Reduction In Fracture Toughness Research Articles

Hydride orientation near pressure tube-end fitting rolled joints

The connection between Zr–2.5%Nb pressure tubes and modified martensitic stainless steel-403 end fittings in Pressurized Heavy Water Reactors (PHWRs) at the rolled joint is a critical site marked by enhanced hydrogen diffusion and elevated tensile residual stresses. The application of circumferential stress above a threshold leads to the formation of radial hydrides. Formation of radial hydride leads to a drastic reduction in fracture toughness and increase in Delayed Hydride Cracking (DHC) velocity. A comprehensive understanding of residual stress, hydride orientation and radial hydride fraction in this region is essential for the assessment of pressure tube structural integrity. In this study, we employ 3D nonlinear finite element analysis to estimate the residual stresses near rolled joints for both 220 MWe and 700 MWe pressure tubes. Additionally, we pioneer an experimental investigation into hydride orientation near roll joints through internal pressurization of hydrided pressure tube and end fitting assemblies. The study delves into the influence of residual stresses due to rolling process on hydride orientation and radial hydride fraction, providing crucial insights for the evaluation of the structural integrity of pressure tubes.

Fracture toughness of AlSi10Mg alloy produced by LPBF: effects of orientation and heat treatment

AbstractIn this study, AlSi10Mg samples were manufactured by laser-powder bed fusion process to explore the fracture toughness dependence on both built orientation and aging treatment. The experiments were performed on as-built and directly-aged (200$$^{\circ }$$ ∘ C/4 h) conditions, with the latter revealed to be a valuable treatment for improving fracture toughness. A comprehensive investigation involving detailed microstructural analysis, grain-orientation mapping, and crack-tip strain measurements was conducted to investigate the mechanisms governing the material behavior. The results revealed that specimens subjected to direct aging display higher toughness, thereby enhancing the fracture resistance of AlSi10Mg. Moreover, a considerable variation in fracture toughness values was observed for the different printing orientations, indicating the existence of manufacturing-induced anisotropy. The findings highlight that this anisotropy mainly correlates with the distinctive microstructure induced by the additive manufacturing process. In particular, this study focuses on the different preferential crack paths dictated by the melt pool boundaries orientation respective the crack propagation direction. A substantial reduction in fracture toughness was observed when the crack propagates along the melt pool boundaries.

Effect of high-temperature thermal fatigue on mode I fracture toughness of gabbro

Investigating variations of rock fracture toughness after high-temperature thermal fatigue is greatly significant for developing deep geothermal resources. This study investigated the mode I fracture toughness of gabbro after high-temperature fatigue treatment by heating a cracked straight-through Brazilian disc (CSTBD) gabbro specimen to 200, 400, 500, and 600 °C, followed by 100 thermal cycles. Additionally, acoustic emission (AE) and digital image correlation (DIC) were used to monitor the failure process of gabbro. The results showed that the peak load, fracture toughness, and fracture energy of gabbro decreased with the increased temperature and number of cycles, which was most significant at 500 and 600 °C. Under mode I loading, cracks developed along the loading direction and connected with the prefabricated crack. Additionally, the regions with higher von Mises equivalent strain (Evm) values were concentrated at the loading points and prefabricated crack of the rock sample. The degree of bending of the primary cracks increased, the number of secondary cracks increased, and the Evm values changed significantly as the temperature increased. The phase transformation of plagioclase feldspar at 450 °C and the oxidation of iron- and magnesium-containing pyroxene at 600 °C changed the internal structure of the rock. Cyclic treatment further exacerbated the thermal damage, developing microcracks within the rock and reducing fracture toughness significantly.

Water weakening and the compressive brittle strength of carbonates: Influence of fracture toughness and static friction

Water is ubiquitous within the pore space of rocks and has been shown to affect their physical and mechanical behaviour. Indeed, water can act on the rock strength via mechanical (i.e., reducing the effective stresses) or chemical effects (e.g., mineral dissolution, mineral alteration, subcritical crack growth, etc.). As rock macroscopic strength is controlled by both fracture toughness and friction at the grain-scale, these parameters should also be affected in presence of water. While some recent studies have measured the effect of water on both fracture toughness and frictional parameters to constrain the water weakening of porous rock compressive strength, the physical parameters, or rock characteristics, that influence this weakening are as of yet unclear. Here, we report a series of laboratory experiments in order to determine the influence of a water-saturated, as opposed to dry, environment on five limestones’ strengths. The uniaxial compressive strength, the mode-I fracture toughness and the static friction parameters are of interest. The experiments show that, for the tested limestones, water-saturated conditions provoke a reduction of the uniaxial compressive strength by up to 53 %. This reduction is accompanied by a reduction of the mode-I fracture toughness by up to 34 % and of the static friction by up to 16 %. Even though the water weakening of the uniaxial compressive strength is not influenced by the sample porosity, the mode-I fracture toughness reduction in the presence of water is accentuated for high-porosity limestones. Additionally, low porosity limestones appear to promote higher static friction reductions in water-saturated environments.

