Philosophical Magazine A最新文献

{"title":"Approaches to modelling chemically induced transformation superplasticity","authors":"C. Schuh","doi":"10.1080/01418610208240045","DOIUrl":"https://doi.org/10.1080/01418610208240045","url":null,"abstract":"Abstract Transformation superplasticity is a Newtonian deformation mechanism observed when polymorphic materials are subjected to small external stresses during their phase transformation. Although mostly studied during thermal excursions, recent investigations have observed this mechanism during excursions in chemical composition in the Ti-H system. In this work, methodologies for modelling this so-called ‘chemically induced transformation superplasticity’ are discussed, simultaneously considering the kinetic moving-boundary diffusion problem associated with the titanium α-β transformation, as well as the internal strains due to chemical swelling and the transformation. Two existing models, including, firstly, an analytical model for thermal-cycling-induced transformation superplasticity and, secondly, a numerical model for creep under conditions of chemical cycling, are adapted to the case of chemically induced transformation superplasticity. Both modelling approaches predict the main features of transformation superplasticity and are found to agree reasonably with the existing experimental data.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123935560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fracture in nanolamellar materials: Continuum and atomistic models with application to titanium aluminides","authors":"A. Ramasubramaniam, W. Curtin, D. Farkas","doi":"10.1080/01418610208240043","DOIUrl":"https://doi.org/10.1080/01418610208240043","url":null,"abstract":"Abstract Molecular statics simulations of crack growth in fully lamellar Ti-Al are performed to elucidate the role of lamellar structure in determining deformation and fracture toughness in nanoscale structures. The lamellar boundaries are highly effective in inhibiting dislocation transfer from one phase into the other, indicating that interfacial dislocation pinning influences the competition between dislocation emission and cleavage. A continuum model for dislocation emission and cleavage fracture of blunted cracks is thus extended to account for dislocation shielding and crack blunting in nanolamellar materials, leading to material classifications of brittle (cleavage with no dislocation emission), ductile (dislocation emission with no cleavage) and quasiductile (dislocation emission followed by cleavage). In the quasiductile regime, the material toughness is predicted to scale with the square root of the lamellar thickness, that is thicker lamellae are tougher, and the number of emitted dislocations at cleavage scales linearly with the lamellar thickness. Simulations of crack growth in nanoscale γ-TiAl surrounded by α2-Ti3Al show quasiductile behaviour with the fracture toughness and number of emitted dislocations scaling as predicted by the model. Simulations of crack growth in α2 surrounded by γ layers show no evidence of cleavage fracture, and hence this phase is ductile. Cracks at the γ-α2 interface are found to blunt and deflect into the γ phase, showing that this interface is not a low-toughness boundary. The fracture toughnesses computed for the γ-TiAl are comparable with those measured experimentally on oriented polysynthetically twinned crystals of Ti-Al. These results indicate that, (i) nanoscale material toughness may scale with grain size owing to the inhibition of dislocation propagation by grain boundaries or interfaces, (ii) the fracture toughness in fully lamellar Ti-Al microstructures is controlled by thin layers of TiAl sandwiched between Ti3Al layers and, (iii) the microcracking observed in these materials may be caused by the spatial variations in TiAl lamellar thickness intrinsic to these microstructures.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115159935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cyclic deformation behaviour and dislocation structure of Ti-5 at.% Al single crystals oriented for double prism slip","authors":"L. Xiao, Y. Umakoshi","doi":"10.1080/01418610208240042","DOIUrl":"https://doi.org/10.1080/01418610208240042","url":null,"abstract":"Abstract Cyclic deformation behaviour of Ti-5at.%Al single crystals oriented for [21 10] was investigated in the total (i.e. elastic + plastic) axial strain amplitude from 0.195% to 0.798% at room temperature in air. The crystals displayed an initial cyclic hardening followed by a striking softening period, and then a saturation stage was reached at different cyclic strain amplitudes, except at the lowest of 0.195% at which the initial hardening stage was absent. The cyclic stress-strain curve in Ti-5 at.% Al single crystal with double prism slip contains a clear plateau with a saturation shear stress of 86–89 MPa over the complete range of applied strain amplitudes. (1010) and (1100) double-prism-slip systems can be distinguished from the traces on the (0001) surface by trace analysis with an optical microscope. Slip marking is planar and becomes denser as the cyclic strain amplitude increases. Two groups of planar dislocation lines lying along the (1010) and (1100) prism plane traces were determined from the (0001) reflection by transmission electron microscopy. The typical dislocation configuration is planar dislocation bands parallel to the [0001] direction in a foil with a (1010) normal; however, long straight dislocations are formed in a (1100) foil. Both the width and the spacing of the slip bands decrease with increase in the cyclic strain amplitude in the (1010) primary slip plane. Finally, the relationship between cyclic plateau behaviour and the saturation dislocation structure of Ti-5 at.