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This study investigates the influence of CaO (0.5, 1 (wt.%)) alloying on the microstructural evolution, texture development and deformation behavior of AZ61 magnesium alloy. The uniaxial tension tests at room (RT) and cryogenic (CT, -150 °C) temperature were performed to investigate the twinability and dislocation behavior and its consequent effect on flow stress, ductility and strain hardening rate. The results showed that the AZ61-1CaO exhibited superior strength/ductility synergy at RT with a yield strength (YS) of 223 MPa and a ductility of 23% as compared to AZ61 (178 MPa, 18.5%) and AZ61-0.5CaO (198 MPa, 21%). Similar trend was witnessed for all the samples during CT deformation, where increase in the YS and decrease in ductility were observed. The Mtex tools based in-grain misorientation axis (IGMA) analysis of RT deformed samples revealed the higher activities of prismatic slip in AZ61-CaO, which led to superior ductility. Moreover, subsequent EBSD analysis of CT deformed samples showed the increased fraction of fine {10-12} tension twins and nucleation of multiple {10-12} twin variants caused by higher local stress concentration at the grain boundaries, which imposed the strengthening by twin-twin interaction. Lastly, the detailed investigations on strengthening contributors showed that the dislocation strengthening has the highest contribution towards strength in all samples.

The primary issue with joining an immiscible magnesium/iron system is the lack of a bonding medium. This research used an aluminium (Al) additive as a bonding medium to facilitate the formation of an interface layer. Immiscible AZ31 magnesium alloy and SPHC low-carbon steel were successfully joined by employing aluminium (Al) powder as an additive in the gap between them with friction stir welding (FSW). The extensive interfacial microstructural analyses confirmed that the aluminium-rich Fe2Al5 intermetallic compound (IMC) formed with a range of 20–25 nm in thickness at the interface between magnesium and iron resulted from the metallurgical reaction between the Al powder additive and base SPHC steel. This IMC phase served as a transitional layer, facilitating the metallurgical bonding between Magnesium and Iron. The tensile strength of the joint was significantly improved by 43%, from 126 MPa without the additive to 180 MPa using the aluminium additive. The formation of the following well-matched interface lattice sites between Fe and Fe2Al5 region was identified: (002)Fe2Al5//(110)Fe, [110]Fe2Al5//[1‾ 13]Fe. The intermetallic Fe2Al5 was composed of nanocrystalline and amorphous interface layers. Furthermore, the fracture of the joint occurred at the interface, indicating a brittle mode of fracture behaviour.

Magnesium (Mg) and its alloys are emerging as a structural material for the aerospace, automobile, and electronics industries, driven by the imperative of weight reduction. They are also drawing notable attention in the medical industries owing to their biodegradability and a lower elastic modulus comparable to bone. The ability to manufacture near-net shape products featuring intricate geometries has sparked huge interest in additive manufacturing (AM) of Mg alloys, reflecting a transformation in the manufacturing sectors. However, AM of Mg alloys presents more formidable challenges due to inherent properties, particularly susceptibility to oxidation, gas trapping, high thermal expansion coefficient, and low solidification temperature. This leads to defects such as porosity, lack of fusion, cracking, delamination, residual stresses, and inhomogeneity, ultimately influencing the mechanical, corrosion, and surface properties of AM Mg alloys. To address these issues, post-processing of AM Mg alloys are often needed to make them suitable for application. The present article reviews all post-processing techniques adapted for AM Mg alloys to date, including heat treatment, hot isostatic pressing, friction stir processing, and surface peening. The utilization of these methods within the hybrid AM process, employing interlayer post-processing, is also discussed. Optimal post-processing conditions are reported, and their influence on the microstructure, mechanical, and corrosion properties are detailed. Additionally, future prospects and research directions are proposed.

