Surface Characteristics Improvement of AZ۳۱B Magnesium by Surface Compositing with Carbon Nano-tubes through Friction Stir Processing

In this research, the compositing of the surface of AZ۳۱B magnesium alloy with CNT was studied by FSP. The parameters under study were rotational speed (۵۰۰-۱۵۰۰ rpm), transverse speed (۱۲-۴۴ mm/min), number of passes (۱-۴), and CNT weight fraction (۰-۲%). Microhardness testing, optical metallography, FESEM, and EDS analysis were employed for the characterization of the samples. The suitable limits for the transverse speed and rotational speed were ۱۲-۲۴mm/min and ۸۷۰-۱۱۴۰ rpm, respectively. The highest hardness in the FSP without compositing was assigned to the transverse speed of ۲۴ mm/min and rotational speed of ۸۷۰ rpm with a hardness of about ۶۰ Vickers and the stir region grain size of less than ۵ microns. The Zener-Holman parameter was calculated for computation and the least value was related to the conditions of the transverse speed of ۱۲-۲۴ mm/min and rotational speed of ۸۷۰ rpm; as a result, the samples with the finest grain size were theoretically and experimentally specified. The most homogenous structure with the highest hardness was related to the three-pass state with a hardness of ۶۹ Vickers. The best rate was the CNT weight percentage with a %۲ weight enjoying the highest hardness. The FESEM images confirmed the suitable distribution of CNTs in the background after the performance of the three-pass processing.

Keywords:

Carbon Nano Tube (CNT) , Friction Stir Processing (FSP) , Surface Composite , Zener-Holloman Parameter