Effect of degassing atmosphere on mechanical properties of semifinished products from granulated aluminum alloys

Powder Metallurgy and Metal Ceramics -     

高温预析出对Al-Zn-Mg-Cu铝合金显微组织和力学性能的影响

通过光学显微镜和IEM观察和力学性能测试,分析了固溶后高温预析出处理对Al-Zn-Mg-Cu铝合金显微组织及力学性能的影响。结果表明:高温预析出可在晶界形成不连续的析出相,465℃预析出在保证合金硬度的同时,使抗应力腐蚀性能提高,随着预析出温度的降低合金的电导率和抗应力腐蚀开裂性能均得到提高。     

Influence of main components and transition metals on the structure and properties of melt-quenched high-strength aluminum alloys of the Al-Zn-Mg-Cu system

The application of melt quenching for the production of high-strength heat-treatable Al-Zn-Mg-Cu aluminum alloys is considered. The complex multifactor mechanism of hardening of these materials is explained on the basis of their structure and mechanical properties, and a quantitative estimation of individual hardening factors is presented. The influence of the main alloy components on the phase composition, structure and properties of the alloys has been analyzed, and the ultimate total contents of the components and their weight ratio that ensure the optimal set of properties are determined. In addition, the advantage of complex allying of these alloys with various groups of transition metals is established. The possibility of implementation of these approaches is illustrated by the example of production of high-strength melt-quenched Al-Zn-Mg-Cu alloys.     

Effect of sintering conditions on the structure and mechanical properties of P/M aluminum base alloys

Conclusions A magnesium addition promotes densification of Al-Cu alloy specimens sintered for short periods of time in the range 595–635C. Longer sintering at 615 and 635C results in higher specimen porosity. At a temperature above 595C Al-Cu alloys experience severe coarsening. Alloying with magnesium does not significantly affect the structure of the alloys. A magnesium addition improves the mechanical properties of an Al-Cu alloy. The extent to which magnesium alters the mechanical characteristics of heat-treated Al-Cu alloys depends on sintering conditions. The highest strength — 340 MPa and =6% — is exhibited by specimens sintered for 45 min at 595C.Deceased.Translated from Poroshkovaya Metallurgiya, No. 9(297), pp. 29–34, September, 1987.     

Effect of plastic deformation on the mechanical properties and the fine-structure parameters of Pb-Ca-Sn alloys

The specific features of structure formation in Pb-Ca-Sn alloys intended for battery current leads are considered. The effect of plastic deformation on the mechanical properties and the fine-structure parameters in Pb-0.1% Ca-0.3% Sn and Pb-0.05% Ca-1.1% Sn alloys is studied. The influence of the initial structure on the mechanical properties and the fine-structure parameters of the alloys is shown, and the variation of the alloy properties under plastic deformation is demonstrated.     

Comparative investigations into the methods of producing semifinished products from zirconium alloys

A comparative investigation have been performed into the mechanical properties, macro-and microstructure of the material of blanks of Zr-1%Nb alloy obtained during the hot treatment of ingots by two methods: forging and radial-shear rolling, as well as the quality characteristics of semifinished and finished articles have been estimated. It has been shown that the forging as compared to rolling allows reaching a greater depth in working through the structure, which enables forming the state of the material with higher characteristics of strength and impact strength, as well as ensures its compactness.     

Effect of lithium on the mechanical properties and microstructure of sic whisker reinforced aluminum alloys

Aluminum-silicon carbide whisker composites containing nominally 3 to 5 pct Li in the matrix alloys have been fabricated and tested. Tensile and compression tests have been conducted at room temperature, and compression creep tests have been conducted at elevated temperatures. Lithium additions were found to increase the strengthening effect of silicon carbide whiskers at room and elevated temperatures. Lithium also reduced the density of the composites and increased the elastic modulus. Transmission electron microscopy showed no obvious chemical reaction between the whiskers and the aluminum-lithium alloy matrix.     

