Intergranular Failure Research Articles

On the Competition between Intergranular and Transgranular Failure within 7xxx Al Alloys with Tailored Microstructures.

7xxx aluminium series reach exceptional strength compared to other industrial aluminium alloys. However, 7xxx aluminium series usually exhibit Precipitate-Free Zones (PFZs) along grain boundaries, which favour intergranular fracture and low ductility. In this study, the competition between intergranular and transgranular fracture is experimentally investigated in the 7075 Al alloy. This is of critical importance since it directly affects the formability and crashworthiness of thin Al sheets. Using Friction Stir Processing (FSP), microstructures with similar hardening precipitates and PFZs, but with very different grain structures and intermetallic (IM) particle size distribution, were generated and studied. Experimental results showed that the effect of microstructure on the failure mode was significantly different for tensile ductility compared to bending formability. While the tensile ductility was significantly improved for the microstructure with equiaxed grains and smaller IM particles (compared to elongated grains and larger particles), the opposite trend was observed in terms of formability.

Ab initio study of tungsten-based alloys under fusion power-plant conditions

Tungsten (W) is considered a leading candidate for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. However, tungsten also presents a very low fracture toughness, primarily associated with inter-granular failure and bulk plasticity, limiting its applications. In recent years, several families of tungsten-based alloys have been explored to overcome the aforementioned limitations of pure tungsten. These include tungsten-based high-entropy alloys (W-HEAs) and tungsten-based Self-passivating Metal Alloys with Reduced Thermo-oxidation or “SMART alloys” (W-SAs). Given their proximity to the plasma, it is crucial to understand how the exposure of these candidate plasma-facing materials (PFMs) to the neutron fluxes expected in fusion reactors impacts their material behavior over time. In this work, we present a computational approach that combines inventory codes and first-principles DFT electronic structure calculations to understand the behavior of transmuting tungsten-based PFMs. In particular, we calculate the changes in the chemical composition, production uncertainties, the elastic and ductility properties, and the density of states for five tungsten-based PFMs when exposed to EU-DEMO fusion first wall conditions for ten years.

Microscopic cracking behaviors of rocks under uniaxial compression with microscopic multiphase heterogeneity by deep learning

Cracking behaviors of rocks significantly affect the safety and stability of the explorations of underground space and deep resources. To understand deeply the microscopic cracking process and mechanical property of rocks, X-ray micro-computed tomography (X-μCT) is applied to capture the rock microstructures. The digital color difference UNet (DCD-UNet)-based deep learning algorithm with 3D reconstruction is proposed to reconstruct the multiphase heterogeneity microstructure models of rocks. The microscopic cracking and mechanical properties are studied based on the proposed microstructure-based peridynamic model. Results show that the DCD-UNet algorithm is more effective to recognize and to represent the microscopic multiphase heterogeneity of rocks. As damage characteristic index of multiphase rocks increases, transgranular cracks in the same grain phase, transgranular and intergranular cracks of pore-grain phase, intergranular and secondary transgranular cracks and transgranular crack between different grains propagate. The ultimate microscopic failure modes of rocks are mainly controlled by the transgranular cracks-based T1-shear, T3-shear, T1-tension, T2-tension and T3-tension failures, and the intergranular cracks-based T1-tension, T1-shear and T3-shear failures under uniaxial compression.

Failure mechanism of HR3C austenitic steel during creep at 650°C

AbstractThis paper investigates the intergranular failure and degradation process of HR3C steel during creep. Substantial microscopic information for the morphological and compositional characteristics of intergranular precipitates were revealed here. The results showed that the intergranular M23C6 carbides precipitated progressively, resulting in a formation of Cr‐depleted region, and coexist with the NbCrN phase at the grain boundary. Besides, the dislocation configuration and density of HR3C steel also changed remarkably after creep, which manifests that the increase of lattice debonding extent and irregular atoms array. The intergranular damage of the M23C6 matrix interface was revealed by the HRTEM observation, and the main damage features were the volumetric defect generation as well as the large‐area distortion of atom lattice around the M23C6, which would contribute to the intergranular crack forming at the end of creep stage.

