M23C6 chromium-rich carbides are common grain-boundary precipitations in Cr-containing steel.The presence of grain-boundary carbides often leads to intergranular brittleness and decreases mechanical properties.This st...M23C6 chromium-rich carbides are common grain-boundary precipitations in Cr-containing steel.The presence of grain-boundary carbides often leads to intergranular brittleness and decreases mechanical properties.This study proposes a deformation and aging technique to obtain a high-volume-fraction dispersion distribution of the hard nano-M23C6 phase by changing the nucleation sites from grain boundaries to deformation coherent twin boundaries produced during cold deformation.The M23C6 precipitation-strengthened austenitic stainless steel has a strength of up to 1.4 GPa but maintains favorable plasticity(>11%).This study provides a novel approach for the control of intergranular brittleness in metallic materials.展开更多
用金相显微镜、定量金相、扫描电镜(SEM)、能谱分析(EDX)及 X 射线衍射(XRD)研究了 0%,4%,6%Ta(质量分数) 3 种成分的低 Cr 高 W 铸造镍基高温合金铸态及热暴露后的显微组织,结果表明:Ta 是强 MC 碳化物形成元素,它形成 MC 碳化物的倾...用金相显微镜、定量金相、扫描电镜(SEM)、能谱分析(EDX)及 X 射线衍射(XRD)研究了 0%,4%,6%Ta(质量分数) 3 种成分的低 Cr 高 W 铸造镍基高温合金铸态及热暴露后的显微组织,结果表明:Ta 是强 MC 碳化物形成元素,它形成 MC 碳化物的倾向低于 Nb、高于 Ti,当合金中 Ta 的原子百分含量超过 Nb 3 倍时,Ta 在 MC 碳化物中的原子百分含量超过 Nb。Ta 是强γ′形成元素,它促进共晶γ′的形成,在合金成分中以等量原子百分含量的 Ta 代替 Al 不会改变合金的共晶γ′数量。在高 W 铸造高温合金中 M6C 是比 MC 更加稳定的碳化物,Ta 的加入不能抑制 1 100℃,500 h 长时热暴露后 MC 完全转变为粒状或片状 M6C。MC 分解时释放的碳还促使α(W,Mo)+C→M6C 反应。对 Ni-1.5Cr-10Co-16W-2Mo-5Al-1Ti-1Nb 基础成分合金,其最佳的含 Ta 量为 4% (质量分数),而且含碳量应低于 0.07%(质量分数)。展开更多
Creep rupture of the reduced activation ferritic/martensitic(RAFM)steel and 316L steel dissimilar joint by friction stir welding was investigated.The creep rupture time of the dissimilar joint was 1941 h at 600℃/100 ...Creep rupture of the reduced activation ferritic/martensitic(RAFM)steel and 316L steel dissimilar joint by friction stir welding was investigated.The creep rupture time of the dissimilar joint was 1941 h at 600℃/100 MPa and 120 h at 650℃/100 MPa.The creep fracture occurred in heat affect zone(HAZ)of RAFM steel side where coarse Laves phase was detected.The formation and coarsening of the Laves phase particles in HAZ of RAFM steel side were the main reasons that caused the creep fracture of the dissimilar joint.The Laves phase particles nucleated adjacent to the large M_(23)C_(6) particles at the grain boundaries where W element segregated and grew fast during creep exposure.The large Laves phase would deteriorate the pinning effect of M_(23)C_(6) carbides and weaken the solid solution strengthening effect.Besides,the size of the Laves phase in HAZ of RAFM steel side was bigger than that in stir zone of RAFM steel side.These reasons explain the creep fracture in HAZ of RAFM steel side of dissimilar joint.展开更多
The precipitation behavior of carbide in K416 B superalloy was investigated by means of creep measurement and microstructure observation. The results show that nanometer M6 C particles discontinuously precipitate in t...The precipitation behavior of carbide in K416 B superalloy was investigated by means of creep measurement and microstructure observation. The results show that nanometer M6 C particles discontinuously precipitate in the γ matrix or along the γ/γ′ interface of the alloy during high temperature tensile creep. Thereinto, the amount of fine M6 C carbide increases as creep goes on, and the coherent interfaces of M6 C phase precipitating from the γ matrix are {100} and {111} planes. The thermodynamics analysis indicates that the solubility of element carbon in the matrix decreases when the alloy is deformed by the axial tensile stress during creep, so as to cause the carbon segregating in the regions of stress concentration and combining with carbide-forming elements M（W, Co）, which promotes the fine M6 C carbide to precipitate from the γ matrix.展开更多
基金supported by the National Natural Science Foundation of China(No.52250130).
