Stability of various particle-stabilised aluminium alloys foams made by gas injection

Abstract

Aluminium alloy foams are created by injecting air into liquid alloys containing non-metallic particles. In addition to an alloy containing the usual SiC particles, other types of metal/particle composites are studied, which are created by in-situ reactions in the melts: two fluoride salts react and form TiB 2 particles, Ca addition or addition of CuO and SiO 2 gives rise to the formation of various oxides and spinel particles. Injecting air into the molten composites through two different steel cannulas leads to the formation of first bubbles and then foam.The entire process is monitored in-situ by X-ray radioscopy. The goal is not only to understand how and what kind of particles stabilise gas injected foams better, but also to reduce the fraction of added particles, which could improve mechanical properties, solve recycling issues and reduce production costs. All the observed composites are shown to have the potential to be processed to metallic foam. Melts containing TiB 2 particles are found to perform as well as those containing SiC even at lower volume fractions. Oxidation of alloy melts promoted by Ca addition gives rise to melts that exhibit good foamability. Melts oxidised by CuO and SiO 2 addition show partial stability. Mg is found to be a required alloying element to create stable foams. Smaller bubbles can be produced using smaller injector needle openings. By reducing bubble size and using new variants of in-situ generated particles, more stable foams can be achieved with a lower number density of stabilising particles.

Effects of stirring speed and flux composition on the recycling of aluminium foams

“…Aluminium foams exhibit unique mechanical, thermal, acoustic, and electrical properties [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], rendering them attractive in transportation, construction, and aerospace applications [16][17][18][19][20][21][22][23][24][25][26]. Now, aluminium foams have reached the maturity of development in terms of process stability, materials properties and costs required for industrial applications [6,10].…”

Effects of Particle Combinations With Different Wettability on Foam Structure and Stability

“…In foam metal preparation process, particles or other elements are usually added to improve the stability of foam structure. For example, Ca is added to the melt and stirred in the ambient atmosphere to form the oxide inside metal melts to achieve foam stability, which is also called thickening (Miyoshi et al, 2000;Song et al, 2000;Heim et al, 2017;Cheng et al, 2018). Moreover, Fe or Si has been added in the basic alloy AlSi9Mg0.6 in the first stage of solidification of eutectic alloys to foam Primary Fe and Si-rich crystals which can improve the foam stability (Heim et al, 2018).…”

Percolation of Primary Crystals in Cell Walls of Aluminum Alloy Foam via Semi-Solid Route

“…Until now, a few studies have reported stabilization mechanisms which are necessary to inhibit the rupturing of the cell walls. Several studies had proposed that the oxidation of alloy melts helps the stabilization of cell walls [3,4]. The stabilization mechanisms of nanoporous foam have been studied not only in the metal foam field, but also in the chemical foam field.…”