No abstract

No abstract

This paper studies the superplasticity of conventional sheets of Ti-1V-4Al-3Mo (α+β) alloy. The flow behavior was investigated in a temperature range of 775 °C-900 °C and a constant strain rate range of 2×10 −4-5×10 −3 s −1 via uniaxial tensile tests. The microstructure evolution during the superplastic deformation was analyzed. The results revealed that, the flow behavior of Ti-1V-4Al-3Mo (α+β) alloy is characterized by strain softening phenomena. The experimental stress-strain data were used to build a power law constitutive model. A processing map, which shows the safe and unsafe regions of deformation, was also constructed for the studied alloy. The optimal deformation regime was attained at a temperature of 875 °C and strain rate of 1×10 −3 s −1 which provided a β phase fraction of 52%. Equiaxed fine-grained α and β structure with size of 2-3 μm as well as dislocation activity inside the α-grains were identified in the optimum deformation regime.

No abstract

Increasing the strain rate at superplastic forming is a challenging technical and economic task of aluminum forming manufacturing. New aluminum sheets exhibiting high strain rate superplasticity at strain rates above 0.01 s−1 are required. This study describes the microstructure and the superplasticity properties of a new high-strength Al-Zn-Mg-based alloy processed by a simple thermomechanical treatment including hot and cold rolling. The new alloy contains Ni to form Al3Ni coarse particles and minor additions of Zr (0.19 wt.%) and Sc (0.06 wt.%) to form nanoprecipitates of the L12-Al3 (Sc,Zr) phase. The design of chemical and phase compositions of the alloy provides superplasticity with an elongation of 600–800% in a strain rate range of 0.01 to 0.6/s and residual cavitation less than 2%. A mean elongation-to-failure of 400% is observed at an extremely high constant strain rate of 1 s−1. The strain-induced evolution of the grain and dislocation structures as well as the L12 precipitates at superplastic deformation is studied. The dynamic recrystallization at superplastic deformation is confirmed. The superplastic flow behavior of the proposed alloy is modeled via a mathematical Arrhenius-type constitutive model and an artificial neural network model. Both models exhibit good predictability at low and high strain rates of superplastic deformation.