QUALITY PERFORMANCE OF AL-SI-MG-CU ALLOYS J. H. SANDOVAL 1 , A. M. A. MOHAMED 2 , F. H. SAMUEL 3 & S. VALTIERRA 4 1,3 University of Quebec at Chicoutimi, Chicoutimi, Quebec, Canada 2 Faculty of Petroleum and Mining Engineering, Suez University, Suez, Egypt 4 Nemak, Research and Development, Garza Garcia, Nuevo León, Mexico ABSTRACT This article was undertaken to investigate the Quality index charts with the purpose of setting the limits of the tensile properties, as well as to compare the mechanical behavior of cast Al-Si-Mg-Cu alloys, to delineate the effect of the solution treatment applied. Tensile properties upon artificial aging in the temperature range of 155–350 o C for times ranging from 2 to 100 hours were also investigated. The results showed that the use of quality index charts is a satisfactory method for presenting tensile test results, for assessing the effect of solution and aging treatment conditions subjected to the modified grain-refined alloys. It is also observed that the quality index, Q, is more sensitive to variations in the tensile ductility than to tensile strength. KEYWORDS: Temperature Range of 155–350 o C, Intersection of the Flow Curves at a Plastic Strain of 0.2%, Respectively INTRODUCTION Aluminum-silicon-copper-magnesium alloys such as the 354 alloys show a greater response to heat treatment as a result of the presence of both Mg and Cu. These alloy types display excellent strength and hardness values although at some sacrifice of ductility and corrosion resistance. These alloys are used for a wide range of applications, including engine cooling fans, crankcases, high speed rotating parts, structural aerospace components, air compressor pistons, fuel pumps, compressor cases, timing gears, rocker arms, machine parts, and so forth [1,2]. Any improvement in mechanical properties is commonly evaluated through the tensile properties. Almost all of the steps in the processing of aluminum, from establishing a composition to heat-treatment, produce a variation in mechanical properties. The fact that tensile properties depend on several variables may go far to explain the confusion existing in connection with the properties of cast aluminum alloys. Quality Index is a pivotal concept originally developed by Drouzy, Jacob and Richard [3] who introduced an empirical parameter Q, or quality index, to characterize the mechanical performance of Al-7%Si-Mg casting alloys. The quality indexis relatedto the tensile strength, UTS, and the plastic strain of the material to fracture, s f , as represented by equation 1. Q = UTS + d log (s f ) (1) While the constant yield strength lines are represented by equation 2 YS = a UTS – b log (s f ) – c (2) Although the concept was developed specifically for alloys 356 and 357, it has occasionally been applied to other alloy systems as well [4-8]. A model developed by Cáceres [6] shows that the iso-Q lines represent contours of constant International Journal Metallurgical & Materials Science and Engineering (IJMMSE) ISSN (P): 2278-2516; ISSN (E): 2278-2524 Vol. 3, Issue 5, Dec 2013, 9-18 ©TJPRC Pvt. Ltd.