Microstructural Factors Research Articles

Biocompatibility and cyclic fatigue response of surface engineered Ti6Al4V femoral heads for hip-implant application

A major problem with femoral head (FH) for hip implant (HI) applications is that it often fails in service. As a result, revision surgery becomes a must. The related trauma is tremendous for the patient, especially the aged ones. This also implies additional expenses. Keeping these aspects of the problem in view, here we report the development of wear, corrosion and fatigue resistant Ti6Al4V alloy based FH; by a duplex surface engineering (DSE) technique. Thus, the DSE based FHs are developed by a novel combination of plasma nitriding (PN) and Ti/TiN multilayer coating (MLC). The MLCs are formed by magnetron sputtering technique. The Ti6Al4V based FHs are called Ti. The only plasma nitrided FHs are called TiPN. The DSE based FHs are called TiPNML. The corrosion resistances are studied in hank's solution. The sliding wear resistance is studied in simulated body fluid (SBF). The biocompatibilities are studied by the standard MTT assay technique. The cyclic fatigue resistance behaviour up to one million walking cycles is studied in SBF in a HIP simulator with the UHMWPE acetabular cups used as the counter bodies in articulation. The results of the corrosion, biocompatibility, wear, and cyclic fatigue resposnses clearly reveal that the performances of the TiPNML and TiPN FHs are much better than that of the Ti based FHs. The reasons behind such spectacular improvement in biocompatibility as well as corrosion, wear and fatigue resistance are explained in terms of the prevalent phases, microstructural factors, wear mechanisms and surface roughness. The implications of the current results in terms of futuristic FH developments for HI applications are discussed. Such futuristic FH development could provide better HI. These prospects would minimize HI failure and hence, revision surgeries. Thus, the related trauma for numerous patients; especially the aged ones; could be significantly reduced.

Cooperative modulation of Fe2(MoO4)3 microstructure derived from absorbent cotton for enhanced gas-sensing performance

Optimizing microstructure factors of metal oxide sensing materials can be important to improve gas sensor performance. Herein, hierarchically hollow microtubes and microchains of monoclinic Fe2(MoO4)3 were prepared by simple immersion-calcination method using absorbent cotton as template. The influences of different calcination temperatures on morphology, particle size, crystallinity and crystal facet were also investigated. In spite of very small specific surface area of 1.64 m2 g−1, the hollow microtube calcined at 650 °C (FMO-650) presents outstanding gas-sensing performance towards H2S owing to the cooperative modulation of microstructure multi-parameters, such as morphology, size, single crystalline state and exposed active family of (100) crystal planes. At the optimum working temperature of 170 °C, the FMO-650 sensor shows high sensitivity to H2S gas with response time being 7 s, and the detection limit of 0.3 ppm is lower than that of any reported Fe2(MoO4)3-based gas sensors. These results clearly indicate that the strategies for optimizing control of microstructure parameters can significantly improve the sensing performance of metal oxide-based materials. In addition, the gas-sensing mechanism of FMO-650 was also discussed in detail.

Strong stress-level dependence of creep-ageing behavior in Al–Cu–Li alloy

The creep responses, mechanical properties and microstructure evolution in an Al–Cu–Li alloy creep-aged under different stress levels have been systematically investigated by creep test, tensile test and high-angle annular dark-field scanning transmission electron microscopy. When the applied stress is lower than the yield strength, the creep deformation exhibits a four-stage behavior with double primary creep. For high-stress-aged samples, the alloys experience an unusual rapid strain increase at the initial holding stage and then exhibit a normal two-stage creep behavior. The stress-exponent analysis indicates the creep mechanism changes from diffusion creep to dislocation climbing with the stress exceeding the yield strength. The apparent preferential alignment of δ′/θ'/δ′ composite precipitates (stress-orienting effect) can be frequently observed in the low-stress-aged samples and is demonstrated to be responsible for the reduced precipitation strengthening potential compared to the stress-free-aged sample. The high-stress-loading induced dislocations result in a considerable increase of both the creep response and mechanical strength. The unusual strain increase is ascribed to the inelastic deformation caused by softening (material strength lower than the holding stress) due to dislocation recovery and solute clusters reversion within a short-time interval. The dislocation hardening compensates the softening induced by the stress-orienting effect of both T1 and δ′/θ'/δ′ composite precipitates in the high-stress-aged samples. Our results reveal the microstructural factors sensitive to the stress-level during both the stress-loading and holding stages determine the stress-level dependent creep-ageing response in Al–Cu–Li alloy.

