| Project Team | Institution | Role | ||
| Assoc Professor Carlos Cáceres | The University of Queensland | Chief Investigator | ||
| Professor Yuri Estrin | Monash University | Associate Investigator | ||
| Professor Mark Hoffman | The University of New South Wales | Chief Investigator | ||
| Mr Charles Loo Chin Moy | The University of Sydney | Postgraduate Student | ||
| Dr Gwenaelle Proust | The University of Sydney | Associate Investigator | ||
| Dr Gianluca Ranz | The University of Sydney | Associate Investigator | ||
| Dr Luming Shen | The University of Sydney | Associate Investigator | ||
| Professor Simon Ringer | The University of Sydney | Chief Investigator | ||
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Executive Summary
Reasonable progress has been made in the area of computational simulation and modelling of the strength of high pressure diecast (HPDC) Mg alloys. Preliminary atomistic simulations on the dislocation-solid solute interaction have been performed. The verification of inverse analysis on the bulk Al alloy is also underway. Research works that are jointly supported by other funding sources and Project B1.4 have resulted in 7 peer-reviewed journal articles in International Journal of Plasticity, International Journal for Multiscale Computational Engineering, Composites Science and Technology, International Journal of Solids and Structures, Mechanics of Advanced Materials and Structures, and International Journal of Materials and Product Technology and 1 peer-review conference paper in the Second International Conference on Smart Materials and Nanotechnology in Engineering. The collaboration among the researchers from Project B1.3 and B1.4 has been very effective. A/Prof Cáceres and his team visited the University of Sydney and a detailed research collaboration plan was developed (Refer to Project B1.3 report).
Reasonable progress has been made in the area of computational simulation and modelling of the strength of high pressure diecast (HPDC) Mg alloys. Preliminary atomistic simulations on the dislocation-solid solute interaction have been performed. The verification of inverse analysis on the bulk Al alloy is also underway. Research works that are jointly supported by other funding sources and Project B1.4 have resulted in 7 peer-reviewed journal articles in International Journal of Plasticity, International Journal for Multiscale Computational Engineering, Composites Science and Technology, International Journal of Solids and Structures, Mechanics of Advanced Materials and Structures, and International Journal of Materials and Product Technology and 1 peer-review conference paper in the Second International Conference on Smart Materials and Nanotechnology in Engineering. The collaboration among the researchers from Project B1.3 and B1.4 has been very effective. A/Prof Cáceres and his team visited the University of Sydney and a detailed research collaboration plan was developed (Refer to Project B1.3 report).
Project Aims/Targets
Project B1.4 aims to understand the strengthening mechanism of high pressure diecast (HPDC) Mg alloys using simulation and modelling approach. The project consists of the following three main components:
Project B1.4 aims to understand the strengthening mechanism of high pressure diecast (HPDC) Mg alloys using simulation and modelling approach. The project consists of the following three main components:
Component 1: Characterise the material properties of hybrid materials.
Hybrid material systems, such as HPDC Mg alloys or multilayer components are increasingly being considered to improve functional performances. As part of this project numerical models will be developed to characterise their mechanical properties exhibited and to investigate their possible failure mechanisms. Three-dimensional finite element models will be developed based on structural observations to gain a deeper understanding of these. The numerical work will focus on both multi-layered samples and HPDC Mg alloys. Indentation tests will be carried out on Al and HPDC Mg alloys to characterize their mechanical properties. For example, in the case of the HPDC Mg alloys it is envisaged that this work will provide insight into the contribution of the intermetallic microstructure to the overall component response.
Component 2: Investigate the effect of solid solute using atomistic simulations at the nanoscale.
In this component, molecular mechanics (MM) and molecular dynamics (MD) simulations will be performed to study the interactions between basal plane edge/screw dislocation and Al solid solute at different temperatures. The parameters to change in the atomistic simulations include the concentration of Al solute in the alloy and temperature. The aim is to establish the relationship between the Alloy strength and Al solute concentration at different temperatures and to understand the solid solute strengthening mechanism in HPDC Mg alloys.
