Brittle Intergranular Fracture Research Articles

Влияние механизма дисперсионного твердения на закономерности пластической деформации и разрушения ванадийсодержащей высокоазотистой аустенитной стали

Nitrogen alloying of austenitic steels increases their corrosion resistance and improves mechanical properties. During heat treatment, high-nitrogen austenitic steels tend to the precipitation hardening and the increase of strength characteristics. In the current paper, the authors studied the effect of the duration of age-hardening at the temperatures of 700 °С and 800 °С on the structure, phase composition, plastic flow behavior, and fracture mechanisms of V-alloyed high nitrogen chrome-manganese austenitic Fe-19Cr-22Mn-1.5V-0.3C-0.86N (mass %) steel. The study revealed that after water-quenching at 1200 °С, the specimens possess the high strength properties, ductility and contain large (300-500 nm) (V,Cr)(N,C) particles. Aging at temperatures of 700 °С and 800 °С facilitates complex reactions of austenite discontinuous decomposition with the Cr 2 N-plate formation in grains and continuous decomposition with the formation of vanadium nitride-based particles in austenite. During the long-term aging (50 h at 700 °C and 10 h at 800 °C), the intermetallic σ-phase appears in specimens. At age-hardening, the observed phase transformations cause the changes in macro- and micro-mechanism of fracture in the specimens of steel under the study. In the initial state, the specimens show mainly the ductile transgranular fracture. After age-hardening, the fracture mechanism changes into the mixed mechanism with the elements of brittle intergranular and ductile transgranular fractures. When increasing the duration of aging and implementation of complex reactions of decomposition of solid solution, the specimens are fractured by the quasi-cleavage mechanism. The specimens aged at temperatures of 700 °С and 800 °С have quite similar precipitation hardening mechanisms, though the increase in aging temperature leads to the rising of the decomposition rate of solid solution. The sequence of transformations described above and the corresponding sequence of changes in the mechanisms of steel fracture are implemented faster when increasing the aging temperature.

Влияние наводороживания на механические свойства и механизмы разрушения высокоазотистых хромомарганцевых сталей, подвергнутых дисперсионному твердению

Currently, many technical problems require a comprehensive study of the properties of materials operating in hydrogen-containing environments. The authors investigated the effect of age-hardening on the hydrogen embrittlement and fracture micromechanisms of high-nitrogen austenitic Fe-23Cr-17Mn-0.1C-0.6N (wt. %) steel. For this purpose, using heat treatments, the authors formed in specimens of Fe-23Cr-17Mn-0.1C-0.6N steel the structural phase states characterized by different distribution and content of dispersed phases. The experiment determined that the accumulation of hydrogen atoms occurs predominantly in the grains in solution-treated specimens without dispersed phases. This causes the effects of solid solution hardening and leads to a change in the micromechanism of steel fracture from a ductile dimple fracture in the absence of hydrogen to a transgranular fracture by the quasi-cleavage mechanism in hydrogen-charged specimens. It was established that the discontinuous decomposition of austenite with the formation of Cr 2 N cells and austenite depleted in nitrogen, predominantly along the grain boundaries causes the formation of a large fraction of interphase (austenite/Cr 2 N particles) boundaries. Cells of discontinuous decomposition promote hydrogen accumulation along the grain boundaries and cause brittle intergranular fracture of hydrogen-charged specimens during plastic deformation. The study showed that in specimens with the discontinuous decomposition of austenite both along the grain boundaries and spreading into the grain body, plenty of intragranular interphase boundaries (Cr 2 N plates in austenite) are formed, which causes the formation of a transgranular brittle fracture in the hydrogen-charged specimens.

