Influence of hydrogen on the mechanical and fracture properties of some martensitic advanced high strength steels in simulated service conditions

This work investigated the influence of hydrogen on the mechanical and fracture properties of four martensitic advanced high-strength steels in simulated service conditions: (i) immersed in 3.5 wt% NaCl solution, and (ii) at substantial applied stress rates. There was little influence of hydrogen for the four MS-AHSS in 3.5 wt% NaCl. Similarly, there was little influence of hydrogen for hydrogen-precharged MS1300 and MS1500 subjected to tensile tests at substantial stress rates. The diffusivities of hydrogen in MS980, MS1300 and MS1500 were similar. The use of a Pt counter electrode during cathodic hydrogen charging is not recommended

The role of the microstructure on the influence of hydrogen on some advanced high-strength steels

The role of microstructure was studied for dual-phase (DP), quenched and partitioned (Q&P), and twinning induced plasticity (TWIP) steels. The hydrogen influence changed the fracture mode at the ultimate tensile strength, there being no subcritical crack growth at a lower stress. The fractures initiated (i) in the hard martensite and/or at the interfaces of ferrite and martensite for DP steels, (ii) in the martensite and/or at the interfaces of retained austenite and martensite for Q&P steels, and (iii) at mechanical twins for TWIP steels. Tempering may improve the resistance to hydrogen of DP and Q&P steels

The influence of hydrogen on the mechanical and fracture properties of some martensitic advanced high strength steels studied using the linearly increasing stress test

The influence of hydrogen on the mechanical and fracture properties of four martensitic advanced high strength steels was studied using the linearly increasing stress test and electrochemical hydrogen charging. The hydrogen influence increased with steel strength, decreasing charging potential, and decreasing applied stress rate. Increased hydrogen influence was manifest in (i) the decreased yield stress attributed to solid solution softening by hydrogen and (ii) the reduced macroscopic ductility, and by the change from ductile cup-and-cone fracture to macroscopically brittle shear fracture, attributed to a dynamic interaction of hydrogen with the dislocation substructure somewhat similar to the HELP mechanism

Hydrogen trapping in some advanced high strength steels

Permeability experiments were used to study hydrogen diffusion and trapping in dual phase (DP), quenched and partitioned (Q&P), advanced high strength steels. The measured reversible hydrogen trap densities indicated that (i) trapping was less significant at a more negative potential, and (ii) the lattice diffusion coefficient of hydrogen could be measured from the partial transients at the most negative potentials. The densities of reversible hydrogen traps evaluated from complete decays from −1.700\ua0V were\ua0∼\ua02\ua0×\ua010 sites cm, and were a factor of two higher than those from partial decay transients between −1.700\ua0V and −1.100\ua0V

Further study of the hydrogen embrittlement of martensitic advanced high-strength steel in simulated auto service conditions

This work examines the influence of hydrogen on the mechanical and fracture properties of martensitic advanced high-strength steels under conditions relevant to automotive service: (i) in 3.5 wt% NaCl at different cathodic potentials, (ii) in acidified 3.5 wt% NaCl and (iii) at substantial stress rates. The hydrogen embrittlement susceptibility of the steels increases at (I) increasingly negative potentials and at lower pH in 3.5 wt% NaCl, and (ii) at high charging potentials in 0.1 M NaOH at substantial stress rates. The hydrogen influence is manifested by a reduction in ductility, and the presence of brittle features on the fracture surface

Optimising degradation and mechanical performance of additively manufactured biodegradable Fe–Mn scaffolds using design strategies based on triply periodic minimal surfaces

Additively manufactured lattices based on triply periodic minimal surfaces (TPMS) have attracted significant research interest from the medical industry due to their good mechanical and biomorphic properties. However, most studies have focussed on permanent metallic implants, while very little work has been undertaken on manufacturing biodegradable metal lattices. In this study, the mechanical properties and in vitro corrosion of selective laser melted Fe–35%Mn lattices based on gyroid, diamond and Schwarz primitive unit-cells were comprehensively evaluated to investigate the relationships between lattice type and implant performance. The gyroid-based lattices were the most readily processable scaffold design for controllable porosity and matching the CAD design. Mechanical properties were influenced by lattice geometry and pore volume. The Schwarz lattices were stronger and stiffer than other designs with the 42% porosity scaffold exhibiting the highest combination of strength and ductility, while diamond and gyroid based scaffolds had lower strength and stiffness and were more plastically compliant. The corrosion behaviour was strongly influenced by porosity, and moderately influenced by geometry and geometry-porosity interaction. At 60% porosity, the diamond lattice displayed the highest degradation rate due to an inherently high surface area-to-volume ratio. The biodegradable Fe–35Mn porous scaffolds showed a good cytocompatibility to primary human osteoblasts cells. Additive manufacturing of biodegradable Fe–Mn alloys employing TPMS lattice designs is a viable approach to optimise and customise the mechanical properties and degradation response of resorbable implants toward specific clinical applications for hard tissue orthopaedic repair

Biodegradable Fe-35Mn-1Ag

This contains results of characterisation test conducted on biodegradable Fe-35Mn-1Ag alloy to understand its in vivo biocompatibility

The prospects for biodegradable zinc in wound closure applications

Zinc is identified as a promising biodegradable metal along with magnesium and iron. In the last 5 years, considerable progress is made on understanding the mechanical properties, biodegradability, and biocompatibility of zinc and its alloys. A majority of these studies have focused on using zinc for absorbable cardiovascular and orthopedic device applications. However, it is likely that zinc is also suitable for other biomedical applications. In this work, the prospects for zinc in the fabrication of wound closure devices such as absorbable sutures, staples, and surgical tacks are critically assessed, with the aim of inspiring future research on biodegradable Zn for this medical application

Resolving the Public Pension Crisis

The hydrogen permeation through dual-phase (DP) and quenched and partitioned (Q&P) advanced high-strength steels (AHSS) is investigated under simulated auto service conditions. The hydrogen concentration in the steels under simulated auto service corrosion in 3 wt% NaCl solution (either at the free corrosion potential or if polarized to the potential of a galvanized steel surface) is lower than that at the least negative cathodic charging potential of −1.100 V in 0.1 M NaOH. Crevice corrosion introduces three times more hydrogen than the corrosion at the free corrosion potential

Expedient secondary functions of flexible piezoelectrics for biomedical energy harvesting

Flexible piezoelectrics realise the conversion between mechanical movements and electrical power by conformally attaching onto curvilinear surfaces, which are promising for energy harvesting of biomedical devices due to their sustainable body movements and/or deformations. Developing secondary functions of flexible piezoelectric energy harvesters is becoming increasingly significant in recent years via aiming at issues that cannot be addressed or mitigated by merely increasing piezoelectric efficiencies. These issues include loose interfacial contact and pucker generation by stretching, power shortage or instability induced by inadequate mechanical energy, and premature function degeneration or failure caused by fatigue fracture after cyclic deformations. Herein, the expedient secondary functions of flexible piezoelectrics to mitigate above issues are reviewed, including stretchability, hybrid energy harvesting, and self-healing. Efforts have been devoted to understanding the state-of-the-art strategies and their mechanisms of achieving secondary functions based on piezoelectric fundamentals. The link between structural characteristic and function performance is unravelled by providing insights into carefully selected progresses. The remaining challenges of developing secondary functions are proposed in the end with corresponding outlooks. The current work hopes to help and inspire future research in this promising field focusing on developing the secondary functions of flexible piezoelectric energy harvesters