Zener Pinning Pressure in Tempered Martensite Lath Structure

2012 ◽  
Vol 715-716 ◽  
pp. 745-750 ◽  
Author(s):  
Dmitro Kolesnikov ◽  
Andrey Belyakov ◽  
Alla Kipelova ◽  
Valeriy Dudko ◽  
Rustam Kaibyshev ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Metallic Matrix ◽  
Laves Phase ◽  
Second Phase ◽  
Tempered Martensite ◽  
Creep Tests ◽  
Zener Pinning ◽  
Second Phase Particles ◽  
Lath Structure

The Zener drag force exerted by M23C6carbides, Fe2(W,Mo) Laves phase and M(C,N) particles for migration of different grain boundaries in P92-type and P911+3%Co heat-resistant steels was calculated. In particular, the prior austenite grain boundaries (PAGB), boundaries of packets and blocks, which are mainly high-angle boundaries (HAGB), were addressed. Zener pinning pressures were determined for each type of dispersoids separately taking into account that the M23C6carbides, Fe2(W,Mo) Laves phase are inhomogeneously distributed such that they are mainly located at the boundaries, and the M(C,N) dispersoids are uniformly distributed throughout the metallic matrix. In the both steels, the pinning pressure from the second phase particles located at grain boundaries is about an order of magnitude higher than that caused by homogeneously distributed MX precipitates. In spite of numerous second phase particles precipitated during tempering, grain growth (although rather moderate) occurred during the creep tests of the studied materials. The driving pressure for grain boundary motion might be mostly associated with high dislocation density retained in the tempered martensite structure. The resulting pressure for grain growth in the P92-type steel under creep conditions at 600 and 650°C is somewhat higher than that for the P911 steel.

Grain Growth in Materials with Mobile Second-Phase Particles

2007 ◽  
Vol 558-559 ◽  
pp. 1021-1028 ◽  
Author(s):  
Vladimir Yu. Novikov
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Second Phase ◽  
Particle Volume ◽  
First Case ◽  
Second Phase Particles ◽  
Material Volume

Grain growth controlled by particles able to move together with grain boundaries is investigated by means of numerical simulation. The particles either located on grain boundaries or randomly distributed over the material volume are shown to retard the growth process. In the first case the growth kinetics is described by a power law Dn −D0 n = kt with the exponent n≤ 3. Growth kinetics under the influence of randomly distributed mobile particles can be approximated by the same law with the exponent n increasing with an increase in the particle volume fraction.

Evolution of Laves-Phase Particles in a Low Carbon 9%Cr Martensitic Steel during Creep at 650°C

2014 ◽  
Vol 922 ◽  
pp. 155-160 ◽  
Author(s):  
Irina Fedorova ◽  
Andrey Belyakov ◽  
Pavel Kozlov ◽  
Vladimir Skorobogatykh ◽  
Izabella Schenkova ◽  
...  
Keyword(s):  
Structural Changes ◽  
Laves Phase ◽  
Second Phase ◽  
Low Carbon ◽  
Creep Tests ◽  
Creep Time ◽  
Term Creep ◽  
Lath Structure ◽  
Evolution Of Microstructure ◽  
Relationship Of

The evolution of microstructure in low carbon heat resistant steel of P92-type modified with 3%Co was examined during creep tests at 923K for 500, 1500, 6000 and 16000 hours. After tempering at 1023K (750°C), the steel was composed of martensite lath structure with numerous precipitates of MX-type carbonitrides and rare M23C6-type carbides. The structural changes during creep tests are characterized by an increase in the sizes of laths and second phase particles. Moreover, the Fe2W Laves-phase precipitates during long-term creep. The Laves-phase particles grow accordingly to power-law relationship of creep time.

scholarly journals Strain Induced Abnormal Grain Growth in Nickel Base Superalloys

2013 ◽  
Vol 753 ◽  
pp. 321-324 ◽  
Author(s):  
Nathalie Bozzolo ◽  
Andrea Agnoli ◽  
Nadia Souaï ◽  
Marc Bernacki ◽  
Roland E. Logé
Keyword(s):  
Grain Growth ◽  
Boundary Migration ◽  
Energy Difference ◽  
Abnormal Grain Growth ◽  
Second Phase ◽  
Zener Pinning ◽  
Second Phase Particles ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
Key Parameter

Under certain circumstances abnormal grain growth occurs in Nickel base superalloys during thermomechanical forming. Second phase particles are involved in the phenomenon, since they obviously do not hinder the motion of some boundaries, but the key parameter is here the stored energy difference between adjacent grains. It induces an additional driving force for grain boundary migration that may be large enough to overcome the Zener pinning pressure. In addition, the abnormal grains have a high density of twins, which is likely due to the increased growth rate.

