Zn-matrix syntactic foams: Effect of heat treatment on microstructure and compressive properties

Molten Metal Infiltration Methods to Process Metal Matrix Syntactic Foams

“…Metal alloys commonly employed by this technique do not have high melting points, according to some studies [17,18,22,72]. Notwithstanding this, recent enhancements of liquid metal infiltration technology has enabled metal alloys with both low to medium (such as those based on tin [33,73], zinc [2,5], magnesium [57] and aluminum [39,56]) and high melting point (such as those based on iron [74,75], titanium [5] and bulk metallic glass or amorphous metals [55,76,77]) to be used to produce SF by this technique.…”

“…This paper reviews infiltration routes used to date, their advantages and drawbacks, the main processing parameters of each route, and a relation of representative studies developed to date on the synthesizing of MMSF by molten infiltration processes. alloy [5]. Unusual characteristics of these materials can be sorted into two big families of materials.…”

“…On the other hand, they can be classified as metal foams due to the porosity contained into filler particles [7]. Available studies on MMSF have shown that these composite foams have high heat insulation, damping of sound and vibration, great energy absorption and high specific stiffness [5]. The combination of properties for these materials are of high interest for the marine, defense, railway, automotive and aerospace industries [2,8,9].…”

“…High melting point alloys, such as those based on Ti [25][26][27], Fe [28][29][30] or steel [17,31,32] are typically processed by P/M techniques. In contrast, low to medium melting point alloys (about from 505 K to 934 K), such as those based on Sn [33,34], Zn [2,5,19], Mg [20,35,36] or Al [37][38][39] are usually processed by liquid metallurgy.Filler particles introduced as reinforcement in MMSF are lightweight aggregates with less density than water. They exhibit two main inner structures, hollow or porous [40][41][42].…”

“…Several studies have reported the utilization of natural-made fillers: Expanded vermiculite [45], pumice [40], lightweight expanded clay aggregate (LECA) [3,46], expanded perlite (EP) [47,48] and expanded glass (EG) [2,49]. In other cases, commercial or human-made lightweight aggregates have been successfully used: fly-ash cenospheres (FAC) [50][51][52], glass microballoons (GMB) [1,5], ceramic spheres (CMB) [11,53,54], carbon hollow spheres [55] and hollow metallic spheres [56]. Pores can contain traces of various gases like CO 2 , N 2 , H 2 O, CO and O 2 [57] as a result of fillers manufacturing methods.Apart from these two physical properties of reinforcements (chemical compositions and inner nature), there are several properties that must be controlled to optimize characteristics such as porosity (thickness-to-size ratio, shell porosity, compressive collapse strength, shrinkage and melting temperature) and wettability (surface roughness, coating properties and interface chemical reactions).In terms of size, Puga et al [3] observed that porous nature brittle fillers (such as LECA) tend to increase MMSF yield strength whilst fillers size and density increases and decreases respectively.…”