Quasi Cleavage Research Articles

Microstructure, deformation and fracture mechanism of Mg-Gd-Y-Zn-Zr alloy with different rolling routes during tension

The microstructure, deformation and fracture mechanism of unidirectional rolling (UR) and cross rolling (CR) Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr alloy during tension were studied. Both rolled alloys exhibit typical bimodal microstructures, with the difference being that UR alloy has elongated grains containing rod LPSO phase, while CR alloy has relatively rounded deformed grains containing lamellar LPSO phase. After tension until fracture, the LPSO phase morphology of the two alloys remains unchanged. CR alloy exhibits a higher yield strength and lower elongation than UR alloy. Although the higher average basal <a> slip Schmid factor result in the lower yield strength of UR alloy, the activation of the high proportion of non-basal slip is responsible for its higher elongation. UR alloy and CR alloy exhibit ductile fracture and quasi cleavage fracture characteristics, respectively. For UR alloy, a variety of dislocations accumulated near grain boundary and the weak slip transfer effects between grains both contributes to the propagation of grain boundary cracks. However, the effects of weak interfacial bonding between metastable lamellar LPSO phase and matrix, along with the similar orientation and higher geometric compatibility of CR alloy, lead to the rapid spread of transgranular cracks.

Coupling effect of post-weld heat treatment and fatigue damage on the hydrogen embrittlement of X80 steel welded joints

The influence of post-weld heat treatment (PWHT) and fatigue damage on the hydrogen embrittlement sensitivity of X80 steel welded joints, obtained using flux-cored arc welding method, was investigated in the study. Compared to the as-welded specimens, the sensitivity of hydrogen embrittlement after PWHT was decreased. However, the coupling effect of PWHT and fatigue damage improved significantly the HE sensitivity. Furthermore, the fracture site of the PWHT + pre-fatigue specimens with hydrogen-charged was transferred to the weld metal, and the fracture was characterized by intergranular fracture, quasi-cleavage (QC) and shallow dimples ductile fracture. The increase of the hydrogen content might be attributed to the evolutions of dislocation and the proportion of high-angle grain boundary caused by fatigue damage. Meanwhile, the size of QC for the hydrogen-charged welded joints was related to the degree of fatigue damage, hydrogen content and microstructure strength.

Comparison of Crack Initiation Sites and Main Factors Causing Hydrogen Embrittlement of Tempered Martensitic Steels with Different Carbide Precipitation States

The dependence of crack initiation sites and main factors causing hydrogen embrittlement fracture on carbide precipitation states has been investigated for tempered martensitic steels with the same tensile strength of 1450 MPa. Notched specimens charged with hydrogen were stressed until just before fracture and subsequently unloaded. The crack initiation site exhibited intergranular (IG) fracture at 21 μm ahead of the notch tip as observed by scanning electron microscopy (SEM) for 0.28% Si specimens with plate-like carbide precipitates on prior austenite (γ) grain boundaries. This crack initiation site corresponded to the vicinity of the maximum principal stress position as analyzed by a finite element method (FEM). The initiation site corresponded to the triple junction of prior γ grain boundaries as analyzed by electron backscattered diffraction (EBSD). In contrast, the crack initiation site exhibited quasi-cleavage (QC) fracture at the notch tip for 1.88% Si specimens with fine and thin carbide particles in the grains. This crack initiation site corresponded to the maximum equivalent plastic strain site obtained by FEM. Additionally, the crack initiated on the inside of prior γ grain boundaries and propagated along the {011} slip plane with higher kernel average misorientation (KAM) values as analyzed by EBSD. These findings indicate that differences in carbide precipitation states changed the crack initiation sites and fracture morphologies involved in hydrogen embrittlement depending on mechanical factors such as stress and strain and microstructural factors.

Dual grain size-effects on hydrogen-assisted fatigue crack growth in 1 GPa-class medium-carbon martensitic steel

The influence of prior austenite grain (PAG) size ranging from 6 to 90 μm on the fatigue crack growth (FCG) of a tempered 0.41%C lath martensitic steel was investigated in a 90 MPa H2 gas environment at ambient temperature. Under the presence of H, severe FCG accelerations accompanying intergranular (IG) cracking along PAG boundaries as well as quasi-cleavage (QC) fracture along martensite block boundaries and {011} crystallographic planes were systematically found. Smaller PAG mitigated the acceleration at a relatively high-stress intensity via suppressing IG cracking. However, PAG refinement instead escalated the acceleration at a low-stress intensity factor where QC facture prevailed. This inverse grain size effect was discussed in terms of the plasticity criterion in triggering QC and its possible dependence on the microstructural length scale.

