The objective of the present study is to carry out high strain rate tensile tests on 7017 aluminium alloy under different strain rates ranging from 0.01, 500, 1000 and 1500 s−1 and at temperatures of 25, 100, 200 and 300 °C. Quasi-Static tensile stress–strain curves were generated using INSTRON 8500 machine. Johnson-Cook (J-C) constitutive model was developed for 7017 aluminium alloy based on high strain rate tensile data generated from split Hopkinson tension bar (SHTB) at various temperatures. This study evidently showed an improvement in dynamic strength as the strain rate increases. The predictions of J-C model are observed to be in consistence with the experimental data for all strain rates and temperatures. The fracture surfaces of specimens tested were studied under SEM. The change in fracture mode has been observed at different strain rates. The shear mode of fracture is dominant at lower strain rates (0.01 and 500 s−1); whereas cup- and cone-like surface representing dimple structure is found at the higher strain rates (1000 and 1500 s−1). The numbers of dimples at high strain rates are more than the quasi-static and intermediate strain rates. It is also observed that the flow stress decreases with increase in temperature. The 7017 aluminium alloy demonstrates thermal softening at higher temperatures. So when the temperature is more than 200 °C at these strain rates, thermal softening is predominant mode of deformation mechanism. It is found that when the temperature increases to 200 °C, the number of dimples rises and the dimple size of 7017 aluminium alloy is larger than at lower temperatures.

Tensile behaviour of aluminium 7017 alloy at various temperatures and strain rates

Effect of laser shock peening on mechanical and microstructural aspects of 6061-T6 aluminum alloy

Microstructure evolution and physical-based diffusion constitutive analysis of Al-Mg-Si alloy during hot deformation

To characterize the hot deformation behavior of commonly used aluminum alloy, a homogeneous Al–Mg–Si–Mn–Cr alloy was analyzed by thermal simulation test at deformation temperature range of 653–803 K and strain rate range of 0.01–10 s−1. The flow stresses were predicted by modified Johnson–Cook model, modified Zerilli–Armstrong model and strain-compensated Arrhenius model. The results show that the three models are able to predict the flow behavior of the alloy. Strain-compensated Arrhenius model has the best simulation ability in predicting flow stresses, while the modified Johnson–Cook model has lower prediction accuracy and the modified Zerilli–Armstrong model has poorer predictive ability at low strain rates. Microstructure evolution shows that subgrain boundaries form at original grain boundaries at first, moving toward to the center of the deformed grains. The dislocation density decreases, while the number and the size of subgrains increase with the decreasing Zener–Hollomon (Z) parameter. Both dynamic recovery (DRV) and dynamic recrystallization take place in hot deformation process. DRV is considered to be the primary dynamic softening mechanism throughout the entire hot deformation range. Continuous dynamic recrystallization and discontinuous dynamic recrystallization operate concurrently at low strain rates and high temperatures. The relationship of subgrain size and predicted flow stress is presented. Moreover, activation volume is introduced to reveal the thermal activation mechanism during hot deformation.

Characterization of hot deformation behavior and constitutive modeling of Al–Mg–Si–Mn–Cr alloy

A consistent and reasonable description of the constitutive behavior of material under the coupled effect of strain, strain rate and temperature on the flow stress of the material is highly essential in current industrial practice to design and optimize the process parameters in manufacturing operations. In order to formulate a suitable constitutive model to predict the elevated-temperature deformation behavior in high strength aluminum alloy, AA7075-T6, isothermal uniaxial tensile tests over a practical range of deformation temperatures (300–623 K) and strain rates (10 −4 –10 −1  s −1 ) were conducted. Two constitutive models, modified-Johnson Cook (m-JC) and modified-Zerilli–Armstrong (m-ZA) models are formulated considering the combined effects of strain, strain rate and temperature on flow stress. The prediction capability of these models is assessed in terms of statistical parameters, correlation coefficient and average absolute error between experimental and predicted flow stress data. In addition, finite element (FE) simulations have been carried out in order to validate the formulated model during orthogonal cutting processes. It was observed that both the models show a very high degree of linear dependence of fit as the value above 0.98. However, the m-ZA model can offer an accurate and precise estimate of the flow behavior for studied workmaterial over m-JC model. Further, the performance of developed model in FE cutting simulations is the most obvious for all moderate machining conditions and can provide relatively good prediction results for the AA7075-T6 machining process.

Zih Chao Tang

Papers

Relationship between mechanical properties and microstructural response of 6061-T6 aluminum alloy impacted at elevated temperatures