RE对铸造Al-6Zn-2.5Mg-1.8Cu合金热裂倾向性的影响

在铸造Al-6Zn-2.5Mg-1.8Cu合金中分别加入0、0.05%、0.1%和0.15%的RE,研究了RE对合金的热裂倾向、微观组织和力学性能的影响。结果表明,RE的加入可细化晶粒尺寸,提高合金的力学性能,降低合金的热裂倾向。在加入范围内,RE含量为0.1%时,热裂倾向性最低,晶粒尺寸最小,力学性能最佳,合金的抗拉强度和伸长率分别为180MPa和3%。     

Al-7Si-Mg合金晶粒的复合细化处理的研究

采用自制的Al-TiC细化剂以及Al-5Ti-B中间合金对Al-7Si-Mg合金进行复合细化处理,研究了复合细化处理工艺对Al-7Si-Mg合金晶粒尺寸和力学性能的影响.结果表明,在复合细化处理后,Al-7Si-Mg合金晶粒尺寸为采用2％的Al-5Ti-B细化处理的66.5％.力学性能测试表明,与采用2％的Al-5Ti-B细化处理相比,复合细化处理使Al-7Si-Mg合金的抗拉强度在T6处理前后分别提高了13.88％和4.96％,伸长率在T6处理前后分别提高了52.3％和89.3％.     

Ca对Mg-7Al-2Si合金热裂倾向的影响

研究了Ca对Mg-7Al-2Si-0.8Zn-0.5Sr-0.4Mn铸造合金热裂倾向的影响.利用等长度金属型制备了热裂试样,采用热裂棒临界直径尺寸和热裂敏感系数评价合金的热裂倾向.借助光学显微镜,扫描电镜(SEM)和能谱仪(EDX)综合分析镁合金的热裂行为.结果表明,Ca的添加细化了合金的显微组织;当Ca含量为3.0％时,热裂棒临界直径尺寸和热裂敏感系数均最低,α-Mg枝晶的断裂面积为0,共晶相的断裂面积为100％.在裂纹形成过程中,共晶相具有向裂纹富集的趋势,形成了可以填充裂纹缝隙的能力,使合金的热裂倾向降低.当合金的热裂倾向较低时,对应较高的抗拉强度.     

浇注温度对Al-7Zn-2.5Mg-Cu合金组织和热裂性能的影响

采用约束棒法评定不同浇注温度下Al-7Zn-2.5Mg-Cu合金的热裂倾向,采用OM观察了合金的显微组织。结果表明,不同浇注温度下,合金的显微组织均为等轴晶结构。随着浇注温度升高,合金的晶粒粗化,晶间共晶数量减少,且由连续分布逐渐转变成半连续分布,热裂倾向增大。但浇注温度为680℃时,合金出现浇不足缺陷。在保证该合金充型能力的前提下,降低浇注温度是减少其热裂倾向的有效途径。     

TiN/Ti细化剂加入量对Al-7.0Zn-2.5Mg-2.5Cu合金铸态组织和性能的影响

采用高能球磨的方法制备了一种纳米TiN/Ti复合晶粒细化剂,研究了该细化剂的加入量对A1-7.0Zn-2.5Mg-2.5Cu合金铸态组织和性能的影响.结果表明,纳米TiN/Ti复合晶粒细化剂对合金具有良好的细化效果.当细化剂的加入量为0.3％时,合金的平均晶粒尺寸由未添加细化剂的297.5 μm细化至178 μm,初生α相细化同时,组织中的共晶体被细化分散.加入量为0.5％时,晶粒尺寸又呈增大趋势.细化剂添加量小于0.3％时,合金的抗拉强度及显微硬度随着细化剂加入量的增大而增加.当细化剂的加入量为0.3％时,抗拉强度与显微硬度均达到最大值,抗拉强度为243.9 MPa,较未添加细化剂试样提高了近10％;显微硬度为HV143.5,较未添加细化剂试样提高了20％.其拉伸断口为脆性解理断口和撕裂棱组成的复合断口.     

Al-10%Mg中间合金细化Al-5%Fe合金的研究

通过改变Al-10%Mg中间合金晶粒细化剂加入量和熔体保温时间,研究了过共晶Al-5%Fe合金微观组织形态及力学性能.试验表明,在过共晶Al-5%Fe合金中加入Al-10%Mg中间合金细化剂,当加入量为1.2%、保温时间为90 min时,细化效果仍较好,Al-5%Fe合金中初生Al3Fe相由粗大板条状变为花朵状和颗粒状,尺寸明显减小,材料的强度和塑性明显提高.     

Sr对Mg-7Al-2Ca-2Si-0.8Zn-0.4Mn铸造合金热裂倾向性的影响

为了考察Sr对Mg-7Al-2Ca-2Si-0.8Zn-0.4Mn铸造合金热裂倾向性的影响,利用等长度金属型制备了含Sr分别为0、0.5％、1.0％和1.5％四组,每组八个尺寸的圆柱试样,采用热裂棒临界直径尺寸和热裂敏感系数评价合金的热裂倾向性.借助光学显微镜(OM),扫描电镜(SEM)和能谱仪(EDX)分析合金的组织、热裂行为和相成分.结果表明,Sr的添加改善了合金的流动性,细化了合金的组织.在Sr含量为1.0％时,热裂棒临界直径尺寸和热裂敏感系数均最低,同时α-Mg枝晶的断裂面积为零,共晶相的断裂面积为100％.共晶相在裂纹形成过程中,具有向裂纹富集的趋势,形成了可以填充裂纹缝隙的能力,从而使合金的热裂倾向性降低.试棒在热裂倾向较低时,对应较高的拉伸强度.     

