Fu-Yuan Dong
,
Peng Zhang
,
Jian-Chao Pang
,
Qi-Qiang Duan
,
Yi-Bin Ren
,
Ke Yang
,
Zhe-Feng Zhang
金属学报(英文版)
doi:10.1007/s40195-016-0370-9
Three high-nitrogen stainless steels with different N contents were successfully processed by equal-channel angular pressing for one pass, and their microstructures and mechanical properties were investigated. It was found that the microstructure of the billet was heterogeneous across the billet thickness, resulting in the difference in the mechanical properties due to the different deformation conditions. A relatively low strength, high uniform elongation, and high work-hardening rate for the samples at the bottom of the billet was achieved in comparison with those processed at the top. Meanwhile, it was observed that the density of deformation twins increased with the content of N; accordingly, the strength and elongation of the alloys increase with the content of N, resulting in a good strength-ductility combination.
关键词:
High-nitrogen
,
stainless
,
(HNS)
,
steels
,
Equal-channel
,
angular
,
pressing
,
(ECAP)
,
N
,
content
,
Twinning
,
Strength
,
Ductility
金属学报(英文版)
The effects of Zr on the microstructures and mechanical properties of microalloyed steels have been investigated by mechanical tests and microstructural observations. The microstructures in the Zr-doped steels are ferrite plus pearlite, which is similar to those in the Zr-free steel. With the increase in the Zr content, the lamellar structure reduces and even disappears. Sulfides and silicates that exist in the Zr-free steel are modified into fine oxides in the Zr-bearing steel. When the Zr contents range from 0.01wt% to 0.03wt%, the low temperature toughness of the steel can be substantially improved while its room-temperature strength and ductility have no apparent change. The refinement of ferrite grain size by the addition of zirconium is one of the main reasons for this toughness improvement.
KEY WORDS zirconium; microalloyed steel; microstructure; mechanical property
20060010
A novel semi-solid slurry-making process was developed, which was a controlled nucleation and growth technique using a specially designed rotational barrel. Experimental study was undertaken to investigate the effects of pouring temperature and rotation speed of barrel on the microstructure of A356 alloy. Localized rapid cooling, combined with vigorous mixing during the initial stage of solidification enhanced wall nucleation and nuclei survival. High nuclei density combined with a much gradual cooling afterwards led to the formation of the near-ideal semi-solid slurry under a large processing window for the pouring temperature. Primary phase presented in mean equivalent diameter of 50-70μm and shape factor of 0.812-0.847, and featured zero-entrapped eutectic.
KEY WORDS semi-solid processing; nucleation; grains growth; interface stability
20060011
Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding (FSW) was investigated through pole figure measurement and X-ray diffraction (XRD) pattern analysis. It was found that at the top and bottom surfaces of friction stir zone (FSZ), (0002) basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and (0002) basal planes showed a random distribution.
关键词:
zirconium
,
Microalloyed
,
steels
,
Microstruc
P.Parameswaran
材料科学技术（英）
Electron enregy loss spectroscopy (EELS) and energy filtering transmission electron microscopy (EFTEM) investigation on 2.25Cr-1Mo steel was carried out to understand the nature of evolution of secondary carbides. The filtered images obtained from two different ageing treatments indicate that the steel evolves to a more stable carbide namely M23C6 in comparison to M2C. Microchemical information was generated from EELS spectra. Suitable choice for estimating the microchemical state was discussed. To evaluate the behaviour of ageing an elemental ratio of Fe to Cr is employed.
关键词:
Ferritic steels
,
Steels
,
2.25Cr-1Mo
,
steels
,
EFTEM
Kai LIU
材料科学技术（英）
The 18%Ni alloy steels provide high strength and toughness, while age-hardenable or PH stainless steels also have good corrosion resistance. This paper focuses on an investigation of the heat treatment, mechanical properties and microstructural development of a new maraging stainless steel. It is reported that the heat treatment process should consist of solution treatment and cryogenic cooling to attain a fully martensitic structure, followed by aging at 813 K. This heat treatment resulted in an ultimate tensile strength of over 1900 MPa combined with good impact toughness. Transmission electron microscopy is used to show that, for the peak-aged condition (813 K/4 h), nano-sized precipitates, e.g. Ni3Mo and/or R-phase, and a high density of dislocations were uniformly dispersed in the lath martensite matrix. The calculated yield strength, based on a revised Orowan mechanism, is in good agreement with the test data. The steel studied has an ultimate tensile strength over 1900 MPa, excellent fracture toughness, and good resistance against over-aging and relatively good corrosion resistance as well.
