Penelitian Dan Analisis Metalurgi Pada Cacat Permukaan Lubang Utama Dari Komponen Paduan Aluminium Hasil Permesinan Untuk Bagian Sayap Pesawat Terbang (Aileron) [Metallurgical Assesment of Main Bore Surface Defect of A Machined Aluminum Alloy Aileron Block]

Abstract

A newly machined aileron block was reportedly exhibiting several pits on its particular main bore area after it has been subjected to sulfuric anodizing process. This defective machined aileron block was made of aluminum alloy AA 2618 forging, designed to accommodate some moving parts internally and connected to a mechanism that may allow the movement of aircraft aileron. In order to determine type and factors that may have caused the occurrence of surface defect on the main bore area of the machined aileron block, it was considered to perform a metallurgical assessment. A number of specimens were prepared for laboratory examinations which included macroscopic examination, chemical composition analysis, metallographic examination, hardness test and SEM (scanning electron microscopy) examination equipped with EDS (energy dispersive spectroscopy) analysis. Results of the metallurgical assessment obtained show that the surface defect occurred on the main bore area of the machined aileron block is mainly influenced by the presence of large precipitates in the aluminum matrix phase of the aileron block material. Formation of these large precipitates may have reduced their coherency with the matrix phase of the aluminum alloy and hence could easily detach them from the surface during machining and formed several abandoned pits thereon