粉末高温合金中夹杂物特性及其质量控制

研究了粉末高温合金中夹杂物特性及对材料断裂行为的影响 ,研究内容包括 :夹杂物的性质及来源、夹杂物在材料变形过程中的形变特征、夹杂物对材料疲劳断裂行为的影响等 ,同时研究了盘件在生产过程中夹杂物质量控制方法 .     

不同成型工艺条件下FGH95粉末高温合金中夹杂物对材料力学性能的影响

本文研究了FGH95粉末高温舍金中夹杂物特性（成分、分类、形貌、尺寸和数量等），及与不同成型工艺的关系，同时研究了合金中夹杂物对合金拉伸、持久和疲劳断裂等力学性能的影响，并提出了制造工艺优选的建议。     

PREP法和AA法制取Inconel 718粉末对比分析

采用等离子旋转电极法和氩气雾化法制备2种Inconel718粉末,对比了2种粉末在粒度、形貌、夹杂和空心粉率等方面的异同。研究结果表明PREP法生产的15μm～53μm的粉末收得率与AA法相当;PREP法制备的粉末形貌为球形,无黏连粉;AA法制备粉末一部分为球形,存在大量非球形粉,且存在黏连粉;PREP法制备的粉末夹杂含量低,夹杂主要为Al2O3、CaO;AA法制备的粉末夹杂含量高,夹杂主要为Al2O3;PREP法制备的粉末内部致密,无颗粒内孔洞;AA法制备的粉末存在颗粒内孔洞。     

夹杂物对粉末高温合金疲劳性能的影响

粉末高温合金FGH95是发动机用的优选材料。通过对该合金的疲劳性能试验和扫描电镜微观观察,发现合金中含有由铝、氧、镁、钛、硅和钇等元素组成的夹杂物。无论室温或者高温条件下,合金的疲劳裂纹源均从夹杂物处萌生,并且夹杂物尺寸越大,距离表面越近,所对应的疲劳寿命越低。     

钢中非金属夹杂物对疲劳性能的影响

本文研究了38CrMoAlA和30CrMnSiA两种钢中所含夹杂物对疲劳性能的影响。研究结果表明:在夹杂物含量基本相同的条件下,夹杂物的大小、形状及分布特徵对疲劳寿命具有明显的影响。夹杂物的颗粒大小直接支配着裂纹的成核与扩展,当夹杂物的平均直径大于40μm时,由夹杂物引起疲劳失效的比率可达95％以上。因此,在控制夹杂物含量的基础上,通过减小夹杂物颗粒尺寸和改变不利的几何形状及分布,可减缓夹杂物对疲劳性能的有害影响。     

脆性夹杂物边界无裂纹形成的锻造应力条件

为研究锻造过程中脆性夹杂边物周围区域的应力场对其边界裂纹形成的影响,给出了平均应力度的定义及计算解析式,以平均球应力度为判据,研究了应力场对脆性夹杂物边界裂纹的影响规律.数值模拟结果表明:脆性夹杂物边界裂纹对平均球应力度的相关度高,将其作为一个参数来表征应力场对脆性夹杂物边界裂纹形成的影响规律是可行的;随平均球应力度代数值的减小,脆性夹杂物边界裂纹的尺寸减小,当平均球应力度代数值小于-2.3时,脆性夹杂物边界无裂纹形成.在Gleeble-3180热模拟试验机上,利用专门的试件和型砧进行了1 220℃热压缩变形试验,通过扫描电镜观察了试件内部脆性夹杂物边界裂纹的形成规律,试验结果与数值模拟结果吻合.     

热加工对硫化物及氧化物夹杂的影响

随着制造业的发展,人们对钢材的质量提出了更高的要求,而夹杂物是影响钢材质量十分重要的因素之一.特别是对高强钢而言,夹杂物对其韧性的影响更加敏感.因此,研究冶炼过程中对夹杂物的控制及后续热轧和热处理工艺对钢中夹杂物的影响,是钢铁材料制造和加工过程中的一个重要课题.夹杂物对钢材的强度、塑性、韧性、抗疲劳性能、耐腐蚀性能都会产生重要影响.要减少夹杂物对钢材性能的影响,需从优化冶炼工艺开始.随着气泡去除夹杂物技术、真空碳脱氧技术及中间包电磁搅拌技术在冶炼过程中的应用,钢材中的夹杂物含量明显降低.然而,在目前工业化的生产环境中,仍然无法实现将钢中的非金属夹杂物完全消除.目前的研究已经表明,热轧和热处理过程对夹杂物也有重要影响,这对进一步控制夹杂物的尺寸、分布、形态,达到减轻夹杂物对钢材性能影响的目的具有重要的意义.因此,目前除了发展新的冶炼工艺以进一步降低钢中的夹杂物含量外,研究和阐明热加工工艺对夹杂物的影响也是研究重点.文中归纳了冶炼过程中先进的夹杂物控制技术及其原理,评述了热变形和热处理过程对夹杂物的数量、尺寸、分布、形态特征及类型产生的影响,对研究钢材在制造、加工过程中夹杂物的变化规律及控制具有参考价值.     