Component 3: Develop a polycrystal constitutive model for Mg-Al alloys at the nano/micro scales.
In this component, a polycrystal constitutive model for Mg-Al alloys will be developed and coupled with the FEM results to isolate the effect of the intermetallic microstructure from the other effects, and thus to gain a better understanding of the deformation of the material. In particular, the proposed polycrystal constitutive model will address texture and hardening evolution simultaneously, incorporate the solid solution effect, implement the Hall-Petch effect and include the effect of possible clustering or precipitates in HPDC Mg alloys. Additional experimental data using TEM and APT are necessary to calibrate the model parameters and to verify the model predictions.
It is expected that the modelling and simulation procedures developed based on the HPDC Mg alloys could be extended and applied to other hybrid materials (e.g. multilayer materials) in the future.
Hybrid material systems, such as HPDC Mg alloys or multilayer components are increasingly being considered to improve functional performances. As part of this project numerical models will be developed to characterise their mechanical properties exhibited and to investigate their possible failure mechanisms. Three-dimensional finite element models will be developed based on structural observations to gain a deeper understanding of these. The numerical work will focus on both multi-layered samples and HPDC Mg alloys. Indentation tests will be carried out on Al and HPDC Mg alloys to characterize their mechanical properties. For example, in the case of the HPDC Mg alloys it is envisaged that this work will provide insight into the contribution of the intermetallic microstructure to the overall component response.
Component 2: Investigate the effect of solid solute using atomistic simulations at the nanoscale.
In this component, molecular mechanics (MM) and molecular dynamics (MD) simulations will be performed to study the interactions between basal plane edge/screw dislocation and Al solid solute at different temperatures. The parameters to change in the atomistic simulations include the concentration of Al solute in the alloy and temperature. The aim is to establish the relationship between the Alloy strength and Al solute concentration at different temperatures and to understand the solid solute strengthening mechanism in HPDC Mg alloys.
Component 3: Develop a polycrystal constitutive model for Mg-Al alloys at the nano/micro scales.
In this component, a polycrystal constitutive model for Mg-Al alloys will be developed and coupled with the FEM results to isolate the effect of the intermetallic microstructure from the other effects, and thus to gain a better understanding of the deformation of the material. In particular, the proposed polycrystal constitutive model will address texture and hardening evolution simultaneously, incorporate the solid solution effect, implement the Hall-Petch effect and include the effect of possible clustering or precipitates in HPDC Mg alloys. Additional experimental data using TEM and APT are necessary to calibrate the model parameters and to verify the model predictions.
It is expected that the modelling and simulation procedures developed based on the HPDC Mg alloys could be extended and applied to other hybrid materials (e.g. multilayer materials) in the future.
Component 1: Characterise the material properties of hybrid materials.
A numerical model has been developed in Abaqus to simulate the indentation of a multi-layered material with alternating material properties. This has been utilised to set-up approximating polynomials of the finite element model based on the Aoki method. This simplification is necessary to enable inverse analysis techniques to be applied for the characterisation of the material properties of the alternating layers which, otherwise, would become prohibitive in terms of computational requirements. The identification process has been validated numerically against computer-generated results.
Work is currently underway to apply the proposed inverse analysis method to Al2024 prepared using different durations of heat-treatment. This is believed to be a very useful validation test to utilise the proposed approach for the characterisation of real material components.
Component 2: Investigate the effect of solid solute using atomistic simulations at the nanoscale.
MM simulations of the interactions between basal plane edge/screw dislocation and Al solid solute at 0 K have been performed. In the simulations, MD code LAMMPS (Plimpton, S.J., 1995) is adopted and embedded atom method (Daw and Baskes, 1983; Daw and Baskes, 1984) is used to describe Mg-Mg, Al-Al and Mg-Al interactions with the potential model parameters being obtained from Mendelev (2009). The suitable simulation cell size and time step that balance the accuracy and efficiency have been identified. It is found from the MM simulation results that the core basal edge and screw dislocations are unstable and will disassociate into two Shockley partial dislocations, as demonstrated in Figure B13 for the edge dislocation. The split distances of the two partial dislocations match well with previous ab initio calculations (See Table B2). As shown in Figure B14, the critical shear stresses of edge and screw dislocations in the basal plane generally increase as the Al content increases, although the drop of strength around at. 4% Al is still not well understood.