Effects of Mo segregation on Charpy absorbed energy in Ti-12Mo alloys

Beta phase stabilizing elements such as Mo have strong tendency to segregate. We have introduced swirly type segregation of Mo in Ti-12Mo (mass %) alloy through groove bar rolling. After solution treatment and low temperature aging, hard omega phase was precipitated heterogeneously, which improved the room temperature tensile elongation values without sacrificing tensile strength. In this study, the effect of Mo segregation and heterogeneous distribution of omega phase on Charpy absorbed energy was investigated in Ti-12Mo alloy. Samples with two types of segregation were prepared; namely, swirly segregation in bar rolled sample and layered segregation in plate rolled sample. For comparison, we have also prepared Ti-12Mo bar samples with lesser Mo segregation, through high temperature thermomechanical treatment. Charpy impact tests were carried out at room temperature, 373 K and 473 K, respectively, using the samples after aging to introduce isothermal omega-phase. The samples with the segregation exhibited higher Charpy absorbed energy, especially at higher temperature of 473 K, while the sample with the swirly segregation showed higher Charpy absorbed energy than that with the layered segregation. The sample with lesser Mo segregation exhibited brittle intergranular fracture surface after Charpy testing. On the contrary, samples with Mo segregation exhibited ductile transgranular fracture surfaces.

Analyzing failure of casing head slip hanger

The reasons for failure of a casing head slip hanger were analyzed by applying the techniques of optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. Results show that the composition and tensile mechanical properties of the slip are all in accordance with the corresponding parameter requirements of standard GB/T 22513-2013. Furthermore, the structure of slip material has not been completely transformed into sorbite with good comprehensive properties, and a significant amount of ferrite still exists in it. The impact toughness results show the characteristics of low-temperature brittleness. Microscopic analysis shows that the corrosion products mainly come from circulating mud during drilling and that the action of stress corrosion generated the initial crack. The fracture characteristics develop from transgranular ductile fractures to local intergranular brittle fracture characteristics. The crack continues to expand along the root of the screw teeth with the stress concentration under the axial load and circumferential Mises stress until brittle breaks occur. To prevent failure from taking place, it is recommended to control the heat treatment process of the slip material to optimize the microstructure and enhance the toughness of the material, to install the slip hanger correctly, and to make sure the slip and casing are tightly held in place.

Grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic Fe41Mn25Ni24Co8Cr2 high entropy alloy

The effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic Fe41Mn25Ni24Co8Cr2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing: ultrafine (sub)grain size (≤0.5 μm), 8.1 μm and 590.2 μm. In the temperature between 298 and 773 K, the material with the large grain size of 590.2 μm exhibited the largest tensile ductility (57 %–82 %) due to its high strain hardening associated with mechanical twinning, but it exhibited the lowest strength due to its large grain size. The material with the ultrafine (sub)grain size exhibited the lowest tensile ductility (3 %–7 %) due to a greatly reduced strain hardening ability after severe plastic deformation, but it exhibited the highest strength due to the dislocation strengthening and grain refinement strengthening. At tensile testing at temperatures above 973 K, recrystallization occurred in the material with the ultrafine (sub)grains during the sample heating and holding stage, leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5 μm. The deformation behavior of the Fe41Mn25Ni24Co8Cr2 with different grain sizes in the high temperature range between 973 and 1173 K, where pseudosteady-state flow was attained in the stress-strain curves, could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic flow. The activation energies for plastic flow for the materials with different grain sizes were similar as ∼199 kJ/mol. In predicting the deformation mechanism, it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation mechanism. The sample with the ultrafine (sub)grains exhibited the large tensile elongations of 30 %–85 % due to its high strain rate sensitivity, m (0.1-0.5) at temperatures of 973–1173 K. The material with the large grain size of 590.2 μm exhibited the very small elongations of 0.2 %–8 % due to its small m values (0.1-0.2) and occurrence of brittle intergranular fracture at the early stage of plastic deformation.

Experimental creep behavior and life prediction through observation and numerical analysis for AISI 310

The present study conducted for the first time a life prediction based on numerical analysis of creep deformation and fracture behavior results of special notched specimens of AISI 310 steel. For this purpose, flat creep specimens with double edge notch were tested under stress is of 225, 160 and 100 MPa at temperatures of 700, 675 and 650 °C. Then it was analyzed the creep behavior of the material through observational and numerical analysis. Furthermore, the Q* parameter was used to establish a novel life predication equation for 310 steel. The creep curves were characteristic of the experiment, with a strong influence of the stress in the creep stage II. Using the Q* parameter, a good agreement was observed between the experimental and the calculated data. The characteristic of fracture surfaces was dependent on both stress and temperature with a transition from ductile fracture, with formation of dimples, to brittle intergranular fractures, evidenced by cavities in the grain boundaries. Coalescence and growth of microcracks on the specimen surface were also observed in a region at 45° from the notch tip, characteristic of the damage propagation caused by the creep test.

