超声波功率对半连续铸造6013铝合金组织与力学性能的影响

采用超声波辅助半连续铸造工艺制备直径310 mm的6013铝合金铸锭,利用金相显微镜、扫描电镜、电子探针分析仪和拉伸试验机,研究了超声波功率对半连续铸造6013铝合金铸锭显微组织与力学性能的影响。结果表明:超声波辅助半连续铸造工艺可以细化铸锭的晶粒和第二相,提高α-Al基体上的元素固溶度。超声波功率越大,铸锭的晶粒和第二相越细小,第二相分布越均匀,α-Al基体中的元素固溶度越高,铸锭的拉伸力学性能越高。当超声波功率增大至350 W时,铸锭的抗拉强度为261. 9 N/mm~2,屈服强度为225. 8 N/mm~2,伸长率为20. 9%,与未施加超声波的铸锭相比,此时铸锭的抗拉强度、屈服强度和伸长率分别提高了10. 7%、13. 6%、14. 8%。     

挤压铸造Al-6.8Zn-2.6Mg-2.3Cu的组织和性能

采用金相、扫描电镜和DSC热分析仪研究了挤压铸造Al-6.8Zn-2.6Mg-2.3Cu合金的显微组织、铸造性能和力学性能,并与Al-5.5Si-4.0Cu合金进行了对比研究。结果表明,熔体温度为720℃和740℃时,Al-6.8Zn-2.6Mg-2.3Cu合金的流动性能比Al-5.5Si-4.0Cu合金分别提高了10.9%和2.9%;挤压压力从0.1MPa增加到75.0MPa时,铸态Al-5.5Si-4.0Cu合金的抗拉强度和伸长率都略高于Al-6.8Zn-2.6Mg-2.3Cu合金,但经过T6热处理后,Al-6.8Zn-2.6Mg-2.3Cu合金的抗拉强度增幅比Al-5.5Si-4.0Cu合金高100MPa以上,这主要是因为Al-6.8Zn-2.6Mg-2.3Cu合金具有更强的时效强化效果。     

基于模糊PID控制的新型镁合金铸造性能研究

对Mg-8Al-0.6Zn-0.4V和Mg-8Al-0.6Zn-0.5Zr两种镁合金进行了常规铸造和模糊PID控制铸造下的力学性能和磨损性能的测试与分析。结果表明:与常规铸造相比,模糊PID控制时Mg-8Al-0.6Zn-0.4V合金的抗拉强度、屈服强度分别增大22、23 MPa,断后伸长率仅减小0.3%,磨损体积减小27.59%;Mg-8Al-0.6Zn-0.5Zr合金的抗拉强度、屈服强度分别增大24、23 MPa,断后伸长率减小0.4%,磨损体积减小28.13%。模糊PID控制有助于提高两种铸造镁合金的力学性能和耐磨损性能。     

挤压铸造压力对Mg-4Zn-1.2Y合金组织及力学性能的影响

采用显微组织观察、拉伸试验、密度测试等研究了不同挤压铸造压力对Mg-4Zn-1.2Y合金显微组织与力学性能的影响。结果表明:随着挤压压力的增加,Mg-4Zn-1.2Y合金的平均晶粒尺寸和第二相体积分数逐渐减小,挤压压力从0增加到150 MPa时,合金晶粒细化明显,挤压压力超过150 MPa后,合金晶粒细化趋势变缓。随着挤压压力的增加,Mg-4Zn-1.2Y合金的抗拉强度、屈服强度、伸长率及密度均逐渐增加。与挤压压力为0 MPa的合金相比,挤压压力150 MPa的合金抗拉强度、屈服强度和伸长率分别提高了24.4%、23.3%和72.7%,力学性能显著提高,挤压压力超过150 MPa后,合金力学性能提高幅度变缓。     

Sc对Al-Zn-Mg-Cu-Zr合金挤压铸造组织性能的影响

采用电阻炉熔炼了Al-7.2Zn-2.2Mg-1.8Cu-0.2Zr和Al-7.2Zn-2.2Mg-1.8Cu-0.2Sc-0.2Zr两种铝合金,在700~720℃挤压铸造成形,并经过465℃×24h+475℃×8h水淬+120℃×24h时效热处理。结果表明,Sc、Zr的复合添加能明显细化α-Al基体和晶间第二相;通过多级固溶和时效处理,显著提高了合金的力学性能,铸件的抗拉强度达到613MPa,屈服强度达到528 MPa,伸长率为6%。     

