Journal Published Online: 18 October 2016
Volume 5, Issue 5

Microstructure and Wear Behavior of a Functionally Gradient Al–Si Alloy Prepared Using the Cast–Decant–Cast (CDC) Process



A bulk functionally gradient Al–Si alloy with two varying Si contents [high (11 %) and low (4 %) hypoeutectic compositions—alloys A and B, respectively] was prepared through a novel casting technique named cast–decant–cast (CDC) process. Casting was done by pouring liquid alloy A first into a mold, allowed to solidify partially in the mold until a layer of ∼15 mm was formed against the mold walls, and decanting the remaining unsolidified alloy A by turning the mold upside down. The superheated liquid alloy B was then poured into the mold and allowed to solidify fully. Optical micrographs of the functionally gradient casting revealed no abrupt interface layer between the high- and low-Si regions, and the scanning-electron-microscopy–energy-dispersive-X-ray (SEM-EDX) analysis carried out across the cross section of the casting showed a linear silicon concentration gradient of ∼10 mm across the interface. Wear tests carried out on the individual sections of alloys A, B, and functionally gradient regions showed that the percentage cumulative weight loss was lower for the functionally gradient region (i.e., higher wear resistance) compared with the high- and low-Si regions. The SEM images taken after wear testing of the functionally gradient region showed finer and smoother wear tracks with very little random delamination of the matrix surface. This is attributed to the presence of both needle-shaped and round-shaped eutectic Si particles and their strong reinforcement in the primary aluminum-rich α matrix, which resulted in higher wear resistance of the functionally gradient region.

Author Information

Nagarajan, D.
Dept. of Metallurgical and Materials Engineering, National Inst. of Technology (NIT), Rourkela, Odisha, IN
Mohana Sivam, P.
Flow Link Systems Pvt. Ltd., Coimbatore, Tamilnadu, IN
Pages: 11
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Stock #: MPC20160055
ISSN: 2165-3992
DOI: 10.1520/MPC20160055