Effects of Temperatures of Rolling and Annealing on Microstructures and Tensile Properties of Low Carbon Ferritic Low Density Steels

The microstructural modification and the effect of cold/warm rolling and annealing on tensile properties of ferritic low density steels containing different amounts of carbon (0.0035 mass%, Steel 1 and 0.04 mass%, Steel 2) and aluminium (6.8 mass%, Steel 1 and 9.7 mass%, Steel 2) were investigated with respect to amount of ferrite, grain size and formation of Fe3Al intermetallic. The Steel 1 was deformed by cold rolling at room temperature and Steel 2 was deformed through warm rolling at 250°C to avoid prior cracks formation. After rolling, samples of Steels 1 and 2 were annealed at 900°C for 5 minutes. The yield strength, ultimate tensile strength and ductility increase while yield ratio decreases with annealing. This is due to formation of Fe3Al intermetallic and reduction of ferrite grain size. Due to high interstitial Carbon in Steel 2, yield point phenomenon was observed which may reduce the formability of the steel. The cracks started during tensile test at the ferrite grains and ferrite grain boundaries and the fracture took place in the quasi cleavage mode in Steels 1 and 2. The grain refinement and the microstructural features due to rolling and annealing are accountable for the good combination of strength and ductility of the both steels.

Fracture toughness of Ti2AlNb alloy with different Al content: Intrinsic mechanism, extrinsic mechanism and prediction model

In this research, two Ti2AlNb based alloys were investigated to reveal the effect of Al content on fracture toughness, and the fracture mechanism of both alloys was discussed from intrinsic and extrinsic aspects. In addition, the crack tip plastic zone model and the prediction model of fracture toughness were established based on tensile properties. The results show that the increase of Al content leads to more O phase content, finer acicular O phase and higher Al content in three constituent phases, thus improving the strength and reducing the ductility and fracture toughness. Meanwhile, the cleavage morphology with tearing ridges on the fracture surface indicates that the fracture mechanism is quasi cleavage fracture. The brittle nature of acicular O phase and equiaxed particles provides nucleation sites of microcrack and promotes crack propagation. As another aspect, the intrinsic mechanism of crack tip bluntness caused by B2 phase and the extrinsic mechanism of crack deflection at grain boundary strengthen the resistance of crack propagation. The increase of Al content brings out the reduction of crack tip plastic zone and crack path tortuosity, which makes a significant decrease in fracture toughness. Moreover, the fracture toughness predicted based on tensile properties is in agreement with that obtained by experiment, and the fracture toughness of two alloys is dominated by intrinsic contribution.

Achieving excellent specific yield strength in non-equiatomic TiNbZrVMo high entropy alloy via metalloid Si doping

In this work, silicide phase was added to the single phase BCC solid solution Ti1.5NbZrV0.4Mo0.6 alloy to improve the mechanical properties. Ti1.5NbZrV0.4Mo0.6Six (x = 0-0.9, mole ratio) high entropy alloys (HEAs) was made by vacuum arc melting. The influence of Si on the microstructure, mechanical properties and fracture mechanisms of the alloy were studied. The addition of Si makes lamellar M5Si3 silicide phase grow in BCC interdendritic, and the silicides change from lamellar to coarse network. The primary BCC dendrite structure gradually changes to strip and hexagonal silicides. Si element prominently increases the yield strength and decreases the density. When x = 0.9, the alloy has yield strength of 2019.2 MPa, the elongation of 16.5% and the density of 5.91 g·cm-3, which exhibits a superb specific yield strength (SYS) up to 341.66 MPa·cm3·g-1. The improvement of mechanical properties is mainly by reason of the silicide phase strengthening. The fracture mechanism changes from quasi cleavage fracture when x = 0.1 to cleavage fracture when x = 0.3-0.7, and then to intergranular fracture when x = 0.9.