The effect of hydrogen and notch orientation in SENT specimens on the fracture toughness of an API 5L X70 pipeline steel

Transporting hydrogen gas through pipelines is an important topic within the context of energy transition. An essential challenge hereto is the phenomenon of hydrogen embrittlement of pipeline steels which includes a reduction in fracture toughness. As the theories accounting for hydrogen embrittlement are still debated, improving fundamental insights into the underlying mechanisms is crucial. Fracture toughness tests on single edge notched tension (SENT) specimens have been performed to examine the influence of hydrogen on the fracture behavior of a pipeline steel. An API 5L X70 steel was selected for this purpose, characterized by a distinctive banded microstructure commonly seen in pipeline steels. The test specimens were extracted from the steel pipe, and a notch in two different orientations was machined. By using a combination of fractography and X-ray micro-CT (Computed Tomography), the fracture mechanisms are revealed. The tearing resistance characteristics of the steel, with and without the presence of hydrogen, are demonstrated through tearing resistance curves. The experiments show that the banded microstructure plays a key role in the results through the development of splits at the microstructural bands. While these splits are also present in uncharged toughness test specimens, they are increasingly present in hydrogen charged specimens suggesting a hydrogen related weakening of the banded microstructure. In addition, it is demonstrated that hydrogen induces an increasingly zigzagged crack path. This is attributed to a potential combination of accelerated void nucleation at the microstructural bands, and accelerated shear-driven fracture.

Experimental study on mode I fracture characteristics of heated granite subjected to water and liquid nitrogen cooling treatments

Liquid nitrogen (LN2) cryogenic fracturing, as a kind of waterless fracturing, is being considered for its potential to enhance the permeability of hot dry rock (HDR) reservoirs. The model I fracture behavior of HDR plays a pivotal role in the HDR fracturing. Therefore, this study focuses on the fracture behavior of the heated granite subjected to water cooling (WC) and liquid nitrogen cooling (LNC) under mode I load. The micro-cracking mechanism of the high-temperature granite under the rapid cooling treatment is analyzed based on the thermo-mechanical coupling grain-based model (GBM). The results indicate that the change in the fracture toughness with the granite temperature has obvious segmental characteristics and the temperature of 200 ℃ is a critical point. Before the critical temperature, the trend of fracture toughness is indistinct with the granite temperature for both cooling methods. However, beyond the critical temperature, the fracture toughness obviously decreases with the increase in the granite temperature, and the LNC is more effective at reducing fracture toughness compared to the WC. With increasing the granite temperature, shear cracks occur earlier during the three-point bending test. A higher proportion of tensile fractures after the LNC treatment is induced by mode I load than after the WC treatment, especially at high granite temperatures. Compared to the WC, the LNC can generate a greater number of microcracks inside the granite, which further results in smaller fracture damage of the LNC-treated granite during mode I load. Ultimately, this leads to improved stimulation performance in terms of reduced fracture resistance and decreased fracture energy requirements for the high-temperature granite cooled by LN2. The results can enhance the understanding of distinctions between LN2 cryogenic fracturing and hydraulic fracturing in geothermal exploitation.

Effect of external magnetic field on electric current-induced fracture of notched thin metallic conductors: Part 2- High magnetic fields

