Showing papers in "Materials Science and Technology in 2009"
TL;DR: In this paper, a review of vanadium microalloyed steels is presented, focusing on quenched and tempered vanadium steels, precipitation during isothermal aging, conventional controlled rolling and during thin slab direct charging.
Abstract: Vanadium as an important alloying element in steels was initially associated with the properties achieved following tempering. Interest in the microstructure was stimulated by the advent of transmission electron microscopes with a resolution of ∼1 nm together with selected area electron diffraction techniques. A second timely development was that of controlled rolling, particularly of plate and sheet products. The scope of this review will include the historical background on quenched and tempered vanadium steels, precipitation during isothermal aging, conventional controlled rolling and during thin slab direct charging and the development of strength and toughness in vanadium microalloyed steels. The characterisation of microstructure, in particular the methods for the analysis of the chemical composition of precipitates has progressed since the availability of X-ray energy dispersive analysis in the 1970s, and the role played by electron energy loss spectroscopy in providing quantitative analysi...
215 citations
TL;DR: In this paper, the properties of Ni-based superalloys have been measured and relationships between properties and the γ′ phase content (which can be represented by mass% Al in the alloy) have been identified.
Abstract: Thermophysical properties for the solid and liquid phases of several Ni based superalloys (CMSX-4, CMSX-10, CM186LC, IN 738 and Rene 80) have been measured. The following properties were measured: heat capacity and enthalpy, thermal expansion coefficient and density, thermal diffusivity, viscosity and surface tension. Analysis of these measurements showed that that γ′ phase (Ni3Al) affected the values for the following properties; C p, enthalpy, electrical resistivity, thermal diffusivity and conductivity. Relationships have been identified between properties and the γ′ phase content (which can be represented by mass% Al in the alloy). These relations were then used to calculate property values of the alloys from chemical composition. Other relations were developed to estimate the viscosities and surface tensions of Ni based superalloys. The predicted property values were found to be in good agreement with the measured values.
111 citations
TL;DR: In this paper, the authors examined the mechanical response for a variety of strain and temperature paths, and related these to microstructural observations, showing that the strain induced martensite transformation in austenitic stainless steels results in materials with attractive combinations of strength and ductility.
Abstract: The strain induced martensite transformation in austenitic stainless steels is of considerable interest, because it results in materials with attractive combinations of strength and ductility. The present work examines the mechanical response for a variety of strain and temperature paths, and relates these to microstructural observations. New evidence of the detailed transformation sequence is presented, along with direct evidence of codeformation of the austenite and martensite. Using different deformation temperature sequences enables the transformation to be changed from one that is heterogeneous to one that propagates axially along the sample. The strain hardening that occurs due to combined plasticity and martensitic transformation results in high kinematic hardening that is revealed by microstructural observations here, and which are linked directly to the mechanical response of these materials described in Part II of the present work.
106 citations
TL;DR: The assessment presented here is an attempt to compile a loose set of guidelines for maximising the impact of any models that are created, in order to encourage thoroughness in publication to a point where the work can be independently verified.
Abstract: Neural networks are now a prominent feature of materials science with rapid progress in all sectors of the subject. It is premature, however, to claim that the method is established. There are genuine difficulties caused by the often incomplete exploration and publication of models. The assessment presented here is an attempt to compile a loose set of guidelines for maximising the impact of any models that are created, in order to encourage thoroughness in publication to a point where the work can be independently verified.
106 citations
TL;DR: In this article, the process characteristics of active flux tungsten inert gas welding and keyhole mode GTAW, two recent developments to GTAW are considered, as is keyholemode plasma arc welding, which is capable of greater penetration and faster processing speeds than conventional GTAW.
Abstract: Titanium alloys used in aerospace structures require joints of high integrity to meet the design requirements. Gas tungsten arc welding (GTAW), laser beam welding (LBW) and electron beam welding (EBW) are all processes capable of creating fusion welded joints. Gas tungsten arc welding offers the potential to achieve welds of equal quality to EBW or LBW at much lower capital costs; however, the application of GTAW involves gaining an understanding of the complex process characteristics. This paper reviews the process characteristics for GTAW titanium alloys and compares these characteristics with EBW and LBW titanium alloys. The characteristics of active flux tungsten inert gas welding and keyhole mode GTAW, two recent developments to GTAW, are considered, as is keyhole mode plasma arc welding. These variants are capable of greater penetration and, in some cases, faster processing speeds than conventional GTAW. Finally, the current knowledge of weld microstructural development in cast and wrought α...
