An Al-Si-Mg composite model system: Microstructural effects on deformation and damage evolution

• Published in: Scripta metallurgica et materialia 1991, Vol.25 (1), p.15-20
• Main Authors: Hunt, W.H, Brockenbrough, J.R, Magnusen, P.E
• Format: Article
• Language: English
• ISSN: 0956-716X
• DOI: 10.1016/0956-716X(91)90346-3

Three Al--Si--Mg alloys (e.g. Al--10.5Si--0.46Mg, Al--15.5Si--0.47Mg, and Al--20Si--0.36Mg) were studied. A rapid solidification powder atomization process was employed to develop a fine, uniform starting microstructure and extend the level of Si which can be incorporated in the alloy without the formation of primary Si in hypereutectic compositions (the eutectic composition is approx 12.7 wt.% Si). Through this route, up to 20 wt.% Si was incorporated without primary Si formation. Magnesium additions were also made to strengthen the matrix through precipitation hardening. Using this model particle-reinforced system, the effects of particle size and volume fraction on deformation and damage evolution have been analytically modelled and experimentally measured. Decreases in work hardening was observed with increases in either particle volume fraction or particle size. This behavior is due to accelerated damage in the form of particle cracking in the higher volume fraction and/or larger particle size materials. This damage process was verified by metallographic me thods and through measured losses in modulus with increasing plastic strain. A model of modulus degradation due to particle cracking shows good agreement with measured values of modulus and cracked particle volume fraction. Graphs, Photomicrographs. 12 ref.--M.W.C.(UK/US).