A numerical model has been developed in Abaqus to simulate the indentation of a multi-layered material with alternating material properties. This has been utilised to set-up approximating polynomials of the finite element model based on the Aoki method. This simplification is necessary to enable inverse analysis techniques to be applied for the characterisation of the material properties of the alternating layers which, otherwise, would become prohibitive in terms of computational requirements. The identification process has been validated numerically against computer-generated results.
Work is currently underway to apply the proposed inverse analysis method to Al2024 prepared using different durations of heat-treatment. This is believed to be a very useful validation test to utilise the proposed approach for the characterisation of real material components.
Component 2: Investigate the effect of solid solute using atomistic simulations at the nanoscale.
MM simulations of the interactions between basal plane edge/screw dislocation and Al solid solute at 0 K have been performed. In the simulations, MD code LAMMPS (Plimpton, S.J., 1995) is adopted and embedded atom method (Daw and Baskes, 1983; Daw and Baskes, 1984) is used to describe Mg-Mg, Al-Al and Mg-Al interactions with the potential model parameters being obtained from Mendelev (2009). The suitable simulation cell size and time step that balance the accuracy and efficiency have been identified. It is found from the MM simulation results that the core basal edge and screw dislocations are unstable and will disassociate into two Shockley partial dislocations, as demonstrated in Figure B13 for the edge dislocation. The split distances of the two partial dislocations match well with previous ab initio calculations (See Table B2). As shown in Figure B14, the critical shear stresses of edge and screw dislocations in the basal plane generally increase as the Al content increases, although the drop of strength around at. 4% Al is still not well understood.
Component 3: Develop a polycrystal constitutive model for Mg-Al alloys from nano to micro scales.
The initial literature search has been done on that aspect of the project. It has been decided to use a Kocks-Mecking-Estrin model to describe the hardening laws of the deformation modes. These hardening laws will be integrated into the VPSC code developed by Tomé and Lebensohn. The mechanical and microstructure data collected by Cáceres’ group will be used to calibrate the model.
The initial literature search has been done on that aspect of the project. It has been decided to use a Kocks-Mecking-Estrin model to describe the hardening laws of the deformation modes. These hardening laws will be integrated into the VPSC code developed by Tomé and Lebensohn. The mechanical and microstructure data collected by Cáceres’ group will be used to calibrate the model.
| Yasi et al. 2009 (ab initio) |
This stud (Mendelev 2009 EAM) |
Yasi et al. 2009 (Sun 2006 EAM) |
Yasi et al. 2009 (Liu 1996 EAM) |
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| Basal edge | 16.7 | 18.8 | 14.3 | 12.7 |
| Basal screw | 6.3 | 6.9 | 6.3 | 1.4 |
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Future Activity Plan
Completion of the validation of the inverse analysis approach for the characterisation of real components made of Al2024 heat-treated for different periods of time will be carried out. This approach will then be extended and applied to identify the mechanical behaviour of the HPDC Mg alloys. The 3D network structure in HPDC Mg alloys will be modeled using an in situ composites approach to provide some insight into the strengthening effect of the network. The data files collected at UQ through the FIB 3D reconstructions will be the base of the FE modelling. Recruitment of a post-doctoral fellow and postgraduate student will progress further activities within this project.
Completion of the validation of the inverse analysis approach for the characterisation of real components made of Al2024 heat-treated for different periods of time will be carried out. This approach will then be extended and applied to identify the mechanical behaviour of the HPDC Mg alloys. The 3D network structure in HPDC Mg alloys will be modeled using an in situ composites approach to provide some insight into the strengthening effect of the network. The data files collected at UQ through the FIB 3D reconstructions will be the base of the FE modelling. Recruitment of a post-doctoral fellow and postgraduate student will progress further activities within this project.