical microstructures produced a tensile yield strength of 0.527 GPa, elongation of 21%, and Vickers microindentation hardness of 2.33 GPa for the Inconel 690 cladding in contrast to a tensile yield strength of 0.327 GPa, elongation of 53%, and Vickers microindentation hardness of 1.78 GPa, respectively for the wrought 316 L stainlesssteel substrate. Aging of both the Inconel 690 cladding and the 316 L stainless-steel substrate at 685?C for50 h precipitated Cr_(23)C_6 carbides in the Inconel 690 columnar grain boundaries, but not in the low-angle(and low energy) subgrain boundaries. In contrast, Cr_(23)C_6 carbides precipitated in the 316 L stainless-steel grain boundaries, but not in the low energy coherent {111} twin boundaries. Consequently, the Inconel690 subgrain boundaries essentially serve as surrogates for coherent twin boundaries with regard to avoiding carbide precipitation and corrosion sensitization.
基金supported financially by the National Science Foundation,USA (No.#DMR-MRI 1530891)
文摘This work aims to elucidate the impact of aluminum-content on microstructure and deformation mechanisms of transformation-induced plasticity（TRIP） steels through macroscale and nanoscale deformation experiments combined with post-mortem electron microscopy of the deformed region.The solid-state transformation-induced mechanical deformation varied with the Al contents,and influenced tensile strength-ductility combination.Steels with 2–4 wt% Al were characterized by TRIP effect.In contrast to 2 Al-TRIP and 4 Al-TRIP steels,twinning-induced plasticity（TWIP） was also observed in conjunction with strain-induced martensite in 6 Al-TRIP steel.This behavior is attributed to the increase in stacking fault energy with the increase of Al content and stability of austenite,which depends on the local chemical variation.The study addresses the knowledge gap with regard to the effect of Al content on austenite stability in medium-Mn TRIP steels.This combination is expected to potentially enable cost-effective alloy design with high strength-high ductility condition.
文摘Mechanical properties were tested for in situ TiB2/A357 composite fabricated by LSM (mixed salts reaction) method. Micro structures of as cast and plastic deformed TiB2/A357 were investigated. The results show that there is a low misfit between (200) Al and (101)TiB2 with [011]//Al [101]TiB2. There is a change from fully dendritic structure of the α-Al of A357 to a rosette-type structure of TiB2/A357. Significant increases in proof stress and Young's modulus can be obtained at low TiB2 additions. There exist dislocation loops around neighboring TiB2 particles with about 0.1μm in diameter and dislocation multiplication near TiB2 particles.
文摘Purpose of the study was to demonstrate the ability of Pleurotus eryngii(PE)extracts to stimulate the production of nitric oxide(NO)and TNF-αas well as to evaluate the cell viability by the use of chicken peripheral blood mononuclear cells(PBMCs)and RAW 264.7 macrophages in vitro.The PE contained 341.0±14.5 mg/g DW,78,2±4.1 Bg/g DW and 38.4+3.3 mg/g DW of crude polysaccharide,adenosine and crude triterpenoid contents,respectively.The results of cell viability assay showed that 95,0%of chicken PBMCs and RAW 264.7 macrophages were survived under the treatment of 9.6 mg/mL of PE extracts by microculture tetrazolium assays(MTAs).Moreover,the cell inhibitory activity did not show the 50%cyto-toxicity effect(ICs0).In addition,no production by stimulated chicken PBMCs and RAW 264.7 macrophages exhibited individually the linear relations with the concentration of PE extracts,and they were approximately 65μM and 45 p.M in 1600μg/mL,respectively.The tendency with the release of TNF-αby RAW 264.7 maerophages also corresponded with concentration of PE extracts.It is concluded,PE extracts act as an immunostimulant for both tested cells but have no serious effect on inhibiting chicken PBMCs viability,and therefore it may be suggested as immune supplements for broilers.