Deformation twinning is profusely activated in the Mg alloys due to lower critical resolved shear stress (CRSS) compared to the non-basal slip systems (prismatic and pyramidal ) and plays a significant role in texture reorientation, grain refinement and enhancement of mechanical performance. Twinning is a sequential process comprising twin nucleation, twin propagation and twin growth, hence several intrinsic and extrinsic parameters that facilitate or suppress the process have been critically reviewed. The dependence of twinning on the grain size, deformation temperature, favorable grain orientation and shear strain have been thoroughly discussed in the context of published literature and an attempt has been made to provide a benchmark conclusive finding based on the majority of works. Furthermore, the subsequent effect of twinning on the mechanical performance of Mg alloys, including ductility, formability and tension-compression asymmetry has been discussed in detail. Lastly, the stability of twins, including stress and thermal stability, is summarized and critical issues related to pertinent bottlenecks have been addressed.

The present study investigates the anisotropic microstructure, nanomechanical and corrosion behavior of Ti–13Nb–13Zr biomedical alloys, which were fabricated using the direct energy deposition (DED) method. The microstructure of the as-deposited material was studied using a field-emission scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). We found anisotropic mechanical behavior using nanoindentation from strain rate sensitivity and creep tests. For the maximum load of 50 mN, the x-y plane (normal to the building direction) shows better indentation hardness and lower strain rate sensitivity value (0.014) compared to the x-z plane (0.022) (parallel to the building direction). The difference in the indentation hardness was mainly attributed to the smaller equiaxed prior-β grains and finer α’ martensitic laths on the x-y plane. In terms of creep behavior, the x-y planes show better creep strength than the x-z plane. Meanwhile, both planes show a very high creep exponent, which signifies a similar creep mechanism, i.e., dislocation based. Moreover, we further found the anisotropic corrosion behavior using electrochemical tests. Corrosion results reveal that the x-y plane is more corrosion-resistant than the x-z plane. In summary, the x-y plane of the direct energy deposited Ti–13Nb–13Zr alloy possesses better strength and corrosion resistance due to its finer microstructure.

The phenomenon of hydrogen embrittlement (HE) in metals and alloys, which determines the performance of components in hydrogen environments, has recently been drawing considerable attention. This study explores the interplay between strain rates and solute hydrogen in inducing HE of Ti6Al4V alloy. For the hydrogen-charged sample, as the strain rate was decreased from 10−2/s to 10−5/s, the ductility decreased significantly, but the HE effect on mechanical strength was negligible. The low strain rate (LSR) conditions facilitated the development of high-angle grain boundaries, providing more pathways for hydrogen diffusion and accumulation. The presence of solute hydrogen intensified the formation of nano/micro-voids and intergranular cracking tendencies, with micro-crack occurrences observed exclusively in the LSR conditions. These factors expanded the brittle hydrogen-damaged region more deeply into the interior of the lattice. This, in turn, accelerated both crack initiation and intergranular crack propagation, finally resulting in a considerable HE effect and a reduction in ductility at the LSR. The current study underscores the influence of strain rate on HE, enhancing the predictability of longevity and improving the reliability of components operating in hydrogen-rich environments under various loading conditions.

In the present study, the effect of annealing treatment on the room-temperature mechanical performance of AZ61, AZ61-0.5CaO and AZ61-1CaO was thoroughly investigated. The as-rolled samples were annealed at 400 °C for 1 h followed by furnace cooling. Microstructural characterization was carried out using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). Moreover, room-temperature uniaxial tensile tests were carried out on the non-annealed and annealed samples along the rolling direction at the strain rate of 10−3 s−1. Microstructural analysis showed the presence of profuse {101¯2} twinning in non-annealed samples and the twinning fraction was increased by the addition of CaO content. SEM showed the formation of precipitates in the AZ61-CaO alloys and TEM confirmed the precipitates to be (Mg, Al)2Ca. The room-temperature tensile tests showed that the mechanical properties of AZ61 were slightly reduced by the addition of CaO, which was attributed to the higher local stress concentration due to the twin–twin interactions. Furthermore, the annealing treatment led to significant enhancement in the YS and UTS of AZ61-1CaO, which is related to the precipitation hardening induced by the intermetallic precipitates.