Due to their distinct physical, chemical, and mechanical features, high-entropy alloys have significantly broadened the possibilities of designing metal materials, and are anticipated to hold a crucial position in key engineering domains such as aviation and aerospace. The fatigue performance of high-entropy alloys is a crucial aspect in assessing their applicability as a structural material with immense potential. This paper provides an overview of fatigue experiments conducted on high-entropy alloys in the past two decades, focusing on crack initiation behavior, crack propagation modes, and fatigue life prediction models.

Purpose: The purpose of this paper is to determine the ultra-high cycle fatigue behavior and ultra-slow crack propagation behavior of selective laser melting (SLM) AlSi7Mg alloy under as-built conditions.Design/methodology/approach: Constant amplitude and two-step variable amplitude fatigue tests were carried out using ultrasonic fatigue equipment. The fracture surface of the failure specimen was quantitatively analyzed by scanning electron microscope (SEM).Findings: The results show that the competition of surface and interior crack initiation modes leads to a duplex S–N curve. Both manufacturing defects (such as the lack of fusion) and inclusions can act as initially fatal fatigue microcracks, and the fatigue sensitivity level decreases with the location, size and type of the maximum defects.Originality/value: The research results play a certain role in understanding the ultra-high cycle fatigue behavior of additive manufacturing aluminum alloys. It can provide reference for improving the process parameters of SLM technology.

Ultrasonic fatigue tests up to 10¹⁰ cycles were performed on a turbine engine titanium alloy (Ti-8Al-1Mo-1V) at the stress ratio (R) of −1 with smooth specimens and at R = −1, 0.1 and 0.5 with notched specimens. As a result, with increase of fatigue life, the source of reduced fatigue life caused by multi-point surface crack initiation changes from crack propagation stage to crack initiation stage in the high cycle fatigue regime. Notch effect further promotes the degeneration of high cycle and very high cycle fatigue strength at R > −1. The bilinear model, extended from the Goodman method, can better estimate the mean stress sensitivity of this titanium alloy. The fatigue mean stress sensitivity and fatigue-creep mean stress sensitivity of this material increased with the increase of fatigue life. The new model, based on the Murakami model, can provide more appropriate predictions for notch fatigue strength.

The penetration of external stimuli (microorganisms, ions, etc.) following to the pore is the key reason for the deterioration of cement and concrete structures. Although the traditional methods such as improving the chemical composition of cement and concrete materials can delay the erosion rate, the inevitable pore structure still makes its deterioration a challenge. Based on this, we reported a protective coating for cementitious materials based on phenol and Ti₃C₂ MXene-modified polyacrylate (MXene-PG/PA). The introduction of phenols enhanced the waterproof properties of polyacrylate by increasing the interaction among molecular chains. Moreover, the introduction of Ti₃C₂ MXene also endows the MXene-PG/PA coating with good light-induced antimicrobial properties. Beneficial to these designs, the MXene-PG/PA coating exhibited good waterproof properties (the water absorption ratio in seawater decreased by 58.2%) and antimicrobial properties (inhibition of E. coli and S. epidermidis activity under light). These results not only confirm that the MXene-PG/PA coating is a potential candidate of protective coating for cement-based materials, but also provide a new strategy for the design of multifunctional protective coatings.

Cyclic deformation at low-stress amplitudes of a rare earth-containing magnesium alloy (Mg–Gd–Y–Zr) was investigated with emphasis on the responsible microstructural relationship between deformation mechanism and fatigue crack initiation. The results show that the microstructural deformation is extremely inhomogeneous at the low-stress amplitudes. Both deformation twinning and non-basal slip are barely observed, and basal slip is the predominant deformation to accommodate micro-plasticity. Fatigue crack initiation occurred at the basal slip bands, causing the morphology of facet on the fracture surface. Therefore, the basal slip is of prime importance in low-stress cyclic deformation and fatigue failure, and fatigue improvement could potentially be obtained through hindering the motion of basal dislocation by microstructural obstacles.