Showing papers in "Materials Science and Technology in 2003"
TL;DR: In this paper, the weldability of friction stir welded hot rolled AZ31B-H24 magnesium alloy sheet, 4 mm in thickness, was evaluated, varying welding parameters such as tool rotation speed and travel welding speed.
Abstract: The weldability of friction stir welded hot rolled AZ31B-H24 magnesium alloy sheet, 4 mm in thickness, was evaluated, varying welding parameters such as tool rotation speed and travel welding speed. Sound welding conditions depended mainly on sufficient heat input during the welding process. Insufficient heat input, which was generated in the case of higher travel speed and lower rotation speed, caused an inner void or lack of bonding in the stir zone. The microstructure of the weld zone was composed of five regions: base metal, heat affected zone, thermomechanically affected zone, stir zone I and stir zone II. Unlike the general feature of friction stir welded aluminium alloys, the grain size of the weld zone was larger than that of the base metal. Stir zones I and II were characterised by partial dynamic recrystallisation and full dynamic recrystallisation, respectively. The hardness of the weld zone was lower than that of the base metal owing to grain growth. A wider range of defect free weldin...
125 citations
TL;DR: In this article, a series of experiments investigating the recrystallisation of single crystal superalloy CMSX-4 have been carried out, and it has been found that a very strong dependence upon temperature is evident.
Abstract: A series of experiments investigating the recrystallisation of single crystal superalloy CMSX-4 have been carried out. Indentation atroom temperature has been used to study the effects of annealing time and temperature, and it has been found that a very strong dependence upon temperature is evident. Annealing above the γ′ solvus temperature results in very rapid growth of recrystallised grains whereas annealing below the γ′ solvus greatly suppresses the advancing grain boundaries. Additionally experiments have been carried out using an electrothermal mechanical test (ETMT) machine, to study the effects of degree of plastic strain and the temperature at which the strain is introduced. The strain threshold for recrystallisation under various annealing conditions has been determined and it has been found that recrystallisation occurs more readily if strain is introduced above 950°C. Finally, apparent activation energies for recrystallisation have been determined by measuring the change in resistivity...
114 citations
TL;DR: In this article, the effect of the initial billet temperature on friction and its consequences on material flow was investigated using the implicit finite element codes FORGE2 and FORGE3.
Abstract: This investigation focuses on simulation of the extrusion process and in particular the effect of the initial billet temperature on friction and its consequences on material flow. The simulation is compared with data obtained from an experimental extrusion press. All the simulations are performed with the implicit finite element codes FORGE2 and FORGE3. The effect of the initial billettemperature on the deformation zone pattern and its consequent effect onfriction using bothnumerical simulationandexperimentalworkare presented.A comparison withexperimentsis made to assess the relative importance ofsome extrusion parameters in the extrusion process and to ensure that the numerical discretisation provided a true simulation of the process. A specific functional relationship to directly measure interfacial friction under conditions approaching those encountered in the quasi-static deformation process is described. The results revealed that the friction factor increases with increase in initial billet ...
93 citations
TL;DR: In this article, it was shown that if elevated temperature aging of aluminium alloys is interrupted with a dwell period at a low temperature (65 °C), age hardening continues due to so-called secondary precipitation.
Abstract: It is shown that, if elevated temperature aging of aluminium alloys is interrupted with a dwell period at a low temperature (65 °C), age hardening continues due to so called secondary precipitation...
90 citations
TL;DR: In this article, a monolithic and copper particulate reinforced magnesium composites were synthesized using an innovative disintegrated melt deposition technique followed by hot extrusion, which showed uniform distribution of Cu and Mg-Cu based intermetallic particulates in the matrix material, good interfacial integrity of the magnesium matrix with reinforcement particulates, and presence of minimal porosity.
