surface characteristics improvement of az31b magnesium by surface compositing with carbon nano-tubes through friction stir processing

In this research, compositing the surface of az31b magnesium alloy with cnt was studied by fsp. the investigated parameters were rotational speed (500-1500 rpm), transverse speed (12-44 mm/min), number of passes (1-4), and cnt weight fraction (0-2%). microhardness testing, optical metallography, fesem, and eds analysis were used for the characterization of the samples. the suitable limits for the transverse speed and rotational speed were 12-24 mm/min and 870-1140 rpm, respectively. the highest hardness in the fsp without compositing was observed at the transverse speed of 24 mm/min, rotational speed of 870 rpm with a hardness of about 60 vickers, and the stir region grain size of less than 5 µm. the zener-holman parameter was calculated and the least value was related to the conditions of the transverse speed of 12-24 mm/min and rotational speed of 870 rpm; as a result, the samples with the finest grain size were theoretically and experimentally marked. the most homogenous structure with the highest hardness was related to the three-pass processed sample with a hardness of 69 vickers. the best rate of cnt weight was 2%, enjoying the highest hardness. the fesem images confirmed the suitable distribution of cnts in matrix after the performance of the three-pass processing.