The Formation Energy of Martensite Nuclei and the Phase Transition Kinetics under the Action of an External Magnetic Field

The formation energy of martensite nuclei in the austenite matrix is calculated. Nanoclusters with ferromagnetic order, which exist in austenite above the Curie temperature, reduce the formation energy of a critical martensite nucleation center when exposed to an external magnetic field. The data obtained are explained by the magnetic separation of the initial phase under the action of a magnetic field. A fluctuation increase in nanovolumes with a ferromagnetic order in austenite increases the energy in a atoms group of the matrix phase with a parallel spins arrangement. As a result, the nucleation rate of the martensite phase increases and the martensitic transformation proceeds more completely.

Features of Martensitic Transformation in Steel during Quenching in a Constant Magnetic Field

The data on the occurrence of martensitic transformation in steel under the action of a magnetic field were obtained by the electric resistivity method. The obtained data indicate the possibility of stress-assisted martensite formation in the temperature range of Ms-Md (in which superplasticity of austenite is observed). This possibility is due to the magnetic heterogeneity of austenite. Nanosized regions with a ferromagnetic order are present in the paramagnetic matrix. They can perceive the energy of the external magnetic field through the magnetostrictive stresses and change the fields of the elastic forces in the crystal lattice. All this leads to a decrease in the energy of formation of the nucleation center.

Влияние электромиграции на зарождение вакансионных островков на поверхности Si(100) при сублимации

By means of in situ ultrahigh vacuum reflection electron microscopy, the nucleation of vacancy islands on wide terraces of the Si(100) surface is investigated. The temperature dependence of the displacement of a vacancy island nucleation center is determined in the process of heating a sample with a dc electric current. On the basis of a theoretical model, the effective electric charge of addimers is estimated in the direction across dimer rows of the surface. The effective charge has a positive sign and does not exceed 15 units of the elementary charge in the temperature range of 1020–1120°C.

Electroless Deposition of Ni-P/SiO2 Composite Coating

Electroless deposit Ni–P/SiO2 composite coating was performed on the steel substrate, DIN EN 10130. The preparation of nickel coating included two main steps. In the first step, the fraction of SiO2 particles sized the tens of nanometres was obtained by sedimentation. In the second step, the composite coating was plated on the steel substrate. The actual deposition process contains the deposition of plain Ni-P interlayer which served as the nucleation center for the deposition of Ni-P/SiO2 composite coating with co-deposited SiO2 particles. The morphology of deposited composite coating was studied by scanning electron microscope (SEM). Amount of individual elements in deposited coatings was determinated by EDS analysis. The microhardness of deposited composite coating was subsequently compared with microhardness value of the plain Ni–P coating.

A polydopamine layer as the nucleation center of MOF deposition on “inert” polymer surfaces to fabricate hierarchically structured porous films

Polydopamine could be used as an effective nucleation center for MOF deposition on “inert” polymer membranes, affording hierarchically structured porous films.

Effect of Al2Ca Compound on Microstructure of As-Cast AZ31 and AZ61 Alloys

The inoculation effect of Al2Ca intermetallic compound on microstructure evolution was examined performed on as-cast AZ31 and AZ61 alloys. The refinement mechanism of Mg-Al alloys was discussed with the Miedema model and edge-to-edge matching model. Al2Ca compound has a good crystallographic matching relation with Mg matrix, which formed in the solidification process. It is considered that Al2Ca can act as a potential and effective heterogeneous nucleation center. The results reveal that the grain refinement effect of Al2Ca compound has more pronounced in AZ31 alloy compared with in AZ61 alloy.

Research on the Controlling Technic of Conclution in If Steel

Combining with the production experience in steel making and rolling plant, the oxide inclusions of IF steel were investigated. In the operation process, the inclusions of IF steel are main Al2O3-TiN. They are granular and dispersed in the steel, and most of sizes are 1~5μm. In the inclusion center, the Al2O3 plays the role of TiN heterogeneous nucleation center. So reducing the Al2O3 inclusion is essential to stabilize the Ti content and strengthen the fixtation to C and N in steel. The quantity of Al2O3 inclusion was closely relation to the operation process. The Al2O3 inclusions can be significantly reduced by taking some measure.