文摘M23C6 chromium-rich carbides are common grain-boundary precipitations in Cr-containing steel.The presence of grain-boundary carbides often leads to intergranular brittleness and decreases mechanical properties.This study proposes a deformation and aging technique to obtain a high-volume-fraction dispersion distribution of the hard nano-M23C6 phase by changing the nucleation sites from grain boundaries to deformation coherent twin boundaries produced during cold deformation.The M23C6 precipitation-strengthened austenitic stainless steel has a strength of up to 1.4 GPa but maintains favorable plasticity(>11%).This study provides a novel approach for the control of intergranular brittleness in metallic materials.
文摘用金相显微镜、定量金相、扫描电镜(SEM)、能谱分析(EDX)及 X 射线衍射(XRD)研究了 0%,4%,6%Ta(质量分数) 3 种成分的低 Cr 高 W 铸造镍基高温合金铸态及热暴露后的显微组织,结果表明:Ta 是强 MC 碳化物形成元素,它形成 MC 碳化物的倾向低于 Nb、高于 Ti,当合金中 Ta 的原子百分含量超过 Nb 3 倍时,Ta 在 MC 碳化物中的原子百分含量超过 Nb。Ta 是强γ′形成元素,它促进共晶γ′的形成,在合金成分中以等量原子百分含量的 Ta 代替 Al 不会改变合金的共晶γ′数量。在高 W 铸造高温合金中 M6C 是比 MC 更加稳定的碳化物,Ta 的加入不能抑制 1 100℃,500 h 长时热暴露后 MC 完全转变为粒状或片状 M6C。MC 分解时释放的碳还促使α(W,Mo)+C→M6C 反应。对 Ni-1.5Cr-10Co-16W-2Mo-5Al-1Ti-1Nb 基础成分合金,其最佳的含 Ta 量为 4% (质量分数),而且含碳量应低于 0.07%(质量分数)。
基金supported by the National Natural Science Foundation of China(52034004).
文摘Creep rupture of the reduced activation ferritic/martensitic(RAFM)steel and 316L steel dissimilar joint by friction stir welding was investigated.The creep rupture time of the dissimilar joint was 1941 h at 600℃/100 MPa and 120 h at 650℃/100 MPa.The creep fracture occurred in heat affect zone(HAZ)of RAFM steel side where coarse Laves phase was detected.The formation and coarsening of the Laves phase particles in HAZ of RAFM steel side were the main reasons that caused the creep fracture of the dissimilar joint.The Laves phase particles nucleated adjacent to the large M_(23)C_(6) particles at the grain boundaries where W element segregated and grew fast during creep exposure.The large Laves phase would deteriorate the pinning effect of M_(23)C_(6) carbides and weaken the solid solution strengthening effect.Besides,the size of the Laves phase in HAZ of RAFM steel side was bigger than that in stir zone of RAFM steel side.These reasons explain the creep fracture in HAZ of RAFM steel side of dissimilar joint.
基金Projects(2010CB631200,2010CB631206)supported by the National Basic Research Program of ChinaProject(50931004)supported by the National Natural Science Foundation of China
文摘The precipitation behavior of carbide in K416 B superalloy was investigated by means of creep measurement and microstructure observation. The results show that nanometer M6 C particles discontinuously precipitate in the γ matrix or along the γ/γ′ interface of the alloy during high temperature tensile creep. Thereinto, the amount of fine M6 C carbide increases as creep goes on, and the coherent interfaces of M6 C phase precipitating from the γ matrix are {100} and {111} planes. The thermodynamics analysis indicates that the solubility of element carbon in the matrix decreases when the alloy is deformed by the axial tensile stress during creep, so as to cause the carbon segregating in the regions of stress concentration and combining with carbide-forming elements M（W, Co）, which promotes the fine M6 C carbide to precipitate from the γ matrix.
基金National Natural Science Foundation of China(51171116)Ministry of Science and Technology of the People's Republic of China(Grant No.2009DFB50350)+1 种基金Research Foundation of Education Bureau of Hubei Province,China(Grant No.Q20122304)Doctoral Starting up Foundation of Hubei Universityof Automotive Technology,China(Grant No.BK201205)
