Nb的非平衡晶界偏聚动力学模拟与实验研究

摘要：Nb是现代高性能钢铁材料中重要的微合金化元素,其在晶界有强偏聚特性。采用3种Nb 空位复合体扩散系数分别对非平衡晶界偏聚进行拟合,根据铁 铌二元合金中Nb在晶界偏聚实验的EPMA测量结果筛选出最终的复合体扩散系数,并据此讨论了低温恒温温度,基体Nb含量,原奥氏体晶粒尺寸对非平衡晶界偏聚动力学的影响,得出了最符合实验结果的铌 空位复合体扩散系数公式。结果表明,在1000℃恒温过程,Nb非平衡晶界偏聚的临界时间在15min左右,临界时间常数为6.57×105。从1200℃固溶态冷却至某低温等温时,随着等温温度的升高临界时间迅速减小,Nb在晶界的最大偏聚量逐渐越小;随着基体Nb含量增加晶界Nb的最大偏聚量线性增加;随着原奥晶粒尺寸的增加临界时间逐渐增大。     

超低碳钢在铁素体生长过程中硼分布的变化

通过对照显微结构与硼的自射线径迹显微照相（ＰＴＡ）,研究了一种超低碳含硼钢在铁素体生长过程中硼分布的变化,发现：在发生等温铁素体相变前,硼已偏聚在奥氏体晶界上;铁素体在奥氏体晶界形核;在有铁素体生成的奥氏体晶界上,硼偏聚减弱;沿晶界长出的小块铁素体中硼浓度明显高于奥氏体,但随铁素体长大,其硼含量逐渐与母相持平。这些现象表明,铁素体长大不受硼在奥氏体中扩散的控制     

超低碳贝氏体钢快速加热奥氏体长大过程中移动晶界上硼的反常偏聚

利用径迹显微照相技术研究了超低碳贝氏体钢焊接热影响区在焊接热循环快速加热过程中硼在奥氏体晶界上的偏聚行为。发现以高密度位贝氏体为原始组织的材料进行快速加热时，新形成的奥氏体晶粒边界上在很高温度下仍会出现反常的晶界硼偏聚。用晶界位错驰原制对这种新的非平衡现象进行了讨论。     

硼在18Ni(2450MPa)马氏体时效钢细化晶粒中的作用

本文研究了含微量硼元素的18Ni马氏体时效钢细化晶粒的方法并指出:在860℃,1h固溶化后,缓慢冷却(炉冷)的基础上,经冷变形后,在700℃预加热和820℃最终固溶处理,可以获得超细化的奥氏休晶粒。其中,硼元素偏聚到再结晶奥氏体晶界上,阻止晶粒长大,是获得细化晶粒效果的决定因素。     

1Cr18Ni9Ti不锈钢中的硫与晶界沉淀

硫含量较低时，９００℃加热后晶界只存在片状ＴｉＣ（和Ｔｉ（ＣＮ））；硫含量较高时，晶界还存在片状Ｔｉ２ＳＣ；１１００加热时，晶界Ｔｉ２ＳＣ片较大、较厚。实验钢中的Ｔｉ２ＳＣ存在关睛种与以前的研究不尽相同的沉淀机制，在９００℃加热时及其后的冷却过程中和６５０℃加热时，点阵中的Ｔｉ、Ｓ和Ｃ向晶界偏聚，Ｔｉ２ＳＣ以片状和粒状沿晶界沉淀。敏化处理时，硫含量较高的钢中，偏聚到晶界的硫原子可能抑制晶界Ｃｒ２３     

2.25Cr-1Mo合金钢回火脆化过时效现象的研究

研究了2.25Cr-1Mo合金钢在回火温度下时效处理时,发生回火脆化和回火脆化的过时效反偏聚现象。应用非平衡偏聚的动力学理论,确定了成分(%)为0.15C、2.32Cr、0.95Mo、0.009P的2.25Cr-1Mo合金钢在650℃140 h回火时钢中磷的非平衡晶界偏聚规律。试验得出,2.25Cr-1Mo合金钢650℃磷非平衡偏聚的临界时间t_c为20 h,晶界磷的原子浓度,由初始状态的0.016%提高至最大值2.79%。根据试验数据进行的动力学计算,得出的计算曲线与试验结果吻合,验证了非平衡晶界偏聚空位-复合体模型的扩散机制。     