Role of trace additions of Mn and Y in improving the corrosion resistance of Mg–3Al–1Zn alloy

The corrosion resistance of conventional and experimental Mg–3Al–1Zn-based alloys with different Mn and Y content was comparatively investigated. After immersion for 72 h in a 0.6 M NaCl solution at 25 °C, an experimental Mg–3Al–1Zn–0.05Mn–0.03Y alloy exhibited a corrosion rate of 0.91 mm y−1, which is about four times slower than that of a conventional Mg–3Al–1Zn–0.3Mn alloy. Microstructural factors underlying the improved corrosion resistance achieved by the trace additions of Mn and Y are discussed.

Microstructure and strength–ductility balance of pure titanium processed by cryogenic rolling at various rolling reductions

In this study, we examined the microstructure and strength–ductility balance of pure Ti processed by cryogenic-temperature rolling (CTR) at various rolling reductions (RRs). The strength–ductility balance of the processed materials was evaluated by multiplying the yield strength by the fracture elongation, which were measured by tensile testing. Generally, the strength–ductility balance deteriorates as metallic materials are strengthened, but remarkably, CTR enhanced the strength–ductility balance while significantly strengthening pure Ti by adjusting the amount of RR. CTR formed numerous thin twins in the grains of the material with suppressed dislocation generation due to the increased twinning activity and relatively decreased slip activity at a low temperature, which cannot be achieved in typical processes performed at or above room temperature. This unique microstructure enhanced the strength–ductility balance of the processed material by intensifying grain refinement and improving resistance to necking instability. However, the strength–ductility balance deteriorated when a large RR was imposed due to the significant changes in the microstructure as the deformation proceeded. Therefore, it is important to adjust the amount of RR for CTR to impart its exceptional ability. We discuss the effects of microstructural factors on the strength–ductility balance in terms of possible strengthening mechanisms and strain-hardening capacity. The present findings could guide the design of optimized CTR for the production of pure Ti plates or sheets with excellent tensile properties and extend their use in industrial applications.

Recycling of construction and demolition waste to fabricate cost-effective anorthite ceramic membranes for enhanced separation of an oil-in-water emulsion

The recycling of construction and demolition waste to prepare cost-effective anorthite membranes was demonstrated by the in-situ synthesis of anorthite. The effects of sintering temperature and calcium loading on the physical properties (porosity, phase composition, microstructure, pore size, nitrogen permeation, and tortuous factor) of the as-synthesized porous membrane were investigated in detail. With the addition of coal cinder and natural bauxite, the anorthite phase was synthesized at 878 °C. Almost all samples had a high porosity of >35% at 900 °C–1000 °C. With the increasing temperature, the porosity of the samples (except for P2 and P4) decreased gradually to close to zero. The variation trend of pore size was consistent with that of the mass fraction of calcium-containing crystals. This occurred because the growth of these crystals as a sintering neck led to the expansion of the pore structure. The increasing temperature caused a decrease of the tortuous factor and an increase of permeance. Due to the presence of anorthite, the as-synthesized membrane became hydroxylated by the alkali-solution treatment and manifested improved hydrophilicity, resulting in an enhanced separation of the oil-in-water emulsion.

On the Fatigue Performance of Friction-Stir Welded Aluminum Alloys.

This work was undertaken in an attempt to ascertain the generic characteristics of fatigue behavior of friction-stir welded aluminum alloys. To this end, different alloy grades belonging to both the heat-treatable and non-heat-treatable types in both the cast and wrought conditions were studied. The analysis was based on the premise that the fatigue endurance of sound welds (in which internal flaws and surface quality are not the major issues) is governed by residual stress and microstructure. Considering the relatively low magnitude of the residual stresses but drastic grain refinement attributable to friction-stir welding, the fatigue performance at relatively low cyclic stress was deduced to be dictated by the microstructural factor. Accordingly, the fatigue crack typically nucleated in relatively coarse-grained base material zone; thus, the fatigue strength of the welded joints was comparable to that of the parent metal. At relatively high fatigue stress, the summary (i.e., the cyclic-plus residual-) stress may exceed the material yield strength; thus, the fatigue cracking should result from the preceding macro-scale plastic deformation. Accordingly, the fatigue failure should occur in the softest microstructural region; thus; the fatigue strength of the welded joint may be inferior to that of the original material.