% Al single crystals is discussed.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133651172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of shock-wave loading on transformation temperatures, elastic and anelastic properties of β1 Cu-Al-Ni martensitic single crystals","authors":"S. Golyandin, S. Kustov, S. Nikanorov, K. Sapozhnikov, A. Sinani, J. Humbeeck, R. Schaller, R. Batist","doi":"10.1080/01418610208240044","DOIUrl":"https://doi.org/10.1080/01418610208240044","url":null,"abstract":"Abstract The effect of high-velocity impact loading on the structure, transformation temperatures, elastic and anelastic properties has been studied for a Cu-Al-Ni shape memory alloy in the β′1 martensitic phase. The impact loading of crystals has been performed by means of a light gas gun, producing compressive plane-strain wave pulses with a duration of about 2 × 10−6 s. The normal component of stress in the direction of the strain wave propagation ranged from 0.5 to 5 GPa and was used as a characteristic of the impact magnitude. The influence of the impact loading on the transformation temperatures and the structure of martenistic variants cannot be discerned in the present experimental results. In contrast with the macroscopic properties of crystals, the elastic and anelastic properties, studied at a frequency of about 100 kHz, are found to be strongly influenced by the impact loading. The difference between the effects of the impact on elastic and anelastic properties and on the macroscopic performance of crystals is interpreted on the assumption that these properties are related to different structural entities. Changes in the system of partial dislocations in the faulted martensite and variations in internal stresses are considered as basic contributors to the observed elastic and anelastic effects. The stability of the temperature range and hysteresis of the martensitic transformation are ascribed to the rather stable (under the present impact conditions) martensitic variant structure.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"441 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131537921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal evolution of deformation zones around microindentations in different types of crystal","authors":"D. Grabco, B. Pushcash, M. Dyntu, O. Shikimaka","doi":"10.1080/01418610208235731","DOIUrl":"https://doi.org/10.1080/01418610208235731","url":null,"abstract":"Abstract Several structural levels of plastic deformation (the superdefect zone, the quasidestructured region, the region with a high dislocation density, the peripheral zone and the region of elastic deformation) have been distinguished around microindentations of various crystal types. The real structure of the deformed zone essentially depends on both the crystal type and the deformation temperature. Four temperature stages (brittle, brittle-plastic, plastic and ductile-plastic) have been noted in the wide temperature interval (T ≈ (0.1-0.9)T ml). It has been revealed that crystals with various types of bond can undergo similar thermal evolution behaviours of the defect structure around the indentation.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115266157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of the adhesion of TiN films using nanoindentation and scratch testing","authors":"M. Toparli, S. Sasaki","doi":"10.1080/01418610208235729","DOIUrl":"https://doi.org/10.1080/01418610208235729","url":null,"abstract":"Abstract The scratch test method is applied to the coated sample using a diamond indenter. This sample is displaced at a constant speed and certain load damage occurs along the scratch path. Using a nanoindentation and nanoscratch technique, the mechanical properties of physically vapour-deposited films were investigated experimentally and numerically. In order to evaluate the microhardness and adhesive properties of thin films, we applied a nanoindentation and scratch test experimentally. The TiN films were deposited on silicon wafers at a thickness of about 1.2 μm by physical vapour deposition. The elastic stress distribution was calculated on the coating material for different loads, friction coefficients and directions using three-dimensional finite-element models. A FORTRAN computer program was developed for the study. The coating material was assumed to be a homogeneous, isotropic and infinite body. This paper compares the measured critical load and calculated critical load for different directions using the scratch test and finite-element method respectively. It has been seen that agreement is reasonably good.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116844772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Indentation hysteresis of glassy carbon materials","authors":"N. Iwashita, J. Field, M. Swain","doi":"10.1080/01418610208235699","DOIUrl":"https://doi.org/10.1080/01418610208235699","url":null,"abstract":"Abstract Indentation hysteresis during both pointed and spherical indentation is a common feature of the observed force-displacement response of glassy carbon materials. Field and Swain proposed a method of analysis of this behaviour with spherical indenters in the form of classic indentation stress-strain curves. They also proposed that the response resulted from limited reversible slip of the graphite-like nanocrystalline structure of these so-called glassy carbon materials. The present work extends the previous study by investigating the influence of the nanocrystalline grain size and the hysteretic response with indenters of sharper apical angle. It is found that the extent of the hysteresis is dependent upon the grain size as is the contact stress for the initiation of yielding. The critical strain for the onset of non-recoverable hysteretic response is clearly identified with sharper-apical-angle indenters. This irreversibility of the hysteretic response is discussed in terms of an analysis proposed by Brown whereby the critical limit for the strain for reversible hysteretic behaviour was related to the percolation limit for plastic shear strain sites within a material.