Project B1: Hybrid Materials
Project Leaders: Professor Mark Hoffman & Professor Yuri Estrin
This Project addresses the development of hybrid structures in light alloy systems, both through natural control of structural evolution and through processing of artificial structures on the micro- and nano-scale. The focus is on the understanding of the role of structural elements in control of mechanical properties, and the development of novel properties through engineering of structural form and scale, using both empirical approaches and advanced computational simulation and modeling. There are four elements to the Project, as illustrated schematically in Figure B1.					Figure B1: Schematic summary of elements of Project B1, Project Leaders and institutions
Program Outline and Strategic Design Targets:
Program B1 is divided into four projects:
B1.1 is focused on the development and design of micro- and nanoscale laminates and the nexus between the two scales. The project looks at processing, microstructure development and mechanical property-structure relationships.
B1.2 is involved with the development of laminate structures containing highly porous cores with a foam or truss microstructure, focussing upon structural integrity, damage resistance and formability.
B1.3 involves the development of Mg-Al alloys with a 3D truss structure and understanding the relationship between the structure of the percolating intergranular intermetallic phase and the yield strength.
B1.4 involves the modelling and simulation of structure of developed in other project, in particular the truss structures of B1.3. The following sections provide details of these projects and their achievements. Table B1 provides an overview of the Program’s aims and design targets.
In regards to development of more damage tolerant Mg, the collaborations with the CAST-CRC have intensified, as a great testament to the recognised benefits of true collaboration between groups focused on greater outputs and research outcomes. The project has seen much experimental work and the fabrication of many tests specimens that are paving a pathway for the generation of principles that can potentially slow the rate of corrosion of typical Mg alloys. This collaborative work is embryonic, but growing, and also involving the CSIRO.
With respect to coatings and claddings, the project has had some great outputs with the bonding process of deformation leading to metallurgical bonding having been confirmed (and the graduation of a postgraduate scholar) however highlighting more work needs to be done to understand the intermixing phenomena at the interface of cold spray coatings. Initial works in partnership with ANSTO, allowing residual stresses measured using neutron diffraction for cold-sprayed coatings, which appeared to depend primarily on the coating material, and not on the process parameters. The coatings work also reveals that a mixed powder size and reinforcement (say with Al2O3) significantly improves coating properties such as bond strength and porosity; with spill over effects such as improved wear and corrosion resistance.
Other Research Outcomes
In the area of real 'surface engineering', we have seen some wonderful outcomes from the Deakin node which for the first time in the Centre was able to produce chemical surface modification upon light alloy substrates. This is a promising new avenue, and one that strengthens the respective project that has been generating outputs based on structural surface modification in the lead up.
Important outcomes that also need to be mentioned are the continued contributions of the researchers to their respective fields. Researchers from the program have been invited to numerous international conferences, have been involved in their respective editorial roles, and even had invited journal manuscripts. Relationships and collaborations have strengthened between research groups such as the CAST-CRC and CSIRO, along with intra-centre collaborations being bolstered, and significant collaboration with other institutes overseas (namely Penn State, Cambridge, Ohio State, Erlangen and Canterbury). Collaboration at such a level is a measure of impact, whilst similarly researchers within the program also hosted numerous high-level visitors from universities around the world - which indicates the enthusiasm with which the research within the centre is being carried out and perceived.
Finally, the work in the program has been attracting increasing industrial attention, with Linkage success and also the incorporation of additional personnel under the Centre umbrella as a part of leveraged projects.
The project has two major streams (Table A1), each with specific strategic design targets. A notable achievement has been the further development of the cluster-strengthened Al-Cu-Mg alloy with yield strength and total elongation of 230 MPa and ~23%, respectively (Figure A1). Such novel properties places the alloy in a new and unexplored region of property space. Work will be conducted to study the effect of structure and processing parameters on the overall performance of the alloy and its commercial viability as a replacement alloy for some 5xxx Al alloys.
Table B1
Project Title & Manager		Project Aims			Design Targets
B1.1 Micro-/Nanoscale Multilayers Manager: Dr Tania Vodenitcharova (UNSW)		1) Tear resistant, high toughness and fatigue resistant multilayered laminate in sheet form. 2) Understanding of the interaction at interfaces between different metal layers and the transition from nanostructured layers to microstructured layers in terms of material properties 3) Development of methods to characterise these layered structures.			• Tear resistant, high toughness and fatigue resistant multilayered laminate in sheet form. • The development of in situ laminate structures with high yield strength and elongation. • A model of the deformation mechanisms across interfaces of metallic laminates, leading to an understanding of the deformation properties of these laminates. • A model to explain the interaction between interfacial properties, or nano effects, and layered properties, or micron effects, in the development and deformation of layered structures. • A mechanism for determining mechanical properties of laminates and constituents using small sample indentation methods.
B1.2 Foam and Truss Laminates Manager: Professor Matthew Barnet (Deakin)		1) Tear resistant, high toughness and fatigue resistant multilayered laminate in sheet form. 2) Understanding of the interaction at interfaces between different metal layers and the transition from nanostructured layers to microstructured layers in terms of material properties			• Design maps for cellular laminates for structural applications. • Constitutive understanding of laminate behaviour under: - Bending and/or contact loading. - Subsequent stress events. • Metallic cellular laminate structures with significantly improved deformation tolerance..
B1.3 3D Network Structures Manager: Assoc Prof Carlos Cáceres (UQ)		1) Understanding the origin of the yield strength, the skin effect, the yielding behaviour, the strain hardening behaviour at low strains. 2) Gain insights into the development of damage and the bounds imposed by the cracking of the intermetallic structure to the hpdc alloys ductility.			• Design micro-truss structures through alloy/process development in Mg-Al alloys. • Design micro-truss structures through alloy/process development in other alloy systems of commercial value.
B1.4 Simulation and Modeling Manager: Dr Luming Shen (USyd)		1) Characterise the material properties of hybrid material. 2) Investigate the effect of solid solute using atomistic simulations. 3) Develop a polycrystal constitutive model for Mg-Al alloys.			• An FE model to characterize the mechanical properties of multilayer materials and HPDC Mg alloys. • An atomistic model to understand the effect of Al solute on the motion of dislocation in Mg alloys. • A constitutive model for Mg-Al alloys to isolate the effect of the intermetallic microstructure from the other effects.