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Journal ArticleDOI

Tensile flow and fracture behaviour of a superplastic Al-Ca-Zn alloy

01 Nov 1990-Journal of Materials Science (Springer)-Vol. 25, Iss: 11, pp 4579-4586
TL;DR: In this paper, the tensile flow behavior in the range 275 to 550 ° C of an ultra-fine-grained superplastic Al-Ca-Zn alloy is reported.
Abstract: The tensile flow behaviour in the range 275 to 550 ° C of an ultra-fine-grained superplastic Al-Ca-Zn alloy is reported. Under certain conditions of temperature and strain rate, superplastic ductility could be established. Fracture surfaces of tensile specimens tested in the above temperature range were examined by scanning electron microscopy and a correlation could be obtained between the ductility, as revealed by the tension tests, and the fracture behaviour. The fractographic studies also suggested a transition in the deformation process from grain deformation (mainly slip) at the lower temperatures to grain-boundary deformation (predominantly grain-boundary sliding) in the vicinity of 425 ° C.
Citations
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Journal ArticleDOI
30 May 2018-JOM
TL;DR: The phase composition of aluminum alloys in the Al-Ca-Fe-Si system, including the distribution of phases in the solid state and solidification reactions, has been studied in this paper.
Abstract: The phase composition of aluminum alloys in the Al-Ca-Fe-Si system, including the distribution of phases in the solid state and solidification reactions, has been studied. It is shown that the addition of iron and silicon to Al-Ca alloys leads to the formation of ternary Al2CaSi2 and Al10CaFe2 compounds. The equilibrium between these compounds implies the occurrence of the quaternary L → Al + Al4Ca + Al2CaSi2 + Al10CaFe2 eutectic reaction. The alloys near this eutectic have the best structure, which is typical of aluminum matrix composites. It is shown that Al-Ca alloys can have high manufacturability during both shape casting and rolling. This is due to the combination of a narrow temperature range of solidification and a favorable morphology for the eutectic, which has a fine structure. The combination of the mechanical and physical properties of the Al-Ca eutectic-based alloys significantly exceed those of branded alloys based on aluminum–silicon eutectics.

26 citations

Journal ArticleDOI
TL;DR: A qualitative and quantitative analysis of the new Al-Ca-Mn-Fe phase diagram in the region of the aluminium corner is carried out using both thermodynamic calculations and experimental methods as mentioned in this paper.

22 citations

Journal ArticleDOI
TL;DR: In this article, the effect of deformation by high pressure torsion (HPT) on the hardening, structure transformations, and thermal stability of two eutectic alloys: binary Al-8.0% Ca and complex Al-3.5% Ca.
Abstract: The study investigated the effect of deformation by high-pressure torsion (HPT) on the hardening, structure transformations, and thermal stability of two eutectic alloys: binary – Al-8.0% Ca and complex-alloyed – Al-3.5% Ca-0.9% Mn-0.5% Fe-0.1% Zr-0.1% Sc. The HPT-deformation of the alloys (5 revolutions) led to the formation of a nanocrystalline structure with a high density of crystal defects. A predominant grain size was 20–40 nm in the binary alloy and 11–34 nm in the complex alloy. HPT resulted in the refinement of the Al4Ca particles for the binary alloy and the transformation of the Al4Ca particles into nanoclusters and segregation for the complex alloy. HPT increased the microhardness of the binary alloy to 1.80–2.05 GPa (~2 times), and of the complex-alloyed alloy to 2.40–2.70 GPa (4.1–4.6 times). The hardening of the complex alloy is retained to higher heating temperatures compared to the binary alloy.

