Creep of aluminum-based closed-cell foams

Abstract

Metal foams creep when loaded mechanically at high homologous temperatures. We have studied the creep behavior of closed-cell aluminum-based foams with relative densities of 0.092, 0.112, and 0.163. Compressive creep tests were performed at 300°C at strain rates ranging from 10 Ϫ9 to 10 Ϫ4 s Ϫ1 . Special efforts were made to produce and characterize a bulk reference material exhibiting the same chemical composition. Results show that the foams exhibit a lower creep strength and a higher stress exponent than predicted by the Gibson-Ashby model for regular foams. The possible mechanisms responsible for this deviation are discussed. A semi-empirical rate equation is established which describes the experimental data well.

Compressive properties at elevated temperatures of porous aluminum processed by the spacer method

“…Zhang et al 6 observed in their investigations of microstructural evolution during creep that a very high stress is induced locally, resulting in a power-law breakdown region. Also, Haag et al 7 showed that porous aluminum has a lower strength and a larger stress exponent, which results from the power-law breakdown region, than predicted by the model for porous aluminum with regular pores. Microstructural inhomogeneity characteristics, such as a significant cell wall curvature and missing cell walls, significantly reduce the strength at elevated temperatures.…”

“…However, much larger stress exponents of [12][13][14][15] have been recently reported for porous aluminum. [5][6][7] These larger stress exponents for porous aluminum may be induced by the following: 5 the powerlaw breakdown region, permanent damage, and absence of load in severely curved cell walls. Zhang et al 6 observed in their investigations of microstructural evolution during creep that a very high stress is induced locally, resulting in a power-law breakdown region.…”

Isothermal and Thermomechanical Fatigue Behavior of Open‐Cell Metal Sponges — Experimental Analysis and Homogenization Modeling

“…where r* is the remote stress and q*/q the relative density of the sponge. This approach was applied in a similar way to closed-cell metal foams, being subject of the studies of Andrews et al [8] and Haag et al [9] Aim of the present study is both, to derive the relevant monotonic and cyclic mechanical data for room temperature, elevated temperature and cycling temperature conditions and to develop a homogenization model that allows a numerical simulation of the deformation and damage processes depending on the cellular microstructure.…”

Compressive Deformation Behavior at Elevated Temperatures in a Closed-Cell Aluminum Foam

“…However, several experimental results revealed that the stress exponents for aluminum foams are 12-15 and these values are much larger than expected for a metallic solid. [4][5][6] This suggests that there should be difference in stress exponents, which characterizes deformation at elevated temperatures, between the metallic foams and the metallic solid. However, there have been few investigations that compare elevated temperature compressive properties of metallic foams with those of their bulk reference metals.…”