RELEVANCE OF THE USE OF THE QUALITY INDEX CONCEPT IN CAST SICP-REINFORCED AL-SI-MG COMPOSITES

The quality index, Q, defined as Q = UTS + k logE1 was introduced as a means to better interpret tensile test data. However, its use in the case of composite materials is often questioned. The difficulty arises from the fact that the elongations obtained are usually close to, or less than, unity. Based on a heat-treatment study of cast Al-Si-Mg/SiC p composites (359/SiCp) and an analysis of the tensile properties obta ined, it is shown that the concept of quality index, as it is commonly applied, is inappropriate in describing the combined effects of UTS a nd E1, and it is much better, instead, to use the probable yield stren gth (PYS) for such materials. Respective expressions for Q and PYS hav e been obtained for the 359, 359/SiC/10(p) and 359/SiC/20(p) alloys st udied.