93 citations
TL;DR: In this paper, a novel grain size dependent strain hardening model is derived from the theory of irreversible thermodynamics, which yields the evolution of the dislocation densities in the grain interior and at the grain boundary, as well as their contributions to the flow stress.
Abstract: A novel grain size dependent strain hardening model is derived from the theory of irreversible thermodynamics. The model yields the evolution of the dislocation densities in the grain interior and at the grain boundary, as well as their contributions to the flow stress. It is found that submicron grain sizes have a lower dislocation density in the grain interior, causing ductility to decrease greatly. The predicted stress–strain curve shapes, uniform elongation and ultimate tensile strength values for interstitial free steels (body centred cubic) and aluminium alloys (AA1100, face centred cubic) show good agreement with experimental observations.
89 citations
TL;DR: In this paper, the kinetics of martensite formation in three Fe-C-Mn alloys has been determined using dilatometry, and is compared with the data for other steels reported in literature.
Abstract: The kinetics of martensite formation in three Fe–C–Mn alloys has been determined using dilatometry, and is compared with the data for other steels reported in literature. Each curve can be well described by the Koistinen–Marburger equation using a composition dependent start temperature and rate parameter α m. The empirical relationship derived for α m as a function of the chemical composition can improve predictions with the Koistinen–Marburger model of the volume fraction martensite at a certain temperature.
88 citations
TL;DR: In this article, a kinetic creep equation for precipitation strengthened alloys has been derived using the climb/glide particle bypass micromechanism, which is applicable only when stresses lie within the range delineated by the dislocation network strength and the athermal yield strength.
Abstract: A kinetic creep equation for precipitation strengthened alloys has been derived using the climb/glide particle bypass micromechanism. It is applicable only when stresses lie within the range delineated by the dislocation network strength and the athermal yield strength — the lower of particle shear strength or Orowan strength. In this ‘dispersion controlled’ creep regime, strain rate is a hyperbolic sinh function of stress and interparticle spacing, making the state of dispersion an important microstructural feature. Existing equations have been used to quantify the evolution of dislocation and particulate microstructures and also stress redistribution between the two phases. The resulting constitutive equation set has been used to predict proof stresses, minimum creep rates and lifetimes for Nimonic 90. Comparison to industry data over a 600–900°C temperature range concludes that proof stresses are creep controlled once temperatures are above 700–725°C. Minimum creep rates and lifetimes over a si...
88 citations
TL;DR: In this article, the microstructural mechanisms which govern the high temperature strength of monocrystalline nickel base superalloys are reviewed in the context of previous work, and the conditions for cutting of the γ/γ′ rafts are stated in a simplified two-dimensional dislocation model.
Abstract: Some open questions concerning the microstructural mechanisms which govern the high temperature strength of monocrystalline nickel base superalloys will be reviewed in the context of previous work. Emphasis will be laid on microstructural effects observed in microyielding, creep, isothermal and thermomechanical fatigue and on the role of the γ/γ′ lattice misfit with respect to γ/γ′ rafting. The conditions for cutting of the γ′ rafts will be stated in a simplified two-dimensional dislocation model. Effects of the connectivity of the coarsened γ/γ′ microstructure and of the orientation of γ/γ′ rafts on the strength properties will be discussed, and potentially beneficial effects of a positive lattice misfit will be addressed. Attention will be drawn to counteracting alloying effects which modify both the lattice mismatch and the diffusion kinetics. The main conclusion is that the optimisation of superalloy properties can only be sought in improving the most important properties without deterioration...
88 citations
TL;DR: The goal of computational materials design is to apply the best scientific understanding to facilitate decisions regarding the optimal tradeoffs that meet desired needs in the most time and resource efficient manner.
Abstract: Computational materials design integrates targeted materials process–structure and structure–property models in systems frameworks to meet specific engineering needs. Design inherently consists of many competing requirements that require judicious decisions regarding key tradeoffs. The goal of computational materials design is to apply the best scientific understanding to facilitate decisions regarding the optimal tradeoffs that meet desired needs in the most time and resource efficient manner. Mechanistic materials design models require adequate fidelity to determine the favourability of one design solution over another but also the ability to be extrapolated over large parameter space to search for design optima in unexplored terrain. Design processes must not only efficiently find optimal solutions, but quickly identify failures. More broadly, materials design can only be as successful as the ability to identify the correct requirements for an application, and those requirements must address no...
