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针对某钢厂生产的38B3汽车用钢,探伤时发现棒材表面有纵向裂纹的现象,采用金相显微镜和扫描电镜对裂纹试样进行观察和分析,结果表明,38B3汽车用钢棒材表面纵裂纹的产生,主要是由于A1、Si、Na等氧化物夹渣分布于连铸坯的表层下面,在轧制过程中由于应力作用沿Al、Si、Na等氧化物夹渣集中处产生裂纹.通过采取相应的措施改善工艺以获得高质量的铸坯.     

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 应用分形理论探讨了钢液中凝聚态夹杂物的性质、凝聚规律及上浮特性。结果表明：两个源碰撞夹杂物颗粒碰撞连结的方式不同,所生成的新凝聚态夹杂物颗粒的形貌特征和分形维数就可能存在较大差异;带有分形特征的凝聚态夹杂物的上浮速度要小于等体积三维球状实体夹杂物的上浮速度;新生凝聚态夹杂物的分形维数相对源碰撞夹杂物较小,所以对凝聚成的大尺寸夹杂物颗粒要对其加强重构,使其变得致密,增大其分形维数,有利于提高其上浮速度;分形维数的测定可以更精确地定量描述夹杂物的形貌特征,完善夹杂物检测的标准。     

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 针对焊接接头不能通过落锤检验问题,对钢轨母材和焊接接头进行取样,采用SEM、硬度、冲击、拉伸等分析方法,对比母材和焊接接头相同部位的断口微观形貌、金相组织、硬度、冲击性能和拉伸性能;采用网格法对夹杂物进行计量分析。结果发现,母材基体存在元素偏析,母材和焊态钢轨里存在大量分布极不均匀的非金属夹杂物;母材硬度波动大、冲击性能低、强度高、韧性差;采用正常焊接工艺所得到的接头力学性能有所提高,但品质不稳定;局部夹杂缺陷是引起钢轨断裂的本质原因。     

高Cr铸造镍基高温合金K4648的母合金净度研究

对两炉冲击韧性存在明显差异的高Cr铸造镍基高温合金K4648进行了对比研究,通过分析两炉母合金的主量元素和气体含量,采用电子束纽扣锭(EB锭)实验观察合金内夹杂物和对母合金用原材料金属Cr的显微组织分析等方法研究了K4648母合金净度。结果表明:1#与2#炉批母合金主量元素无明显差别。1#母合金由于气体元素O含量高达(20.5±7.5)×10-6,远高于2#合金的6×10-6,造成其室温冲击韧性(aku)不及2#合金的一半,低于技术条件要求的19.6J/cm2。电子束纽扣锭(EB锭)实验可有效地将K4648中的夹杂物汇聚,经分析主要是富Y,Ce的氧化物和富Al氧化物。证明高Cr铸造镍基高温合金K4648中添加稀土元素Y,Ce可有效攫取合金中自由态的O和S,生成稳定的稀土氧化物或硫化物,起到净化合金的作用。K4648母合金原材料中金属Cr基体中固溶有15%(质量分数)的元素O,还分布有富Cr氧化物和Cr,Al,Si的复合氧化物。此外,还存在含N、贫O区域,该区域的维氏显微硬度可达8.2GPa,是Cr基体1.3GPa的6倍,证明N使金属Cr的硬度明显升高。     

Structural characterization of amylose-long chain fatty acid complexes produced via the acidification method

Amylose molecular inclusion complexes, or V-amylose, have been studied as a possible nano-sized delivery system for unsaturated fatty acids. This study aimed to study three different structural levels of V-amylose produced via an acidification method. Molecular attributes were studied using XRD, DSC and ¹³C CP/MAS NMR, nanostructures using SAXS and AFM, and the microscopic level by SEM and AFM. ¹³C labeled fatty acids revealed head groups were entrapped in both COO- and COOH forms. SAXS data, showed that conjugated linoleic acid yield particles with the highest values for parameters like average crystalline lamellar thickness (φ = 0.46) and characteristic particle dimension (R_g = 1011). AFM revealed surface roughness increases from 7.72 ± 4.34 nm to 11.54 ± 6.05 nm during the formation of V-amylose. The insights described contribute to the understanding of V-amylose structure and help establish a model for V-amylose structure which may prospectively be used in the fabrication of a novel delivery system.     