Effect of Heat Treatments on Microstructural Evolution and Tensile Properties of 15Cr12MoVWN Ferritic/Martensitic Steel

In this study, the phase transformation temperature of 15Cr12MoVWN ferritic/martensitic steel was determined by differential scanning calorimetry to provide a theoretical basis for the design of a heat treatment process. An orthogonal design experiment was performed to investigate the relationship between microstructure and heat treatment parameters, i.e., normalizing temperature, cooling method and tempering temperature by evaluating the room-temperature and elevated-temperature tensile properties, and the optimum heat treatment parameters were determined. It is shown that the optimized heat treatment process was composed of normalizing at 1050 °C followed by air cooling to room temperature and tempering at 700 °C. Under the optimum heat treatment condition, the room-temperature tensile properties were 1014 MPa (UTS), 810.5 MPa (YS) and 18.8% (elongation), while the values are 577.5 MPa (UTS), 469 MPa (YS) and 39.8% (elongation) tested at 550 °C. The microstructural examination shows that the strengthening contributions from microstructural factors were the martensitic lath width, dislocations, M23C6, MX and grain boundaries of prior austenite grain (PAG) in a descending order. The main factors influencing the tensile strength of 15Cr12MoVWN steel were the martensitic lath width and dislocations.

Surface-Based Analysis of Leaf Microstructures for Adsorbing and Retaining Capability of Airborne Particulate Matter in Ten Woody Species

We evaluated surface-based analysis for assessing the possible relationship between the microstructural properties and particulate matter (i.e., two size fractions of PM2.5 and PM10) adsorption efficiencies of their leaf surfaces on ten woody species. We focused on the effect of PM adsorption capacity between micro-morphological features on leaf surfaces using a scanning electron microscope and a non-contact surface profiler as an example. The species with higher adsorption of PM10 on leaf surfaces were Korean boxwood (Buxus koreana Nakai ex Chung & al.) and evergreen spindle (Euonymus japonicus Thunb.), followed by yulan magnolia (Magnolia denudata Desr.), Japanese yew (Taxus cuspidata Siebold & Zucc.), Japanese horse chestnut (Aesculus turbinata Blume), retusa fringetree (Chionanthus retusus Lindl. & Paxton), maidenhair tree (Ginkgo biloba L.), and royal azalea (Rhododendron schlippenbachii Maxim.). There was a higher capacity for the adsorption of PM2.5 on the leaf surfaces of B. koreana and T. cuspidata, followed by A. turbinata, C. retusus, E. japonicus, G. biloba, and M. denudata. In wax layer tests, T. cuspidata, A. turbinata, R. schlippenbachii, and C. retusus showed a statistically higher PM2.5 capturing capacity than the other species. Different types of trichomes were distributed on the adaxial and abaxial leaves of A. turbinata, C. retusus, M. denudata, pagoda tree (Styphnolobium japonicum (L.) Schott), B. koreana, and R. schlippenbachii; however, these trichomes were absent on both sides of the leaves of G. biloba, tuliptree (Liriodendron tulipifera L.), E. japonicus, and T. cuspidata. Importantly, leaf surfaces of G. biloba and S. japonicum with dense or thick epicuticular leaf waxes and deeper roughness revealed lower PM adsorption. Based on the overall performance of airborne PM capture efficiency, evergreen species such as B. koreana, T. cuspidata, and E. japonicus showed the best results, whereas S. japonicum and L. tulipifera had the lowest capture. In particular, evergreen shrub species showed higher PM2.5 depositions inside the inner wall of stomata or the periphery of guard cells. Therefore, in leaf microstructural factors, stomatal size may be related to notably high PM2.5 holding capacities on leaf surfaces, but stomatal density, trichome density, and roughness had a limited effect on PM adsorption. Finally, our findings indicate that surface-based microstructures are necessarily not a correlation for corresponding estimates with leaf PM adsorption.

