Microstructure-properties relationship in two Al-Mg-Si alloys through a combination of extrusion and aging

Aluminum alloys containing magnesium and silicon as the major solutes are strengthened by precipitation of the metastable precursors (β″) of the equilibrium β (Mg₂Si) phase. In this study, dynamic aging of two Al-Mg-Si alloys—the 6061 (Al-1.34% Mg₂Si) and 6069 (Al-2.25% Mg₂Si) alloys—was conducted through equal channel angular extrusion (ECAE). Equal channel angular extrusion-assisted dynamic aging provides the potential for improving mechanical properties. The aging time scale is reduced from ∼1,000 min. for conventional static peak aging to ∼10 min. by using ECAE-assisted dynamic aging. Compared to the significant strengthening effect in static aging treatment, a notable further increase in ultimate tensile strength is achieved by dynamic aging: over 40 MPa for the 6061 alloy and 100 MPa for the 6069 alloy. Microstructures of both aged alloys were characterized using transmission electron microscopy; dislocation-assisted precipitation was observed to be the primary precipitate nucleation and growth mechanism during the dynamic aging process. It is concluded that ECAE-assisted dynamic aging is controllable and efficient in executing aging treatment that could result in superior mechanical properties of Al-Mg-Si alloys.     

Effect of multi-temperature aging on the characterization of aluminum based castings heat treated using fluidized bed technique

The current study investigates the influences of the fluidized bed heat treatment on the quality indices and microstructural characterization of A356.2 and B319.2 castings. Traditional heat treatment technology, employing circulating air convection furnaces (CF), was used to establish a relevant comparison with fluidized sand bed (FB) for the heat treatment of the alloys investigated, employing T6 continuous aging cycles or multi-temperature aging cycles. The results of alloys subjected to multi-temperature aging cycles reveal that the strength results obtained after the T6 continuous aging treatment of A356 alloys are not improved by means of multi-temperature aging cycles, indicating therefore that the optimum properties are obtained using a T6 aging treatment. The optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 230 °C/2 h followed by 180 °C/8 h, rather than T6 aging treatment. In the case of multi-temperature aging cycles, the modification factor has the most significant role in improving the quality index values of 356 and 319 alloys. The FB heattreated alloys have the highest strength values for all heat treatment cycles compared to CF heat-treated alloys; however, the FB has no significant effect on the quality values of 319 alloys compared to the CF.     

CALCULATION OF THE DAMPING OF THE Zn-27Al ALLOY BASED ON THE MICRO INTERFACE SLIDING MODEL

The microstructures of the Zn-27Al alloy after modification, solid-solution treatment, and natural aging were studied. It was clarified why the damping properties of Zn-27Al alloys, after treatment, had advanced most on the basis of analyzing the microstructures. Approximate expressions have been educed, which can be used to quantificationally work out the damping of the Zn-27Al alloy on the basis of the micro interface sliding model. By comparing the testing damping properties of the foundry Zn-27Al alloys and the Zn-27Al alloys after modification, solid solution, and natural aging, it was shown that the expressions were rational.     

Applying ANOVA and DOE to study the effect of manganese on the hardness and wear rate of artificially aged Al-4.5wt%Cu alloys

The addition of manganese may constitute an important means for imparting the mechanical properties of Al-4.5wt%Cu alloys that have been artificially aged. The literature, however, comprises conflicting reports on the effect of manganese on these alloys. Thus, this work tries to reach results that are more conclusive by utilizing statistical approaches such as Design of Experiments and the Analysis of Variance. Accordingly, different percentages of manganese additions under different aging times were investigated in this study for their effect on hardness and wear rate. Manganese was added in concentrations of 0.2, 0.4, 0.6, 0.8 and 1wt%. Following the solution treatment, aging was applied for time durations of 1, 2 and 3 h. Aging temperature was held constant at 200 °C. Results showed that Mn concentration and aging time have significant effect on alloy hardness and wear rate.     