83 citations
TL;DR: In this article, the levels of residual stress in the vicinity of linear friction welds in Ti-6Al-4V (Ti-64), a conventional α-β titanium alloy, and Ti- 6Al-2Sn-4Zr-2Mo (Ti 6242), a near α titanium alloy with higher temperature capability, are mapped and contrasted.
Abstract: In this paper, the levels of residual stress in the vicinity of linear friction welds in Ti–6Al–4V (Ti-64), a conventional α–β titanium alloy, and Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near α titanium alloy with higher temperature capability, are mapped and contrasted. The alloys have significantly different high temperature properties and the aim of this work was to investigate how this might affect their propensity to accumulate weld residual stresses and their response to post-weld heat treatment. Measurements are reported using high energy synchrotron X-ray diffraction and the results are compared to those made destructively using the contour method. The strain free lattice plane d 0 variation across the weld has been evaluated using the biaxial sin2Ψ technique with laboratory X-rays. It was found that failure to account for the d 0 variation across the weld line would have led to large errors in the peak tensile stresses. Contour method measurements show fairly good correlation with the diffraction...
TL;DR: The influence of nitrogen on tensile properties of 316L stainless steels has been studied for nitrogen levels of 0·07, 0·11,0·14 and 0·22 wt-%.
Abstract: The influence of nitrogen on tensile properties of 316L stainless steels has been studied for nitrogen levels of 0·07, 0·11, 0·14 and 0·22 wt-%. Tensile tests have been carried out at several temperatures in the range 300–1123 K. Nitrogen was found to be beneficial for tensile strength at all the test temperatures. Yield strength and ultimate tensile strength were found to increase linearly with increase in nitrogen content at all the test temperatures. Tensile ductility showed a non-monotonic variation with nitrogen content and test temperature. Equations have been developed to predict yield strength and ultimate tensile strength of 316L stainless steel as a function of nitrogen content and tensile test temperature.
TL;DR: In this article, the 25 years of materials science and technology have been studied, and the authors present a survey of the state-of-the-art technologies and their applications.
Abstract: (2009). 25 years of Materials Science and Technology. Materials Science and Technology: Vol. 25, No. 1, pp. 1-6.
TL;DR: The first successful production of niobium treated steel by the Great Lakes Steel Corporation of the USA was reported in 1958 as discussed by the authors, which was the first step towards the development and exploitation of microalloy steels.
Abstract: Although steels containing small amounts of vanadium or titanium had long been available, the rapid development and exploitation of microalloy steels was initiated by the recognition of the advantages of adding a small amount of niobium to C–Mn steels. This occurred in 1958 with the first successful production of niobium treated steel by the Great Lakes Steel Corporation of the USA. Various factors contributed towards this development including the availability of a supply of relatively low cost ferroniobium in the late 1950s and the discovery at this time of very large deposits of niobium bearing ores in Brazil and Canada which guaranteed the stability of future supply and price. Further development of microalloy steels was held back by a lack of knowledge of the exact role of niobium in influencing steel properties. Research carried out at The University of Sheffield in 1959–1960 provided a fundamental understanding of the effect of niobium. This was the first of many scientific investigations t...
TL;DR: In the mid-1950s, hot-rolled carbon steels exhibited high carbon contents, coarse ferrite-pearlite microstructures, and yield strengths near 300 MPa.
Abstract: In the mid-1950s, hot rolled carbon steels exhibited high carbon contents, coarse ferrite-pearlite microstructures, and yield strengths near 300 MPa. Their ductility, toughness and weldability were poor. Today, a half-century later, hot rolled steels can exhibit microstructures consisting of mixtures of ferrite, bainite and martensite in various proportions. These structures are very fine and can show yield strengths over 900 MPa, with acceptable levels of ductility, toughness and weldability. This advancement was made possible by the combination of improved steelmaking, microalloying technology and better rolling and cooling practices. The purpose of this paper is to chronicle some of the remarkable progress in steel alloy and process design that has resulted in this impressive.
TL;DR: In this article, the authors report the results of a blind round robin test dedicated to the measurement of the retained austenite content of different TRIP assisted multiphase steels.