Effect of Sulfur on Antimony-Induced High-Temperature Ductility Deterioration of C-Mn Steel

The recycling of steel scrap is becoming more and more developed to save resources and protect the environment. However, impurities such as antimony in steel scrap cannot be economically and effectively removed, resulting in an inevitable accumulation of impurities. Once the impurity concentration exceeds a certain limit, they will have a great impact on the ductility deterioration and hot shortness of steel. It has been shown that sulfide can inhibit the precipitation of residual elements, such as copper at grain boundaries, in steel. The effect of sulfur on the thermoplasticity of antimony-containing C-Mn steel at 700–1100 °C was examined using a Gleeble 1500 thermodynamic simulation device (Gleeble, Poestenkill, NY, USA). Area reduction (RA%) was used to evaluate the thermal ductility. The 0.16 mass % Sb extended the range of the ductile grooves, reducing the RA% at 750–950 °C. Antimony (Sb) was found to segregate at the boundaries tested by an electron probe microanalyzer. Additionally, scanning electron microscopy was used to examine the fracture morphology, which exhibited the characteristics of intergranular failure. In contrast, the addition of sulfur to the steel compensated for the deterioration of the thermal ductility caused by the Sb.

Simulation of neutron irradiation-induced recrystallization of tungsten

<sec>Tungsten is the candidate for divertor target material in future fusion reactors. The tungsten divertor target is expected to long serve in a harsh environment of high temperature and high-energy neutron irradiation. This can lead to neutron irradiation-induced recrystallization of tungsten, thereby increasing the possibility of intergranular brittle failure and compromising the safe operation of the divertor. Thus, clarifying the mechanism of neutron irradiation-induced tungsten recrystallization is important. However, the current model, which only considers the irradiation-enhanced effect on recrystallization driving force, underestimates the irradiation effect on recrystallization compared with the results observed in recent high-temperature neutron irradiation experiments in the HFIR reactor. It indicates that other irradiation effects can also influence the recrystallization process.</sec><sec>In this study, we introduce the irradiation-enhanced grain boundary migration factor (<i>R</i>) into the established irradiation-induced recrystallization kinetic model, on the assumption that the grain boundary migration velocity is proportional to the self-diffusion coefficient. The simulation results show that after considering both irradiation-enhanced recrystallization driving force and grain boundary migration effect, the calculated half-recrystallization time (<inline-formula><tex-math id="M4">\begin{document}${t}_{{X}\text{}=\text{}0.5}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20230531_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20230531_M4.png"/></alternatives></inline-formula>) at 850 ℃ from the model matches the one obtained in the neutron irradiation experiment in the HFIR reactor. This result indicates that the irradiation-enhanced grain boundary migration effect is one of the important factors affecting irradiation-induced recrystallization. In addition, the difference between irradiated and unirradiated <i>t</i><sub><i>X</i>=0.5</sub> decreases with temperature increasing. This phenomenon is due to the fact that as the temperature increases, the contribution of irradiation defects to the driving force for recrystallization decreases owing to the irradiation defect recombination. Moreover, the increase of thermal activation diffusion coefficient is more significant than the increase of the irradiation-enhanced diffusion coefficient. These findings suggest that the thermal activation effect eventually dominates the recrystallization process over the irradiation effect as temperature increases.</sec>

Confinement-dependent failure criterion for high-strength concrete in multiaxial stress states

High-strength concrete is becoming progressively wide applications in modern civil engineering structures because of its excellent mechanical properties and workability. However, most of the commonly adopted failure criteria were developed based on the low-strength concrete (cylinder compressive strength less than 40 MPa), and they may not accurately reflect the behavior of high-strength concrete due to the changes in its failure modes from intergranular failure to transgranular failure. The systematic analysis of databases consisting of 2120 experimental results of concrete multiaxial test collected from a wide range of existing literature has been carried out. It was found that the ratios of concrete ultimate strengths under uniaxial tension and equibiaxial compression to its uniaxial compressive strength (fc0) were negatively correlated with the uniaxial compressive strength. While under triaxial compression, the ultimate strength enhancement was affected by the uniaxial compressive strength and the degree of confinement (σm/fc0) simultaneously. On this basis, through the careful discussion of the morphological characteristics of concrete cracks after multiaxial failure, the concepts of the weakly and heavily confined states of concrete under triaxial compression were developed quantitatively, and the critical degree of confinement σm/fc0 = −0.8 was proposed. Under the heavily confined state, the ultimate strength enhancement of the high-strength concrete was less than that of the low-strength concrete, whereas there was no difference between them under the weakly confined state. A confinement-dependent failure criterion was formulated that utilized the piecewise compressive meridian to achieve a more rational description of the multiaxial ultimate strength for high-strength concrete. With the suggested failure criterion, a peak axial stress model for confined concrete was proposed. As verified by the experimental data of concrete confined by fiber-reinforced polymer (FRP) wraps from existing literature, which contains both high-strength and low-strength concrete, the proposed model showed better prediction accuracies with less scatters than the existing counterparts. This study can also be a reference for the research of the multiaxial failure criterion of other concrete-type materials.