回归再时效对超高强铝合金力学性能及组织的影响

在传统的回归再时效(retrogression and re-aging,RRA)工艺(峰时效)基础上降低预时效或再时效温度,对Fe和Si杂质含量高的超高强Al-Zn-Mg-Cu合金挤压棒材进行RRA处理,通过拉伸性能和疲劳性能测试以及扫描电镜和透射电镜观察,研究RRA工艺对合金力学性能与组织的影响。结果表明:降低预时效或再时效温度都可明显提高该合金的塑性和抗疲劳损伤性能,略微降低合金的抗拉强度。采用峰时效温度(120℃)RRA处理后的合金,晶内的主要析出相为尺寸较大的η′相,不能被位错切割,合金强度较高(674 MPa),但塑性和抗疲劳损伤性能差,伸长率为11.1%,最终应力强度因子幅值ΔK=26.8 MPa·m1/2;降低时效温度可增加析出相中GP区粒子的比例,减小η′相的尺寸,从而提高塑性变形能力以及抗疲劳损伤性能。     

Effect of combined deformation on the structure and properties of copper and titanium alloys

The effect of a combination scheme of severe plastic deformation and subsequent cold rolling or electroplastic rolling on the deformability, microstructural evolution, and mechanical properties of copper, titanium of various purities, and a titanium alloy of an equiatomic composition is studied. The combined deformation method is shown to create a number of new nanostructured and ultrafine-grained states with a high strength and ductility.     

Effects of strain rate and anisotropy on the tensile deformation properties of extruded AlZnMg alloys

Two extruded AlZnMg alloys have been investigated in uniaxial tension, emphasizing the mechanical anisotropy and strain-rate effects. A strong mechanical anisotropy was found in the extruded profiles which had recrystallized and nonrecrystallized microstructures. The recrystallized alloy had a lower strength level and less variation in ductility and formability parameters than the nonrecrystallized alloy. Mg in solid solution causes dynamic strain aging (DSA) in both alloys. With increasing strain rate, the DSA became less effective and the strain localization caused by DSA vanished. Thus, the room-temperature formability, in the solution heat-treated and quenched condition, may be improved significantly by a sufficient increase of the strain rate. Additional tests on an as-cast sheet-ingot AlMg alloy were performed to isolate the effect of Mg from Zn in solid solution. These tests confirmed the effect of strain rate on the tensile behavior.     

Prediction of the structural state and properties of pressed aluminum semifinished products with the use of a QFORM CAD system

On the ground of achievements of modern materials science and advances in the development of computer simulation systems of the plastic deformation processes, the conditions of formation of the structure and mechanical properties of pressed semifinished products are analyzed using AK6 alloy as an example. The most effective methods for controlling the structure and mechanical properties of semifinished products are shown on the basis of the effect that various factors have on intensifying the processes. The regularities of the effect that the temperature-rate parameters have on the mechanical properties of the AK6 alloy are established by the results of laboratory investigations of rods compacted by various modes.     

Effect of cerium addition on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy

Effect of cerium addition on the microstructure and mechanical properties of an Al-Zn-Mg-Cu alloy have been investigated. In this study, aluminum alloys with up to 0.4% cerium content have been prepared by melting, metal mould casting followed by thermo-mechanical processing. The alloys were extensively characterized by optical and transmission electron microscopy, followed by mechanical property examination by tensile tests as well as nanoindentation tests. It was observed that cerium addition results in up to 5% grain refinement of the cast dendritic structure as well as up to 38% refinement of the heat treated microstructure. Transmission electron microscopy (TEM) has revealed the uniform distribution of fine GP zones and some semi coherent β(MgZn₂) precipitates in the Al rich matrix. Further TEM results show that when the Ce content was changed from 0.1% to 0.4%, precipitate size increased from 5 to 50nm and the precipitate morphology changed from spherical to needle shape. Evaluation of mechanical properties through tensile and nano-indentation tests have exhibited that both Young’s modulus and tensile strength increases with Ce addition up to 0.3% and subsequently decrease.     

三级固溶处理对Al-Zn-Mg-Cu系铝合金组织和剥落腐蚀性能的影响

针对Al-Zn-Mg-Cu系铝合金热处理工艺中存在的不足,提出固溶-降温析出-再固溶的三级固溶热处理工艺,通过金相显微镜和扫描电镜(SEM)分析以及硬度、电导率、腐蚀剥落性能测试,研究三级固溶处理对Al-Zn-Mg-Cu系铝合金锻件的微观组织及剥落腐蚀行为的影响.结果表明:三级固溶处理可使晶界析出相明显粗化、离散度增大.同时,三级同溶处理可使Al-Zn-Mg-Cu系铝合金抗剥落腐蚀性能得到明显改善,抗拉强度仍能保持在610 MPa左右;与常规固溶相比,该合金经三级固溶+峰值时效处理后的电导率由30.8%(IACS)提高到33.2%(IACS),抗剥蚀等级由EB+提高为EA.