镍基粉末高温合金中夹杂物导致裂纹萌生和扩展行为的研究

采用扫描电镜原位拉伸和原位疲劳的方法,跟踪观察了人工植入Al2O3夹杂物的镍基粉末高温合金P/M Rene95中夹杂物导致裂纹萌生、扩展乃至断裂的过程,结果表明,无论是在单轴拉伸还是低周疲劳实验中,裂纹均首先萌生于脆性非金属夹杂物Al2O3处,大于一定尺寸的夹杂物,还会使该裂纹扩展成为导致合金断裂的主裂纹,从而大大降低合金的屈服强度、断裂强度及低周疲劳寿命.     

非金属夹杂物特性对钢铁材料疲劳性能影响的研究进展EI北大核心CSCD

本文综述了非金属夹杂物对钢铁材料疲劳性能的影响及研究现状,从夹杂物的角度出发,首先介绍非金属夹杂物特征提取的最新研究进展,分别从实验测量方法和数学公式科学统计方法两方面进行论述;其次根据夹杂物对于疲劳损伤的主要原理,介绍5种应用较为广泛的定量化分析夹杂物特征参数与钢材疲劳性能的数学模型;然后以夹杂物的形貌特征、力学性能以及与基体之间的相互作用为出发点,探究非金属夹杂物的特性对重载零件钢材疲劳性能的影响。最后指出从多角度解析非金属夹杂物对钢材疲劳性能的主要作用机理,构建非金属夹杂物对钢材疲劳寿命预测模型是未来该领域的研究重点。     

钢凝固过程元素偏析和夹杂物生成预报模型研究进展

钢中的非金属夹杂物对钢的加工和服役性能有重要影响,夹杂物的准确预测和表征可以为优化控制夹杂物形态和性质提供指导。近年来,由于计算机和数学物理模型的不断发展,钢中夹杂物预测模型也得到了很大发展。本文总结和分析了钢凝固过程中元素偏析、夹杂物生成预报模型和精炼-连铸耦合夹杂物预测模型的最新进展。这些模型均可在一定程度上预测钢中夹杂物的组成和数量,但难以预测夹杂物形成的过程。基于此,本文提出一种基于二步形核理论预测凝固过程中夹杂物析出的新思路。     

The preparation of AI2O3/Ni composites by a powder coating technique

In the present study, nickel particles are coated onto the surface of alumina powder by an impregnation technique. The densification behaviour and the microstructural evolution of the nickel coated alumina powder during sintering are investigated. The strength and the toughness of the resulting Al₂O₃/Ni composites are determined. As the nickel content is less than 13 vol%, fully dense composites can be prepared by pressureless sintering. The matrix grain size decreases as nickel inclusions are added. The strength and the toughness of alumina can be increased by 23 and 42% by adding 5 and 8vol% nickel, respectively. The toughening effect is attributed to plastic deformation of ductile inclusions and crack deflection by the inclusions. The strengthening effect is attributed to microstructural refinement.     

Effect of rigid inclusions on the sintering of mullite synthesized by sol-gel processing

The effect of crystalline particulate inclusions of mullite or zirconia on the sintering and crystallization of a mullite powder matrix was investigated as a function of the inclusion volume fraction and size. The mullite powder was synthesized by sol-gel processing and, within the limits of X-ray diffraction, was amorphous. Composites containing up to 22.5 vol % zirconia reached almost full density after sintering at 1500 °C for 1 h. Under identical conditions, the sintered density of the composites containing crystalline mullite inclusions was considerably lower. The zirconia inclusions were inert but the mullite inclusions enhanced the independent nucleation and growth rate of the mullite crystals in the matrix. The lower sintering rate of the matrix reinforced with crystalline mullite is attributed to the enhanced matrix crystallization.     

Structure and properties of composite iron-based coatings obtained by the electromechanical technique

The influence of the electrolyte temperature and current density on the content of inclusions of powder particles in composite coatings obtained by the electrochemical technique has been investigated. It has been found that the wear resistance of iron coatings with inclusions of powder particles of aluminum, kaolin, and calcium silicate increases from 5 to 10 times compared to coating without inclusions of disperse particles, and the friction coefficient therewith decreases from 0.097 to 0.026. It has been shown that the mechanical properties of iron obtained by the method of electrochemical deposition depend on their fine structure. The regimes of deposition of iron-based coatings have been optimized. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 23–27, September–October, 2007.     

