The present work aims to study the tribological behavior of an extruded ZK60 alloy in the presence of Ce; in a previous study, among ZK60 alloys with different Ce addition rates, an alloy with 3 wt% of Ce was found to exhibit the most promising mechanical (e.g., hardness and strengths) properties, while its wear behavior remained unknown. The results of microstructural examinations by optical and electron microscopes show that Ce addition reduces the grain size from 6.1 to 2.0 μm. Besides, in addition to the precipitates already distributed in the base alloy (Mg₇Zn₃), Ce could promote the formation of a new precipitate (MgZn₂Ce), increasing the total fraction of the precipitates. These microstructural evolutions enhance the strengths of the studied ZK60 alloy, as the yield and tensile strengths increase from 212 to 308 MPa and from 297 to 354 MPa, respectively. A pin on disc tribometer was employed to study the wear behavior of the developed alloy under different normal loads (5, 20, 40, and 60 N). The results show that the base and Ce-added alloys exhibit almost a similar frictional behavior, while the wear resistance of the Ce-added alloy is higher within the load ranges applied: (i) in low load conditions (5 and 20 N), where the abrasive wear is the active mechanism, the precipitates in the Ce-added alloy could enhance the wear resistance. (ii) Under the load of 40 N, oxidative wear is also an operative wear mechanism, leading to a sharp increase in the wear rate of the alloys. In this condition, Ce could provide a protective oxide layer, which could improve the wear resistance of the alloy. (iii) At a load of 60 N, both studied alloys exhibit a similar wear rate due to a severe oxidation condition. Therefore, beyond this loading condition, the microstructural evolutions (e.g., change in precipitation behavior) caused by Ce addition can no longer contribute to the enhancement of wear resistance. Graphic

This paper investigates the free vibration behavior of a rotating functionally graded conical shell, reinforced by an anisogrid lattice structure. The material properties of the shell are assumed to be graded in the thickness direction. The governing equations have been derived based on classical shell theory and considering the effects of centrifugal and Coriolis accelerations as well as initial hoop tension due to shell rotation. The smeared method is also employed to superimpose the stiffness contribution of the stiffeners with those of the shell to obtain the whole structure's equivalent stiffness parameters. The resulting equations, which are the coupled set of three variable coefficient partial differential equations in terms of displacement components, are solved by the Galerkin method for different boundary conditions. The obtained frequencies are compared with the available literature and the finite element software results. Finally, new results are discussed to show the effect of various parameters such as shell geometrical and material properties, stiffeners, rotating speed, and boundary conditions on natural frequencies.

In this study, WE43 alloy matrix composites, reinforced with 2.5, 5, 7.5, and 10 wt% B₄C particles have been produced by the stir casting technique at 750 °C. Cast ingots of the matrix alloy and the composites were then subjected to hot rolling at 480 °C. After that, the effect of B₄C additions (0–10 wt%) as well as hot rolling on the microstructure and mechanical properties of WE43 alloy were investigated. Microstructural characterization following hot rolling revealed a relatively uniform distribution of B₄C particles, well-bonded B₄C particles to the matrix, and a minimal porosity level. Further, both as-cast and hot-rolled composites have shown considerable grain refinement and hence improved mechanical properties compared to unreinforced alloy. Twinning was the dominant deformation mechanism in the hot-rolled WE43 alloy, whereas dynamic recrystallization occurred extensively in hot-rolled composites. It was observed that tensile strength and hardness values were improved not only as B₄C content increased but more due to the rolling effect; however, elongation to fracture was reduced. Maximum ultimate tensile strength of ∼284 MPa and yield strength of ∼259 MPa with an improved hardness to ∼97 HB were obtained for the hot-rolled WE43-10%B₄C composite.