http://www.uniroma2.it/didattica/tbs2/deposito/Manufacture,_characterisation_and_application_of_cellular_metals_and_metal_foams.pdf

Manufacture, characterisation and application of cellular metals and metal foams

SLM lattice structures: Properties, performance, applications and challenges

Magnesium alloys are promising light structural materials. The present paper focuses on fine-grained magnesium-based materials. Grain refinement is attained by hot working without additional treatments. Also, a very small grain size of less than 1 μm is obtained by equal channel angular extrusion. A good combination of high strength and high ductility at room temperature is attained by grain refinement. Furthermore, fine-grained magnesium-based materials exhibit superplastic behavior at high stain rates (≥10−1 s−1) or low temperatures (≤473 K). These point out the importance of grain refinement to process magnesium-based materials with excellent mechanical properties.

Review Processing and mechanical properties of fine-grained magnesium alloys

An experimental investigation into the strain rate sensitivity of a closed-cell aluminum foam at room temperature and under compression loading is conducted. The nominal strain rates are varied by four orders of magnitude, from 3.33×10−5 to 1.6×10−1 s−1. Within this range, experimental results show that the plastic strength and the energy absorbed increase (by 31 and 52.5%, respectively) with increasing strain rate. However, the plastic strength was found to increase bilinearly with the logarithm of strain rate, whereas dense metals tend to show only a linear response. As is the case with dense metals, the strain rate sensitivity of the foam was not a constant value, but found to be dependent on the strain and incremental change in strain rate. These results are explained with the aid of suitable micromechanical models such as microinertial effects against the bucking of cell walls at high strain rates that are unique to foams.

Strain rate sensitivity of a closed-cell aluminum foam

Superplasticity in thin magnesium alloy sheets and deformation mechanism maps for magnesium alloys at elevated temperatures

Experimental study of energy absorption in a close-celled aluminum foam under dynamic loading

Superplasticity in a doubly extruded magnesium based composite, ZK60 reinforced with 17 vol.-%SiC particles, was investigated. The influences of strain rate on the flow stress and elongation in the composite were characterised. It was found that the composite exhibited superplasticity (elongation > 400%) at high strain rates (∼ 0.1 s−1). In addition, the material showed a high strain rate sensitivity of 0.5 and an activation energy of 81 kJ mol−1 in the superplastic region. Based upon these results, it was proposed that the dominant deformation mechanism is grain boundary sliding accommodated by a grain boundary diffusion process. A comparison of the superplastic behaviour was also made between the doubly extruded and singly extruded composites.

T. G. Nieh

Papers

Experimental study of energy absorption in a close-celled aluminum foam under dynamic loading

Superplasticity in doubly extruded magnesium composite ZK60/SiC/17p