Effects of post heat treatment on microstructure and mechanical properties of Ti5553 parts made by laser powder bed fusion

Rapid heating and solidification rates involved in additive manufacturing result in non-homogenous microstructural features, microsegregation and residual stresses, leading to deteriorated mechanical properties. Although the rather new Ti-5553 (Ti‐5Al‐5Mo‐5V‐3Cr) metastable β-Ti alloy is printable by laser powder-bed fusion (LPBF), it exhibits poor mechanical strength compared to conventionally forged components due to the lack of second phase strengthening in the as-printed state. Therefore, post-processing heat treatment is essential to enhance the mechanical properties of the printed parts. In this research work, LPBF-made Ti-5553 specimens were subjected to varying heat treatment cycles to modify their corresponding microstructure in terms of the morphology and distribution of α particles. Differential Scanning Calorimetry (DSC), X-Ray diffraction (XRD) patterns, and electron backscatter diffraction (EBSD) results suggest that solutionizing at the upper α + β region (800 °C) offers a good combination of finer grain size and satisfactory α dissolution. On aging in the range of 500 – 700 °C for 0.5 – 4 h, growth of α particles with different morphologies was observed. A combination of multiple α morphologies, including Widmanstätten, lenticular, cylindrical and lamellar was identified based on the heat treatment conditions. Consequently, a wide range of microhardness from 300 to 500 HV was observed due to phase transformations in the microstructure, which control the mechanical properties. The subsequent tensile tests validated the improved mechanical properties further as the tensile strength increased from 780 ± 10–1640 ± 6.29 MPa, compared to the as-printed specimens. Examination of the fracture surfaces revealed intergranular failure following aging at 500 °C due to segregation of α particles at grain boundaries. At 600 °C, the fracture was initially intergranular, which slowly transformed to a ductile fracture with time. At 700 °C, the fracture was mainly ductile irrespective of the aging duration.

The effect of microstructural changes on the rupture behavior of gas turbine damping bolt superalloy (Nimonic 90) after long service time

The present study investigated the microstructure of superalloy gas turbine damping bolt. These damping bolts were selected from new and service-exposed ones made of nickel-based Nimonic 90, which had been served for a long time. The microstructure of new sample had an austenitic matrix with many twins. These twins were located in the intergranular and intragranular regions of the primary carbides. Fine gamma-prime precipitates also could be found in the field. However, due to the high amount of service time, the arranged structure turned into a complex one in which the Sigma and Mayo phases with the Widmanstätten pattern appeared near the grain boundaries. Therefore, secondary continuous carbides formed near the grain boundary, and γ′ precipitates grew, which increased the hardness of the samples by about 30 Vickers. The mentioned microstructural changes reduced the creep rupture to 140 MPa at 870 °C in 11 h, while the sample had a creep life of about 21 h. This indicates that the resulting microstructural changes reduced brittleness and creep life. The soft intergranular failure mechanism in the new damping bolt became an intergranular mechanism. Moreover, the effects of intragranular failure were also abundant.

Microstructure-based polycrystalline finite element modeling of Inconel X-750 irradiated in a CANDU reactor

Aging of Inconel X-750 spacers in Canada Deuterium Uranium (CANDU) reactors is managed through a combined program of in-service inspection, component removal for material surveillance testing, research and development, and fitness-for-service evaluation. Crush tests of ex-service spacer coils have shown that the load carrying capacities of Inconel X-750 spacers decrease with operating time. The spacers also exhibit reduced ductility and inter-granular failure that is typical of helium (He)-embrittlement. Examination of ex-service spacers confirmed that material interfaces (mainly grain boundaries) were perforated by He-bubbles. Assuming that the grain boundary bubble coverage dictates the grain boundary strength and thus the failure load of the polycrystalline component, we have simulated the degradation and inter-granular failure of the spacer coils at low and high operating temperatures.The observed inter-granular fracture has been simulated by a cohesive zone model that governs the grain boundary de-bonding process. The grain boundary strength is related to the perforation by He-stabilised cavities. The model of grain boundary traction separation consists of three parts: (i) a rate-theory calculation to predict grain boundary coverage; (ii) a local material degradation model to quantify helium induced grain boundary strength reduction; (iii) a traction separation model to simulate grain boundary de-cohesion. The results show that the accumulation of He-stabilised cavities on grain boundaries causes material failure at lower stresses and strains that are dependent on the irradiation temperature and the neutron exposure. The load carrying capacity of the X-750 spacers decreases non-linearly with irradiation and the rate of change is decreasing with increasing dose.