Abstract: The present paper reports the results of a blind round robin test dedicated to the measurement of the retained austenite content of different TRIP assisted multiphase steels. Various surface and volume techniques, i.e. light microscopy, X-ray diffraction, electron backscattered diffraction (EBSD), magnetic saturation, thermal diffusivity and laser ultrasonics, were used by different partners. The compiled results show a quite large variability of the estimated retained austenite content, particularly for well established techniques, such as X-ray diffraction (XRD) and magnetisation. On the other hand, emerging techniques like EBSD, thermal diffusivity and laser ultrasonics warrant further investigations.
TL;DR: In this paper, the authors investigated the possibility of improving the strength-ductility relation in a metastable β-titanium alloy through plasticity induced transformation (PiTTi).
Abstract: Investigations into the possibility of improving the strength–ductility relation in a metastable β-titanium alloy (Ti–10V–2Fe–3Al) through plasticity induced transformation (PiTTi) have been carried out Various heat treatments in the β and/or α+β condition were performed to study their influence on both the microstructure and solute partitioning, which eventually control the PiTTi effect Stress induced martensite formation promoting such effect has been observed upon compression testing for β and β+(α+β) microstructures The stress–strain curves exhibiting stress induced martensite show a ∼20% increase in strength, while still retaining a reasonable ductility level Microstructural parameters such as grain size and solute concentration (especially V) in β have been related to the alloy's ability to exhibit PiTTi
TL;DR: In this article, the formation mechanism and exfoliation restacking behaviors of the obtained MoS2 nanostructures were investigated, and it was shown that the obtained nano-MoS2 nanoplatelets could exfoliate only partly by the exfolation technology because of their chemical stability.
Abstract: MoS2 nanostructures were prepared by heating MoS3 precursors which were synthesised by acidifying the mixed solution of Na2MoO4 and Na2S or CH3CSNH2 (TAA). The formation mechanism and exfoliation restacking behaviours of the obtained MoS2 nanostructures were investigated. The MoS3 precursor prepared from TAA was composed of hollow nanoballs while that from Na2S comprised microsized particles. Heating the obtained MoS3 hollow nanoballs under H2 at 780°C led to MoS2 hollow nanoballs. Owing to high temperatures decreased the layer space of MoS2, MoS2 nanoballs were changed into polyhedral structures at 960°C. However, calcining the prepared MoS3 microsized particles resulted in MoS2 nanoplatelets both at 780 and 960°C. The prepared MoS2 nanoballs could exfoliate only partly by the exfoliation technology because of their chemical stability. However, MoS2 nanoplatelets exfoliated completely in exfoliation treatment and formed nano-MoS2 monolayer suspension. The restacked production of the obtained nano...
TL;DR: The Alloys by Design project as mentioned in this paper developed and refined an integrated array of models to assist in the rapid development of nickel-based superalloys, which must be stable, creep resistant, castable and coatable.
Abstract: The Alloys by Design project aims to develop and refine an integrated array of models to assist in the rapid development of nickel based superalloys. A viable alloy must be stable, creep resistant, castable and coatable. By incorporating the complex interactions between composition, microstructure and processing of the alloys into models, a wider range of compositions can be explored enabling more innovative design strategies. Each of these issues is addressed at a range of appropriate levels from the atomic scale to the continuum.
TL;DR: In this paper, a strategy for use of microalloyed steels in long products, including bar and forging steels, is presented based on alloying and processing characteristics applicable to this class of steels.
Abstract: A strategy for use of microalloyed steels in long products, including bar and forging steels, is presented based on alloying and processing characteristics applicable to this class of steels. The approach, which defines in temperature/composition space specific composition and processing temperatures for different product types, helps guide selection of microalloy additions for specific applications. Results of several recent product developments characteristic of thermomechanically processed and heat treated bar steels are also presented to illustrate opportunities available for the expanded use of microalloy additions in long products.
TL;DR: Differential scanning calorimetry (DSC) is a thermal analysis technique that measures the energy absorbed or released by a sample as a function of temperature or time.
Abstract: Differential scanning calorimetry (DSC) is a thermal analysis technique that measures the energy absorbed or released by a sample as a function of temperature or time. Analysis by DSC has wide applications for examining solid state reactions and solid–liquid reactions in many different materials. Analysis of the kinetics of reactions may be assessed by activation energy analysis methods. In recent years, DSC has been applied in the examination and analysis of bulk ultrafine grained materials processed through the application of severe plastic deformation. This overview examines these recent reports with reference to materials processed using the procedures of equal channel angular pressing, high pressure torsion and accumulative roll bonding. In addition, some critical issues related to DSC analysis are also discussed.