Abstract: The requirements for reduced fuel consumption and limited emission have triggered high consumption of magnesium in recent years due to its inherently low density and ensuing potential to exhibit advantageous specific mechanical properties. In the present study, monolithic and copper particulate reinforced magnesium composites were synthesised using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation of the composite samples showed uniform distribution of Cu and Mg- Cu based intermetallic particulates in the matrix material, good interfacial integrity of the magnesium matrix with reinforcement particulates, and the presence of minimal porosity. Physical properties characterisation revealed that the addition of copper as reinforcement marginally reduced the coefficient of thermal expansion (CTE) of pure magnesium. Mechanical properties characterisation revealed that the addition of copper in magnesium led to significant improvement in ha...
89 citations
TL;DR: In this paper, the effects of concurrent precipitation on recrystallisation during the isothermal annealing of a supersaturated and deformed Al-Miner alloy have been investigated, and it is shown that strain induced boundary migration of very large boundary areas is an important mechanism in this temperature range.
Abstract: The effects of concurrent precipitation on recrystallisation during the isothermal annealing of a supersaturated and deformed Al – Mn alloy have been investigated. At low annealing temperatures precipitation on the prior boundaries prevents recrystallisation whereas at high temperatures recrystallisation is complete before precipitation occurs. In the temperature range 375 – 500°C, recrystallisation is affected by precipitation and complex microstructures containing high fractions of low angle boundaries are formed. It is shown that strain induced boundary migration of very large boundary areas is an important recrystallisation mechanism in this temperature range. The interactions between precipitation and recrystallisation are analysed in terms of a simple model. The heating rate is shown to substantially affect the recrystallisation behaviour.
87 citations
TL;DR: Transformation induced plasticity (TRIP) steels are a promising solution for the production of cars with low body mass because of the combination of high strength and large uniform elongation.
Abstract: Transformation induced plasticity (TRIP) steels are a promising solution for the production of cars with low body mass because of the combination of high strength and large uniform elongation that ...
85 citations
TL;DR: Grain size refinement is an important strengthening mechanism in Al-Mg 5000 series alloys, which have a relatively large Hall-Petch slope compared with other Al alloys as discussed by the authors.
Abstract: Grain size refinement is an important strengthening mechanism in Al-Mg 5000 series alloys, which have a relatively large Hall-Petch slope compared with other Al alloys. In addition, the high work h...
82 citations
TL;DR: In this article, the microstructural change related with the hardness profile has been evaluated for friction stir welded, age hardenable 6005 Al alloy, and sound joints were successfully formed under a wide range of friction stir welding conditions.
Abstract: The microstructural change related with the hardness profile has been evaluated for friction stir welded, age hardenable 6005 Al alloy. Frictional heat and plastic flow during friction stir welding created fine and equiaxed grains in the stir zone (SZ), and elongated and recovered grains in the thermomechanically affected zone (TMAZ). The heat affected zone (HAZ), identified only by the hardness result because there is no difference in grain structure compared to the base metal, was formed beside the weld zone. A softened region was formed near the weld zone during the friction stir welding process. The softened region was characterised by the dissolution and coarsening of the strengthening precipitate during friction stir welding. Sound joints in 6005 Al alloys were successfully formed under a wide range of friction stir welding conditions. The maximum tensile strength, obtained at 507 mm min-1 welding speed and 1600 rev min-1 tool rotation speed, was 220 MPa, which was 85% of the strength of the...
77 citations
TL;DR: The mechanical and metallurgical properties of friction welded joints between type 5052 aluminium alloy and type A36 steel have been studied in this article, where a very fine and equiaxed grain structure was observed near the interface.
