Suitability of various complex hydrides for foaming aluminum alloys

Abstract

Some hydrides that could replace TiH 2 as the hitherto most suitable blowing agent for foaming aluminum alloys were investigated. Hydrides taken from the group MBH 4 (M 5 Li, Na, K) and LiAlH 4 were selected since these have not been studied in the past although their decomposition characteristics appear to be suitable. Foamable precursors of alloy AlSi8Mg4 were manufactured by pressing blends of metal and blowing agent powders. Powders, precursors and precursor filings were studied by mass spectrometry to obtain the hydrogen desorption profile. Foaming experiments were conducted with simultaneous x-ray radiographic monitoring. Two Li-containing blowing agents were found to perform well and can be considered alternatives to TiH 2 .

Review: Closed-Cell Metallic Foams Produced via Powder Metallurgy

“…This point was also investigated by Ibrahim et al who reported a 50 • C gas release onset temperature decline between 15.27 µm and 4.32 µm TiH 2 particles [45,66]. However, the heating rate [67] and the compaction process [56] also influence the blowing agent decomposition behavior. For example, since as-received TiH 2 powders typically contain a thin oxide layer, the uniaxial compaction process to produce the foamable precursor can result in the fracture of TiH 2 particles (and hence the oxide layers), resulting in the exposure of non-oxidized fresh TiH 2 surfaces, which can release gas at lower temperatures.…”

“…Examples of blowing agents and their reported gas release onset temperatures. Data from [27,39,42,45,[54][55][56][57][58][59][60][61][62][63].…”

Influence of foaming agents on mechanical and microstructure characterization of AA6061 metal foams

“…This occurs probably due to surface oxides in TiH 2 blowing agent broken-up easily during compaction which tends to reduce the temperature of gas release, and accumulated released gas correspond to area around blowing agent builds up pressure results in crack formation in the compact. 49,50 The stress-strain curves seen to have non-linear trend, with the deformation magnitude is low for magnesium hydroxide and titanium hydride compared to wax powder. Increased amount of deformation renders the fracture zone pile up, wherein the whole deformation is concentrated and fracture at a maximum stress of 6.16 MPa for wax powder.…”

Fabrication, Processing, Properties, and Applications of Closed-Cell Aluminum Foams: A Review

“…In these systems, AlSi 6 Cu 4 , AlSi 6 Cu 6 , and AlSi 8 Mg 4 are more commonly used [79]. FAs mainly include TiH 2 [77], CaCO 3 [89], ZrH 2 [90], Mg-Al alloy powders [91], LiAlH 4 [92], etc. TiH 2 has the best foaming result.…”