La对Al-5Mg-0.2Zr合金组织和性能的影响

采用铸锭冶金法制备了含稀土La的Al-Mg-Zr合金,通过金相显微镜、扫描电镜、能谱和X射线衍射及力学性能测试,观察分析了0.2%的La微合金化对Al-5Mg-0.2Zr合金微观组织和力学性能的影响。结果表明,在Al-5Mg-0.2Zr合金中添加0.2%的La能显著细化合金晶粒,合金的平均晶粒尺寸下降到68μm,同时有效地避免了Al3Zr析出相的粗化和偏聚,使合金抗拉强度、屈服强度及伸长率分别增加到了165.5MPa、112.5MPa和7.5%。     

Cu和Ce对Mg-1.5Zn-0.2Mn合金组织和力学性能的影响

本文通过光学显微镜、拉伸试验机对比研究了Ce、Cu元素对Mg-1.5Zn-0.2Mn合金组织和力学性能的影响。研究结果表明,Cu、Ce元素对铸态Mg-1.5Zn-0.2Mn合金晶粒细化效果并不明显,但经350℃热变形后,能显著细化挤压态Mg-1.5Zn-0.2Mn合金的晶粒组织,其中Ce细化晶粒的效果更加明显,而且Ce能够抑制合金的动态再结晶。此外,Cu、Ce元素的添加均能提高Mg-1.5Zn-0.2Mn合金沿ED和TD方向的屈服强度和抗拉强度,其中Ce元素提高幅度更大,Mg-1.5Zn-0.2Mn-0.2Ce合金ED、TD方向屈服强度分别为185 MPa和162 MPa。与此同时,这两种元素还可以改善Mg-1.5Zn-0.2Mn合金板材强度的各向异性,其中Cu元素的改善效果更明显。     

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%。     

Zn元素对Mg-6Al-2Nd-2Ca组织和性能的影响

采用金属型重力铸造方法制备了Mg-6Al-2Nd-2Ca和Mg-6Al-2Nd-2Ca-1.2Zn合金,并对铸态合金进行均匀化处理和热挤压加工,通过金相显微镜、X射线衍射仪、扫描电镜、能谱仪、透射电镜和万能拉伸实验机等分析测试方法,研究了Zn元素对Mg-6Al-2Nd-2Ca合金显微组织和力学性能的变化。实验结果表明：Zn元素的加入有助于细化晶粒,Zn在合金中主要以固溶体的形式存在,降低了Al在α-Mg基体中的固溶度,生成更多的Al-Nd相。两种合金经过均匀化处理后,与铸态相比显微组织更加均匀,第二相数量略有减少。经热挤压后,两种合金中的硬脆相被挤碎,晶粒得到明显的细化,力学性能明显提升,在细晶强化、第二相强化的共同作用下Mg-6Al-2Nd-2Ca-1.2Zn合金表现出优良的力学性能,其抗拉强度、屈服强度和断后伸长率分别为294.0 MPa、197.1 MPa、11.6%。     

Fe含量对挤压铸造Al-Zn-Mg-Cu合金组织和力学性能的影响

采用不同压力的挤压铸造方法制备了不同Fe含量的Al-7.1Zn-2.4Mg-2.1Cu合金,研究了Fe含量和压力对挤压铸造合金组织和力学性能的影响,并重点分析了合金的断裂行为.结果 表明:铸态下,合金中富铁相为汉字状A16 (CuFe),T4热处理后,富铁相A16(CuFe)部分转变为富铜的Al7 Cu2 Fe相.相比重力铸造合金,挤压铸造高铁含量Al-7.1Zn-2.4Mg-2.1Cu合金力学性能得到显著的提升,降低了富铁相的危害,这主要归因于压力作用下组织细化和铸造缺陷的减少.75 MPa压力下,含铁量为0.55 mass％的合金经T4热处理后的抗拉强度为464 MPa,屈服强度为325 MPa,伸长率为8.9％.     

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.     

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.     

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.