Al-Si合金变质元素及其交互作用

铸造Al-Si合金具有轻量化、流动性好、气密性好、收缩率小和热膨胀系数低等优点,已成为铸造业中最受重视的结构材料之一。铸造Al-Si合金的力学性能主要取决于组织中的α-Al相、共晶硅、初生硅、金属间化合物、缺陷以及它们的形态、尺寸和分布,其中硅相和富Fe相的形貌、尺寸及分布对合金性能的影响尤为显著。未变质的Al-Si合金中针片状共晶硅和针状β-Fe相严重割裂基体,粗大块状初生硅和针片状共晶硅尖端和棱角部位产生应力集中,导致合金的性能尤其是塑性、强度和耐磨性显著降低。此外,硬脆的粗大初生硅还会加快机加工刀具的磨损,加工后零部件的表面光洁度也较差,无法满足实际生产的需要。快速凝固、电磁搅拌、超声处理、机械振动等特殊工艺技术虽然可以在一定程度上改善铸造铝硅合金的微观组织和性能,但是都需要专门的设备和特殊的条件,使其应用受到限制。变质处理不需要任何特殊设备,只需添加少量变质元素,就可以实现对其中α-Al相、共晶硅、富Fe相、细化初生硅等的有效调控,具有成本低、方法简单、效果显著等特点,已成为改善Al-Si合金组织、提高性能最有效的途径。然而,各变质元素的变质机理及它们之间的交互作用极其复杂,如何充分发挥各变质元素及它们之间积极的交互作用是当前的研究热点。近年来对单一变质元素的变质作用机理和效果的研究进展迅速,先后发现了Na、Sr、Sb、P、Ti、Mn和RE等都对铸造铝硅合金有一定的变质作用,并且对它们的变质时效性以及经济性都有了充分的认识。与此同时,也有许多研究者开始关注多元素的交互变质作用并在Sr-X、P-X、Mn-X、Ti-X等二元交互变质方面取得了重要的成果,使变质技术更加经济、有效和灵活。本文综述了铸造Al-Si合金常用单一变质元素的特点、变质作用机理和局限性,系统归纳了Sr、P、Ti、Mn和RE与其他元素间的交互作用规律,筛选出具有协同变质作用的二元/多元变质元素交互作用对,以期为深入探究二元/多元变质元素交互作用的机理,开发更高效、多样、绿色的复合变质剂及变质处理方法提供参考。     

铝硅合金变质处理及去除超标镁锌的研究

系统研究了锶盐及其复合变质剂对铝硅合金的变质效果,以及几种处理方法对铝合金中杂质元素镁、锌的影响规律。所得主要结果是:锶盐可以使铝硅合金的硅相由针杆状变为长度尺寸在100μm以下的短杆状或弯曲的纤维状。锶盐变质剂存在着与锶变质相同的变质潜伏期现象,将锶盐与钠盐或磷盐复合变质能够消除这种现象。所研究的变质剂加入量小,提高合金的力学性能和使用性能;真空蒸发处理能够有效地降低铝合佥中的杂质锌量,向铝合金中吹入氟利昂与氮气的混合气体或加入六氯乙烷熔剂都能够有放地降低铝合金中的杂质镁量,根据铝合金的含镁量确定氟利昂的吹入量或六氮乙烷的加入量。     

Al-10Ce中间合金对α-铝变质的研究

用X射线衍射、光学显微镜、扫描电镜和能谱等分析Al-10Ce中间合金的相组成和微观形貌,研究Al-10Ce中间合金对α-铝的变质处理效果及对α-铝的长效性变质和重熔稳定性变质,并与钠盐变质进行了对比.结果表明:Al-10Ce中间合金用量对变质效果的影响很大,Al10Ce中间合金用量为0.30%左右时达到最佳变质效果,用量少变质效果差,用量过多则形成过变质.用Al-10Ce中间合金对α-铝进行变质,可取得极好的变质效果,变质持续时间比钠盐变质剂更长久且具有更好的重熔稳定性.     

