摘要 :
The work presented in this paper focuses on the effect of the presence of non-equilibrium -ferrite on the impact properties of a supermartensitic stainless steel. To generate homogeneous -ferrite containing microstructures the mat...
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The work presented in this paper focuses on the effect of the presence of non-equilibrium -ferrite on the impact properties of a supermartensitic stainless steel. To generate homogeneous -ferrite containing microstructures the material was, in the first part of the present study, subjected to a series of high temperature furnace heat treatments. Three microstructures possessing variable ferrite content and different grain sizes were generated. Charpy impact results indicate that the presence of 14% -ferrite in a martensitic matrix of 60 m prior austenite grain size, raises the ductile to brittle transition temperature (DBTT) by about 50°C compared with a fully martensitic microstructure of 80 m. For a similar grain size, reducing the amount of -ferrite from 14 to 2% restored the DBTT to a level comparable to that of the tempered parent material. A Gleeble simulator was used to create the range of microstructures found in a weld heat affected zone (HAZ). Testing of the simulated HAZ indicated that toughness was not significantly affected by the presence of -ferrite. The DBTT was comparable to that of the parent material and lower than that of the heat treated specimens containing 14% -ferrite.
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摘要 :
Mixed microstructures consisting of fine plates of upper bainitic ferrite separated by thin films of stable retained austenite have seen many applications in recent years because of their impressive combination of strength and tou...
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Mixed microstructures consisting of fine plates of upper bainitic ferrite separated by thin films of stable retained austenite have seen many applications in recent years because of their impressive combination of strength and toughness. There may also be some martensite present in the microstructure, but its formation can be controlled increasing the stability of the retained austenite. On the other hand, carbides are avoided by the judicious use f silicon as an alloying element. The aim of the present work was to see how far these concepts an be extended in the order to achieve the highest ever combination of strength and toughness in bulk-samples subjected to continuous cooling transformation.
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摘要 :
A Gaussian processes computer program has been used to model the mechanical properties of polycrystalline nickel-base superalloys as a function of their chemical composition and heat treatment. The models are able to reproduce wel...
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A Gaussian processes computer program has been used to model the mechanical properties of polycrystalline nickel-base superalloys as a function of their chemical composition and heat treatment. The models are able to reproduce well-known metallurgical trends, and to estimate the behaviour of new alloys. On this basis, several new creep-resistant alloys for power plant applications have been proposed. The candidate alloys have been scrutinised further using phase diagram calculations to reveal their equilibrium phase constitutions. This design process has led to a shortlist of alloys on the basis of their expected properties, microsructural stability and cost.
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摘要 :
The abilities of artificial neural networks and Gaussian processes to model the yield strength of nickel-base superalloys as a function of composition and temperature have been compared on the basis of simple well-known metallurgi...
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The abilities of artificial neural networks and Gaussian processes to model the yield strength of nickel-base superalloys as a function of composition and temperature have been compared on the basis of simple well-known metallurgical trends (influence of Ti, Al, Co, Mo, W, Ta, of the Ti/Al ratio, γ' volume fraction and the testing temperature). The methodologies are found to give similar results, and are able to predict the behaviour of materials that were not shown to the models during their creation. The Gaussian process modelling method is the simpler method to use, but its computational cost becomes larger than that of neural networks for large data sets.
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摘要 :
A general method for brazing ceramics to metals using a compliant metallic foam as a buffer layer has been developed. Using stainless steel foams, bonds between alumina and 316 stainless steel with shear strengths up to 33 MPa hav...
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A general method for brazing ceramics to metals using a compliant metallic foam as a buffer layer has been developed. Using stainless steel foams, bonds between alumina and 316 stainless steel with shear strengths up to 33 MPa have been achieved. The resultant ductility enhances the resistance of the joint to thermal cycling; AlN-Inconel 600 bonds exhibited good thermal shock resistance. Alumina-stainless steel bonds withstood more that 60 thermal cycles between 200 and 800 ℃ in air.
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