炭化物析出状態の異なる焼戻しマルテンサイト鋼における水素脆化き裂発生点とその主要因子の比較

The dependence of crack initiation sites and main factors causing hydrogen embrittlement fracture on carbide precipitation states has been investigated for tempered martensitic steels with the same tensile strength of 1450 MPa. Notched specimens charged with hydrogen were stressed until just before fracture and subsequently unloaded. The crack initiation site exhibited intergranular (IG) fracture at 21 μm ahead of the notch tip as observed by scanning electron microscopy (SEM) for 0.28% Si specimens with plate-like carbide precipitates on prior austenite (γ) grain boundaries. This crack initiation site corresponded to the vicinity of the maximum principal stress position as analyzed by a finite element method (FEM). The initiation site corresponded to the triple junction of prior γ grain boundaries as analyzed by electron backscattered diffraction (EBSD). In contrast, the crack initiation site exhibited quasi-cleavage (QC) fracture at the notch tip for 1.88% Si specimens with fine and thin carbide particles in the grains. This crack initiation site corresponded to the maximum equivalent plastic strain site obtained by FEM. Additionally, the crack initiated on the inside of prior γ grain boundaries and propagated along the {011} slip plane with higher kernel average misorientation (KAM) values as analyzed by EBSD. These findings indicate that differences in carbide precipitation states changed the crack initiation sites and fracture morphologies involved in hydrogen embrittlement depending on mechanical factors such as stress and strain and microstructural factors.

Layer control method and mechanical anisotropy of titanium alloy based on double-hot-wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) is an important manufacturing technology for fabricating large-size titanium alloy parts, which has important application prospects in aerospace and other fields. However, the grain size and mechanical anisotropy of WAAM materials have a certain impact on the application. In this paper, the influence of two kinds of layer control methods based on DHWAAM on grain size is studied. The β grain morphology of the layer cooling method is mostly the mixed morphology of small-size short columnar grain and equiaxed grain, while the continuous deposition method is coarse columnar grain. The layer cooling method is beneficial to grain refinement. The tensile results show that the ultimate tensile strength (UTS) of the layer cooling method is 6.5 % higher than that of the continuous deposition method, but the elongation has no significant change. In addition, the mechanical anisotropy of the titanium alloy fabricated by DHWAAM was also studied. The mechanical properties of the tensile samples at different angles were different. The% in plane anisotropy (%IPA) of UTS was 4.48. The fracture mode is quasi cleavage fracture. The pore defects (unfused pores and gas pores) in DHWAAM were characterized by XCT. The formation mechanism of different pore types is analyzed as well.

Strengthening and toughening effect of laser melting deposited Nb–16Si–20Ti–3Al with nano-ZrC additions

The phase composition, microstructure, and properties of Laser Melting Deposited (LMD) Nb–16Si–20Ti–3Al alloys with different nano-ZrC (0, 2.5, 5.0, 10.0 wt%) addition were detailed investigated in this study. Results showed that the LMDed Nb–16Si–20Ti–3Al alloy was composed Nb-based solid solution (Nbss) and Nb3Si. The addition of nano-ZrC promoted the decomposition of the Nb3Si phase and the eutectic transformation from Nb3Si to (Nbss+γ-Nb5Si3) eutectic structure. With the content of nano-ZrC increased from 2.5 wt% to 5.0 wt%, the (Nbss+γ-Nb5Si3) eutectic structure was significantly refined. Nb-rich TiC phase precipitated at the grain boundaries of (Nbss+γ-Nb5Si3) eutectic structure by the titanium in the alloy reacted with nano-ZrC additions. With the content of nano-ZrC increased to 10.0 wt%, coarse and irregular primary γ-Nb5Si3 phase and dendritic TiC were observed in the Nb–Si alloy. The fracture toughness was improved from 5.1 MPa m½ to 17.1 MPa m½ by adding an optimized amount of nano-ZrC (5.0 wt%) due to the refinement of (Nbss+γ-Nb5Si3) eutectic structure and dispersion distributed nano-ZrC in the alloys. The Nb–16Si–20Ti–3Al alloy with 5.0 wt% nano-ZrC addition has the maximum compressive strength of 1836 MPa and a compressive strain of 12.6%. The crack deflection seems an important toughening mechanism for Nb–16Si–20Ti–3Al alloys containing nano-ZrC. The fracture mode of each Nb–16Si–20Ti–3Al alloys with (0, 2.5, 5.0, 10.0 wt%) addition exhibited a brittle quasi cleavage fracture.

