Materials Science Forum Vol. 735

Abstract: Aluminium alloys with a chemical compositions of Al–5.8%Mg–0.52%Mn–0.2%Sc–0.07%Zr–0.16%Fe-0.1%Si and Al-5.4%Mg-0.34%Mn-0.2%Sc-0.07%Zr-0.07%Fe-0.02Si (in weight %), denoted as 1570 and 1570C, respectively, were processed by equal-channel angular pressing (ECAP) at 300°C up to strain ε~12. Extensive grain refinement provided the formation of fully recrystallized structure with the average grain sizes of 0.7 and 0.6 μm, respectively. Tensile tests were carried out in the temperature interval 200–550oC at strain rates ranging from 10-4 to 10-1 s-1. Very high tensile elongations (>1000%) were achieved in the both alloys at T350oC and strain rates higher than 10-3 s-1.

Abstract: Blow forming accompanied with superplasticity makes possible the forming of complex parts, which cannot be formed by cold press forming. The conventional superplastic AA5083 alloy ‘ALNOVI-1’ developed by the Furukawa-Sky Aluminum Corp. shows high superplasticity because of its fine grain and is widely used for blow forming. However, for mass production of components, an Al-Mg alloy with finer-sized grains is needed. In this research, the newly developed high Mn version of the Al-Mg alloy ‘ALNOVI-U’ is used, and this material possesses grains finer than those of the conventional AA5083 alloy. The effects of finer grain size on the blow formability at high strain rates over 10^-2/s and the properties of the resulting moldings were studied.

Abstract: A numerical simulation of superplastic double-sided roll forming of aluminium alloy discal part is presented in this paper. The numerical results show strain and strain rate distribution, grain refinment, transformation from general hot forging to superplastic forming. The superplastic forming includes two stages: the small deformation stage is controlled by plastic deformation and grain refinment, and the large deformation stage superplastic deformation is main deformation mechanism.

Abstract: The manuscript considers the possibility of using of superplastic deformation at hot forging of aluminum alloys. The analysis has been conducted concerning the use of different methods for imparting ultra-fine grain structure to aluminum alloys in terms of their workability. The deformation and heat processing for thermo-strengthened aluminum alloys has been proposed in which superplastic deformation is combined with hardening. The effect of such processing on mechanical and corrosion properties of aluminum alloys is shown. The model processing of a component is demonstrated at forging under superplasticity conditions often surpass the advantages obtained.

Abstract: The Zn-22Al alloy with fine-equi-axed has been well known as a typical superplastic metallic material [1]. In the present study, The Zn-22Al alloy ingot of 20mm thickness was homogenized, either air-cooled or water-quenched, and then hot-rolled to a thickness of 2mm. Microstractural observation, showed that in the air-cooled specimens lammellar microstructure was formed after homogenization, and become fragmented to fine-grained microstructure as the hot rolling process proceeded. In the water-quenched specimens, equi-axed fine-grained microstructure with grain size under 2.1μm was attained and maintained throughout the hot rolling process.

Abstract: Unique superplastic elongations up to 4100% were achieved at 450°C in the strain rate range of 10^-2-10^-1 s^-1 for Al-Mg-Sc-Zr alloy with a grain size ~1 μm processed by warm-to-hot equal channel angular pressing. Such a behavior is attributed to the synergy of complementary factors resulted in high homogeneity and stability of ultrafine-grained microstructure and superplastic flow, involving large proportion of high-angle grain boundaries, presence of dispersoids of aluminides of transition metals and negligible amount of coarse excess phases.

Abstract: This article describes the high rate superplastic forming. The high rate superplastic forming technology is a new complex process,which integrates hot stamping and superplastic forming .It has feature of rapidity of the hot stamping and character of excellent formability of the superplastic forming.We obtained the best proportion of the hot forming and the superplastic forming through simulation experiment, and formed a car’s abonnet by applying the proportion.Compared with the high rate superplastic forming,the forming quality is better than that of hot forming. and the forming time is less than that of superplastic forming. Result shows that ,the high rate superplastic forming technology can meet the requirements for mass production.

Abstract: In this work, the superplastic behavior of AZ31, AZ61 and AZ80 magnesium alloys was investigated. The alloys were hydrostatically extruded at only 150 °C to get fine grained microstructures (−2, 10⁻³ and 10⁻⁴ s⁻¹. It was found that all alloys exhibited superplasticity at 200 °C, 175 °C and 225 °C for AZ31, AZ61 and AZ80 alloys, respectively. Low temperature dynamic recrystallisation played an important role for generating a finer and homogeneous microstructure during testing which enhances the deformation behavior of the alloys at these temperatures.

Abstract: Friction stir processing (FSP) causes fine-equiaxed microstructure[1]. In this study, microstructure and mechanical properties of a 7075 aluminum alloy subjected to multipass FSP, MP-FSP, are assessed. A new zone, PBZ, has been discovered between stir zones, SZs. The SZs are composed of fine-equiaxed grains, while PBZs are composed of two types of (fine-equiaxed and coarse-elongated) grains, both of which are still finer than those of base metal. Elongation at 773K of MP-FSPed specimen becomes larger than that of base metal, based on superplastic deformation due to the finer microstructure. Local elongation is smaller in PBZ than in SZ.

Abstract: This work presents a formation of ultrafine-grained microstructure (d ~ 0.2 μm) with high fraction of high-angle boundary in industrial Ti–6Al–4V alloy produced by the hot compression of a sample with the acicular α′martensite starting microstructure . It is found that heterogeneous nucleation becomes dominant in the case of the α’ starting microstructure.α