Microstructure design of cast Al alloys for high temperature

01.11.2010 - 31.01.2013
Research funding project
Al-alloys are very attractive materials due to their low density, excellent mechanical properties and relative low price compared to Ti and Mg alloys. Particularly, cast Al-Si alloys are widely used in the automotive and aircraft industries. Cast Al-Si alloys with >7wt.% of Si can form a three-dimensional (3D) eutectic-Si network embedded in the ductile Al-matrix. This contributes to the strength of these alloys by load transfer from the Al-matrix to the stiffer highly interconnected eutectic Si. The addition of transition elements such as Ni and Cu are considered to be effective for increasing the high temperature strength of cast Al-Si alloys by forming stable aluminides. Recently, our group has shown that adding ~ 1wt% Ni to a eutectic Al-Si alloy can form a highly interconnected 3D structure of aluminides together with the eutectic Si. Furthermore, the aluminides and the eutectic Si present a large degree of contiguity resulting in a long-range hybrid 3D structure. Contrarily to the case of Ni-free Al-Si alloys, the interface between the eutectic Si and the aluminides is retained during heat treatments. Thus, spheroidisation and disintegration of the eutectic Si is suppressed. As a consequence, both the aluminides and the eutectic Si maintain their complex interconnected structures. The thermomechanical properties of multiphase materials, as it is the case of Al-Si based cast alloys, are strongly influenced by the geometrical arrangement of their constituents. Furthermore, highly interconnected rigid structures embedded in a metallic matrix can result in an improvement of the elevated temperature strength. The description of the 3D architectures resulting from the addition of aluminide forming elements, such as Ni and Cu, to eutectic Al-Si alloys as well as the determination of their load carrying capacity is an open scientific challenge. The objective of the proposed project is to elaborate knowledge-based methods which improve the mechanical properties at elevated temperatures by investigating: a) the interaction between eutectic Si and different aluminides in cast Al-Si based alloys. For this, the 3D architectures formed by the eutectic Si and the aluminides in different thermal conditions will be characterized by advanced tomographic methods. b) the reinforcement capability at high temperature of the structures mentioned in a). This will be done by studying specific thermomechanical properties of the alloys and performing in situ bulk diffraction experiments to determine the load carrying capability of the phases¿ architecture.

People

Project leader

Project personnel

Institute

Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Austrian Science Fund (FWF)

Research focus

  • Materials Characterization: 100%

Keywords

GermanEnglish
Al-Si GusslegierungenAl-Si cast alloys
Synchrotron Tomographiesynchrotron tomography
3D Mikrostruktur3D microstructure
Lastaufteilungload partition
Aluminidealuminides

Publications