In-situ observation of high-temperature failure behavior of pipeline steel and investigation on burn-through mechanism during in-service welding

The risk of burn-through is a major concern when conducting in-service welding repair for oil-gas pipelines. The governing mechanism of burn-through has not hitherto been studied systematically. Here we perform a comprehensive analysis of the dynamic process of burn-through and the high-temperature failure behaviors of pipeline steel. Firstly, the in-service welding experiments were conducted to analyze the characteristics of burn-through. Influenced by the welding stress and especially the internal medium pressure, radial deformation of the pipe wall happens under the molten pool, thereby causing tensile stress. The pipeline metal under the molten pool contains the fusion zone and coarse grain zone. In order to study the crack initiation and propagation mechanism of the coarse grain zone and the fusion zone, the in-situ high-temperature tensile tests and in-situ high-temperature metallographic tests were carried out, respectively. The results indicate that during in-service welding process, the crack initiation mechanism of different microzones is different. For the fusion zone, the grain boundary melting leads to intergranular brittle fracture. While for the coarse grain zone, the stress concentration caused by grain boundary sliding makes the cracks appear easily at grain boundaries and triple junctions. Therefore, burn-through has intergranular cracking morphology. Microcracks originate from the fusion zone and penetrate along the weakened grain boundaries in the direction that perpendicular to the tensile stress and merge to form macroscopic cracks. Once the cracks penetrate to the inner wall, burn-through happens. We expect that these results would be valuable for clarifying the mechanism of burn-through and enriching the welding theories under severe conditions.

Complex study of grain boundary segregation in long-term irradiated reactor pressure vessel steels

Grain boundary (GB) embrittlement of reactor pressure vessel steel occurs at the long-term operation through the radiation-enhanced segregation of impurities. All the known techniques of studying the GB segregation have their advantages and disadvantages, and complete information can be obtained only through a comprehensive analysis by different methods.In this paper the level of GB segregation in VVER-1000 RPV steels with high nickel content was assessed by combined methods of Auger electron spectroscopy (by the P monolayer coverage and atomic concentration of other elements); atom probe tomography (by the Gibbsian interfacial excess) and fractographic analysis (by the maximum fraction of brittle intergranular fracture).The results obtained by different methods are in good agreement and show that phosphorus GB segregation increases with the increase of fast neutron fluence, GB concentration of Ni and Mn, the bulk concentration of Ni and Mn, and correlates with the fraction of brittle intergranular fracture.

Synchrotron-based holotomography and X-ray fluorescence study on the stress corrosion cracking behavior of the peak-aged 7075 aluminum alloy

The demand to reduce weight in the automobile industry necessitates an enhanced understanding of the stress corrosion cracking (SCC) mechanism of 7xxx series aluminum wrought alloys. Thus, the SCC susceptibility of 7075 aluminum wrought alloy wires, with respect to the heat treatment condition, solution annealed, peak-aged and overaged, was investigated via slow strain rate testing in 3.5 wt % sodium chloride solution. The SCC crack, initiated in a notched tensile specimen of the peak-aged condition, was investigated in detail by means of synchrotron-based high resolution holotomography and X-ray fluorescence as well as STEM in order to understand the correlation of microstructural features and cracking behavior. The local crack initiation and macroscopic crack propagation was found to be dependent on the stress fields, which were simulated by the finite element method. In the peak-aged condition, the SCC crack propagated microscopically along the grain boundaries leading to a brittle intergranular fracture. The SCC mechanism in the peak-aged condition was related to a combination of hydrogen embrittlement and an anodic-dissolution-induced notch effect that was attributed to a continuous seam of grain boundary (GB) precipitates.

