EFFECT OF MAGNESIUM ENHANCEMENT ON MECHANICAL PROPERTY AND WEAR BEHAVIOUR OF LM6 ALUMINUM ALLOY
For last several decades aluminium and aluminium alloys are widely used in automotive industries because for their favourable properties like low density (about 2700 Kg/m 3 ), good malleability, high formability, high corrosion resistance and high electrical and thermal conductivity. High machinability and workability of aluminium alloys are prone to porosity due to gases dissolved during melting processes. However, in the engineering application pure aluminium and its alloys still have some problems such as relatively low strength, unstable mechanical properties and low wear resistance. The microstructure can be modified and mechanical properties, wear resistance can be improved by alloying, cold working and heat treatment. In this regards, the present paper reports the influences of enhancement of magnesium contents on the mechanical properties and wear behavior of LM 6 aluminum alloy. Index Terms: LM 6 Aluminum alloy, wear rate 1. Introduction: Aluminium and aluminium alloy are gaining huge industrial significance because of their outstanding combination of mechanical, physical and tribological properties over the base alloys. These properties include high specific strength, high wear and seizure resistance, high stiffness, better elevated temperature strength, controlled thermal expansion coefficient and improved damping capacity (1). These properties obtained through addition of alloying elements, cold working and heat treatment. Alloying elements are selected based on their effects and suitability. For the purpose of understanding their effects and importance, alloying elements for majority of alloys are best classified as major and minor elements, microstructure modifiers or impurities, however the impurity elements in some alloys might be major elements in others (2). LM6 is one of the most important Aluminium alloy falls under Aluminium - Silicon alloying system in which aluminium is the predominant metal and high levels of silicon (4% to 13%) are added that contributes to give good casting characteristics and increases fluidity, by which we can produce castings of thick as well as thin sections according to the required design. Other typical alloying elements are Copper, Magnesium, Manganese, Silicon, Zinc, Iron, Nickel, Lead and Tin.
Effects of Copper and Magnesium on Phase Formation Modeling and Mechanical Behavior in AL-CU-MG Alloys
The current work emphasizes the establishment of a relationship between microstructure, and copper and magnesium addition in aluminum based alloys. Aluminum alloys containing 4 and 6% copper and 0.50 and 1% magnesium were cast from commercially pure aluminum ingots and homogenized at 400 o C. Images of the microstructures of the as-cast and homogenized alloys were acquired, and image analysis of the phases was performed on the acquired images to obtain area fractions of the phases present in the microstructure. Using the CALPHAD modeling method, thermodynamic modeling of the alloys was carried out in the equilibrium cooling condition since after homogenization for a prolonged time the alloys should reach a close to equilibrium cooling condition. Phase fractions predicted in modeling were matched closely with image analysis data, given that phases present in the homogenized alloys can be interpreted through modeling in the equilibrium cooling condition. EDX analysis of the samples identified the phases present in the alloys as Al2Cu, Mg2Si and Al7Cu2Mg. With increasing copper content, it was found both in modeling and experimentally that the amount of Al2Cu phase increased, which improved the hardness values of the alloys. However, in the homogenized condition, the hardness values slightly decreased compared to those of the as-cast condition due to retention of a lower fraction of Al2Cu phase in the homogenized condition. This was ascertained in the modeling of the alloys. In contrast, Mg2Si and Al7Cu2Mg phases were formed when magnesium was added in the predefined amount; however, these phases were not found to be effective at improving the hardness of the alloys, and the hardness values were barely modified. Apparently, the hardness enhancement after magnesium addition occurred due to a solute effect. To observe the phase effect of magnesium in aluminum alloys, binary alloys of aluminum-magnesium should be cast.
Testing digital circuits using a Mixed-Signal Automatic Test Equipment
This paper presents the results of parametric testing of digital ICs using a dedicated Mixed Signal Automatic Testing Equipment. Due to the prohibitive price of the ATE equipment and dedicated Device Interface Board (DIB) for digital Integrated Circuits (ICs), a DIB for analog circuits was used to perform the testing. Despite the challenges presented by the experiments, the results prove to be accurate for the performed tests, according to the data sheet of the digital ICs and production test data provided by the manufacturer.