Influence of Cu and Ni on the Hot Ductility of Low C Steels with Respect to the Straightening Operation When Continuous Casting

Cu-containing steels can suffer from hot shortness unless Ni is added to protect them but whether this problem also influences the straightening operation is not clear. Previous work on hot ductility has found that only when the tensile samples from Cu-containing steels are oxidised can any deleterious influence of copper be found. However, this paper shows that oxidation is not essential. It is more complex than that and, as Cu has been suggested for TRIP steels at levels up to 2.5% Cu to increase their strength and ductility, a greater understanding is required, both of hot shortness and cracking during straightening. The present paper explores the hot ductility behaviour of steels alloyed with Cu and Ni in the straightening temperature range, 700–1000 °C, when tested in air and in an argon atmosphere. Segregation of Cu to the sulphides and grain boundaries occurred allowing the formation of fine Cu2S particles at the austenite grain boundaries favouring intergranular failure and this was more pronounced under oxidising conditions and required strain. It was concluded that a Cu addition, as well as causing hot shortness at higher temperatures will also cause cracking problems in the straightening temperature range in the more sensitive to cracking grades of steel and although the problems are different they are nevertheless interrelated and provided there is sufficient Ni, both may be avoided.

Inhibiting weld cracking in high-strength aluminium alloys

Cracking from a fine equiaxed zone (FQZ), often just tens of microns across, plagues the welding of 7000 series aluminum alloys. Using a multiscale correlative methodology, from the millimeter scale to the nanoscale, we shed light on the strengthening mechanisms and the resulting intergranular failure at the FQZ. We show that intergranular AlCuMg phases give rise to cracking by micro-void nucleation and subsequent link-up due to the plastic incompatibility between the hard phases and soft (low precipitate density) grain interiors in the FQZ. To mitigate this, we propose a hybrid welding strategy exploiting laser beam oscillation and a pulsed magnetic field. This achieves a wavy and interrupted FQZ along with a higher precipitate density, thereby considerably increasing tensile strength over conventionally hybrid welded butt joints, and even friction stir welds.

Diffusion-limited Nonequilibrium Phase Transformation of Nickel/Aluminum Dissimilar Materials during Laser Welding Part I: Precipitation-strengthened Polycrystalline Nickel-based Superalloy

Polycrystalline heterogeneities of grain growth, phase transformation and tensile properties are discussed by metallography, spectroscopy and fractography when choosing laser welding with butt-joint configuration to satisfactorily minimize effect of inappropriate weld pool shape on microstructure and mechanical properties of γʹʹ precipitation hardable nickel-based superalloy in aerospace industry. There is parabolic relationship between weld penetration and diffusion-limited nucleation, growth and coarseness of secondary dendrite arm spacing alongside fusion boundary through nonequilibrium solidification process, which is dendritically susceptible to grain growth variation and metallurgical discontinuities. The amount, size, morphology and distribution of nonequilibrium intermetallic phase near the dendrite boundaries are kinetically and thermodynamically rely on weld pool shape whose crystal structure is incoherent with γ solid solution austenite phase and increases preference for crack initiation and propagation of brittle intergranular and ductile dimple fracture failures to enormously contribute to losses of strength and ductility. Unsymmetrical keyhole weld is thermometallurgically inconvenient for amelioration of microstructure and mechanical properties on either side, and adversely mitigates resistance to hypereutectic-aided dendrite embrittlement. Beneficial grain refinement and suppression of detrimental nonequilibrium intermetallic phase at the same time are challenging. This problem is an integral part of inhomogeneous microstructure and mechanical properties. The finer grain size occurs, the larger grain boundary area is available for Laves/γ eutectic-type reaction and vice versa. Contributions of coarse grain kinetics and metallurgical reaction thermodynamics to weld disintegration and fracture failure mechanism of tensile properties are explained by microstructure characterization of multicomponent and multiphase weld. Finally, it is imperative to dendritically balance these important factors to minimize inevitable interface solidification products and anomalous substructure growth, and reasonably advance superior mechanical properties of reliable weld.

