The valence electron structures of alloying cementite θ-(Fe, M)3C and ε-(Fe, M)3C andthose of the biphase interfaces between them and α-Fe are calculated with Yu's empirical electrontheory of solid and molecules. The calculation results accord with the actual behavior of alloys.
In this paper, crystal growth instability of diamond was studied in a Fe-Ni-C system at high temperature-high pressure (HPHT). As any other crystal from solution, the flat or smooth growth interface of the diamond crystal is highly sensitive to growth conditions.The growth front interface should be of great importance to understand the diamond growth process.The presence of cellular growth interface by transmission electron microscopy indicated that there existed a narrow constitutional supercooling zone in front of the growth interface .Several parallel layers with cellular interface by TEM directly suggested that the diamond grows from the solution of carbon in the molten catalyst layer by layer, which is in accordance with the result obtained by scanning electron microscopy in this paper.Impurities are trapped by rapidly advancing growth layers during the diamond growth and they impose a great effect on the growth front stability.As the growth front interface approaches the impurity particle to a distance of about 10^-5-10^-7 cm, appreciable molecular forces begin to operate between them,and the impurity particle is trapped as the growth rate reaches a critical value.As a result,the driving force for crystallization under the impurity particles becomes smaller ,the front buckles under the particle.An impurity naturally reduces the growth rate to a different extent.
The second phase in multi-phase alloys has connection with many important phenomena such as aging strengthening,dispersion strengthening,secondary hardening,crystal refinement.In this paper,the interface conjunction factors of the interface between MC(M=V,Nb,Ti) and austenite and martensite are calculate out.The relationship between these factors and the characteristics are analyzed.The reason for the second phases being fine and dispersing and their strengthening and toughening effect on the alloy is explained using the relationship.Based on the relationship,the valence electron structure of the interface between the second phase particles and the matrix can be optimized by changing the alloying elements,which make it possible to design the composition of alloys from the valence electron structure of the second phase particles.