Abstract: The mechanical and metallurgical properties of friction welded joints between type 5052 aluminium alloy and type A36 steel have been studied in the present work. Joint strength increased with increasing upset pressure and friction time until it reached a crictical value. The strength of the joint settled at a lower value, compared with that of the base metal, in the case of increasing friction time, caused by the formation of an intermediate phase (intermetallic compound, oxides). The microstructure of 5052 alloy was greatly deformed near the weld interface, and underwent dynamic recrystallisation owing to frictional heat and deformation resulting from the friction welding process. Therefore, a very fine and equiaxed grain structure was observed near the interface. Elongated grains were observed outside the dynamic recrystallisation region at the peripheral part, while the A36 steel side was not deformed. The hardness of the near interface was slightly softer than that of the 5052 alloy base metal...
74 citations
TL;DR: In this paper, an artificial neural network was used to model the start temperature of engineering steels based on their chemical composition and the grain size of the austenite grain, and the results revealed the role of these factors in the stabilisation of alloying elements in steels.
Abstract: The stabilisation of austenite, a phenomenon that frequently occurs, renders the transformation from austenite to martensite difficult. The straightforward method of analysing the effect of a specific factor on the stabilisation of austenite is through its influence on the martensite start temperature M s. The present work outlines the use of an artificial neural network to model the M s of engineering steels based on their chemical composition and austenite grain size. The results are focused on elucidating the role in the stabilisation of austenite of alloying elements in steels, including less common elements such as vanadium and niobium, as well as the austenite grain size. Moreover, a physical interpretation of the results is presented.
TL;DR: In this paper, the reverse transformation of martensite to austenite and the volume fraction of retained Austenite have been studied in an Fe-3Si-13Cr-7Ni (wt-%) martensitic stainless steel by means of dilatometry, transmission electron microscopy and X-ray diffraction.
Abstract: The reverse transformation mechanism of martensite to austenite and the volume fraction of retained austenite have been studied in an Fe-3Si-13Cr-7Ni (wt-%) martensitic stainless steel by means of dilatometry, transmission electron microscopy and X-ray diffraction. Below a heating rate of 10 K s-1, the reverse transformation of α' to γ occurs by diffusion, whereas it occurs by a diffusionless shear mechanism above 10 K s-1. After reversion treatment at low temperatures, filmlike retained austenite is observed along α' lath boundaries, while reversion treatment at high temperatures produces granular retained austenite inside the α' laths in addition to filmlike retained austenite. The volume fraction of retained austenite at room temperature increases with increasing reversion treatment temperature, exhibiting a maximum at ~625° C, above which it decreases with increasing reversion temperature.
TL;DR: In this paper, Gaussian processes are used to model the tensile and creep rupture properties of superalloys as a function of their composition and processing parameters, making use of large databases on existing alloys.
Abstract: Models have been developed and used as tools to design a new 'made to measure' nickel base superalloy for power plant applications. In Part 1, Gaussian processes are used to model the tensile and creep rupture properties of superalloys as a function of their composition and processing parameters, making use of large databases on existing alloys. The models are able to estimate the actual influence of alloying elements on the mechanical properties over a wide range of temperature and stress. They have been used, in conjunction with general metallurgical concepts and industrial requirements, as a basis for the design of a new Ni-Cr-W-Al-Ti-Fe-Si-C-B superalloy with desirable properties. It is estimated that the proposed forgeable and weldable alloy should have a creep rupture life at 750° C of 100 000 h under a stress of 100 MPa, with a huge reduction in price compared to existing commercial alloys with similar properties. In a following paper, Part 2, an attempt is made to design against the format...
TL;DR: SiCp/Al composites containing high volume fraction SiC particles were fabricated using a pressure infiltration casting process, and their thermophysical properties such as thermal conductivity and coefficient of thermal expansion (CTE) were characterised as discussed by the authors.