Cr对含FeT业纯铜组织和力学性能的影响

研究了Cr的不同加入量（ωcr=0％、0．3％、0．75％和1．2％）对含Fe工业纯铜组织和力学性能的影响。结果表明,Cr与Cu不能形成化合物,可有限固溶于纯铜中,超过部分形成过剩的第二相。固溶时效热处理可析出细小弥散的第二相质点。随Cr含量增大,铸态合金材料的强度、硬度增加。热处理可使铸态力学性能得到进一步提高。少量的Fe对合金的力学性能是有益的。     

时效温度对ZK60镁合金组织和性能的影响

对ZK60镁合金在100～220℃进行时效处理,通过金相组织分析、断口扫描分析及力学性能测试,研究了时效温度对ZK60镁合金的显微组织与力学性能的影响.结果表明:时效处理能明显改善ZK60镁合金的组织和力学性能.其力学性能随时效温度升高呈规律性变化,网络结构是力学性能变化的主要原因.得出ZK60镁合金力学性能的优化时效温度为190℃.     

Strengthening effects of rare earths on wrought Mg---Zn---Zr---RE alloys

The strengthening effect of rare earths (REs) on wrought Mg---Zn---Zr---RE alloys has been studied. It has been shown that the RE elements have a pronounced strengthening effect on the Mg alloys. Homogenization of the cast ingots and the quenching-plus-aging treatment of the extruded bars decreased the strength, whereas aging of the extruded bars increased the strength. It is proposed that the strengthening mechanism is due to RE-containing particles that are able to suppress the dynamic recrystallization during the hot extrusion process, and to promote the dispersive strengthening effect of RE-containing particles in these materials.     

Observations of dynamic strain aging in polycrystalline NiAl

Dynamic strain aging has been investigated at temperatures between 77 and 1100 K in eight polycrystalline NiAl alloys. The 0.2% offset yield stress and work hardening rates for these alloys generally decreased with increasing temperature. However, local plateaus or maxima were observed in conventional purity and carbon doped alloys at intermediate temperatures (600–900 K). This anomalous behavior was not observed in low interstitial high-purity, nitrogen doped, or in titanium doped materials. Low or negative strain rate sensitivities (SRS) were also observed in all eight alloys in this intermediate temperature range. Coincident with the occurrence of negative SRS was the occurrence of serrated flow in conventional purity alloys containing high concentrations of Si in addition to C. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main species causing strain aging in polycrystalline NiAl is C but indicate that residual Si impurities can enhance the strain aging effect.     

非晶态镍磷合金的组织结构与性能

研究了化学沉积非晶态镍磷合金的组织结构与性能。结果表明,随着沉积层中磷含量的增加,合金的非晶化趋势提高,非晶态镍磷合金层的硬度和耐磨性能下降,且明显低于晶态镍磷合金;经过大于６１３Ｋ的时效处理,非晶态镍磷合金晶化且有Ｎｉ３Ｐ生成,沉积层的硬度和耐磨性得以提高并超过晶态合金;非晶态镍磷合金经过时效处理晶化后且组织结构发生变化,耐腐蚀性能下降,硬化性能则提高。     

Effect of melt treatment on impact toughness of 356 type alloys

The effects of melt treatment in particular the types of grain refiners as well as Sr modification on the impact properties A356·2 alloys in as cast and heated treat conditions have been investigated. The results show grain refining is very effective parameter in improving the alloy toughness when the alloy is well modified. The best values for total absorbed energy of T6-tempered alloys are achieved after using 0·04%Ti in the form of Al–5%Ti–1%B and Al–10%Ti master alloys. A significant degradation in impact properties is observed due to the Sr–B interaction in some cases leading to the formation of Sr₆B compound. The improvements in toughness are mainly due to the change in silicon particle morphology and to the dissolution and fragmentation of intermetallics during the solution heat treatment process at 540°C for 8 h prior to quenching and artificial aging.     