Al-5Ti-B对6061铝合金细化效果及其机理研究

研究了Al-5Ti-B中间合金添加量、保温时间及浇注温度等参数对6061铝合金细化效果的影响及其细化机理。结果表明,Al-5Ti-B中间合金细化6061合金的优化工艺参数为:Al-5Ti-B添加量范围0.3wt%~0.5wt%,保温时间10~30 min,浇注温度为720℃。共晶反应机制可能是Al-5Ti-B中间合金对6061合金具有细化作用的主要原因,共晶反应产生的α(Al)可以作为晶粒长大的基底,同时TiB_2可以促进共晶反应的发生,因而Al-5Ti-B对6061合金具有较好的细化效果。     

Al-3B对亚共晶Al-Si合金的晶粒细化作用

从热分析角度研究Al-3B对Al-7Si的晶粒细化作用,B对Al-7Si晶粒细化的最佳加入量为0.03%。考察了Al-3B对不同Si含量亚共晶铝硅合金的晶粒细化作用,B对高硅含量亚共晶铝硅合金的晶粒细化效果更好。分析了B对亚共晶铝硅合金的细化机理,认为Al-B共晶理论可以有效解释试验现象。     

Al-5%Ti-0.25%C对Al-Si活塞合金组织和性能的影响

探讨了Al-5%Ti-0.25%C中间合金对共晶Al-Si活塞合金组织和力学性能的影响.结果表明,加入0.5%的Al-5%Ti-0.25%C中间合金后,初晶Si的平均尺寸由原来的45μm降为40μm,共晶Si变短,而且能细化共晶团,提高常温抗拉强度.Al-5%Ti-0.25%C中间合金的加入量达到1%时,常温抗拉强度不再继续提高.加入Al-Ti-C中间合金后随着静置时间的延长,常温抗拉强度变化并不明显.     

Prospects of the Use of Synergetic Approach to Solution of Problems of the Science of Nanomaterials

A synergetic approach to solution of problems of self-controlled synthesis of nanostructures and creation of self-organizing nanotechnologies is considered in connection with the superproblem of creation of materials with functional properties resembling those of biosystems. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 55 – 61, July, 2005.     

Kinetics of the oxidation of metals — Influence of self-diffusion of metal

The importance of the self-diffusion of a metal during its oxidation by a gas is treated for the cases of nonstoichiometric oxides having either interstitial cation or cation vacancies. We have established a general relationship for the reaction rate when a mixed diffusion process occurs. From this relationship, we have shown that the pressure dependence can be different, according to whether the rate-determining process is the self-diffusion through the metal or through the product.     

胫骨生物陶瓷复合材料的微结构增韧机理

扫描电镜观察显示胫骨是一种由羟基磷灰石和胶原蛋白组成的自然生物陶瓷复合材料.羟基磷灰石具有层状的微结构并且平行于骨的表面排列.观察也显示这些羟基磷灰石层又是由许多羟基磷灰石片所组成,这些羟基磷灰石片具有长而薄的形状,也以平行的方式整齐排列.基于在胫骨中观察到的羟基磷灰石片的微结构特征,通过微结构模型分析及实验,研究了羟基磷灰石片平行排列微结构的最大拔出能.结果表明,羟基磷灰石片长而薄的形状以及平行排列方式增加了其最大拔出能,进而提高了骨的断裂韧性.     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Ab-initio calculation of enthalpies of formation of intermetallic compounds and enthalpies of mixing of solid solutions

A large number of ab-initio calculations of energies of formation of intermetallic compounds have been performed in the last 15 years. The currently used methods are listed. The paper presents a review of the aluminium based compounds which have been studied. Comparisons of calculated and experimental enthalpies of formation are provided for aluminim-3d and-4d transition metal alloys at equiatomic composition. The modelling of the enthalpies of mixing of solid solutions based on a given lattice is described.     

试论洋务派教师聘任的思想

洋务派在洋务学堂的办学活动中,为了解决西学专业学科的教学困难,采用了聘请外籍教师的应急措施.他们以真才实学,合同制管理作为主导思想,并认为这种解决师资的途径只是权宜之计,并非久远.从客观上看,洋务派的教师聘任思想有深刻的历史影响.     

Mechanism of Nucleation of Precipitates of Carbides of Refractory Metals Under Hot Rolling of Automotive Sheet Steel

Metal Science and Heat Treatment - The problem of formation of properties in microalloyed sheet steels is considered. The cause and the possible mechanism of precipitation of carbides of refractory...     

燃煤机组锅炉烟气脱硝灰中氨含量测定

NOx是大气环境的主要污染物之一,其主要来源为火力发电机组。依靠低氮燃烧技术,远达不到排放要求。选择性催化还原脱硝(简称SCR)技术是目前效率最高、最成熟、应用最广泛的电厂烟气脱硝技术。目前,在线氨逃逸监测技术存在诸多问题,影响了氨逃逸监测数据的准确度和稳定性。在燃料种类、炉膛结构、受热面布置、过量空气量、炉膛气流分布以及脱硝催化剂类型等条件确定的情况下,控制好氨加入量及其逃逸量是保证NOx脱除率的关键所在。燃煤锅炉除尘飞灰氨含量可侧面反映脱硝氨逃逸率的状况。根据国外的文献报道,正常情况下,电除尘灰中氨含量一般在50mg/kg-100mg/kg范围内。由于国内尚无灰中氨含量的测定方法,亦无脱硝运行对飞灰含氨量影响的数据积累。本文通过大量试验,确定了灰中氨溶解条件(如溶解时间、搅拌状态、灰水比、灰样量及其稳定性等),制定了灰中氨含量测定方法。