Abstract: SiCp/Al composites containing high volume fraction SiC particles were fabricated using a pressure infiltration casting process, and their thermophysical properties, such as thermal conductivity and coefficient of thermal expansion (CTE), were characterised. High volume fraction SiC particulate preforms containing 50–70 vol.-%SiC particles were fabricated by ball milling and a pressing process, controlling the size of SiC particles and contents of an inorganic binder. 50–70 vol.-%SiCp/Al composites were fabricated by high pressure infiltration casting an Al melt into the SiC particulate preforms. Complete infiltration of the Al melt into SiC preform was successfully achieved through the optimisation of process parameters, such as temperature of Al melt, preheat temperature of preform, and infiltration pressure and infiltration time after pouring. Microstructures of 50–70 vol.-%SiCp/Al composites showed that pores resided preferentially at interfaces between the SiC particles and Al matrix with incr...
TL;DR: The precipitation and Ostwald ripening behavior of V4C3 particles during the tempering of a ternary Fe -C -V martensitic steel have been characterised and modelled, taking account of local equilibrium, the capillarity effect, and simultaneous cementite enrichment and dissolution as mentioned in this paper.
Abstract: The precipitation and Ostwald ripening behaviour of V4C3 (plate shaped) particles during the tempering of a ternary Fe - C - V martensitic steel have been characterised and modelled, taking account of local equilibrium, the capillarity effect, and simultaneous cementite enrichment and dissolution. Particles of V4C3 are represented as parabolic cylinders of revolution, with the tip radius chosen to yield the maximum lengthening rate. Transmission electron microscopy has been used to validate the theory; measurements of the average length, volume fraction, and number density of particles showed good agreement with experimental observations.
TL;DR: In this article, the potential of the microemulsion technique to synthesise different nanocrystalline ferrites (nickel ferrites, zinc ferrites) with such a narrow particle size distribution was illustrated.
Abstract: To use the unique properties of nanocrystalline ferrites in magneto-optical devices, it is important that they have a narrow particle size distribution. The present paper illustrates the potential of the microemulsion technique to synthesise different nanocrystalline ferrites (nickel ferrites, zinc ferrites) with such a narrow particle size distribution. The results of preliminary characterisation by field emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction are presented, confirming the nanocrystalline and spinel crystallographic structure of nickel ferrites.
TL;DR: In this paper, the authors review the literature on the diffusion of liquids through polymers that are undergoing large deformations, and discuss the difficulties associated with modelling such a process, the inadequacy of simple equations such as Fick's equation or Darcy's equation to describe the problem with regard to characterising the stresses and strains in the polymer through which the liquid is diffusing, and the change in its material properties during swelling and the need for an alternate approach.
Abstract: The intention of this overview is to review the literature on the diffusion of liquids through polymers that are undergoing large deformations, and to discuss the difficulties associated with modelling such a process. The inadequacy of simple equations such as Fick's equation or Darcy's equation to describe the problem with regard to characterising the stresses and strains in the polymer through which the liquid is diffusing, and the change in its material properties during swelling and the need for an alternate approach are discussed. Finally, the problem of swelling is studied within the context of the theory of mixtures and it is shown that such an approach is very well suited for the analysis of the problem.
TL;DR: In this paper, phase transitions in Ti-6Al-4V were studied by means of high temperature X-ray diffraction using a resistance heated furnace in high vacuum and Cu Kα radiation.
Abstract: Phase transitions in Ti-6Al-4V were studied by means of high temperature X-ray diffraction using a resistance heated furnace in high vacuum and Cu Kα radiation. The α and β phases could be observed conveniently using the (10.0), (00.2) and (10.1) peaks of the α structure and the (110) peak of the β. The phase composition of the specimen at selected times and temperatures was determined from spectra recorded in the range 32-45 ° (2θ), the scan time being ~8 min. The technique was successfully used to monitor the kinetics of the α-β transition during heating and the β-α transition during cooling, including the transformation kinetics during isothermal holds. Measurements of the interplanar distance change with temperature for the crystallographic planes of α and β phases enabled derivation of the overall thermal expansion for the alloy using a rule of mixtures.
TL;DR: Carbon based materials and clusters can have various structures and properties Apart from crystalstalline and ordered forms of carbon, a wide variety of disordered formsof carbon are there.
