Sökning: "Coarsening"

Visar resultat 21 - 25 av 58 avhandlingar innehållade ordet Coarsening.

1. 21. Evolution of Microstructure in Two Austenitic Alloys at High Temperatures

   Författare :Jenny M Erneman; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; N ; Thermo-Calc; Nb C; gamma prime; DICTRA; APFIM; quantitative metallography; AISI 347; Alloy 800; energy filtered TEM; sigma phase;

   Sammanfattning : A niobium stabilised AISI 347 austenitic stainless steel was investigated after static ageing and creep deformation at temperatures between 500°C and 800°C for times up to 88 000 h. Coarse and fine NbX precipitates and also s-phase precipitates were formed in the temperature range 500-700°C. LÄS MER

3. 22. Phase equilibria and thermodynamic properties of high-alloy tool steels : theoretical and experimental approach

   Författare :Johan Bratberg; John Ågren; Bengt Hallstedt; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; thermodynamic modelling; thermodynamic calculations; tool steels; high-speed steels; CALPHAD; Other materials science; Övrig teknisk materialvetenskap;

   Sammanfattning : The recent development of tool steels and high-speed steels has led to a significant increase in alloy additions, such as Co, Cr, Mo, N, V, and W. Knowledge about the phase relations in these multicomponent alloys, that is, the relative stability between different carbides or the solubility of different elements in the carbides and in the matrix phase, is essential for understanding the behaviour of these alloys in heat treatments. LÄS MER

4. 23. Melt convection in welding and crystal growth

   Författare :Minh Do-Quang; Gustav Amberg; Andreas Ludwig; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering physics; thermocapillary convection; gas-tungsten arc welding; floating zone; parallel computing; finite element method; Teknisk fysik; Engineering physics; Teknisk fysik;

   Sammanfattning : A parallel finite element code with adaptive meshing was developed and used to study three dimensional, time-dependent fluid flows caused by thermocapillary convection as well as temperature and dopant distribution in fusion welding and floating zone crystal growth. A comprehensive numerical model of the three dimensional time-dependent fluid flows in a weld pool had been developed. LÄS MER

5. 24. Modelling the microstructural changes in steels due to fusion welding

   Författare :John Ion; Luleå tekniska universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Materialteknik; Engineering Materials;

   Sammanfattning : Theoretical, physically-based models of fusion welding are developed, and calibrated using experimental data from practical welds. The following heat-affected zone phenomena are investigated: grain growth, precipitate dissolution and coarsening, martensite formation and hardness. LÄS MER

7. 25. Creep modelling of particle strengthened steels

   Författare :Hans Magnusson; Rolf Sandström; Göran Engberg; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Particle strengthening; dislocation climb; ferritic steels; dislocation evolution; creep rate modelling; Materials science; Teknisk materialvetenskap;

   Sammanfattning : Materials to be used in thermal power plants have to resist creep deformation for time periods up to 30 years. The role of alloying elements for creep strength of 9-12% Cr steels is analysed. The creep strength in these steels relies on minor additions of alloying elements. LÄS MER