In the companion report (Telpande et al., n.d.), we discussed the impact of a weak external magnetic field (up to 0.4 T) on the electric current-induced fracture of pre-notched thin metallic conductors, revealing a linear decrease in critical current density, jc, necessary for crack propagation. This study extends the investigation to explore the effects of stronger external magnetic fields (0.6–1 T) on the fracture of pre-notched, current-carrying metallic foils. The experimental analysis reveals a substantial, albeit linear, drop (up to 40 %) in jc under stronger magnetic fields. Interestingly, calculations of the dynamic stress intensity factor, KIE,t, which assesses the interplay between applied current density and external magnetic field, indicate crack growth under a strong magnetic field even when KIE,t is below the plane stress critical stress intensity factor, KIC. A remarkable phenomenon emerges: the application of electric current pulses combined with strong external magnetic fields induces observable surface undulations near the notch tip. A comprehensive 3D finite element model, integrating linear and nonlinear buckling analyses under multiphysics stimuli, attributes these undulations to localized buckling near the notch tip. This buckling-induced stress redistribution near the crack tip contributes to an overall reduction in fracture toughness due to mode mixity, leading to the fracture of the Al foil below KIC. This investigation, along with the companion report (Telpande et al., n.d.), significantly advances our understanding of the effects of magnetic fields on the fracture of current-carrying conductors.

Sex-specific effects of Fat-1 transgene on bone material properties, size, and shape in mice.

Western diets are becoming increasingly common around the world. Western diets have high omega 6 (ω-6) and omega 3 (ω-3) fatty acids and are linked to bone loss in humans and animals. Dietary fats are not created equal; therefore, it is vital to understand the effects of specific dietary fats on bone. We aimed to determine how altering the endogenous ratios of ω-6:ω-3 fatty acids impacts bone accrual, strength, and fracture toughness. To accomplish this, we used the Fat-1 transgenic mice, which carry a gene responsible for encoding a ω-3 fatty acid desaturase that converts ω-6 to ω-3 fatty acids. Male and female Fat-1 positive mice (Fat-1) and Fat-1 negative littermates (WT) were given either a high-fat diet (HFD) or low-fat diet (LFD) at 4wk of age for 16wk. The Fat-1 transgene reduced fracture toughness in males. Additionally, male BMD, measured from DXA, decreased over the diet duration for HFD mice. In males, neither HFD feeding nor the presence of the Fat-1 transgene impacted cortical geometry, trabecular architecture, or whole-bone flexural properties, as detected by main group effects. In females, Fat-1-LFD mice experienced increases in BMD compared to WT-LFD mice; however, cortical area, distal femur trabecular thickness, and cortical stiffness were reduced in Fat-1 mice compared to pooled WT controls. However, reductions in stiffness were caused by a decrease in bone size and were not driven by changes in material properties. Together, these results demonstrate that the endogenous ω-6:ω-3 fatty acid ratio influences bone material properties in a sex-dependent manner. In addition, Fat-1 mediated fatty acid conversion was not able to mitigate the adverse effects of HFD on bone strength and accrual.

Fracture behavior of high-temperature granite subjected to liquid nitrogen cooling: Semi-circular bending test and crack evolution analysis

Liquid nitrogen fracturing is an effective technique for stimulating reservoirs in hot dry rock exploitation. The application of low-temperature liquid nitrogen to high-temperature granite generates thermal stress, thereby altering its mechanical properties and fracture behavior. This study focused on type I fracture characteristics by conducting semi-circular bending tests on high-temperature granite treated with liquid nitrogen. The fracture behavior was analyzed using acoustic emission (AE) and digital image correlation methods. The fractured surface morphology was examined using laser scanning, and fractal theory and tortuosity analysis were employed to assess the fracture surface roughness. Scanning electron microscopy (SEM) provided insight into the impact of liquid nitrogen cooling on fracture characteristics. The findings indicated that treated granite specimens below 150℃ exhibited an increased peak load, fracture toughness, and fracture energy compared to untreated specimens. SEM images revealed isolated microcracks in specimens at 25℃ and 150℃, which effectively passivated pre-existing notches and increased fracture toughness. For granites above 200℃ following liquid nitrogen treatment, P-wave velocity, peak load, fracture toughness, and fracture energy decreased significantly as temperature increased. AE signals were observed earlier for granites at higher temperatures. The length of the fracture process zone increased with temperature, and the crack tip opening displacement exhibited a step-like increase at 600℃ under loading. The fractal dimension of the fracture surface varied with temperature, whereas the tortuosity exhibited a substantial increase with increasing temperature. As the temperature difference increased, an increasing number of microcracks appeared, forming interconnected networks that compromised the rock integrity, ultimately leading to reduced fracture toughness and the development of a rougher failure surface.

