Notch tensile and dry sliding wear studies on Mg-Nd-Gd-Zn alloy

Abstract

This main purpose of the present research is to investigate the properties of wear and tensile in smooth and notch conditions of the heat-treated Mg-Nd-Gd-Zn alloy. The material applications such as complex helicopter gear box casing, piston and brake actuating components demands tensile data in notch conditions and wear characterizations. The alloy was characterized for microstructure, hardness, tensile properties in smooth and notch conditions and tribological properties such as wear resistance and friction coefficient. The microstructure examination revealed equiaxed grain structure with the size of about 42μm. The XRD results confirms the presence of Mg3 (Nd) precipitates. Smooth and notched samples were evaluated to determine the effect of notch radii and ductile-brittle transition. Notched samples show 25.31% improvements in strength compared to the smooth sample with the marginal reduction in ductility (1.3-1.8%). The fractography results for notched specimens exhibited cleavage, intergranular mode whereas the smooth specimens exhibited quasi cleavage, inter and transgranular modes. At 10N, the wear rate and friction coefficient change from 8.83 x 10-5 mm3/min to 7.11 x 10-5 mm3/min (24.2%) and to 0.29 and 0.26 (11.5%) respectively when the sliding velocity increases from 1 to 5 m/s. Similarly, at 20N, the wear rate and friction coefficient change from 9.11 x 10-5 mm3/min to 0.75 x 10-6 mm3/min (12.7%) and 0.29 to 0.23 (26.1%) respectively when the sliding velocity increases from 1 to 5 m/s. With the increase of load, plastic deformation is dominant controlling the wear rate. With the increase of sliding speed, oxidation is dominant controlling the wear rate and friction coefficient. Mixed modes of wear mechanisms such as abrasion, oxidation, delamination, third body assisted wear and melt wear were observed.