MICROSTRUCTURAL PROPERTIES AND PHASE CONSTITUENTS OF 5A06 ALUMINIUM MATRIX SURFACE COMPOSITE FABRICATED BY FRICTION STIR PROCESSING

A novel aluminium matrix surface composite added Al-based amorphous, whose layer depth was 5 mm, was fabricated by friction stir processing (FSP), at an air cooling. The surface composite region shows the obvious sandwich structure. It is considered to be a combination between the base metal and the amorphous strip via the FSP. The average hardness of the surface composite is about HV97, higher than the base metal is about HV80. The maximum tensile strength of the processed aluminium plate with the surface composite is 410 MPa. XRD results indicate that the constituent phases of the surface composite mainly include α-Al, Mg2Al3, MnAl6 and La3Al11 Moreover, no obvious amorphous diffraction peaks are observed in the XRD results. However, a large number of ultrafine grained structures can be observed in the surface composite. The average grain size of them is ~90–400 nm constitutes the surface composite. These ultrafine grained structures are composed of the α-Al and α-Al amorphous structures.