Influence of titanium additions on the properties of Al−Zn−Mg system cast alloys

Conclusion Addition of titanium increases the strength and plasticity of Al–Zn–Mg system casting alloys. The alloys with 0.2–0.3% Ti have the best mechanical properties. These alloys strengthen during natural and artificial aging without preliminary hardening. The highest strength is reached after hardening and artificial aging. Fracture of the alloys after heat treatment has a ductile character. Local deformation occurs nonuniformly in the alloys. The alloys are not prone toward general or intergranular corrosion.All-Union Scientific-Research Institute for Electrical Machinery. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 48–50, February, 1990.     

Improvement of strength and ductility of Al-Cu-Li alloy through cryogenic rolling followed by aging

To develop an improved approach in achieving an excellent combination of high strength and ductility, the solutionized Al-Cu-Li plates were subjected to rolling at cryogenic and room temperatures, respectively, to a reduction of 83%, followed by aging treatment at 160 °C. The results indicate that Al-Cu-Li alloys through cryogenic rolling followed by aging treatment possess better mechanical properties. Rolling at cryogenic temperature produces a high density of dislocations because of the suppression of dynamic recovery, which in turn promotes the precipitation of T₁ (Al₂CuLi) precipitates during aging. Such high density of T₁ precipitates enable effective dislocation pinning, leading to an increase in strength and ductility. In contrast, room temperature rolled alloys after aging treatment exhibit lower strength and ductility due to low density of T₁ precipitates in the grain interior and high density of T₁ precipitates around subgrain boundaries.     

Effects of aging on the microstructures and mechanical properties of extruded AM50 ＋ xCa magnesium alloys

The effects of aging treatment on the microstructures and mechanical properties of extruded AM50 ＋ xCa alloys （x=0, 1, 2 wt.%） were studied. The results indicated the secondary phase Mgl7Al12 precipitated from the saturated α-Mg solid solution while Al2Ca changed slightly when the aging time was increased. The hardness of extruded AM50 ＋ xCa al- loys increased initially to its peak, and then dropped to reach its original hardness with the increase in aging time. With the increase in aging temperature, the hardness of the AM50 ＋ 2Ca ahoy decreased, whereas the hardness of AM50 and AM50 ＋ 1Ca alloys decreased in the initial stages of aging treatment and increased in the later stages of aging treatment. The tensile strengths of AM50 and AM50 ＋ 1Ca alloys increased after aging treatment for the precipitation of Mg17Al12 phase, which increases the resistance against dislocation movement at the grain boundary; with increase in aging temperature, their tensile strengths increased. For AM50 ＋ 2Ca alloy, the tensile strength declined after aging at 150℃ and 175℃, while it increased slightly at 200℃. The ductility of AM50 ＋ xCa alloys （x = 0, 1, 2 wt.%） declined after aging treatment.     

镁合金预变形时效处理工艺的研究现状

分析了预变形工艺对镁合金孪生行为的影响,论述了不同类型的镁合金在预变形时效处理工艺下的析出行为,阐明了该工艺下镁合金力学性能的变化规律及强化机制,并提出了通过变形工艺可以调控镁合金的析出行为,使镁合金的晶内组织向着有利于提升力学性能的结构发展,最后对预变形时效处理工艺未来的研究方向进行了展望。     

热处理对轧制AM50+xCa组织及力学性能的影响

研究了固溶、时效对轧制AM50＋xCa（x=0.1％,2％,质量分数）镁合金组织和力学性能的影响。结果表明：合金轧制后,随着固溶时间的增加,Mg17Al12相通过原子扩散弥散嘲溶到镁基体中;而Al2Ca相比较稳定,部分变细,逐渐断开并出现球化现象。随着时效时间的增加,Mg17Al12相以细粒状从过饱和的镁基体中析出;而Al2Ca相比较稳定,其数量和形状变化极小。固溶处理后,合金硬度和拉伸强度有所下降;时效处理后,合金硬度增加到峰值后下降,拉伸强度略有升高。固溶、时效处理肟轧制AM50和AM50＋1Ca镁合金的颦性有所增加;而轧制AMSO＋2Ca镁合金固溶后塑性有所增加,时效后塑性有所下降。     

Structural transformations in steel 03Kh11N10M2T in dynamic aging

The use of aging under a load (dynamic aging) provides an elevated set of properties in spring steels and alloys. Results of a study of structural transformations in maraging steel 03Kh11N10M2T in dynamic aging are presented. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 2–4, October, 1998. See the beginning of the compilation in No. 9 (1998).     

