An Experimental Study on Friction Stir Processing of AA-7020 Aluminum Alloy

ABSTRACT: Friction stir processing (FSP) as a promising thermo mechanical approach aims on altering the microstructural and mechanical properties of material in order to obtain the highest performance (increasing or decreasing of hardness and tensile) in terms of properties, cost and lead time. This study addresses FSP of AA-7020 aluminum alloy. The effect of variation in the ratio of rotational and translational speeds (i.e., ω/f) is examined on the mechanical properties and microstructure of AA-7020 aluminum alloy. The value of ω/f (ω is rotational speed f is feed rate) is varied from 22 rev/mm to 125 rev/mm. The results show that with increasing ω/f, the grain size decreases. When ω/f (ω is rotational speed f is feed rate) ranges from 22 to 28, average hardness, ultimate strength and yield strength increase from 75 HV to 103 HV, from 313 to 364 MPa and from 173 MPa to 208 MPa, respectively. However, for ω/f ranging from 28 to 125, a reduction has been noticed in these properties. Regarding microstructure, it is found that the size of grain in the processed zone is small and the direction of grain is random. Besides mechanical properties, observations regarding the effect of ω/f on surface quality are also made to show that larger values of ω/f lead to poor surface texture. Keywords: Friction Stir Processing, Hardness, Impact, Quality, Microstructure, Tensile, AA-7020. …………………………………………………………………………………………………………………………