Circular economy-driven additive manufacturing: A model for recycling PLA/copper composites through multi-extrusion processing

ISO 52,900 material extrusion (MEX) 3D printing utilises materials to manufacture customisable components. End of life parts lead to accumulation of nondegradable plastic wastes with detrimental environmental impacts. Circular methods to close the loop will reduce the wastes that would end up in landfill. Recycling polylactic acid (PLA) has been reported to negatively impact the mechanical properties compared to the virgin material. We investigate the addition of copper microparticles, found in old electronic parts, to recycled PLA and its effects on the mechanical properties. We pelletise the extruded filament and use it as the feedstock for another further extrusion to simulate the recycling process. The first extrusion showed a good copper dispersion in the PLA matrix, the novelty of the second pass was to create a model to evaluate mechanical performance. Commercially available 60wt% copper filament was used as a benchmark. Tensile strength and modulus of extruded filament were found to be 48.8 MPa and 2.3 GPa for sample with quarter copper loading, respectively. All extruded filaments outperformed commercial filament in fracture toughness, with values of 1.06 MPa√m for quarter copper loading and 1.1 Mpa√m for half copper loading, with re-extrusion reducing fracture toughness by 34% and 9%, respectively.

Effect of ECAP on fracture toughness and fatigue endurance of DED-processed Ti-6Al-4V investigated on miniaturized specimens

Additive manufacturing (AM) has revolutionised the production of complex components with custom mechanical properties. However, as-deposited AM-ed materials often exhibit inferior mechanical behaviour compared to conventionally manufactured counterparts because of defects generated during the deposition. In this study, the effects of equal channel angular pressing (ECAP) on fracture toughness and fatigue endurance of Ti-6Al-4V titanium alloy manufactured by direct energy deposition (DED) are investigated. The aim of this study is to compare the mechanical performance of the material in the as-deposited and ECAP-ed states, exploiting the potential benefits of ECAP in improving the properties of additively manufactured components. ECAP processing is used to induce severe plastic deformation (SPD) and create a unique microstructure in Ti-6Al-4V specimens. As-deposited and ECAP-ed specimens were evaluated using stress intensity factor (SIF) analysis, fatigue crack growth, and high cycle fatigue tests using miniaturized specimens. Fractographic analysis was performed using scanning electron microscopy (SEM) to examine the fracture surfaces and identify the underlying failure mechanisms. The results revealed that while ECAP led to a slight increase in porosity, it significantly reduced fracture toughness and had a negligible effect on the rate of propagation of fatigue cracks. In addition, the ECAP-ed specimens showed reduced fatigue endurance of the material.

Influence of nanofiller agglomeration on fracture properties of polymer nanocomposite: Insights from atomistic simulation

Nanofillers tend to agglomerate inside the matrix of a polymer nanocomposite (PNC). Crack propagation mechanism gets modified in various ways near these agglomerated regions, which adversely affects the performance of nanocomposite. While such observations are reported in the literature, a detailed atomistic-scale study quantifying and analyzing these changes in fracture properties has not been reported. Reactive molecular dynamics simulations are conducted in this work to study the effects of agglomeration on fracture properties. The model material here is polymethyl methacrylate (PMMA) with carbon nanotube (CNT) reinforcement. Generally functionalization improves the resistance of PNC to crack propagation due to enhanced interfacial bonding. However, for agglomerated CNTs even functionalization does not improve the fracture toughness, since the crack propagates completely through the polymer matrix. Thus the CNTs do not participate in resisting the crack. Furthermore, the shear strain distribution along the CNT surface revealed that the CNTs and the polymer surrounding them act as a monolithic unit, resulting in reduction in fracture toughness and ductility. The agglomerated CNTs are also found to contribute towards strain accumulation and failure of PNC at a lower global strain level. These atomic-scale insights help in better understanding of damage mechanics of a PNC.

Observed reduction in fracture toughness of AlN and AlN–Mo ceramic matrix composites with carbon additive

The fracture toughness of AlN ceramic matrix composites containing carbon (0.5 vol%), yttria (5.0 vol%), and Mo (0.0–4.0 vol%) was evaluated using Vickers indentation. The results of these measurements were compared to a carbon-free, commercial AlN (ST-200 ALN) as well as to AlN and AlN–Mo compositions from the literature. The presence of added carbon was found to correlate with a 21% reduction in fracture toughness of the 0.0 vol% Mo carbon-containing sample, compared to commercial ST-200 AlN, in both the A-orientation (indentation parallel to the pressing direction) and the B-orientation (indentation perpendicular to the pressing direction). Mo additions at small loading fractions (~ 0.25 vol%) were found to exhibit greater-than-expected increases in fracture toughness in the A-orientation, when compared to literature data on AlN–Mo composites. This increase in fracture toughness correlates to the removal of elemental carbon in the AlN matrix through reaction with the Mo additive, forming Mo2C, localized at the Mo particle sites. Further increasing Mo loading was observed to result in generally increasing fracture toughness values, as would be expected from literature data.Graphical abstract