Fatigue strength of additively manufactured 316L austenitic stainless steel

The microstructures and mechanical properties of the 316L austenitic stainless steel fabricated using binder jet printing (BJP) and selective laser melting (SLM) were investigated and compared with those of the conventionally manufactured (CM) alloy, with particular emphasis on the unnotched fatigue resistance. Results show that the work hardening behavior, ductility, and fatigue strength (σf) of the BJP specimens, which contain significant amounts of pores, are surprisingly comparable to those of the CM alloy. In contrast, the SLM specimens are considerably stronger, especially in terms of the yield strength, less ductile, and far inferior in terms of σf although the porosity in them is relatively smaller as compared to the BJP specimens. These results are rationalized by recourse to the distinct microstructures in the two additively manufactured alloys, which stem from the different processing conditions experienced by them. The planar slip regime that prevails in the early stages of plastic deformation of the BJP alloys and a combination of other microstructural factors lead to the arrest of small cracks that nucleate at the corners of the pores, both under quasi-static and cyclic loads; as a result, neither ductility nor fatigue strength are adversely affected by the porosity in the BJP alloys. In the SLM alloy, the cellular structure, which enhances the yield strength considerably, is too fine whereas the columnar grains are minimally misoriented and coarse enough to induce any crack deflection or arrest. Implications of these results in terms of possible directions for designing AM alloys with high mechanical performance are discussed.

Influence of combined laser heat treatment and ultrasonic impact treatment on microstructure and corrosion behavior of AISI 1045 steel

This work aimed to study the influence of a laser heat treatment (LHT), ultrasonic impact treatment (UIT), and their combinations on the corrosion behavior of AISI 1045 carbon steel in saline solution. Microstructural features and phase state formed in the near-surface layers by LHT-induced transformations and UIT-induced plastic deformation were observed by optical microscopy, X-ray diffraction analysis, and transmission electron microscopy . The surface roughness, hardening intensity, and residual stresses were also analyzed. The results of the polarization experiments showed an essential increase of corrosion potential, corrosion current attenuation and increase in the protection efficiency of the passive film indicating a slowdown of the corrosion rate of the of 1045 steel specimens by the LHT and combined (UIT + LHT, LHT + UIT) techniques, while the single UIT process was less effective. In addition to the LHT-formed oxide layer, the following microstructural factors affect the enhanced corrosion resistance of 1045 steel: the lowered surface roughness, compressive residual stresses, the martensite formation instead of ferritic/pearlitic structure, an increase in the carbon content in the iron lattice due to cementite dissolution, refinement of the martensitic grains. The combined LHT + UIT process is concluded to be the most effective method providing the anti-corrosion performance of 1045 steel.

The effect of microstructure on the relationship between grain boundary sliding and slip transmission in high purity aluminum

The relationship between grain boundary sliding (GBS) and slip transmission is investigated experimentally at grain boundaries in 99.99% aluminum with a through-thickness, coarse-grained microstructure deformed in tension at 190 °C. Using scanning electron microscope-enabled digital image correlation (SEM-DIC) and electron backscatter diffraction (EBSD), high-resolution strain fields and microstructural information were measured to examine the influence of microstructural neighborhoods on interactions between GBS and slip transmission and strain localization. Several distinct cases are presented that highlight important microstructural factors that govern deformation near grain boundaries. The findings include (1) direct transmission and GBS were anti-compatible and facilitated by opposing boundary types (low misorientation and high energy grain boundaries respectively); (2) increased GBS activity was correlated with decreased indirect transmission behavior; (3) GBS accommodation at triple junctions was enabled by intragranular plasticity; and (4) the local intragranular plastic strain discontinuity between grains determined the magnitude of GBS gradients. This work provides insight into the nature of these mechanisms and can be used to identify strain transfer criteria that can lead to improved GBS-sensitive crystal plasticity models.

Supercritical CO2 extraction of pelletized oilseeds: Representation using a linear driving force model with a nonlinear sorption isotherm

This work develops a general, predictive model for the SuperCritical (SC) CO2 extraction of pelletized oilseeds. Cumulative SC-CO2 extraction curves of small (S, dp = 2.5 mm) and large (L, dp = 4.0 mm) cylindrical evening primrose seed pellets were modeled simultaneously using a Linear Driving Force (LDF) approximation modified to consider the nonlinear oil partition between CO2 and the substrate and extrapolated using the actual solubility of oil in CO2 at extraction conditions (40 °C and 45 MPa). Model best-fitting parameter was a single interparticle porosity (εp) of pellets considering equilibrium conditions after static extraction, and mass transfer kinetics during dynamic extraction. The adaptation of general model to bisized mixtures containing 25–75% S-pellets, predicted experimental results better than a monosized version (same Sauter mean diameters) because of the negative impact on overall cumulative extraction curves of slow-extracting L-pellets. Finally, a simplified version of the general model was developed that neglected the intraparticle porosity (εp = 0) and used a microstructural factor (FM∝(εp)−2) in the general model as the best-fitting parameter. This simplified model saved 33% of computational time at the expense of overestimating extraction rates, particularly at the beginning of the diffusion-controlled period, which diminished as εp decreased and FM increased.

