ENHANCING THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF RARE EARTH LA MODIFIED HYPEREUTECTIC AL-SI ALLOY USING FRICTION STIR PROCESSING TECHNIQUE
The properties of cast hypereutectic Al-Si alloys are dependent on fine silicon morphology and smaller size of intermetallic formed during solidification. Rare earth (La) elements addition is being used to alter the morphology of silicon particles to small sizes. However, La formed multi-compounds with elements in the base alloy, which appear as coarse needle-like or plate-like structures and can interrupt, and hinder the full modification of Si particles, in turns pose detrimental effect to strength of the alloy. The aim of this study is to enhance the microstructure and properties of Al-18Si-0.9Cu-1Ni-1%La alloy modified with La rare earth element by using FSP technique. FSP is a new processing technique facilitate by the frictional heat generation between tool and the work piece. FSP can triumph over the detrimental properties due to coarse needle-like or plate-like intermetallic structures and coarse large size non-uniformly distributed Si particle in the Al matrix, creates finer and smaller sizes of particles and uniform distribution, thus enhanced properties. The surfaces of cast Al-18Si-0.9Cu-1.5Ni-1%La were subjected to single pass stir FSP using two tool traverse speeds and fixed tool rotation speed. Optical and scanning electron microscopy analysis, tensile test, and hardness test were used to correlates between metallography examinations, and mechanical properties, to quantify the effects that the process FSP induced on the alloy. The microstructure, tensile strength, and micro hardness, of the alloy can be enhanced after FSP. Tensile strength, elongation, and hardness were increased to about 1.7 times, 5 times, and 5.37% respectively compared to the unprocessed base alloy. Presence of fine microstructure constituent, fragmenting of silicon, La intermetallic particles to fine and smaller sizes, and elimination of porosity was found to be important factors for the enhanced properties. Silicon, intermetallic particles, and porosity decreased to 51.14�m�, 25.0�m�, and 13.03 ECD were achieved with higher tool traverse speed 42mm/min. The challenge within this research is to extend the application of hypereutectic Al-Si alloys.
Authors : Abdulmalik, S.S., Ahmad, R., Feriyanto, D. and Hammajam, A.A.
Category : Open Access Volume (Issue) : 11(2) Date Uploaded : 3rd November 2025