过共析钢中TiN夹杂形成热力学分析

根据过共析钢(特别是碳质量分数为0.90%~0.95%的钢种)凝固过程氮钛元素的溶质再分配机制,对钢中TiN夹杂的形成进行热力学计算。结果表明:随着钢中碳质量分数的增加,在凝固前沿液相形成TiN夹杂所需的氮钛浓度积逐渐降低,同时各钢种都是在凝固后期(固相分数在90%以上)达到形成TiN夹杂的热力学条件。在最后凝固区域,由于钢液补缩不充分,钢的组织出现不同程度的疏松,造成TiN夹杂与钢坯疏松共存的现象。为控制碳质量分数为0.90%~0.95%的钢种中的TiN夹杂,需要进一步降低凝固前沿液相中氮钛浓度积。     

热镀锌钢板表面夹杂缺陷的分析

主要对热镀锌钢板表面典型夹杂缺陷宏、微观形貌、缺陷区成分进行了分析,研究其形成原因并提出了相应对策。     

铆镙负用铝脱氧的实验研究

对ＺＬ１８Ａ钢进行了用铝脱氧，控制钢中夹杂物和酸铝含量的研究。确定了铝合适加入量范围和影响钢中酸溶铝含量的因素。     

The Nature of Stress and Electric-displacement Concentrations around a Strongly Oblate Cavity in a Transversely Isotropic Piezoelectric Material

In this paper we explore the nature of stress and electric-displacement concentrations around a strongly oblate spheroidal cavity that possesses a finite dielectric permittivity. We start out from Eshelby’s general inclusion method but give specific account on the important class of piezoelectric ceramics whose structure is represented by the 6 mm symmetry. It is found that under axial electromechanical loading these concentrations are governed by a dimensionless parameter η, defined as (k₀/k₃₃)/(c/a), that involves the ratio of the dielectric permittivity of the medium inside the cavity k₀, to that of the transversely isotropic piezoelectric ceramic k₃₃, and the aspect ratio of the cavity c/a. When the medium inside the cavity is an impermeable one it is found that both the axial stress and axial electric displacement can have direct contribution to the concentration factors, but when the medium is a conducting one only the applied stress has an effect on it. Our analysis further indicates that it is the parameter η – not k₀/k₃₃ or c/a alone – that plays the key role here; when η< 0.01, the cavity can be effectively treated as an impermeable one, while for η> 100 it can be treated as a conducting case. Numerical results for several PZT ceramics suggest that under a pure tensile stress the ceramic tends to fracture on the equatorial plane, but under a pure electrostatic load it tends to develop radial cracks normal to the edge of the cavity.     

球墨铸铁中Ti-Ce复合夹杂物的研究

以稀土镁球墨铸铁为研究对象,用扫描电镜观察了其中的夹杂物,并进行元素面扫描分析,结合热力学计算结果和动力学条件,分析了Ti-Ce-S复合夹杂物的形成过程.结果表明,Ti-Ce-S复合夹杂物呈块状,分布在珠光体和铁素体的晶界处,尺寸为3 μm;球化处理过程中,CeS为TiS的形成提供非均匀形核核心,Ce对TiS的还原作用是促进Ti-Ce-S复合夹杂物形成的主要因素,Ti-Ce还与镧、钡、镁等元素复合形成夹杂物,分别是Ti-Ce-La-S、Ti-Ce-Ba-S、Ti-Ce-Ba-Si-S、Ti-Ce-V-C和Ti-Ce-La-Mg-C-N-S复合夹杂物.钛、铈等元素间的充分反应和此类夹杂物的有效去除是保证球化效果的重要因素.