UQ eSpace

Abstract

Aluminium Vacuum Brazing (AVB) has been a popular metal-joining process in the aerospace industry (Elrefaey, 2012). AVB, when carried out successfully, prepares high strength aluminium parts for complex service conditions (C.H.Cadden, 2006). This manufacturing process essentially uses a low-melting point aluminium filler alloy to join aluminium components such as heat exchangers and liquid closed enclosures for aircrafts (Moller & Grann). The aim of this thesis is to assist an aerospace industry partner in identifying possible issues with their current AVB process, as some of their parts have failed in recent times post brazing. Identification and validation of prevalent issues will allow the company to improve their processes in the near future and hence minimize any production losses. This thesis may also impact the overall aerospace industry in the future, if the findings from the project are to be used by other industry manufacturers. The analysis types for this thesis comprised of a preliminary literature review, Energy Dispersive X-ray Analysis (EDS) on sample parts and a detailed Finite element analysis (FEA) carried out to simulate the processing environment. Following these preliminary analyses, the most likely causes for part failure were identified as inappropriate heating cycle parameters, such as Excessive time at soak and Thermal expansion due to non-uniform heating characteristics inside the furnace. These findings were then presented to the industry partner during a site visit. Following consultation with the industry partner and reviewing previous findings, it was clear that the most realistic drivers for failure are in-fact localised thermal expansion resulting from inappropriate fixture placements, an impure vacuum environment and/or vaporisation of the filler alloy due to excessive soak times. The overall findings from this thesis are very critical as the ambiguity of the initial problem has now been resolved and the broad problem is now narrowed down to more specific areas for any future investigations.