18 citations

Journal ArticleDOI
TL;DR: In this article, a tensile test of the 2099 Al-Li alloy was performed at the temperature range from 250 to 450°C and the strain rate range from 0.001 to 5.0 s−1.
Abstract: Hot deformation behavior and processing maps of the 2099 Al-Li alloy are investigated by tensile test at the temperature range from 250 to 450 °C and the strain rate range from 0.001 to 5.0 s−1. The typical true stress-true strain curves show that the flow stress increases with increasing the strain rate and decreasing the deforming temperature. All curves exhibit rapid work hardening at an initial stage of strain followed by remarkable dynamic softening. Based on the flow stress behavior, the processing maps are calculated and analyzed according to the dynamic materials model (DMM). The processing maps exhibit an instability domain in the temperature and strain rate ranges: T = 250-260 °C and $$\dot{\upvarepsilon }$$ = 0.1-0.5 s−1. The maps also exhibit an optimum hot working condition in the stability domain that occurs in the temperature of 400 °C for a strain rate of 0.001 s−1 and having a maximum efficiency of 60%. The microstructural examinations exhibit the occurrence of dynamic recovery (DRV) during hot deformation of the 2099 alloy which is the dominant softening mechanism in the alloy. The fracture behavior changes from a brittle fracture to a ductile fracture as strain rate decreases and temperature increases.

18 citations

Journal ArticleDOI
TL;DR: A review of the application fields of metallic calcium and its influence on the structure and properties of various alloys are considered in this article, where several groups of new promising Ca-containing aluminum alloys: (i) alloys hardening without quenching due to the isolation of nanodimensional particles of Al3Zr, Al3Sc, and Al3(Zr) phases; (ii) high-strength alloys alloyed with traditional hardening elements of the aluminum solid solution, such as zinc and magnesium; and (iii) composite alloys having more
Abstract: Calcium is one of the most widespread and, consequently, low-cost metals on Earth. It has been applied for a long time in modifying and alloying alloys of heavy metals, in particular, lead and copper. It is used as a modifier in cast irons and steels. Calcium began being applied for alloying light alloys based on aluminum and magnesium comparatively recently. In this review, the application fields of metallic calcium and its influence on the structure and properties of various alloys are considered. Alloys based on aluminum–calcium eutectic have been systematically investigated over last few years, and it has been established that they possess casting properties no worse than these of silumins, and they can be hot-rolled and cold-rolled with a high degree of deformation. Ternary and more complex phase diagrams of systems including calcium are constructed and multicomponent alloys based on them are investigated. All these circumstances make it possible to outline several groups of new promising Ca-containing aluminum alloys: (i) alloys hardening without quenching due to the isolation of nanodimensional particles of Al3Zr, Al3Sc, and Al3(Zr,Sc) phases; (ii) high-strength alloys alloyed with traditional hardening elements of the aluminum solid solution, such as zinc and magnesium; and (iii) composite alloys having more than 20% eutectic intermetallic compounds in the structure. All these materials have reduced density, an improved set of operational properties, increased corrosion resistance, and high manufacturability when producing cast and deformed half-finished products.

15 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the microstructural aspects of Dimpled Rips in metals and alloys are reviewed and models describing the dimpled rupture process are given and discussed in light of experimental observations.
Abstract: The microstructural aspects of dimpled rupture in metals and alloys are reviewed. The models describing the dimpled rupture process are given and discussed in light of experimental observations. Practical means of improving resistance to fracture by dimpled rupture are presented.

164 citations

Journal ArticleDOI
TL;DR: In this paper, a superplastic aluminum alloy based on the hitherto unexploited AlCaZn eutectic system is described, and the super-plastic forming behavior of a 5.5wt.%Zn alloy and the mechanical properties at room temperature after forming are determined.

42 citations

Journal ArticleDOI
TL;DR: The time required for the attainment of steady state superplastic flow is predicted and experimentally verified in this paper, where the effect of strain rate, grain size and test temperature on the shape of the true stress-true strain curve (up to and just beyond the onset of steady-state flow) is considered.

19 citations

Journal ArticleDOI
TL;DR: In this paper, the deformation of fine-grained Al-5wt.%Ca-5w.%Zn eutectic alloy has been investigated and the alloy showed superplastic behaviour between 400 and 500°C with a maximum tensile elongation of 500% and a maximum strain rate sensitivity parameter of 0.32.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the forming limit diagram and strain distribution under punching stretching at room temperature of an AI-Ca-Zn (superplastic) alloy have been evaluated and tensile behaviour up to 200°C is reported.
Abstract: The forming limit diagram and strain distribution under punch stretching at room temperature of an AI-Ca-Zn (superplastic) alloy have been evaluated. Tensile behaviour up to 200° C is reported. The fracture surfaces have been examined by scanning electron microscopy and the results are analysed to support the failure criterion proposed earlier by Marciniaket al.

6 citations