Microstructural Characterization of Laser-Deposited Al 4047 Alloy
- PDF / 1,271,137 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 114 Downloads / 216 Views
INTRODUCTION
ALUMINUM is the second most used metal in the world after iron. Aluminum alloys with silicon as a major alloying element are widely used materials for casting military, aerospace, and automotive components such as pistons, cylinder blocks, and liners of IC engine.[1,2] Al-Si alloys comprise 80 pct of the aluminum casting alloys due to their excellent combination of properties such as sound castability, low thermal expansion coefficient, good weldability, and high corrosion and wear resistance. The Al-Si system is a simple binary eutectic system in which eutectic reaction occurs at 850.6 K (577.6 C) and 12.6 pct silicon. It is commonly accepted that if the Si content ranges from 11 to 13 wt pct, such an alloy is called a eutectic alloy. The primary microstructural features of Al-Si alloys strongly depend on alloy composition and temperature profile at the solidification interface. Depending on the composition and solidification rate, the microstructure of Al-Si alloys usually consists of primary aluminum plus eutectic, fully eutectic, or mixture G.P. DINDA, Materials Scientist, and A.K. DASGUPTA, Project Manager, are with the Center for Advanced Technologies, Focus: HOPE, Detroit, MI 48238. Contact e-mail: [email protected] S. BHATTACHARYA, Research Fellow, formerly with the Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, is now with Carnegie Mellon University, Pittsburgh, PA. H. NATU, Project Engineer, formerly with The POM Group Inc, Auburn Hills, MI 48326, is now with Magod Laser, Bangalore, India. B. DUTTA, Chief Operating Officer, is with The POM Group Inc, Auburn Hills, MI 48326. J. MAZUMDER, Professor, is with the Department of Mechanical Engineering, University of Michigan. Manuscript submitted March 28, 2012. Article published online December 5, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
of primary silicon and eutectic. However, it has been reported[3–5] that a range of hypereutectic alloys form a fully eutectic microstructure during rapid solidification. Moreover, the eutectic silicon morphology changes from plates to fibers when the growth rate is increased. The mechanical properties of Al-Si alloys strongly depend on the size, shape, and eutectic spacing of Si, dendrite arm spacing (DAS), and grain size of primary Al or Si. In general, the refinement of the primary and eutectic phase improves the mechanical properties, such as yield strength, wear resistance, and ductility. Structural refinement can be achieved by a well-known chemical modification method by the addition of stress-level several elements such as sodium, antimony, potassium, calcium, strontium, and barium.[6–8] Another most common microstructural refinement process is the rapid solidification which causes a fine eutectic structure, small dendrite cells, small DAS, and small grain size. A considerable amount of work has been performed on rapid solidification of Al-Si alloys by melt-spinning,[9–11] surface treatment with high energy beam,[12] melt atomization,[13,14] and laser surface melting.[4,15–
Data Loading...