关键词:
Maraging stainless steels
,
steels
,
Precipitation
,
High
,
stren
K.M.Wu
金属学报(英文版)
lntragranular ferrite was formed at inclusions in a vanadium microalloyed steel with excess amount of sulfur. The chemical composition of inclusions in the steel was analyzed by SEM-EDS. The inclusions were mainly composed of MnS and aluminum oxides. The precipitation of MnS at aluminum oxides might result in Mn depletion, which, in turn, promotes the formation of intragranular ferrite. Optical and SEM observations and threedimensional (3D) reconstruction demonstrated that intragranular ferrite was formed at inclusions. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite was nearly equiaxed whereas it was plate-like or lath-like at lower temperatures.
关键词:
steels
,
null
,
null
胡锋
,
周立新
,
张志成
,
张国宏
,
吴开明
中国材料进展
doi:10.7502/j.issn.1674-3962.2015.07.15
微纳结构超高强度钢是兼具高强度、高塑性和高韧性的一类重要高性能钢铁结构材料.超细马氏体、贝氏体组织对于其强度起了决定性作用,对塑性和韧性起决定作用的为残留奥氏体.因此,如何通过调整化学成分和热处理工艺等手段调控残留奥氏体微结构,来实现精细组织结构和优良综合力学性能,成为新一代钢铁材料研究领域重要的课题.首先从钢铁材料强韧化机制出发,指出微观组织的精细化及硬相与软相的合理调控,是发展新一代钢铁材料的重要途径.然后针对近年来发展起来的超级贝氏体钢、Q&P钢、Q-P-T钢等具有微纳组织结构的超高强度钢,从合金设计、热处理工艺及组织结构与力学性能、磨损性能和疲劳性能的关系等方面进行综述与分析,最后指出微纳结构超高强度钢有待进一步深入研究与开发的问题.
关键词:
钢铁材料
,
相变
,
贝氏体
,
马氏体
,
残留奥氏体
张亚明
,
李美栓
腐蚀科学与防护技术
对4种不同级别的钢在600℃～800℃氧化和海水淬冷 交替作用下的循环腐蚀行为进行了研究.在实验条件下，绝大多数材料均发生了严重的氧化 .特别在800℃下，所有材料氧化失重明显.材料施加渗Al涂层后，极大地改善了它们的抗 氧化性能，且材料级别越低，改善作用越明显.海水中的NaCl对材料的高温腐蚀有显著的加 速作用，造成渗Al涂层快速退化.循环淬冷造成渗Al涂层外层发生开裂，且在蒸馏水中比在 海水中淬冷时形成的裂纹数量多且宽度大.
关键词:
钢
,
aluminide coatings
,
oxidation
王振尧
,
于国才
,
韩薇
腐蚀科学与防护技术
通过大气暴露试验和实验室的浸渍干燥湿润复合循环试验，结合腐蚀产物的表面分析，研究了4种钢在沈阳地区的大气腐蚀规律和模拟大气腐蚀过程的腐蚀规律.结果表明：在大气暴露试验和室内模拟加速腐蚀试验中，4种钢的腐蚀产物都具有不同程度的保护性，腐蚀规律可用ΔW=Ktn公式描述，室内外腐蚀试验结果有较好的相关性.采用001 mol/L NaHSO3+0.001 mol/L NaCl介质为加速剂, 通过干湿复合
循环试验,可模拟钢在沈阳大气环境中的腐蚀过程，近似推测户外长期暴露试验的结果.
关键词:
钢
,
atmosphericcorrosion
,
accelerated corrosion tes
