Kai LIU
材料科学技术（英文）
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
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Precipitation
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High
,
stren
P. Fernandez G. Gonzalez I. Alfonso I.A. Figueroa
材料科学技术（英文）
Two ternary Al-2.2Zn-0.95Mg and Al-5.5Zn-2.1Mg (in wt pct) alloys, with Zn:Mg ratios close to 2.5 were produced by conventional ingot casting metallurgy. The ingots were solution heat treated at 500°C for 0.5 h and aged at 180°C for times between 0.5 and 80 h. The structural characterization was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Vickers microhardness measurements (HV). The study was focused on the investigation of the precipitates formation and the relationship between hardness and lattice parameter for α-Al. The results showed that there was an inverse correlation for all the experimental conditions, and the aged peaks coincided with lattice parameter minima. Significant precipitates formation only occurred for the alloy containing 5.5 wt pct Zn and 2.1 wt pct Mg, provoking an important strengthening and variations in the lattice parameter, however, this was not observed for the alloy containing 2.2 wt pct Zn and 0.95 wt pct Mg. A plausible explanation of the increment of hardness values could be the presence of a well distributed μ phase (MgZn2). At initial stages of the precipitation process, μ' was the most abundant precipitate while the phase τ was observed at overaged conditions. These results showed that the aging response of the conventionally cast Al-Zn-Mg alloys could be obtained using the lattice parameter of the α-Al matrix, even for alloy systems with low precipitates formation.
关键词:
Aluminum alloy
,
X-ray diffraction
,
Precipitation
,
Lattice parameter
,
Hardness
A.A.Al-Aql
,
M.S.Al-Salhi
,
M.I.Ansari
材料科学技术（英文）
Precipitation study was carried out in Ni-35 at. pct Cr alloy by measuring electrical resistivity at different ageing temperatures and long ageing times. During ageing, it was observed that electrical resistivity initially rose with ageing time and then fell after very long ageing at a constant temperature. The initial increase in resistivity during ageing may be attributed to the formation of GP zones/Cr-rich precipitates at early stages by nucleation process and decrease in resistivity, and after attaining a maximum, is due to the growth of precipitate particles and subsequently by coarsening of these precipitates. The results of electrical resistivity measurements during ageing were confirmed by X-ray diffraction analysis indicating the formation of a Cr-rich phase and a Cr3Ni2 phase in the Ni matrix.
关键词:
Precipitation
,
null
,
null
,
null
,
null
赵晓丽
,
李玲霞
,
王春芳
,
王昌
钢铁
对2209双相不锈钢焊缝在690℃进行不同时间时效处理,采用了透射(TEM)、相分析、冲击测试等手段,研究了析出相的形貌、分布及其类型和含量以及析出相对冲击功的影响.结果表明,析出相为M23C6和σ相,主要在铁素体和奥氏体晶界和铁素体内析出.随着时效时间的延长,析出相逐渐长大并增多,冲击功逐渐降低.在扫描电镜下观察冲击断口形貌为韧窝和准解理,断裂类型由韧性到脆性断裂.
关键词:
双相不锈钢
,
焊缝
,
时效时间
,
析出相
,
冲击性能
张云
,
范必威
,
彭达平
稀有金属
doi:10.3969/j.issn.0258-7076.2001.02.018
进行了酸浸石煤萃取液铵盐直接沉钒的工艺研究，对沉钒的主要影响因素，如加铵系数、溶液 pH值、沉钒时间、温度等均进行了详细实验，得出了合理的沉钒工艺参数：在 pH=4.0，加铵系数 3.5；沉钒时间 60～90 min， 以及温度不低于 80℃的条件下，从含钒 16～20 g/L 的萃取液中沉钒，沉钒率可达 98% 以上，产品质量达国家标准。研究还表明，由于 SO42-，CO32-，Na＋，Cl- 等的影响，从酸浸石煤萃取液沉钒与从水浸液沉钒相比，一些工艺参数如 pH、KNH3 等有较大差别。
关键词:
沉淀
,
五氧化二钒
,
萃取
,
石煤
,
酸浸
王亚松
,
徐云鹏
,
李大伟
,
刘浩
,
厉晓蕾
,
陶硕
,
田志坚
催化学报
doi:10.1016/S1872-2067(14)60278-3
基于沸石咪唑骨架材料在离子液体和低共熔溶剂中冷却结晶的析出方式，开发了一种离子热法合成沸石咪唑骨架材料的新途径，采用X射线衍射、扫描电镜、核磁共振光谱、红外光谱以及热重分析等方法对制备的产物进行了表征，研究了合成条件对产物结晶度、尺寸和形貌的影响，探讨了沸石咪唑骨架材料在离子热合成体系中的溶解-结晶析出机理。研究发现，冷却速率能够影响产物形貌，急速冷却时， sod (RCSR代码)型产物的形貌为球形， zni (RCSR代码)型产物为棒状或平板状；程序控制冷却时， sod型产物的形貌为多面体， zni型产物呈团簇状。
关键词:
离子热合成
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沸石咪唑骨架材料
,
溶解-结晶机理
,
溶解度
,
冷却析出
包翠敏
,
谭朝鑫
,
庄春瑜
,
陈蕊
材料科学与工程学报
doi:10.14136/j.cnki.issn1673-2812.2016.01.016
本工作研究了时效处理工艺对沉淀强化奥氏体不锈钢J75的显微组织及力学性能的影响.在固定其他热处理工艺参数的情况下,分别对时效温度及时效时间进行研究,结果表明:随着时效温度由600℃升高到760℃,J75钢晶粒度变化不明显,但沉淀强化相的形状和数量均受到影响,强度及硬度在时效温度为720℃时出现峰值;随着时效时间由8h增加到48h,J75钢的显微组织及性能均未发生明显变化.
关键词:
J75钢
,
时效温度
,
时效时间
,
晶粒度
,
强化相
