Papers by Author: Laurent Bucher

Abstract: Aluminum alloys are increasingly used in automotive and aeronautic applications to produce high performance, lightweight parts. Among the reasons for this, is the emergence of high integrity processes (HIP), which widens the field of application for cast aluminum alloys. In fact, metallurgical quality and consistency that characterize components produced by HIP are necessary for critical safety components. In addition to attaining maximum strength, critical safety components need to be ductile and resistant to cyclic loading. According to the North American Die Casting Association, rheocasting is a high integrity process capable of producing parts with fewer defects than conventional casting process. Rheocast components are known to have better mechanical properties than permanent mold castings. Moreover, they can be heat-treated which is impractical in the case of classical die cast components. However, the fatigue behavior of rheocast aluminum alloys has been investigated since about 2000 and few results have been published on this subject. This paper reviews the studies of fatigue behavior of aluminum semi-solid cast components. Published experimental results on high cycle fatigue resistance (S-N diagrams), long crack propagation, crack closure effects and short crack particularities are presented.

Abstract: The semi-solid forming (SSF) of aluminum alloys offers many advantages over conventional casting processes. Nevertheless, the semi-solid forming is still far from its full commercial potential and mainly used in specific niche markets. The market positioning requires simple, low cost, and versatile SSF processes that are capable of processing a wide range of alloy composition including wrought alloy compositions. However, wrought alloys must be adapted to obtain the desired semi-solid processing ability and proper mechanical properties. The processing of these attractive alloys with the SEED process offers the possibility to better target specific applications and customers’ needs. In the present paper, the alloy development of AA-6061 aiming to minimize the hot tearing propensity during forming process is reported. An overview of the industrial SEED process used to produce the semi-solid AA-6061 feedstock is presented. The mechanical properties of the cast parts subjected to a specific heat treatment were evaluated. As part of the joint effort between Alcan International Limited and the National Research Council of Canada (NRC), the fatigue results obtained from the semi-solid AA-6061 die cast parts will be also reported.