TL;DR: In this paper, the performance of hydrogen embrittlement, fatigue properties and impact toughness of ultra high strength transformation induced plasticity aided steels with bainitic ferrite matrix (TBF steels) has been discussed.
Abstract: The performance of hydrogen embrittlement, fatigue properties and impact toughness of ultra high strength transformation induced plasticity aided steels with bainitic ferrite matrix (TBF steels) has been discussed. Some characteristics and deformation transformation mechanism of the retained austenite has also been discussed. It has been observed that mechanical stability and volume fraction of the interlath retained austenite phase in the TBF steels play an important role in increasing delayed fracture strength, fatigue limit and impact toughness.
TL;DR: In this paper, the reported varied degree of improvement in wear resistance by cryotreatment has been attributed to the operating test conditions that govern the modes and mechanisms of wear of AISI D2 steel specimens.
Abstract: This report aims to reveal the cause of wide variation in the reported degree of improvement in wear resistance of cryotreated tool steels. Sliding wear tests at different normal loads have been carried out on conventional and cryotreated AISI D2 steel specimens together with SEM examinations and EDX microanalyses of the surfaces and subsurfaces of the worn specimens and that of the generated debris. The obtained results reveal that when the modes and mechanisms of wear are similar for both types of specimens, mild oxidative at lower load or severe delaminative at higher load, the improvement in wear resistance is 1·6–2·2 times. At the intermediate load, the modes and mechanisms are dissimilar, and the observed improvement is as high as 53·2 times. The reported varied degree of improvement in wear resistance by cryotreatment has been attributed to the operating test conditions that govern the modes and mechanisms of wear.
TL;DR: In this article, a multicomponent model which can simulate the microstructural evolution of a coated Ni-based superalloy system has been developed, which consists of a one-dimensional finite difference diffusion solver to calculate the component distribution, a power law based model for predicting surface oxidation and a thermodynamic calculation routine for determining the phase evolution.
Abstract: A multicomponent model which can simulate the microstructural evolution of a coated Ni based superalloy system has been developed. The model consists of a one-dimensional finite difference diffusion solver to calculate the component distribution, a power law based model for predicting surface oxidation and a thermodynamic calculation routine for determining the phase evolution. Apart from forecasting concentration and phase profiles after a given thermal history, the model can estimate the losses due to oxidation and the remaining life of a coating based on a concentration and/or phase fraction dependent failure criteria. The phase constitution and concentration profiles predicted by the model have been compared with an experimental NiCoCrAlY coated CMSX-4 system, aged for times up to 10 000 h between 850 and 1050°C, and many experimental features can be predicted successfully by the model. The model is expected to be useful for assessing microstructural evolution of coated turbine blade systems.
TL;DR: In this article, an explosively clad HSLA steel with austenitic stainless steel of AISI 304L grade was subjected to hot rolling followed by a quenching and tempering treatment to achieve better mechanical properties.
Abstract: The present work aims at studying structure–property correlations in an explosively clad HSLA steel with austenitic stainless steel of AISI 304L grade. The clad plate was subjected to hot rolling followed by a quenching and tempering treatment to achieve better mechanical properties in the base plate. Optical microscopy studies revealed that the interface between the two steels was wavy in the as clad plate and the waviness decreased substantially due to hot rolling. Subsequent heat treatment has not shown any significant effect either. The base plate had tempered martensite/bainite structure in as clad or heat treated conditions and ferrite-pearlite-bainite structure in hot rolled condition. The grains were finer and elongated near the interface. The stainless steel exhibited equiaxed grain structure in as clad, hot rolled or heat treated plates. Tensile properties and charpy impact energy of the base plate were lowered due to hot rolling and then increased substantially due to heat treatment. Th...
TL;DR: In this paper, the authors investigated the tensile strength of roll-bonded titanium alloy and stainless steel joints at the bonding temperature of 760°C, and achieved a reduction of 20% and a rolling speed of 38 mm s−1.
