Effect of CNT on microstructure, dry sliding wear and compressive mechanical properties of AZ61 magnesium alloy

Carbon nanotubes (CNTs) reinforced AZ61 magnesium alloy was successfully fabricated through stir casting method with the concentration of (0, 0.1, 0.5, 1) wt.% CNTs followed by age heat treatments. The influence of the CNTs concentration on compressive mechanical properties, dry sliding wear behavior and microstructure of synthesized composites have been investigated using compression test, hardness, block on wear apparatus, scanning electron microscope and X-ray diffraction (XRD) respectively. The comparative study of as-cast and aged CNTs/AZ61 composites have been analyzed. The experimental results reveal that the addition of CNTs content in AZ61 magnesium alloy causes the decrease in mass wear loss and coefficient of friction, improves grain refinement and compressive strength. Three dominant wear mechanism (i.e. abrasion, oxidation, and delamination) have been observed. The compression strength of composites increases with the increase in CNTs contents for both aged and as-cast composite. The addition of CNTs contents has very small effects on fracture strain of as-cast composites and aging has remarkable effects to increase fracture strain which increases up to 0.5 wt%CNTs/AZ61 and then decrease for 1 wt%CNTs/AZ61. Evaluation of microstructure revealed that CNTs have grain refining eligibility and cause the diffusion of secondary phases to improve the strength. The diffusion of phases in aged CNTs/AZ61 composites causes the formation of shallow cavities at grain boundaries. Results analysis indicated that aged-CNTs/AZ61 composites exhibit enhanced wear and mechanical properties with load-bearing capacity, grain refinement and modification at grain boundaries than as-cast composites.