Effect of adding Ti and rare earth elements on properties of Cu-14Al-4Ni shape memory alloy

The effect of Ti and rare earth elements (RE: Ce + La) addition on properties of Cu-14Al-4Ni shape memory alloy (SMA) with austenitic structure at room temperature was studied by implementing different characterization methods. The experimental results proved that combined adding of Ti and RE has significantly decreased the grain size and improved mechanical properties of the alloy. Microstructural observations showed that addition of Ti and RE caused secondary phases formation in the austenitic microstructure of the alloy at room temperature. The fracture strain was improved from 2% for Cu-Al-Ni to 2.9 and 3.5% for Cu-Al-Ni-Ti and Cu-Al-Ni-Ti-RE, respectively. Furthermore, the fracture mode altered from complete brittle intergranular fracture to a mixture of intergranular fracture and transgranular cleavage fracture with some localized dimples around particles of the secondary phases. The martensitic transformation characteristics have been also modified by adding Ti and RE. Thus, these elements can be considered as an efficient tool for tuning functional properties of Cu-Al-Ni SMAs.

Effect of Zn addition on the microstructure and mechanical properties of Mg-0.5Ca-0.5RE magnesium alloy

The microstructure and mechanical properties of Mg–Zn-0.5Ca-0.5RE magnesium alloy, with zinc contents of 0, 2, 4, and 6 wt%, were studied. A significant effect of Ca and rare earth (RE) elements (via mischmetal addition) on the grain refinement of cast ingots was observed with the consequent enhancement of ultimate tensile strength (UTS). Moreover, while the grain size was refined by the addition of Zn, no significant α-Mg grain refinement occurred beyond 2 wt% Zn addition. The Mg12RE intermetallic compound was observed in all alloys while the Mg7Zn3 phase formed at the grain boundaries of Zn-containing alloys. Based on the competition of grain refinement as a favorable factor and formation of unfavorable grain boundary phases, the Mg–4Zn-0.5RE-0.5Ca (ZEX400) alloy showed the highest UTS among the cast alloys. Intense grain refinement introduced by the extrusion process and the fracturing and dispersion of the grain-boundary phases resulted in the significant enhancement of strength and ductility and the appearance of ductile fracture surface for the extruded Mg–4Zn-0.5RE-0.5Ca alloy. It was found that high Zn content (∼6 wt%) limits the usability and hot working temperature range of the alloys due to the problem of hot shortness and intergranular brittle fracture. Therefore, the addition of 4 wt% Zn was recommended for industrial practice. This work revealed the significant effects of alloying (with Ca, RE, and Zn) and hot extrusion process for microstructural refinement and enhancement of mechanical properties of Mg alloys.

Three-dimensional phase-field modeling of porosity dependent intergranular fracture in UO2

During reactor operation, the formation of bubbles at the grain boundaries can alter the fracture properties and subsequently the thermo-mechanical behavior of nuclear fuels. In this work, we discuss a phase-field fracture model, its implementation in MOOSE (Multiphysics Object-Oriented Simulation Environment), and its application to simulate porosity dependent brittle intergranular fracture. The presence of gas bubbles on grain boundaries has a non-negligible impact on crack initiation and propagation. Three-dimensional simulations are performed to investigate the influence of bubble geometry, porosity and loading conditions on the fracture strength. The correlation between fracture strength and porosity suggested by numerical simulations has a good agreement with experimental measurements.

Effect of scanning strategy on microstructure and mechanical properties of selective laser melted reduced activation ferritic/martensitic steel

Two types of scanning strategies were adopted to study the effect of scanning strategy, i.e., bidirectional scanning without (SS-X) and with 45° deviation from X/Y-axis and 90° rotation (SS-XY45) between adjacent layers, on microstructure and mechanical properties of reduced activation ferritic/martensitic (RAFM) steel fabricated by selective laser melting (SLM). The SLM-built RAFM steel exhibited a better combination of strength and ductility than the previously reported counterparts. The SS-X had higher yield strength of 911 MPa and higher elongation of 18.7% than the SS-XY with yield strength of 893 MPa and elongation of 15.0%. The results reveal that the variation in the yield strength was mainly ascribed to the different grain size and the improved ductility was associated with the modified grain structure that altered the tensile fracture mode with concurrent occurrence of intergranular brittle and transgranular ductile fracture. This finding provides an alternative to fabricate high-performance RAFM steel by tailoring the microstructure with different scanning strategies.