The influence of water on the failure characteristics of sandstone under uniaxial compression conditions by acoustic emission and NMR observation

Revealing the failure characteristics and damage process of rocks soaked in water is particularly critical for preventing and controlling geological disasters. To this end, we employed nuclear magnetic resonance (NMR) and an ultrasonic system to capture the variation in the T2 spectrum, different pore waters and P-wave velocity during soaking (from 0 to 120 h). Furthermore, an acoustic emission (AE)-uniaxial compression test was carried out to analyse the AE characteristics (e.g., hits, absolute energy, and events), and strength of sandstone under different soaking times. The AF (the ratio of AE counts to duration)-RA (the ratio of the AE rise time to amplitude) is used to distinguish the tensile failure shear failure of sandstone during soaking. The results showed that the increase in soaking time decreased the bound water percentage and strength while increasing the P-wave velocity and capillary water percentage. An interesting phenomenon was that the failure mode was transformed due to soaking based on the evolution of the AE response. From the above results and classical water-weakening mechanisms, we suggest that the weakening process after loading can be divided into three stages. In the initially soaking, the reduction in fracture toughness and frictional more serious caused the increase in the occurrence of tensile failure. The quartz hydrolysis and chemical deterioration may aggravate the shear failure and intergranular fracture during long-term soaking. This study clarifies the transformation of weakening mechanisms during soaking and is of great significance for understanding the microscopic damage processes in rock failure.

The interrelation of crack propagation behaviors and lamellar structure in a new near α titanium alloy at low temperature

In this work, crack propagation behaviors and fracture mechanism of CT20 alloy with lamellar α at the temperatures ranging from 20 to − 90 °C were investigated and revealed. The results showed the fracture toughness of CT20 alloy was decreased from 430.89 KJ/m2 to 171.67 KJ/m2, and the fracture mechanism was gradually changed from typical ductile fracture to quasi-cleavage fracture with the decreasing testing temperature. The reduction of fracture toughness was mainly influenced by the internal factor (the crack tip plastic zone) and external factor (the tortuosity of the crack propagation path), in which the contribution of the internal factor increased from 87.06% to 95.68% as the temperature decreased. Therefore, the high contribution of the internal factor means the plastic zone at the crack tip could mainly affect the crack propagation behaviors. The lamellar α was found to be deformed by the plastic zone, and then inhibited the crack propagation and deflected its propagation direction at 20 °C, which consumed the additional deformation energy and increased the fracture toughness. With the decline of the plastic zone from 0.526 mm to 0.107 mm, the lamellar α deformation and the crack propagation resistance were significantly reduced at − 90 °C, which accelerated crack propagation and decreased the fracture toughness.

Mode I fracture mechanisms and crack evolution behavior of three-dimensional braided composites

Three-dimensional braided composites possess higher inter-laminar fracture toughness than two-dimensional laminates, while the mode I fracture toughness behavior of three-dimensional braided composites is still unknown. Here we report mode I fracture behavior of three-dimensional braided carbon fiber/epoxy composites tested with the double-cantilever beam method. The samples with a pre-crack were tested using the MTS device, and the fracture process was recorded to calculate the fracture toughness. The effects of different loading rates on fracture behavior were compared. The strain field at the crack tip was obtained by the digital image correlation technique. The damage morphologies were scanned by X-ray microcomputer tomography. It was found that the bridging effect of braiding yarns prevents cracks from initiation and propagation, while the intertwining points of the braiding structure cause crack bifurcation. The braided architecture provides an effective way to hinder crack propagation. The stiffness of composites tends to decrease as the loading rate rises. The higher loading rate results in a lower critical load level for crack propagation and reduces fracture toughness. The results show that the three-dimensional braided structure is an effective method for increasing the fracture toughness. We hope the results can be used for the design of higher fracture toughness composite structures.