Abstract: Vacuum hot roll bonding of titanium alloy and stainless steel using a nickel interlayer was investigated. No obvious reaction or diffusion layer occurs at the interface between stainless steel and nickel. The interface between titanium alloy and nickel consists of an occludent layer and diffusion layers, and there are the intermetallic compounds (TiNi3, TiNi, Ti2Ni and their mixtures) in the layers. The total thickness of intermetallic layers at the interface between titanium alloy and nickel increases with the bonding temperature, and the tensile strength of roll bonded joints decreases with the bonding temperature. The maximum tensile strength of 440·1 MPa was obtained at the bonding temperature of 760°C, the reduction of 20% and the rolling speed of 38 mm s–1.
TL;DR: In this paper, the authors present bulk residual stress distributions, as measured by neutron diffraction, for the configuration of a single pass gas tungsten arc weld bead deposited on to a 20 mm thick SA508 steel substrate.
Abstract: In steel welds, the development of residual stress is often complicated by the solid state phase transformations that occur upon cooling. Here the authors present bulk residual stress distributions, as measured by neutron diffraction, for the configuration of a single pass gas tungsten arc weld bead deposited on to a 20 mm thick SA508 steel substrate. Two specimens were manufactured, one with a low heat input (1·2 kJ mm−1) and another with a high heat input (2·4 kJ mm−1). The resulting microstructures and residual stress distributions are discussed in terms of the differing thermal excursions across each weld. In regions that are austenitised during welding, the transformation strain on cooling is shown to compensate in part for thermal contraction strains. Accordingly, phase transformations in SA508 steel led to significant reductions in stress within the weld bead and much of the heat affected zone, while the highest tensile stresses were located immediately outside the heat affected zone bounda...
TL;DR: In this paper, the authors investigated the heat affected zone microfissuring in electron beam welds of two Allvac 718 PLUS (718 Plus) alloys with different boron and phosphorus contents.
Abstract: Heat affected zone (HAZ) microfissuring was investigated in electron beam welds of two Allvac 718 PLUS (718 Plus) alloys with different boron and phosphorus contents. Two preweld solution heat treatments were used and microfissuring susceptibility was evaluated by measuring the HAZ crack lengths in both alloys after bead on plate welding. The segregation behaviour of boron and phosphorus was studied before and after welding by secondary ion mass spectrometry (SIMS). Hot ductility behaviour of the alloys in the standard solution preweld heat treatment was also examined. The results of crack measurements, segregation studies and hot ductility tests correlated well with each other. It was observed that besides constitutional liquation of Nb rich MC type carbides, segregation of B and P largely influenced the microfissuring susceptibility of the alloy. Heat affected zone microfissuring increased with an increase in B + P concentrations and with an increase in the preweld solution heat treatment temper...
TL;DR: In this article, the failure behavior of similar and dissimilar resistance spot welded joints of low carbon and austenitic stainless steel sheets was studied under tensile shear test with attention focused on the failure mode.
Abstract: In this paper, the failure behaviour of similar and dissimilar resistance spot welded joints of low carbon and austenitic stainless steel sheets was studied under tensile shear test with attention focused on the failure mode. Results showed that the microstructure of the fusion zone and the hardness distribution across the weld have a profound effect on the failure behaviour. Similar spot welds of stainless steel sheets exhibit the highest tendency to fail in interfacial failure mode, compared to low carbon steel similar spot welds and dissimilar low carbon and stainless steel spot welds. This behaviour is explained by the consideration of pullout failure location and hardness profile characteristics of each joint. It was shown that the failure mode transition is controlled by the hardness ratio of the fusion zone and the pullout failure location. In the case of dissimilar resistance spot welding, the hardness of the fusion zone which is governed by the dilution between two base metals, and the f...
TL;DR: In this article, the observed trends in mechanical properties are explained on the basis of observed microstructure, fracture behaviour, electron probe microanalysis and X-ray diffraction. And they showed that post-weld heat treatment applicable to either Inconel 718 or EN24 led to reduction in toughness and increase in strength.
Abstract: Nickel based superalloy Inconel 718 and low alloy steel EN24 are welded by continuous drive friction welding in annealed condition and then post-weld heat treated (PWHT). The welds exhibit low strength and high toughness in the as welded condition. Post-weld heat treatment applicable to either Inconel 718 or EN24, led to reduction in toughness and increase in strength. Toughness degradation after PWHT as per Inconel 718 was predominant. The observed trends in mechanical properties are explained on the basis of observed microstructure, fracture behaviour, electron probe microanalysis and X-ray diffraction.