Hydrogen embrittlement of the 7B05‐T5 aluminum alloy for high‐speed trains

AbstractThe effect of hydrogen cathodic charging on the mechanical behavior of the 7B05‐T5 aluminum alloy has been studied. The hydrogen susceptibility of the 7B05‐T5 aluminum alloy was evaluated by slow strain rate tensile testing. The tensile tests revealed that the ductility of the 7B05‐T5 aluminum alloy decreased when charged cathodically for 96 hr with a constant current density of 2 mA/cm 2. The charged 7B05‐T5 aluminum alloy exhibited pitting corrosion at the surface layers and brittle intergranular fracture at the deeper layers of the alloy. The decrease in the ductility of the aluminum alloy was attributed to hydrogen‐reducing atomic binding force.

Influence of tempering treatments on mechanical properties and hydrogen embrittlement of 13 wt% Cr martensitic stainless steel

The influence of tempering treatments on mechanical properties and hydrogen embrittlement (HE) of 13 wt% Cr martensitic stainless steel (MSS) have been investigated by Charpy impact tests and slow strain rate tensile (SSRT) tests followed by fracture surface examination. The austenitized and quenched specimens were tempered at 300, 550 and 700 °C for 2.5 h. The MSS tempered at 550 °C showed brittle intergranular (IG) fracture after impact tests indicating its susceptibility to temper embrittlement. The experimental results showed that the 13 wt% Cr MSS is sensitive to HE. The as-quenched condition showed cracking during hydrogen pre-charging itself. Hydrogen pre-charging duration increased the susceptibility to HE of tempered MSS. The maximum HE susceptibility was observed for specimen tempered at 550 °C with a drastic reduction in strength and strain to failure. Tempering at 300 and 550 °C showed brittle IG fracture with hydrogen pre-charging in SSRT tests whereas increased IG region with ductile dimples was observed for specimen tempered at 700 °C with increase of pre-charging duration. The reason for maximum susceptibility to HE of specimen tempered at 550 °C is due to synergistic interaction of hydrogen and impurities segregated at prior austenitic grain boundaries.

Selective laser melting additive manufacturing of pure tungsten: Role of volumetric energy density on densification, microstructure and mechanical properties

Due to the intrinsic properties of tungsten, such as high melting point and high thermal conductivity, selective laser melting of pure W parts experiences many challenges. In this study, the effects of volumetric energy density on the densification behavior, microstructure evolution and mechanical performances of SLM-processed pure tungsten parts were investigated. A maximum density of 19.0 g/cm3 (98.4% of the theoretical density) was obtained at the optimal energy density of 1000 J/mm3 and its microstructure was free of pores and balling phenomenon. The formation mechanism of pores and cracks was systematically investigated. The microhardness and compressive strength of SLM-processed pure W parts reached 474 HV and 902 MPa, respectively, which were comparable to the samples produced by conventional manufacturing methods. The morphology of fracture demonstrated that the fracture mechanism of SLM-processed pure W parts was brittle fracture and intergranular fracture was the main fracture mode. Dry sliding wear tests showed that the wear mechanism changed with the energy density. For pure W parts processed by SLM at the optimal parameters, the adhesion of hardened tribolayers was formed. In this case, the reduced coefficient of friction (COF) of 0.45 and a low wear rate of 1.3 × 10−5 mm3·N−1·m−1 were obtained.

Failure analysis of a furnace roller in continuous annealing line after long-term service at high temperatures

The rollers used to convey steel strips in a continuous-annealing furnace were deformed after about 12 years of service, resulting in an unevenness of the rolled strips. In this study, failure causes of the furnace rollers were investigated in terms of degradation of microstructure and mechanical properties of the roller material. After a long period of high temperature service, the microstructure of the material has changed significantly. A large number of network-like carbides precipitated at the grain boundaries, and these carbides have been greatly coarsened. It was also found that a great number of σ-phase have formed on the coarsened carbides, and that the volume fraction of the σ-phase on the grain boundaries has exceeded 50%. In addition, creep cavities have been found in the grain boundaries. Especially in regions with dense grain boundaries, the cavities formed at the intersection of grain boundaries have been linked into chains, which tend to develop into cracks. The grain boundaries of the furnace roller material after service has been severely embrittled. Both tensile and impact fracture surfaces show brittle intergranular fracture characteristics. Compared to the unused material, the tensile strength and impact toughness of the failed roller decreased significantly due to the deterioration of the microstructure. Because of the degraded mechanical properties, the rollers are prone to deformation under the service loads, thus cannot guarantee the normal production of strip steels. The results of this study provide a reference for evaluating the remaining life of furnace rollers after long-term service at elevated temperatures.