Fracture behavior of Hastelloy X elaborated by laser powder bed fusion: Influence of microstructure and building direction

Laser Power Bed Fusion (LPBF) results in complex meso and microstructures, which significantly change the fracture mechanisms of Hastelloy X superalloys. This article aims to investigate the role played by original crack orientation (perpendicular or co-linear to sample lasing planes) on the fracture toughness values of LPBF HX. Single notched three-point bending samples were manufactured vertically (V) or horizontally (H) to estimate the fracture toughness for these two original crack directions. The highest value (about 1360 kJ/m²) is computed in V specimens with an original crack parallel to the lasing plane whereas a value of 1042 kJ/m² is estimated in H specimens with the second crack orientation. Compared to the values obtained in cast specimens, the fracture toughness of LPBF specimens is virtually 5–6 times higher. A non-self-similar cracking is specific to V specimens revealing a more tortuous crack path than in H specimens with self-similar cracking. In both cases, ductile failure is driven by both transgranular and intergranular modes. Nevertheless, the strong morphological texture contributes to promote intragranular fracture mode in V specimens which requires more energy than the one dissipated by an intergranular failure associated to H samples. Consequently, the fracture toughness is significantly higher in V specimens. • Fracture tests were conducted on Hastelloy X specimens elaborated by Laser Power Bed Fusion with two build directions. • In H specimens, intergranular fracture is dominant due to the grain boundaries aligned with the initial notch. • In V specimens, transgranular fracture occurs along with grain boundaries perpendicular to the initial notch. • The morphological texture is responsible for the fracture toughness anisotropy.

Hydrogen-Induced Dislocation Nucleation and Plastic Deformation of 〈001〉 and 〈11¯0〉 Grain Boundaries in Nickel.

The grain boundary (GB) plays a crucial role in dominating hydrogen-induced plastic deformation and intergranular failure in polycrystal metals. In the present study, molecular dynamics simulations were employed to study the effects of hydrogen segregation on dislocation plasticity of a series of symmetrical tilt grain boundaries (STGBs) with various hydrogen concentrations. Our study shows that hydrogen both enhances and reduces dislocation nucleation events from STGBs, depending on different GB structures. Specifically, for STGBs, hydrogen does not affect the mode of heterogeneous dislocation nucleation (HDN), but facilitates nucleation events as a consequence of hydrogen disordering the GB structure. Conversely, hydrogen retards dislocation nucleation due to the fact that hydrogen segregation disrupts the transformation of boundary structure such as Σ9 () STGB. These results are helpful for deepening our understanding of GB-mediated hydrogen embrittlement (HE) mechanisms.

Characterization of IASCC crack tips extracted from neutron-irradiated flux thimble tube specimens in view of a probabilistic fracture model

This study reports the properties of irradiation assisted stress corrosion crack tips extracted by means of focused-ion beam from 60 to 80 dpa neutron-irradiated O-ring specimens tested under straining conditions under a pressurized-water reactor environment. Various crack tip morphologies and surrounding deformation features were analyzed as a function of applied stress, surface oxidation state and loading form - constant versus cyclic. All investigated cracks exhibit grain boundary oxidation in front of the crack tip, with the extent of oxidation being proportional to applied stress. These findings clearly demonstrate that, under the subcritical crack propagation regime, the grain boundary oxide grows faster than the crack. On the other hand, crack tips appertaining to specimens with removed oxide layer at the outer surface show comparatively less oxidation at the crack tip, which could indicate towards crack initiation from regions that exemplify lower stress, such as the O-ring inner surface. Cyclic loading is found to have a more pronounced effect on the crack tip microstructure, demonstrating increased deformation twinning and α′-martensitic transformation, which signifies towards an increased susceptibility to intergranular failure. Still, the extent of crack tip grain boundary oxidation in this case agrees well with expected values for maximum stress applied during cyclic loading. All results are interpreted based on the probabilistic subcritical crack propagation mechanism and provide strong support to a stress-driven internal oxidation model.