Analysis of Hydrogen-Assisted Brittle Fracture Using Phase-Field Damage Modelling Considering Hydrogen Enhanced Decohesion Mechanism

This study proposes a hydrogen-assisted fracture analysis methodology considering associated deformation and hydrogen transport inside a phase-field-based formulation. First, the hydrogen transport around a crack tip is calculated, and then the effect of hydrogen enhanced decohesion (HEDE) is modeled by defining the critical energy release rate as a function of hydrogen concentration. The proposed method is based on a coupled hydrogen mechanical damage under phase-field and implemented through a user subroutine in ABAQUS software. The test using compact tension (CT) sample is investigated numerically to study the hydrogen embrittlement on 45CrNiMoVA steel. Experimentally, the microstructural fracture presents a mixed brittle fracture mode, consisting of quasi-cleavage (QC) and intergranular (IG) fracture with hydrogen. This fracture mode is consistent with the suggested HEDE mechanism in the model. The simulation results show that hydrogen accumulates at the crack tip where positive hydrostatic stress is located. Moreover, the model estimates the initial hydrogen concentration through iterations. The simulated load-line displacement curves show good agreement with the experimental plots, demonstrating the predictive capabilities of the presented scheme.

Flow stress and work hardening behaviour of Mg-3Al-1Zn alloy

In the present study, the uniaxial tensile flow stress behaviour and work hardening behaviour of AZ31B alloy has been investigated across a wide range of temperature (25 °C–250 °C) at quasi-static strain rates (10−1·s−1–10−3·s−1). The flow stress behaviour of the AZ31B sheet has been analysed at different temperatures, quasi-static strain rates and sheet orientations. It has been found that flow stress behaviour is highly influenced by the variation of temperatures, strain rates, and sheet orientations. The various important mechanical properties such as yield strength, ultimate tensile strength, percentage elongation, strain hardening exponent, and strain rate sensitivity have been determined. There has been a significant improvement in ductility (201.71%) of AZ31B alloy at 250 °C compared to 25 °C. The decrement in yield strength and ultimate strength has been found to be 47.52% and 53.66%, respectively. It has been observed that the AZ31B alloy is found to be more strain rate sensitive at elevated temperature (m = 0.11, at 250 °C) as compare to 25 °C. The various empirical hardening equations such as Hollomon, Ludwik, Ludwigson, Swift, and modified Voce have been formulated for a wide range of temperatures, strain rates, and sheet orientations. The K-M plots show three-stage of work-hardening behaviour for AZ31B alloy. Based on the performance comparison of different models, the Swift and Modified Voce efficiently predict the flow curve with correlation (more than 99%) at different temperature ranges. The fracture surface is analysed by FESEM. The quasi cleavage and river-like pattern are observed for the room temperature fractured specimen. The increase in temperature converts the mode of fracture from cleavage to ductile fracture.

Notch tensile and dry sliding wear studies on Mg-Nd-Gd-Zn alloy

This main purpose of the present research is to investigate the properties of wear and tensile in smooth and notch conditions of the heat-treated Mg-Nd-Gd-Zn alloy. The material applications such as complex helicopter gear box casing, piston and brake actuating components demands tensile data in notch conditions and wear characterizations. The alloy was characterized for microstructure, hardness, tensile properties in smooth and notch conditions and tribological properties such as wear resistance and friction coefficient. The microstructure examination revealed equiaxed grain structure with the size of about 42 μm. The XRD results confirms the presence of Mg3 (Nd) precipitates. Smooth and notched samples were evaluated to determine the effect of notch radii and ductile-brittle transition. Notched samples show 25.31% improvements in strength compared to the smooth sample with the marginal reduction in ductility (1.3%–1.8%). The fractography results for notched specimens exhibited cleavage, intergranular mode whereas the smooth specimens exhibited quasi cleavage, inter and transgranular modes. At 10N, the wear rate and friction coefficient change from 8.83 × 10–5 mm3 min−1 to 7.11 × 10–5 mm3 min−1 (24.2%) and to 0.29 and 0.26 (11.5%) respectively when the sliding velocity increases from 1 to 5 m s−1. Similarly, at 20N, the wear rate and friction coefficient change from 9.11 × 10–5 mm3 min−1 to 0.75 × 10–6 mm3 min−1 (12.7%) and 0.29 to 0.23 (26.1%) respectively when the sliding velocity increases from 1 to 5 m s−1. With the increase of load, plastic deformation is dominant controlling the wear rate. With the increase of sliding speed, oxidation is dominant controlling the wear rate and friction coefficient. Mixed modes of wear mechanisms such as abrasion, oxidation, delamination, third body assisted wear and melt wear were observed.