Microstructure and inclusion of Ti–6Al–4V fabricated by selective laser melting

Selective laser melting (SLM) was used in fabricating the dense part from pre-alloyed Ti-6Al-4V powder. The microstructural evolution and inclusion formation of as-fabricated part were characterized in depth. The microstructure was characterized by features of columnar prior β grains and acicular martensite α'. High density defects such as dislocations and twins can be produced in SLM process. Investigations on the inclusions find out that hard alpha inclusion, amorphous CaO and microcrystalline Al₂O₃ are three main inclusions formed in SLM. The inclusions formed at some specific sites on melt pool surface. The microstructural evolution and inclusion formation of as-fabricated material are closely related to the SLM process.     

Properties of porous FeAlO y /FeAl x ceramic matrix composite influenced by mechanical activation of FeAl powder

Porous ceramic matrix composites FeAlO _y /FeAl _x with incorporated metal inclusions (cermets) were synthesized by pressureless method, which includes hydrothermal treatment of mechanically alloyed FeAl powder followed by calcination. Their main structural, textural and mechanical features are described. Variation of FeAl powder alloying time results in non-monotonous changes of the porosity and mechanical strength. Details of the cermet microstructure and its relation to the mechanical properties are discussed.     

Intensification of diffusion nickel plating of 5KhNM steel

We have investigated the influence of iron powder added to a saturating mixture on the diffusion nickel plating of 5KhNM steel. It is shown that iron powder substantially decreases the migration of carbon from steel, due to which its decarburization and the number of inclusions in the diffusion layer decrease, refines the surface layers of samples, and intensifies the diffusion nickel plating.     

激光熔覆原位自生TiC颗粒增强镍基复合涂层的组织与耐磨性

采用预置粉末法在45钢表面进行激光熔覆镍基Ni60A+x%(SiC+Ti)(质量分数,下同)复合粉末涂层的实验研究。使用往复式磨损试验机对不同涂层材料的熔覆层进行干摩擦磨损实验,利用金相显微镜、扫描电镜(SEM)观察和分析熔覆层的显微组织与磨损形貌。结果表明:复合粉末通过原位反应生成弥散分布的TiC颗粒增强复合涂层,随着(SiC+Ti)含量的增加,颗粒状TiC的尺寸和数目逐渐增加;复合粉(SiC+Ti)含量达到60%时,微观组织有气孔和夹杂缺陷;复合粉(SiC+Ti)含量为48%时,熔覆层耐磨性最佳;复合涂层的磨损主要为磨粒磨损,机理为微观切削和挤压剥落。     

Mechanical anisotropy in the zirconia toughened alumina

The two kinds of the hydrothermally crystallised zirconia powders were used to toughen alumina matrix. The one composed of isometric crystallites of tetragonal symmetry, the other one of elongated monoclinic particles. In the sintered ZTA material either isometric or elongated particles form tetragonal disk shaped inclusions. Zirconia inclusions originating from the elongated particles tend to arrange crystallographically on the uniaxial compaction. This resulted in the material showing different ultrasonic wave velocity, Young modulus, crack lengths and fracture toughness along directions perpendicular and parallel to the compaction force. An explanation of this phenomenon is suggested. Zirconia inclusions originating from the powder composed of isometric crystallites lead to the material of isotropic mechanical properties.     

水淘洗法分离镍基高温合金粉末中陶瓷类夹杂物

详细介绍了水淘洗方法分离固体颗粒的原理,从实践上建立了镍基高温合金粉末陶瓷类夹杂物的分级分离法,进行实验验证,并分析了水淘洗方法的可靠性。     

Characteristics of diamond regrowth in a synthetic diamond compact

A transmission electron microscopic study of a commercial sintered diamond compact is reported that identifies and characterizes the diamond that has regrown between the grains of the original diamond powder during the high-pressure, high-temperature manufacturing process of the compact. The majority of the original grains are strongly deformed whereas the regrown diamond shows little or no plastic deformation. The dislocations in diamond regrown between the original grains occur in low-angle boundaries and other configurations typical of grown-in dislocations in crystals. The manufacturing process involves infiltrating the diamond aggregate by molten cobalt, and the regrown diamond is characterized by the presence of cobalt inclusions in sizes ranging from a few tenths of a micrometre down to a few nanometres, possessing the same orientation and lattice parameter as the diamond host. Graphite inclusions also occur in regrown diamond, few in comparison with cobalt inclusions and in random orientation. The graphite crystals exhibit axial ratios, (c/a), lowered by several per cent due to the containment pressure exerted by the diamond host.