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978-3-8439-3592-0, Reihe Werkstoffwissenschaften
Erhöhung des Leichtbaupotentials und Einstellung maßgeschneiderter mechanischer Eigenschaften von AlSi-Strukturgussbauteilen mittels konturnaher Abschreckverfahren
152 Seiten, Dissertation Universität Erlangen-Nürnberg (2018), Softcover, A5
The current goal of many automotive manufacturers is to reduce the weight of their vehicles to satisfy rising customer requirements and environmental protection aims. One way to reduce the weight of the vehicle structure is to use multifunctional large scale structural castings, in which many previously separate parts can be cast as one component. Additionally, the use of precipitation-hardened alloys, which have increased strength, enables the reduction of wall thickness and thus the weight of structural elements. A heat treatment of the components, which consists of solution annealing, quenching and aging is required for the material to satisfy crash test standards. Of these process steps, quenching has a great influence on the resulting mechanical properties. Current quenching techniques for complex component geometries result in inhomogeneous cooling rates and thus varied mechanical properties.
Within this work, a new method using locally adjusted quenching rates via a pressured air nozzle field was developed for structural cast parts, which differs strongly from the more conventional quenching with moving air. The main advantage of this concept lies in the possibility of locally adjustable volume flow of the cooling air, which enables significantly faster cooling rates and the possibility to realize wall thickness independent homogeneous cooling rates across entire complex parts.
Additionally it has been demonstrated by further experiments, that graded mechanical properties can be achieved by using locally variable cooling rates. For example, ductile flanges for better riveting or reinforced load paths, which exhibit higher mechanical strength, can be produced within one structural part.
Furthermore, the novel quenching method offers the possibility to correct, within certain limits, the geometrical distortion, that results from the casting process or the solution annealing. This also results in cost savings that nearly compensates the additional costs of the new quenching process.
As a result of this work, a significantly increased property profile of structural cast components can be achieved by using a compressed air nozzle field. This increases the application field of multifunctional, large scale, structural cast components in car bodies, offering the possibility to further reduce the vehicle weight.