Gleeble模拟热轧工艺对磷非平衡晶界偏聚的影响

 采用Gleeble 3500热模拟试验机研究了轧制和卷取温度下磷元素晶界偏聚与热轧板高温热塑性的关联机制。研究结果表明,含磷钢中磷元素晶界偏聚符合空位-磷原子复合体非平衡共偏聚理论,800 ℃以上轧制温度对磷元素晶界偏聚引起的钢板脆性影响较小,而在500～650 ℃温度范围存在磷元素偏聚导致的热塑性低谷区,且在该温度区施加1%拉伸预应变将加剧磷元素晶界偏聚和钢板脆性。因此,本试验成分含磷钢热轧生产中卷取温度设定应避免550 ℃塑性低谷。     

CSP线SPA-H表面裂纹与加热制度关系的研究

采用光学显微镜、扫描电镜、马弗炉等设备对CSP线SPA-H铸坯不同加热温度、加热时间、保温时间条件下表面裂纹的密度、深度、氧化圆点层等进行了研究,结果表明:原始板坯或不同加热条件下,试样氧化层内均出现不同程度的Cu富集,并且随着温度的增加,界面不平直度明显增加,氧化圆点层增厚。在1000～1080℃之间,在基体界面处有大量的铜的富集相,以分散或半连续式分布,在界面基体的晶界也发现有铜的偏聚;在1110℃保温30min时,随着Cu的熔解,界面处的铜向氧化层和基体内渗透,界面处富铜相较于其熔融温度下的少,而氧化层和氧化圆点层中的Cu富集相以及偏聚增多;试样温度加热至1140℃时,Cu富集相大多分布于离界面20μm的氧化层内,以及氧化圆点层的晶界和氧化圆点界面处偏聚,氧化层与基体界面处只存在极少的Cu的富集相;试样温度加热至1200℃时,Cu的富集相集中在氧化层中,晶界处的Cu扩散至奥氏体内,减少了晶界的弱化作用。     

18Ni马氏体时效钢的热塑性试验

用热模拟试验机研究了18Ni钢焊接接头半熔化区的韧性,测定了18Ni钢热塑性曲线.文章认为半熔化区韧性较低的原因是由于热循环温度高于1300℃或试样从高温缓慢冷却到700℃时,晶粒明显粗大化以及脆性相和杂质元素在晶界偏聚,致使晶界性能变坏试样呈沿晶断裂.     

铁镍合金中硼原子-空位复合体扩散系数的计算

提出一种计算溶质原子-空位复合体扩散系数的方法.该方法通过分析晶界偏聚过程中溶质原子.空位复合体的扩散机制,建立溶质原子-空位复合体变温扩散方程,以实验测定的连续冷却过程偏聚阶段溶质贫化区宽度为已知条件,数值求解溶质原子.空位复合体扩散系数.将此方法应用于含硼1×10-5%(质量分数)Fe-40%Ni-B合金体系,得到硼原子-空位复合体扩散系数为8.0×10-7exp(-1.28/KT)(m2·s-1).     

China's Major Non-ferrous Metals Imports & Exports

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Zinc Production by Province in 2014

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80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.     

Seven Rare Earth Projects Involving Close to 3 Billion Yuan Investment Landed In the HighTech Zone

正On May 22,Baotou Rare Earth Industry Cooperation Consultation MeetingProject Agreement-signing Ceremony was held in Ningbo,nearly 40 enterprises from Ningbo,Guangdong,Hunan,and Shanxi participated in project consultation.After multi-lateral communication,agreements were signed for a total of 7 rare earth projects successfully.