FRECKLE FORMATION AND CHARACTERIZATION OF A Ni-Cr-Mo-Fe-W ALLOY

The freckle formation and their phase characterization in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in a Ni-Cr-Mo-Fe-W alloy. These results show that in freckle areas a large number of M6 C, u and P phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and C during solidification, which results in small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give an reasonable interpretation of the freckle feature for this alloy.     

原子荧光光谱法测定祛斑霜中的汞

采用盐酸处理祛斑霜样品，用还原气化-原子荧光光谱法测定其中的汞，研究了仪器测定条件和不同样品处理方法对测定的影响。结果表明样品处理方法对测定结果影响不大；此方法的加标回收率在96％以上，相对标准偏差为2．5％；此方法具有快速、简便和灵敏的特点。     

PHASE TRANSFORMATION AND CHARACTERISTICS IN FRECKLE AREAS FOR INCONEL 625 SUPERALLOY

The freckle formation and their phase characterizatics in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in an lnconel 625 alloy. These results show that in freckle areas a large number of M6C, MC, Laves and 8 phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and Nb during solidification, which results in almost of these freckle areas covered by these complex precipitated phases and induces small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give a reasonable interpretation of the freckle feature for this alloy.     

2011-2016年贵州省市售化妆品汞含量测定研究

对2011—2016年贵州省市售多类化妆品中汞含量进行检测分析,以了解全省市售化妆品中汞的分布情况,并分析其安全风险。实验采用微波消解法对样品进行预处理,氢化物原子荧光光度法对样品中的汞含量进行测定。结果表明,832批次样品中512批次检出汞,检出率61.5%;40批次样品汞含量超过国家标准,超标率4.8%;研究出现汞超标的样品中,国产宣称美白或祛斑类产品超标率最高,为11.5%,该类超标产品中83.3%超过国家标准1 000倍。     

偏析对DZ483镍基高温合金糊状区内液相密度的影响

为研究DZ483合金在凝固过程中的元素偏析行为对糊状区内液相密度的影响,采用等温凝固结合水淬法对合金进行不同温度下的凝固实验.利用OM和SEM观察试样的凝固组织,利用EDS测量固相和剩余液相的元素含量,并根据剩余液相的成分计算其密度.结果表明,DZ483合金的开始凝固温度略低于1335℃,在1325℃液相中开始析出富含Ta和Ti的MC;W和Co为负偏析元素,Mo,Ta和Ti为正偏析元素,而Al和Cr几乎不发生偏析;剩余液相的密度随温度降低基本呈下降趋势,但在1325至1315℃之间有所回升.计算结果表明,温度对液相密度的影响很小,合金元素的偏析对液相密度的影响占主要地位.其中,Mo和Ta的偏析导致液相密度增加,而Ti和W的偏析导致液相密度明显降低.备合金元素的偏析对密度变化的贡献由大到小顺序为:Ti>Ta>W>Cr>Mo>Al>Co.MC的形成消耗了大量的Ti和Ta,对合金元素的偏析造成一定的影响,从而导致液相密度在1325至1315℃之间有所增加.     

镍基高温合金定向凝固斑点偏析的数值模拟研究

为了研究铸造高温合金中的斑点偏析，建立了描述多元合金凝固过程传输行为的数学模型。基于伪二元相图方法，模型给出了液相线温度与固相分数及液相多元溶质浓度的耦合关系式。利用该模型对Ni-5．8Al-15．2Ta（质量分数，％）合金铸锭的垂直定向凝固过程进行了模拟。结果表明：该模型能够反映多组元镍基高温合金凝固过程中斑点偏析的形成及发展过程。凝固界面前沿附近热-溶质双扩散对流引起的密度倒置，是诱发斑点偏析的主要原因。在糊状区中形成的偏析通道中，富集溶质从糊状区流向液相区，通道周围局部流动可以通过糊状区从液相区补充通道中的流动。凝固初期形成的通道不能稳定存在，多个通道合并促使局部凝固前沿优先生长，最终形成稳定的偏析通道。     

Ni—Cr—Mo—Fe—W合金中宏观“黑斑”缺陷特征的形成

采用晶萃取碳复下基层等实验技术，研究了Ｎｉ－Ｃｒ－Ｍｏ－Ｆｅ－Ｗ合金宏观”黑斑”缺陷特征的微观形成机制。该合金中“黑斑”缺陷的形成归因于钨、钼等元素在这里 。富集的钨钼元素主要以数量较多，尺寸较大的富含钼，钨的Ｍ６Ｃ和Ｐ相的形式存在于晶界上，使“黑斑”区的晶粒细小、晶界易受侵蚀且弱化。     

Numerical simulation of vacuum arc remelting nickel based superalloy

Based on the process in a special steel plant, the vacuum arc remelting process of nickel based superalloys was simulated to investigate the effect of current intensity, melting rate, and helium gas cooling on macrosegregation of Nb and formation of freckles. The ingot has severe macrosegregation in the upper and 1/4 part of the ingot. With the current intensity increasing, the magnetic field in the upper part of the ingot increases, and macrosegregation and freckles increase gradually both in the upper and 1/4 part of the ingot. With the melting rate increasing, the depth of the molten pool increases, the macrosegregation of Nb increases in the upper part of the ingot, and the freckles increase significantly in the 1/4 part of the ingot. When helium is introduced into the ingot during smelting, the cooling rate increases greatly, the macrosegregation and freckles reduce significantly in the ingot, and the maximum segregation position moves to the top of the ingot.     

团状模塑料注塑成型"花斑"缺陷分析

本文从材料性能、注塑工艺、模具结构以及真空设备等方面分析了团状模塑料（Bulk Molding Composite简称BMC）注塑成型制品的“花斑”缺陷产生的原因与机理。     

GH169合金制件中黑斑和白斑偏析的超声检验

通过对所搜集到自然缺陷试样的超声检验，研究ＧＨ１６９合金中黑斑和白斑偏析的可探性。