Abstract: Carbon based materials and clusters can have various structures and properties Apartfromcrystalline and ordered forms ofcarbon,a wide variety ofdisordered formsofcarbon are thereThese disordered or amorphouscarbons are of importance in many applications as well as in basic research Carbon black and glassy carbon are well known forms of disordered carbon and are widely used in industries There is also a potential application for disordered carbon as a scatterer material in a low temperature thermal nuclear reactor Depending on precursor materials and processing parameters, amorphous carbons can have different structures Investigations from various researchers have revealed a variety ofstructural models fromthe turbostratic model to paracrystalline,schwartzite or quinoidal models The bonding nature also varies from sp2 to sp3 or a mixture of both Different techniques are used to characterise these disordered carbons depending on their uses It includes diffraction studies, microscopy, spectr
TL;DR: In this article, the coarsening process of MX carbonitrides during creep and its effect on creep behavior have been investigated for P92 steel (9Cr-0.5Mo-1.8W-VNb).
Abstract: The coarsening process of MX carbonitrides during creep and its effect on creep behaviour have been investigated for P92 steel (9Cr-0.5Mo-1.8W-VNb). At 1023 K after long term aging, creep rupture strength and tertiary stage creep rate rapidly decrease and increase, respectively. The stress exponent n of minimum creep rate decreases with increasing temperature, and the value of n at 1023 K was evaluated to be 5.7. MX carbonitrides coarsen during creep and the coarsening process corresponds to the early stage of Ostwald ripening. Creep deformation accelerates the coarsening of the MX carbonitrides. At 1023 K, the coherent strain between the MX carbonitrides and matrix reduces to a negligibly small value at times longer than 550 h, leading to a decrease in the resistance to dislocation motion. This contributes to the rapid increase of creep rate in the tertiary stage and the abrupt decrease of creep rupture strength in the long term.
TL;DR: In this paper, it was shown that recrystallisation occurred with dissolution of the γ - γ eutectic phase in the dendritic core at 1300 ° C. Residual stresses assisted dissolution of existing phases.
Abstract: Nickel base superalloy CMSX - 2 single crystal bars were shot peened to induce surface residual stresses. Partial solutionising at 1300 ° C revealed a relationship between dissolution of the γ ′ phase into the matrix and recrystallisation. Recrystallisation occurred with dissolution of γ ′ phase in the dendritic core at 1300 ° C. Recrystallisation had preferentially begun at the dendritic core exposed at the shot peened surface and then gradually proceeded to the interdendritic regions. Phases more resistant to dissolution such as the coarse γ ′ particles and the γ - γ ′ eutectic phase in the interdendritic region dissolved into the matrix with recrystallisation, even at 1300 ° C, which is lower than the solutionising temperature of the alloy. Residual stresses assisted dissolution of the existing phases. The recrystallised grains grew preferentially in the dendritic core where rapid dissolution of γ ′ phase occurred. The growth of the recrystallised grains was impeded by the coarse γ ′ particles ...
TL;DR: Early initiation of surface cracks on grain boundaries normal to the applied stress caused a relatively high creep rate in surface recrystallised specimens as mentioned in this paper, however, the life under vacuum was reduced.
Abstract: Nickel based superalloy CMSX - 2 single crystal bars were shot peened to induce residual stresses at the surface. Full solutionising of shot peened specimens resulted in well developed recrystallised grains at the surface. Early initiation of surface cracks in recrystallised specimens at 982 ° C and 240 MPa in air did not reduce creep life, however, the life under vacuum was reduced. Early initiation of surface cracks on grain boundaries normal to the applied stress caused a relatively high creep rate in surface recrystallised specimens. Creep behaviour at 871 ° C, 500 MPa in air was similar to that at 982 ° C, 240 MPa under vacuum. Surface oxidation during creep at 982 ° C effectively hindered crack propagation, especially in recrystallised specimens.