Microstructure Evolution in a P911 Steel under Creep Conditions

2011 ◽  
Vol 409 ◽  
pp. 223-227
Author(s):  
Alla Kipelova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Microstructure Evolution ◽  
Second Phase ◽  
Tempered Martensite ◽  
Laves Phases ◽  
Heat Resistant Steel ◽  
Second Phase Particles ◽  
Austenite Grains ◽  
The Stability ◽  
Lath Structure ◽  
Carbide Particles

Microstructure evolution in a P911 heat resistant steel was examined under conditions of aging and creep at a temperature of 600°C and an applied stress of 200 MPa. The tempered martensite lath structure (TMLS) evolved after heat treatment consisted of prior austenite grains (PAG), packets, blocks and laths. The mean transverse lath size and the interior dislocation density were about 345 nm and 3.5 × 1014 m-2, respectively. Various second phase particles precipitated upon tempering. Fine MX carbonitrides were homogeneously distributed throughout the tempered martensite laths, while relatively coarse M23C6 carbide particles were located on high-and low-angle boundaries. Upon creep test, precipitation of Laves phases was found. The stability of TMLS during creep is discussed in detail.

Effect of Particle Size on the Zener Limit: A Monte Carlo Simulation Approach

2012 ◽  
Vol 560-561 ◽  
pp. 152-155 ◽  
Author(s):  
Kalale Raghavendra Rao Phaneesh ◽  
Anirudh Bhat ◽  
Gautam Mukherjee ◽  
Kishore T. Kashyap
Keyword(s):  
Monte Carlo Simulation ◽  
Particle Size ◽  
Grain Size ◽  
Monte Carlo ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Second Phase ◽  
Particle Sizes ◽  
Second Phase Particles ◽  
Average Grain Size

2D Potts model Monte Carlo simulation was carried out on a square lattice to investigate the effects of varying the size of second phase particles on the Zener limit of grain growth, in two-phase polycrystals. Simulations were carried out on a 1000^2 size matrix with Q-state of 64, dispersed with second phase particles of various sizes and surface fractions, and run to stagnation. Different grain growth parameters such as mean grain size, largest grain size, fraction of second phase particles lying on grain boundaries, etc., were computed for the pinned microstructures. The pinned average grain size or the Zener limit increased with increase in particle size, as per the classic Smith-Zener equation. The Zener limit scaled inversely with the square root of the particle fraction for all particle sizes, while it scaled exponentially with the fraction of second phase particles lying on the grain boundaries (ϕ), for all particle sizes tested.

Morphology of Σ3{/70.53°} grain boundaries in a C15 intermetallic compound

1994 ◽  
Vol 52 ◽  
pp. 684-685
Author(s):  
Fuming Chu ◽  
D. P. Pope ◽  
D. S. Zhou ◽  
T. E. Mitchell
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Crystallographic Analysis ◽  
Laves Phase ◽  
Second Phase ◽  
Bright Field Image ◽  
Boundary Edge ◽  
Arc Melting ◽  
Fcc Lattice ◽  
Diffraction Patterns

A C15 Laves phase, HfV2+Nb, shows promising mechanical properties and here we describe the structure of its grain boundaries. The C15 Laves phase has a fcc lattice with a=7.4Å. An alloy of composition Hf14V64Nb22 (including a C15 matrix and a second phase of V-rich bcc solution) was made by arc-melting. The alloy was homogenized at 1200°C for 120h. Preliminary study concentrated on Σ3{<110>/70.53°} grain boundaries in the C15 phase using Philips 400T and CM 30 microscopes.The most-commonly observed morphology of Σ3{<110>/70.53°} grain boundaries in the C15 phase is a faceted boundary. A bright field image (BFI) of the faceted boundary and the corresponding diffraction patterns with the grain boundary edge-on are shown in Fig. 1(a). From the diffraction patterns using a <110> zone axis for both grains, it is obvious that this is a Σ3{<110>/70.53°} grain boundary. Crystallographic analysis shows that the Σ3{<110>/70.53°} grain boundaries selectively facet with the following relationships between the two grains: {111}1//{111}2, {112}1//{112}2, {111}1//{115}2, and {001}1//{221}2.

Structural Changes in a 9%Cr Creep Resistant Steel during Creep Test

2012 ◽  
Vol 715-716 ◽  
pp. 895-900
Author(s):  
Valeriy Dudko ◽  
Andrey Belyakov ◽  
Vladimir Skorobogatykh ◽  
Izabella Schenkova ◽  
Rustam Kaibyshev
Keyword(s):  
Structural Changes ◽  
Subgrain Size ◽  
Large Strain ◽  
Particle Growth ◽  
Second Phase ◽  
Second Phase Particles ◽  
Creep Rupture Test ◽  
Lath Structure ◽  
Creep Regime ◽  
Effective Stabilization

Structural changes in a 9%Cr martensitic steel after 1%, 4% creep and creep rupture test at 650°C and stress of 118 MPa were examined. Heat treatment provided the formation of tempered martensite lath structure (TMLS) in the steel. The precipitations of second phase particles along block and lath boundaries provide effective stabilization of the TMSL under annealing/aging condition. This structure hardly changed under creep conditions in grip portion of crept sample. Significant coarsening of both the second phase particles and the martensite laths takes place in neck portion. In addition, the latter ones lose their original morphology and are replaced by large strain-induced subgrains. It should be noted that the increase of subgrain size is in almost direct proportion to the particle growth during the creep to 4% strain. The rapid growth of martesite laths followed by their evolution to deformation subgrains takes place within the tertiary creep regime.

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