热处理对1420铝锂合金晶间腐蚀和剥蚀性能的影响

铝锂合金在相应的介质中存在晶间腐蚀和剥蚀倾向，组织结构不同导致合金的腐蚀性能不同。通过分别对经固溶（ST）、欠时效（UA）、峰时效（PA）和过时效（OA）处理后1420铝锂合金腐蚀性能的分析研究，表明经峰时效处理后的耐蚀性最差，固溶处理具有最佳的耐晶间腐蚀和剥蚀性能。     

人工时效与自然时效对Al-7Si-0.6Mg铝合金组织与力学性能的影响

研究了人工与自然双重阶段时效对铸造Al-7Si-0.6Mg合金的力学性能影响.试验结果表明:A1-7Si-0.6Mg合金经535℃×10h(固溶)+水淬+165℃×1 h(人工时效)+24h(自然时效)+165℃×5 h(人工时效)热处理工艺后,其抗拉强度321MPa、伸长率12％,相对T6热处理工艺试样其抗拉强度及伸长率分别提高了7.7％和140％;其室温拉伸断口中存在大量的等轴韧窝,尺寸细小且分布均匀,属于韧性断裂方式;人工与自然双重阶段时效对A1-7Si-0.6Mg力学性能提高的机制主要是共晶硅的球粒化与分布、Mg2Si沉淀强化、析出相Si相与位错间的交互作用.     

Fe-Cu二元合金中的B2析出相及时效硬化(英文)

研究了不同成分的Fe-Cu二元合金在过饱和固溶体状态下晶粒尺寸和硬度之间的关系,分析了Cu元素的固溶强化作用。研究了Fe-Cu二元合金的时效硬化现象和Cu元素的析出过程。结果表明Fe-Cu二元合金硬度值增加近一倍。通过透射电镜观察到随时效时间的增加,析出相的尺寸逐渐增大,形状由球形变为棒状。电子衍射花样分析得知,时效处理硬度达到最大值时对应的析出相具有B2型晶体结构,与基体之间保持平行位向关系。透射电镜观察到位错与析出相之间存在典型的引力型交互作用,由于软析出相对运动位错的钉扎效应而使Fe-Cu二元合金得到有效强化。     

Influence of Fluidized Bed Quenching on the Mechanical Properties and Quality Index of T6 Tempered B319.2-Type Aluminum Alloys

The current study aimed to investigate the effect of fluidized sand bed (FB) quenching on the mechanical performance of B319.2 aluminum cast alloys. Traditional water and conventional hot air (CF) quenching media were used to establish a relevant comparison with FB quenching. Quality charts were generated using two models of quality indices to support the selection of material conditions on the basis of the proposed quality indices. The use of an FB for the direct quenching-aging treatment of B319.2 casting alloys yields greater UTS and YS values compared to conventional furnace quenched alloys. The strength values of T6 tempered B319 alloys are greater when quenched in water compared with those quenched in an FB or CF. For the same aging conditions (170°C/4h), the fluidized bed quenched-aged 319 alloys show nearly the same or better strength values than those quenched in water and then aged in a CF or an FB. Based on the quality charts developed for alloys subjected to different quenching media, higher quality index values are obtained by conventional furnace quenched-aged T6-tempered B319 alloys. The modification factor has the most significant effect on the quality results of the alloys investigated, for all heat treatment cycles, as compared to other metallurgical parameters. The results of alloys subjected to multi-temperature aging cycles reveal that the optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 240 °C/2 h followed by 170 °C/8 h, rather than T6 aging treatments. The regression models indicate that the mean quality values of B319 alloys are highly quench sensitive due to the formation of a larger percent of clusters in Al-Si-Cu-Mg alloys. These clusters act as heterogeneous nucleation sites for precipitation and enhance the aging process.