Al-Mg-Si, Al-Fe-Si and Al-Fe model alloys are cast at three different cooling rates. In-situ SEM observation of tensile tests has been used to characterize the strength levels of various coarse intermetallic compound (IMC) particles such as Mg2Si, AlmFenSip and AlmFe which are usually observed in practical aluminum alloys. Particular attention is given to the chemical composition, size and aspect ratio of each broken particle. AlFeSi particles close to Al(8)Fe(2)Si1 and Al10Fe3Si3 are formed by metal mold and Graphite mold castings, respectively and AlFeSi particles having various composition ratios are formed by furnace cooling, which are transformed into AlFe3 by subsequently being exposed at 858 K. Almost all of the AlFeSi particles formed during the metal and Graphite mold castings remain intact, while Mg2Si, AlmFe and other AlFeSi particles are damaged extensively. In-situ strength levels of the damaged particles are also estimated utilizing Eshelby inclusion method.