A flexible, high-strength, conductive shape memory composite fabric based on continuous carbon fiber/polyurethane yarn

Shape memory textiles, as an active stimulus-responsive smart material, play an important role in sensors and actuators, which have tremendous potential for various fields. High mechanical performance and multiple-stimulus responses are urgently demanded in practical applications. In this work, a conductive composite yarn of continuous carbon fiber coated shape memory polyurethane by melt-extrusion method was fabricated and woven into fabrics. The microstructure and related influence factors on the mechanical property as well as shape memory behavior all have been characterized. Based on the advantages of carbon fiber and polyurethane, the full-textile structured composite fabric revealed remarkable shape memory behavior under thermal and electrical stimulation and possessed excellent mechanical property as well as flexible deformations ability, which makes it promising to apply in wearable smart textiles, biomedicine, aerospace, and other fields.

Effect of microstructural features on the thermal conducting behavior of carbon nanofiber–reinforced styrene-based shape memory polymer composites

This article presents a novel hierarchical micromechanics approach to carefully investigate the thermal conductivities of styrene-based shape memory polymer composites containing carbon nanofibers. The research is mainly focused on the simulation of carbon nanofiber/shape memory polymer interfacial thermal resistance and carbon nanofiber agglomeration as two critical microstructural features of carbon nanofiber–shape memory polymer composite materials. The computed results are compared with the available experimental measurements. It is found that both of those microstructural factors along with carbon nanofiber non-straight shape significantly affecting the thermal conducting behavior must be incorporated in the analysis to have a more realistic prediction. The thermal conductivity of carbon nanofiber–reinforced shape memory polymer composites reduces significantly due to the effects of carbon nanofiber/shape memory polymer interfacial resistance and carbon nanofiber agglomeration and waviness. It is suggested to uniformly disperse carbon nanofibers into the shape memory polymers and reduce interfacial resistance for improving the carbon nanofiber–styrene composite thermal properties. In addition, the present study reveals that the effective thermal conductivities of the shape memory polymer composites reinforced by aligned carbon nanofibers are greatly enhanced over those of the shape memory polymer composites containing randomly dispersed carbon nanofibers. The effects of percentage, waviness parameters, degree of agglomeration, material properties, length and diameter of carbon nanofibers as well as interfacial thermal resistance value on the thermal behavior of carbon nanofiber–reinforced styrene-based shape memory polymer composites are investigated.

25.11% efficiency silicon heterojunction solar cell with low deposition rate intrinsic amorphous silicon buffer layers

Here we report a certified efficiency of up to 25.11% for silicon heterojunction (SHJ) solar cells on a full size n-type M2 monocrystalline-silicon (c-Si) wafer (total area, 244.5 cm2). An ultra-thin intrinsic a-Si:H buffer layer was introduced on the c-Si wafer surface using a 13.56 MHz home-made RF-PECVD with low deposition rate showing superior surface passivation. The ultra-thin i-a-Si:H film with both higher microstructure factor (R*) and H content evidently increases the SHJ solar cell open-circuit voltage (VOC) by 2 mV, and moreover, short-circuit current (ISC) and fill factor (FF) are also notably improved, resulting in a 0.52% absolute cell efficiency enhancement, in which FF is the main cause. In order to explore high conversion efficiency SHJ solar cells, both home-made RF-PECVD and commercial VHF-PECVD (40.68 MHz) are employed for deposition of the i-a-Si:H passivation layer. As a result, the efficiency of RF-PECVD-prepared SHJ cell is 0.21% higher than that of VHF-PECVD-prepared, mainly driven by VOC and ISC boost. This work offers a useful tool for fabrication of high performance SHJ solar cells which could be employed in mass production.