Observation of hydrogen trap and hydrogen embrittlement of 430 ferritic stainless steel

The hydrogen distribution and content in AISI430 ferritic stainless steel (FSS) were revisited via time-of-flight secondary ion mass spectrometer (TOF-SIMS) and thermal desorption spectroscopy (TDS) in this paper. As irreversible hydrogen traps, carbides have stronger hydrogen trapping capabilities and the activation energy of hydrogen desorption (Eb) is 44.37 KJ/mol, which is higher than the lattice/grain boundaries (GB) (18.18 KJ/mol). Hydrogen changed the stress level state at the crack tip and increased the crack growth rate. High hydrogen concentration promoted the hydrogen-enhanced decohesion (HEDE) mechanism, causing the microcracks to preferentially nucleate at the interface between the carbide and the matrix, with the fracture mode changed from micro-void coalescence (MVC) fracture to quasi-cleavage (QC) fracture.

Effect of hydrogen on the mechanical properties and fracture modes of annealed 430 ferritic stainless steel

The change of fracture morphology after traditional electrochemical hydrogen charging and the microstructure of the hot-rolled AISI430 ferritic stainless steels (FSSs) specimens annealed at different temperatures (720°C–1060 °C) was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) technology. We systematically illustrated the effect of annealing temperature on its hydrogen embrittlement sensitivity, hydrogen-induced mechanical property changes, and the transformation of microstructure on the change of hydrogen-induced fracture mode. The experimental results prove that: the hydrogen embrittlement susceptibility of FSSs increases significantly from the α single-phase region to the α+β dual-phase region. Due to the presence of intergranular carbides, the annealed specimens in the α single-phase region still retain high plasticity during the tensile test after hydrogen charging, and the yield strength is significantly improved, which is attributed to the change of the strain field around the intergranular carbide by hydrogen. In the presence of hydrogen, the formation of crack holes of annealed specimens in the α single-phase zone and the formation of quasi-cleavage (QC) + cleavage fracture (C) morphology of annealed specimens in α+β dual-phase zone are the result of the synergistic effect of hydrogen enhanced localized plasticity (HELP) and hydrogen enhanced decohesion (HEDE) mechanisms. When the annealing temperature reaches 940 °C, transgranular secondary cracks were observed in the vicinity of the fracture of the annealed specimen, which mainly propagate towards {001}//ND-oriented ferrite grains, accompanied by the high strain zone of the crack boundary.

Effect of sintering temperature on microstructure and properties of MIM420 stainless steel

ABSTRACT This paper investigates the effect of different sintering temperatures on the microstructure and mechanical properties of 420 stainless steel prepared by metal injection molding (MIM). The results show that in the temperature range of 1300 to 1360, the internal structure of MIM420 stainless steel is mainly lath martensite and the fracture mode is quasi cleavage fracture. With the increase of sintering temperature, the relative density, strength and hardness of MIM420 stainless steel increase, and the carbon and oxygen content decreases, but the strength decreases when the sintering temperature exceeds 1340. When the sintering temperature reaches 1360, the sample will be slightly over sintered, so the appropriate sintering temperature is 1340. At 1340, the relative density, hardness, bending strength and ultimate tensile strength of the sample are 98.2 ± 0.4%, 54 ± 1HRC, 1229 ± 28 MPa and 1111 ± 26 MPa respectively.