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"304 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115908568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Finite-element analysis of deformation during indentation and scratch tests on elastic-perfectly plastic materials","authors":"J. Bucaille, E. Felder","doi":"10.1080/01418610208235712","DOIUrl":"https://doi.org/10.1080/01418610208235712","url":null,"abstract":"Abstract We have studied the distribution of plastic strain around normal indentation and scratches in elastic-perfectly plastic materials. A three-dimensional finite-element analysis of a cone scratching and indenting elastic-perfectly plastic materials is presented. The indenter is the axisymmetric equivalent cone of the Berkovich indenter, with semiapical angle θ = 70.3°. The plastic behaviour of the material is modelled with the yield stress σ0. No strain hardening and no sensitivity to the strain rate occur. The elasticity of the material is modelled with Young's modulus E, which varies from 2.79 to 2793 GPa. In fact, the behaviour of the scratched or indented material depends on the parameter X = (E/σ0) cotθ, called the rheological factor (X = 1, …, 1000). For small rheological factors, the deformation is mainly elastic; for high rheological factors, the deformation is essentially plastic, and in this case the behaviour of the material is close to the behaviour of a metal. The contact between the indenter and the mesh is frictionless. We have defined a mean representative strain in indentation and scratch tests. This value is independent of the scratch length and the penetration depth. It has been shown that the mean representative strain increases with X, and that it is larger in scratch tests than in indentation tests.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117229520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The transition from elastic to plastic behaviour in an Al-Cu-Fe quasicrystal studied by cyclic nanoindentation","authors":"S. Dub, N. Novikov, Y. Milman","doi":"10.1080/01418610208235725","DOIUrl":"https://doi.org/10.1080/01418610208235725","url":null,"abstract":"Abstract Comparative mechanical tests of an Al-Cu-Fe quasicrystal and a tungsten (001) single crystal have been carried out using cyclic nanoindentation by a Berkovich indenter. The first loading-unloading cycle up to 30 mN formed the initial indent. On reloading of the indenter up to 50 mN, a transition from elastic to plastic deformation of the material was observed. To reveal the region of the transition better, the reloading curve was differentiated with respect to time. It was found that, for tungsten, the transition from elastic to plastic behaviour was smooth. The transition began at 25 mN and terminated at 34mN only. During the transition the strain rate in the indent trebled. In the Al-Cu-Fe quasicrystal, the transition from elastic to plastic deformation was very abrupt. No evidence of plastic deformation in the indent was observed up to 32 mN. Only a further increase in the load by 0.35mN caused the onset of plastic deformation. A pop-in was observed in the reloading curve at this point. The displacement increased by about 10 nm and the pressure in the indent dropped by 360 MPa. This was probably due to the destruction of the quasicrystalline structure and the formation of the crystalline structure. A plastic crystalline phase appeared to be pressed between the indenter and the hard quasicrystal substrate and then to be extruded from the indent. Because of this, the pressure in the quasicrystal drops during the transition from elastic to plastic deformation.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128440409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The activation energies of antiphase-boundary tube annihilation in Fe-Al","authors":"D. Wu, I. Baker","doi":"10.1080/01418610208235735","DOIUrl":"https://doi.org/10.1080/01418610208235735","url":null,"abstract":"Abstract Analysis of the exothermic peaks obtained at different heating rates during continuous heating in a differential scanning calorimeter of a quenched B2-structured Fe-40at.% Al single crystal yielded a value for the activation energy for vacancy annihilation of 131 ± 8 kJ mol−1, which is very close to the accepted value. Having shown the utility of this method, it was used to determine the activation energies associated with the annihilation of antiphase-boundary (APB) tubes from cold-rolled Fe-40at.% Al and Fe-83 at. % Al single crystals. The activation energies obtained were 101 ± 9kJ mor−1 and 67 ± 9kJ mol−1 respectively. Magnetic measurements showed that the rolled Fe-43 at.% Al specimens need less time and a lower temperature to anneal out the APB tubes produced during rolling compared with Fe-40 at.% Al specimens, consistent with the lower activation energy in this alloy.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129911438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}