Effect of initial microstructure on the deformation heterogeneities of 316L stainless steels fabricated by selective laser melting processing

The selective laser melting (SLM) is a popular additive manufacturing (AM) technique used for the fabrication of metal parts. In the present study, two 316L stainless steel specimens (SLM-I and SLM-II) with different microstructures were fabricated with different levels of energy density by changing the laser power and scanning speed, which are the main SLM process conditions. The deformation and fracture behavior of miniature SLM specimens under uniaxial tension were experimentally measured via optical microscopy (OM), field emission scanning microscopy (FE-SEM), and an electron back-scattered diffraction (EBSD) technique. In order to analyze the deformation heterogeneities under uniaxial tension, the inverse pole figure (IPF) map, kernel average misorientation (KAM) map, Taylor factor (TF) map, grain boundaries (GBs), Σ3 twin boundaries (TBs), and melt pool boundaries (MPBs) developed in deformed SLM specimens were analyzed at different strain levels. The effect of microstructural factors on the deformation heterogeneities of SLM specimens was explained by the evolution of KAM, GBs, MPBs, and Σ3 TBs. The initial microstructures of the SLM specimens significantly influenced the generation and propagation of cracks under uniaxial tension.

Mechanical Property of Ultrafine Elongated Grain Structure Steel Processed by Warm Tempforming and Its Application to Ultra-High-Strength Bolt

Our strategy is to enhance the fracture property of ultra-high-strength low-alloy steels with a yield strength of 1.4 GPa or over by arresting the propagation of brittle cracks in hierarchical, anisotropic, and ultrafine-grained structures. This provides a fail-safe design in addition to suppressing crack initiation. The present article reviews the strength, ductility, toughness, and delayed fracture resistance of ultra-high-strength low-alloy steels with ultrafine elongated grain structures processed by the deformation of tempered martensitic structures at elevated temperatures (referred to as warm tempforming). The evolution of heterogeneous microstructures during warm tempforming using multi-pass caliber rolling is discussed, as are the microstructural factors controlling the strength and fracture properties of warm tempformed steels. Furthermore, we apply warm tempformed steels with ultrafine elongated grain structures to the fabrication of ultra-high-strength bolts.

Effects of interfacial microstructure on mechanical properties of Stellite-hardfaced coating during long-term aging

Disbonding and delamination of Stellite-hardfaced coatings from high-temperature valves have presented a major challenge to the power generation industry. In order to study how the interfacial microstructure of Stellite-hardfaced coatings might damage valve integrity during service, a series of aging experiments were conducted at temperatures ranging from 550 to 650 °C over three durations within a one-year period. After high-temperature exposure, the hardfacing interface was characterized using innovative Charpy U-notch specimens. It was observed that the impact energy decreased significantly (by at least 92%) after aging. The fractographic analysis revealed that the fractures of the aged hardfacing specimens were brittle. It is proposed that the interfacial layer formed during aging provides a brittle crack propagation pathway. The reduction in absorbed impact energy is mainly associated with the formation of hard and brittle M23C6 carbides along the hardfacing interface. The more the M23C6 carbides grow, the smaller the absorbed impact energy becomes. The presence of the σ phase would also contribute to the decrease of the absorbed impact energy. It is proposed that the microstructural factors contributing to the delamination of Stellite-hardfaced coatings in service are the formation of hard and brittle M23C6 carbides and σ phase.

Understanding Crack Formation Mechanisms of Ti–48Al–2Cr–2Nb Single Tracks During Laser Powder Bed Fusion

The crack formation mechanisms of Ti–48Al–2Cr–2Nb single tracks processed by laser powder bed fusion were extensively investigated in a wide range of laser powers and scan speeds. The crack patterns were categorized by their directionalities, which were parallel (longitudinal crack) and/or perpendicular (transverse crack) to the scan direction. For the representative process conditions of the keyhole, transition, and conduction modes, cracking behaviors were characterized by combining the fractography and the microstructural analysis. Further, thermal-mechanical finite element method simulations were performed to predict the distribution of temperatures and thermal stresses during the melt pool formation. On the basis of the combined results, the cracks formed in keyhole, transition, and conduction modes were clarified as a solidification crack and/or a thermal crack. In addition, the formation of these cracks was thoroughly understood in terms of thermal stresses and microstructural factors that affect the crack susceptibility. Finally, comprehensive mechanisms responsible for cracking of Ti–48Al–2Cr–2Nb single tracks under laser powder bed fusion were proposed for different process conditions (the keyhole, transition and conduction modes).