Dislocation-aided electrochemical behavior of precipitates in stress corrosion cracking of Al–Zn–Mg–Cu alloys

The effects of electrochemical behavior of precipitates and dislocations on the stress corrosion cracking (SCC) of Al–Zn–Mg–Cu alloys were investigated. Fine anodic η (MgZn2) precipitates were readily dissolved, providing continuous channels for intergranular cracking, and coarse cathodic Cu-rich precipitates led to localized pitting attack of the surrounding matrix. This indicates that both precipitates promote intergranular SCC failure. Additionally, SCC resistance was decreased by stress localization owing to the high dislocation density on coarse Cu-rich particles. Our results demonstrate that tailoring the alloying content combined with T6 heat treatment is beneficial for increasing SCC resistance to compensate for the harmful effect of precipitates on SCC.

Effects of recycled aggregate combinations and recycled powder contents on fracture behavior of fully recycled aggregate concrete

This paper studied the fracture behavior of fully recycled aggregate concrete (FRAC), which was prepared with 100% recycled coarse and fine aggregates (RCA and RFA) and partial recycled powder (RP). Three-point bending tests on center-notched beams were conducted to evaluate the effects of aggregate combinations and RP contents on the meso-scale fracture mechanism and macro-scale fracture parameters of FRAC. It was found that the FRAC mostly presented transgranular or intergranular failure with RCA or RFA, respectively. The RCA substitution had little effect on the critical crack opening displacements, but the RFA and RP substitution increased and decreased them, respectively. Only the incorporation of RFA led to a reduction of the initial cracking toughness of FRAC. The employment of RAs, especially RCA, reduced the fracture energy Gf and unstable fracture toughness KIcun, while the use of RP had a limited impact. The results of the characteristic length showed that RAs made the fracture behavior of concrete more brittle while RP played an opposite role. Both Gf and KIcun reduced with the decrease of tensile strength. The former was remarkable in FRAC due to the variation of aggregate combination whereas the latter was more likely associated with the aggregate size.

Intergranular ductile failure of materials with plastically heterogeneous grains

In several precipitation hardened alloys that are susceptible to intergranular ductile failure, precipitation does not always occur uniformly throughout the microstructure, and regions close to grain boundaries may remain precipitate-free. These precipitate-free zones (PFZs) in the material microstructures result in plastically heterogeneous grains, since PFZs are expected to have lower yield strength but higher strain-hardenability compared to the precipitate containing grain interior. Experimentally, the presence of PFZs in precipitation-hardened alloys has been associated with both increase and decrease in materials’ ductility, with or without significant change in the strength. Thus, to understand and rationalize the experimental observations, we have carried out extensive microstructure-based finite element calculations of intergranular ductile failure in materials under tensile loading conditions. In the calculations, both the grain boundaries and PFZs are discretely modeled, and a wide range of the values of yield strength, strain-hardenability and width of PFZs in the material microstructures are analyzed. Our results show that the effects of PFZs on the overall mechanical response of the material strongly depend on the values of yield strength and strain-hardenability of PFZs. Furthermore, there exists an optimum combination of the values of these two parameters that can result in the overall ductility and tensile strength of the material microstructures with PFZs being greater than the microstructures without PFZs.

The Influence of Precipitation, High Levels of Al, Si, P and a Small B Addition on the Hot Ductility of TWIP and TRIP Assisted Steels: A Critical Review

The hot ductility of Transformation Induced Plasticity (TRIP) and Twinning Induced Plasticity (TWIP) steels is reviewed, concentrating on the likelihood of cracking occurring on continuous casting during the straightening operation. In this review, the influence of high levels of Al, Si, P, Mn and C on their hot ductility will be discussed as well as the important role B can play in improving their hot ductility. Of these elements, Al has the worst influence on ductility but a high Al addition is often needed in both TWIP and TRIP steels. AlN precipitates are formed often as thin coatings covering the austenite grain surfaces favouring intergranular failure and making them difficult to continuous cast without cracks forming. Furthermore, with TWIP steels the un-recrystallised austenite, which is the state the austenite is when straightening, suffers from excessive grain boundary sliding, so that the ductility often decreases with increasing temperature, resulting in the RA value being below that needed to avoid cracking on straightening. Fortunately, the addition of B can often be used to remedy the deleterious influence of AlN. The influence of precipitation hardeners (Nb, V and Ti based) in strengthening the room temperature yield strength of these TWIP steels and their influence on hot ductility is also discussed.