TL;DR: In this paper, the effect of major and trace elements on the life of superalloys and coatings in the presence of pure Na2SO4, NaCl and vanadium containing environments is discussed.
Abstract: Modern gas turbine engines require high performance materials and coatings to ensure high efficiency. The selection of high performance materials and coatings depends on the nature and concentration of alloying elements. The composition of materials and coatings, in particular, plays a major role in enhancing the life of gas turbine engines by exhibiting good resistance to oxidation and hot corrosion, which are major problems in gas turbine engines. The performances of several superalloys containing different alloying elements and MCrAlY type coatings containing a variety of major and minor alloying elements are described in detail. The effect of major and trace elements on the life of superalloys and coatings in the presence of pure Na2SO4, NaCl and vanadium containing environments is detailed. The relevant reaction mechanisms leading to the failure of superalloys and coatings are discussed. The major factors involved when selecting alloying elements for the preparation of superalloys to manufact...
TL;DR: In this paper, the authors investigated the influence of different alloying conditions on the dissolution of zirconium in magnesium alloys and found that due to the highly alloyable microstructure of Zirmax, the dissolution was generally complete within a few minutes in the temperature range 730 to 780°C.
Abstract: To capitalise on the strengthening potential of zirconium as a potent grain refiner for magnesium alloys, the mechanisms of adding zirconium to magnesium and its subsequent grain refining action need to be understood. Using a Mg- 33.3Zr master alloy (Zirmax supplied by Magnesium Elektron Ltd) as a zirconium alloying additive, the influence of different alloying conditions on the dissolution of zirconium in magnesium was investigated. It was found that owing to the highly alloyable microstructure of Zirmax, the dissolution of zirconium was generally complete within a few minutes in the temperature range 730 to 780°C. Prolonging and/or intensifying stirring were found to have no conspicuous influence on further enhancing the dissolution of zirconium. In all cases studied, the average grain size increased with increasing holding time at temperature while the total zirconium content decreased. The finest grain structure and highest total zirconium content corresponded to sampling immediately after sti...
TL;DR: The CEC funded thematic network CREEPAL (BRRT -CT98 -5101) was established in 1998 to collect and disseminate information on the long term creep and thermal mechanical cycling behaviour of aluminium alloys as discussed by the authors.
Abstract: The CEC funded thematic network CREEPAL (BRRT -CT98 -5101) was established in 1998 to collect and disseminate information on the long term creep and thermal mechanical cycling behaviour of aluminium alloys. This paper presents some of the information gathered by consortium members and some additional industrial information related mainly to forging alloys. A short history of the use of aluminium alloys at elevated temperature is presented. The principal considerations required when evaluating aluminium alloys for use at temperatures in the 100-350°C range are detailed. The important microstructural mechanisms of creep in aluminium alloys are reviewed and the physical metallurgy of Hiduminium-RR.58 (2618A) is examined. The alloys that have found commercial application at elevated temperature are listed. Recent developments are described and opportunities for further development considered.
TL;DR: In the scratch test, the scratch velocity may suggest that low strain rates are valid, but the local strain rates can be many orders of magnitiude higher as exemplified by atomic force microscopy as mentioned in this paper.
Abstract: Atomic force microscopy and scanning electron microscopy techniques have been used to examine the surface deformation experienced by high density polyethylene during the scratch test. The scratch deformation process involves stretching of fibrils and microfibrils resulting in the formation of surface openings. At the molecular level the chains of molecules unfold and align in the direction of the moving indenter. In the scratch test, the scratch velocity may suggest that low strain rates are valid, but the local strain rates can be many orders of magnitiude higher as exemplified by atomic force microscopy. A number of modes of deformation are encountered during scratching. They include deformation bands, crazing, tearing, microcracking, regular cracking, and grooving. Crazing-tearing is the predominant mode of scratch deformation. It is envisaged that the sequence of tearing along the craze involves formation of deformation bands, development of craze, followed by tearing. Atomic force and scanni...
