High strength cellular aluminium foam for the automotive industry
Science Daily reported that aluminum foam exhibits unique properties when compared to its dense form, particularly its lightweight characteristics. Generally, the foam can be divided into two categories; closed cell and open cell, both have different characteristics and applications.
The features of the closed cell are, the pores structure is isolated and they are not connected to each other. This type of aluminum foam is suitable for application that requires high level of energy and sound absorption characteristics. It has been used widely in many structural parts, particularly in areas exposed to high damping capacity, for example in the automotive front bumper component.
Meanwhile, the open cell, owing to greater level of connectivity of the pores, the structure has been accepted and used in thermal management applications. One such promising application is as a heat exchanger, particularly as a cooling medium to transfer heat, due to the development of its porous structure, which provides greater surface area, thus, enabling improved heat transfer efficiency. Producing a combined structure of open and closed cell in one volume component appears to be a difficult process due to the different processing techniques involved and their individual limitations.
Therefore, in this study, an innovative processing route for high strength cellular aluminum foam by integrating porous and dense structures is presented. The CAF is well known as a light weight product exhibiting high level of inter-connected porosity which is very useful as a thermal management application, particularly as a heat transfer or cooling medium. However, the level of strength for the CAF is not really promising when it is subjected to high impact; thus, limit its potential application, particularly in the automotive industry.
Subsequently, an alternative route by integrating dense and porous structure has been investigated. The solid aluminum at the centre acts as a pillar providing excellent strength for the surrounding foam structure. The product has demonstrated functionally graded properties which is possible for applications that require both properties of heat transfer and high strength.
The product was fabricated using infiltration of NaCl space holder combined with central solid aluminum foam. It is well known that NaCl has a greater melting point than that of aluminum. Therefore, when aluminum melts, the liquid fills the interstitial spaces between the NaCl grain. Prior to melting, the NaCl is sieved according to the desired porous structure.
Source – Science Daily