一种复合强效变质剂对亚共晶Al－Si合金组织及性能的影响EI

本文通过所研制的复合变质剂对新型亚共晶铝硅合金进行变质处理，α－Ａｌ晶粒明显变细，分布均匀，分叉率增加。共晶硅尺寸减小，分枝增加，并可在熔拣温度下保温４ｈ或重熔５次以上仍保持变质效果。经变质后的组织为共晶硅粒状化处理创造了有利条件，使铝硅合金的综合力学性能明显提高。     

铝合金变质处理的研究

本实验是研究不同种类变质剂对铝硅合金力学性能及组织的影响。在变质剂定量的情况下,只改变变质剂的种类这一个参数。采用原料为纯铝与单晶硅制备而成的铝硅中间合金,在加精练剂与不同种类的变质剂的情况下重熔,把所得金属液浇注成拉伸试样,热处理后测试其抗拉强度、延伸率、硬度与观察金相组织。结果表明,在保持原有优良性能的基础上,加入的混合变质剂,0.3%稀土+3.0%三元盐(15%KCl+40%NaCl+45%NaF),使其力学性能有很大的提高,抗拉强度提高到121MPa,维氏硬度达到52;通过金相组织观察可发现初晶硅得到了明显的细化。     

Al-Mg2Si原位复合材料的变质及添加合金元素

Al-Mg_2Si原位复合材料由于其优良的性能已经广泛应用在航空和汽车工业中。介绍了磷、稀土、锶等变质元素对初晶和共晶Mg2Si相良好的变质效果,以及不同变质元素的变质机理;并讨论了不同合金元素的添加对Al-Mg_2Si原位复合材料的组织以及力学性能的影响。通过总结国内外关于Al-Mg_2Si原位复合材料的研究成果,指出未来的研究应向多元复合变质以及合金元素对材料组织性能影响的机理研究方向发展,从而找到更好的手段来进一步改善Al-Mg_2Si原位复合材料的组织与性能。     

稀土及锶对铸造铝硅合金的协同变质作用EI

本文介绍了稀土和锶对ZL102及ZL104两种合金的协同变质作用。这两种铝硅合金只用稀土变质在砂型铸造时,其金相组织和力学性能与未变质的相差不多;若仅用锶变质,两种合金砂型铸造试样针孔度在5级以上,均不能满足砂型铸造生产要求。在这两种合金中加入0.2％稀土及0.04％锶时,变质效果良好,针孔度也低。     

AlSi5合金的制备

铝硅合金是一种典型的共晶合金,组织中的β相的性能与纯硅相似,在常规铸态条件下,共晶硅呈片状,初晶硅呈多角形块状和板状.硅相很脆,大大降低了合金的强度和塑性.因此,AlSi合金的性能和β相的形态与分布密切相关,尤其对于Si含量高的AlSi合金.本文综述了各种改善A1Si合金性能的制备方法(包括变质熔炼、快速凝固以及粉末冶金方法等),比较了各种方法制得材料的组织性能特点.同时研究了铸态和加工态AlSi5合金的组织结构特点.实验结果表明,经过轧制+退火处理后,α相晶粒尺寸＜50μm,α相和硅相的分布得到改善.     

铝硅合金热疲劳过程的应力应变分析

对铝硅合金进行了热疲劳模拟实验和应力、应变分析。铝硅合金的导热系数高,高温弹性模量低,温度涨落过程产生的宏观热应力低于同一温度下合金的屈服应力和疲劳极限;而铝、硅热膨胀系数的差异将在铝硅相界等局部区域产生远大于宏观热应力的微观热应力,并因此萌生热疲劳裂纹。通过变质工艺改变硅相形态,可改善合金的抗热疲劳性能。     

稀土La对ZLIO1A组织、性能的影响

本文研究了稀土La在不同的加入量和不同的保温时间下的变质效果,在T6热处理下,对ZL101A的显微组织和力学性能的影响。结果表明：La是铝硅合金的一种优良的长效变质剂,改善合金组织和性能的效果显著,特别是细化共晶硅。在一定La加入量范围内,保温时间的长短影响其变质效果t在较大的冷却速度下可得到细小的显微组织,随着合金中La加入量的增加合金的力学强度（Rm）和延伸率（A）增加。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。