Effect of carbon addition on microstructure and mechanical properties of as-cast nickel-based heavy density matrix alloy reinforced by high tungsten content

In present work, a novel carbon-doped interstitial strengthening nickel-based heavy density matrix alloy reinforced by high tungsten content (Ni-W-Co) was prepared by conventional casting technology using a laboratory vacuum induction melting (VIM) furnace. The effects of carbon addition on as-cast microstructure and phase constituents were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). And the tensile properties and microhardness were tested as well. Results demonstrated that the present heavy density alloy has a single-phase FCC structure and exhibits typical dendrite characteristics. The carbon content (0–0.021 wt%) presents little influence on as-cast microstructure and phase constituents, but significantly improves the mechanical properties. Both tensile strength and ductility of the matrix alloy were increased synchronously with the addition of interstitial carbon atoms on account of the interstitial strengthening. The tensile fracture morphology revealed the transition from complete ductile dominated features to a mixed fracture mode consisting of quasi cleavage and ductile fractures. Minor carbon addition can trigger an obvious increase for lattice parameters and thus contribute to the strength improvement, and the increase in lattice friction stress enhanced the work-hardening rate and postponed the necking of C-addition alloy compared with C-free alloy.

Effect of fatigue damage on the hydrogen embrittlement sensitivity of X80 steel welded joints

The effects of fatigue damage on the hydrogen embrittlement (HE) sensitivity of X80 steel welded joints, obtained using flux-cored arc welding method, were investigated in the study. Results show that both the yield and tensile strength increased for all the hydrogen-charged welded joints and decreased with the accumulation of fatigue damage. The fracture surface is the mixture of local quasi-cleavage (QC) surrounded by shallow dimples ductile fracture for hydrogen-charged welded joints, whilst that of hydrogen-free welded joint is typical dimple ductile fracture. The presence of fisheye morphology might be related to the hydrogen, local strain accumulation in the vicinity of inclusions and dislocations evolution caused by the cyclic load. The mechanism is the synergistic action of hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP). However, the pinning effect of hydrogen on the dislocation motion is the dominant role.

In-Situ Hollow Sample Setup Design for Mechanical Characterisation of Gaseous Hydrogen Embrittlement of Pipeline Steels and Welds

This work discusses the design and demonstration of an in-situ test setup for testing pipeline steels in a high pressure gaseous hydrogen (H2) environment. A miniature hollow pipe-like tensile specimen was designed that acts as the gas containment volume during the test. Specific areas of the specimen can be forced to fracture by selective notching, as performed on the weldment. The volume of H2 used was minimised so the test can be performed safely without the need of specialised equipment. The setup is shown to be capable of characterising Hydrogen Embrittlement (HE) in steels through testing an X60 pipeline steel and its weldment. The percentage elongation (%El) of the base metal was found to be reduced by 40% when tested in 100 barg H2. Reduction of cross-sectional area (%RA) was found to decrease by 28% and 11% in the base metal and weld metal, respectively, when tested in 100 barg H2. Benchmark test were performed at 100 barg N2 pressure. SEM fractography further indicated a shift from normal ductile fracture mechanisms to a brittle transgranular (TG) quasi-cleavage (QC) type fracture that is characteristic of HE.

The fundamental difference between cleavage and hydrogen-assisted quasi-cleavage in ferritic materials revealed by multiscale quantitative fractographic and side surface characterization

The fracture surfaces and cracks in technically pure iron, Fe-2.5% Si alloy and low-carbon steel grade S235JR produced by quasi-cleavage (QC) hydrogen-assisted cracking (HAC) as well as by true cleavage (TC) were studied and compared on different scales through the quantitative and qualitative fractographic and side surface examinations. The mixed type QC/TC fracture surfaces were obtained using two-step mechanical testing methods involving the tension of the through-notched specimens under in-situ hydrogen charging followed by rapid fracture in liquid nitrogen. The side surface and fractographic examinations, including the quantitative facets analysis, were conducted using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and electron-backscattering diffraction (EBSD) technique. It is established, that the QC and TC fracture surfaces demonstrate fundamentally different morphological and topological features in all materials investigated. It is found that, depending on the material, the average angle of misorientation (AM) between the QC facets is 1.5–2 times lower than that of the TC facets. Thus, it is concluded that the crystallographic orientation of QC facets is generally different from TC. Owing to this feature, the path of the QC HAC through the microstructure of all investigated materials is featured by the remarkably lower spatial out-of-plane deviation on the scale equal to or larger than a few facets. Conversely, on the scale of an individual facet, the path of QC HAC deviates to a greater extent than that of the TC crack. This fundamental difference between QC HAC and TC cracking is found to be not significantly influenced by the chemical composition of the ferritic alloys.