The effect of age-hardening mechanism on hydrogen embrittlement in high-nitrogen steels

The effect of age-hardening regime on peculiarities of hydrogen-assisted fracture and tensile properties in two high-nitrogen Fe-23Cr-17Mn-0.1C-0.6N and Fe-19Cr-22Mn-1.5V-0.3C-0.9N steels was studied. A large number of intergranular (austenite/austenite) and interphase boundaries (austenite/coarse particle) provides high fraction of trapping sites for hydrogen atoms in V-alloyed steel. This leads to a change in fracture regime from transgranular brittle mode in coarse-grained V-free steel to intergranular brittle fracture of hydrogen-assisted surface layers in fine-grained V-alloyed steel with coarse (V,Cr)(N,C) particles. The formation of cells (Cr2(N,C) particles and austenite) along the grain boundaries due to discontinuous precipitate-hardening reaction facilitates predominantly interphase hydrogen-assisted fracture for both steels. The complex reaction of the particle-strengthening mechanisms including discontinuous precipitation with formation of austenite/Cr2(N,C)-plates interfaces or homogeneous nucleation of coherent (V,Cr)(N,C) particles in austenite (age-hardening regime 700 °C, 10 h) promotes mainly transgranular cleavage-like fracture mode under hydrogen-charging. The structural scheme is proposed to describe a change in hydrogen-assisted fracture micromechanisms and tensile properties of the steels with different density and distribution of interphase and intergranular boundaries.

Atomistic simulation of fracture in UO2 under tensile loading

Density-functional-theory (DFT) calculations and molecular dynamics simulations were performed to resolve the fracture behavior in UO2 under tensile loading. By molecular dynamics simulation, potential dependence was identified on the existence of transient plastic deformation prior to intergranular fracture in polycrystalline UO2, so we further improved the Morelon interatomic potential based on GGA + U calculations to obtain reliable fracture behavior in UO2. Using the improved potential, the fracture behaviors in polycrystalline and single crystal UO2 under tensile loading were investigated. In polycrystalline UO2, brittle intergranular fracture was observed, and no phase transition was found. In single crystal, Fm3¯m-Pbcn and Fm3¯m-P42/mnm structural transitions were observed under <100> tensile loading. The non-coherent interfaces between Pbcn and P42/mnm phases play a critical role in microcrack formation. Under <110> tensile loading, only Fm3¯m-P42/mnm transition was detected and the interface between Fm3¯m and P42/mnm structures was coherent, so no crack was found until the end of the simulation with strain of 25% in <100> direction.

Detection of embrittlement in low alloy steels due to thermal aging by small punch test

The applicability of miniaturised small punch tests (SPT) to capture thermal aging degradation of two commonly used low alloy steels (LAS) viz. Mn-Ni-Mo and Cr-Mo-V steels, was investigated. This was done by comparing the SPT results to the results of the conventional Charpy V-notch (CVN) tests, fractographic analysis and results of chemical etching test. Both the steels were subjected to accelerated thermal aging at 450 °C (8400 h for Mn-Ni-Mo steel and 5600 h for Cr-Mo-V steel). For both LAS, conventional CVN tests showed reduction in the impact energy and fractographic analysis indicated increase in the percentage brittle fracture with thermal aging. Fractographs indicated intergranular (IG) brittle fracture for the Mn-Ni-Mo steel and transgrannular (TG) brittle fracture for the Cr-Mo-V steel. This was corroborated by the chemical etching tests that showed preferential attack at prior austenitic grain boundaries (PAGBs) for Mn-Ni-Mo steel and conspicuous absence of such IG attack for Cr-Mo-V steel. SPT could clearly capture the embrittlement due to thermal aging for both the LAS as investigated by the conventional CVN testing. However, SPT could not establish the ductile to brittle transition temperature (TSP) as the lower shelf energy was not reached even at the lowest possible test temperature (-196 °C). SPT has been successful in capturing the indications of embrittlement due to thermal aging for both the LAS i.e. it is able to show the loss of ductility and increase in the fraction of brittle fracture. However, the use of SPT, at least in the present form, as an alternative to the most commonly used CVN test, for the materials studied is not recommended.