TL;DR: In this paper, the effect of atomic radius of alloying elements on the dimension of interstitial sites in the host alloy and the sublattice of TiCx has been studied using scanning and transmission electron microscopy.
Abstract: The effect of 0.2 wt-%C on the microstructure of beta titanium alloys Ti-15X(Fe, Cr, Mn, Mo, Ni, Co, Cu, and V) has been studied using scanning and transmission electron microscopy. It has been found that coarse eutectic TiCx tends to be formed in beta titanium alloys containing Fe, Cr, Mo, and Mn, and relatively finer homogeneous TiCx is formed in alloys containing V, Ta, Co, Ni, or Cu. The volume fraction of TiCx in alloys containing Cu, Co, and Ni is much less than that in other beta titanium alloys. The oxygen content of the matrix is lower than that of Ti2C in Cr or alloys containing Mn and higher than that of Ti2C in alloys containing Mo or Ni. These observations are discussed in terms of the role of phase diagrams and the effect of atomic radius of alloying elements on the dimension of interstitial sites in the host alloy and the sublattice of TiCx.
TL;DR: In this article, the deformation microstructures and local textures in a high purity Al 0.3 wt −%Mn alloy with two different initial grain sizes, have been investigated after cold rolling and annealing, using high resolution electron backscattered diffraction.
Abstract: The deformation microstructures and local textures in a high purity Al–0.3 wt–%Mn alloy with two different initial grain sizes, have been investigated after cold rolling and annealing, using high resolution electron backscattered diffraction. It was found that in contrast to a recently investigated Al–1.3 wt–%Mn alloy, recrystallisation preceded precipitation, and that the deformation and recrystallisation were generally similar to other single phase aluminium alloys. In the large grained material, it was found that the evolution of the deformation microstructure was strongly dependent on the grain orientation, and that this in turn strongly affected the grain size, texture, and heterogeneity of the material on recrystallisation. In contrast, the finer grained material developed more homogeneous microstructures, and the deformation and annealing textures were typical of those reported for dilute aluminium alloys.
TL;DR: In this article, a TEM of the as quenched and tempered C-Mn-Cr steels was performed and the results showed that the YS/UTS ratio was usually of the order of 0.9.
Abstract: Improved grades of cast steels were prepared by microalloying C–Mn–Cr steels (0.15–0.22C, wt-%) with V (0.1)+Ti (0.01) or V (0.11)+Nb (0.034)+Ti (0.01) combinations. When quenched and tempered an ultimate tensile strength (UTS) of the order of 784–1078 MPa (80–110 kg mm2) and an elongation ranging from 10 to 35% were achieved. However, the YS/UTS ratio was usually of the order of 0.9, which indicates that these steels did not undergo enough plastic deformation before failure under tensile stress. Examination by TEM of the as quenched as well as the quenched and tempered samples yielded the following information. All the as quenched steels had lath martensite morphology with retained austenite entrapped in the interlath region. After water quenching from 950°C an appreciable volume fraction of undissolved precipitates remained in the steels. Retained austenite broke down during tempering at 400°C and above producing a chain of rod like carbides. During tempering partial recrystallisation of the lat...
TL;DR: In this paper, an improved model is described to predict variations in fracture toughness of high strength aluminium alloys with volume fraction, size, and characteristics of the contained multiscale second phases, in an integrated manner.
Abstract: An improved model is described to predict variations in fracture toughness of high strength aluminium alloys with volume fraction, size, and characteristics of the contained multiscale second phases, i.e. ellipse shaped constituents, sphere shaped dispersoids, and disc shaped precipitates, in an integrated manner. Results show that predictions are in broad agreement with values measured experimentally for an aged Al-Cu-Mg alloy. Furthermore, the model was employed torelate the anisotropic fracture toughness ofalloy plate to its orientation. A diagramis presented to illustrate the relationship between yield strength and fracture toughness of the aged alloy.