Effect of Normalizing on Semi Float Axle Shaft Performance - Case Study

The primary function of axle shaft in semi float rear axle is to transmit the power to wheels. These shafts would experience the torsional load along with bending load as well. Hence shaft metallurgical structure at case & core would become very important. The objective of this study is to understand the importance of normalizing heat treatment process carried out at post forging treatment. Bench test Performance study conducted by comparing the normalized shaft Vs nonnormalized shaft. Ultimate torsion test, torsional impact test & shaft side impact test conducted on both the shafts. The ultimate torsion test result shows JAEL of normalized shaft is 5106Nm & non normalized shaft is 4718Nm. The drop is 7.6%. The torsional impact test shows peak torque of normalizing shaft is 9384Nm & non normalizing shaft is 8386Nm. The drop is 10.6%. The side impact test shows impact energy of normalized shaft is 2903 Jouls & non normalized shaft is 2321Joule. The drop is 20%. The fractography shows ductile fracture in normalized shafts & nonnormalized shaft shows brittle. This is evident by complete fracture (breakage) in non- normalized shaft & bend in (not broken) normalized shaft. Micro structural comparison shows the grain size in normalized shaft is finer but non- normalized shafts are coarser. During the impact test, the fracture occurs by sudden heavy load applied on part surface, causes the tremendous shock load in the shaft. As a result microcracks generates at multiple points & propagates through the grain boundary. This phenomenon reduces fracture toughness characteristics & hastens the dislocation movements. Normalized shaft having finer grain size, shows sufficient ductility before final fracture but non normalized shaft do shows brittle nature due to coarser grain size. Relatively non normalized shaft shows lesser ability to absorb impact energy, JAEL torque & peak torque. The coarser grain size is easing the fracture in non- normalized shaft.

Translucent and Highly Toughened Zirconia Suitable for Dental Restorations

Background: There is a limit to improving the characteristics of zirconia with only one kind of stabilizing element such as yttrium. The purpose of this study is to systematically evaluate the effects of various co-doped elements on mechanical and optical properties and to develop a novel composition of zirconia with enough properties to apply to dental restorations. Methods: Forty-four kinds of zirconia were prepared by combining trivalent cations yttrium (Y) and ytterbium (Yb), and pentavalent cations niobium (Nb) and tantalum (Ta) oxide as stabilizers. The combined contents ranged from 0 to 5.6 mol% for Y2O3, 0 to 4.2 mol% for Yb2O3, 0 to 1.5 mol% for Nb2O5, and 0 and 1.2 mol% for Ta2O5. These specimens were determined for fracture toughness and opacity. X-ray diffraction studies were undertaken to evaluate the microstructural change. Results: The present study revealed that adding of the trivalent cations Y and Yb reduced fracture toughness and opacity, whereas the addition of pentavalent cations Nb and Ta to zirconia stabilized with trivalent cations increased both properties. There was no clear difference in the effects of Y and Yb, Nb, and Ta. Conclusions: Considering many factors, the following composition is optimal: 3–4.2 mol% Y2O3 and/or Yb2O3 stabilized zirconia with up to 1.5 mol% Nb2O5 has sufficiently high fracture toughness values and sufficiently high translucency suitable for dental restorations.

Models of Toughening of Ceramic/Graphene Composites: a Brief Review

We briefly review the analytical models that describe toughening and fracture toughness reduction in ceramic/graphene composites. We consider such mechanisms of toughening as crack deflection and crack bridging. We examine the effect of pores and fracture along ceramic/graphene interfaces on the fracture toughness reduction at a high graphene volume fraction. The effect of grain boundary sliding on the fracture toughness of ceramic/graphene composites is also considered.

The role of hydrogen in the corrosion-induced reduction of KR critical fracture toughness and intergranular secondary cracking in a high-strength aluminium alloy

It is shown that short-term exposure of AA2024-T3 material to an exfoliation corrosion (EXCO) solution leads to a reduction of non-plane strain fracture toughness and the formation of secondary surface cracks during plastic straining. The study aims to establish whether the secondary cracking effect and the fracture toughness reduction are due to corrosion-induced hydrogen embrittlement. It is hypothesized that, if hydrogen-embrittlement is the cause of the intergranular secondary cracking (ISC) and fracture toughness degradation, post-exposure heat treatment would restore the mechanical property degradation and reduce the ISC formation through the desorption of diffusible hydrogen. It was found that the solution and ageing heat treatments restored the fracture toughness of the alloy. However, the ISC behaviour persisted. The results are discussed and interpreted in terms of hydrogen embrittlement theory.