Influence of mechanical and thermal treatments on microstructural transformations in cast irons and properties of synthesized diamond crystals

Abstract

Influence of MechAnIcAl AnD therMAl treAtMents on MIcrostructurAl trAnsforMAtIons In cAst IronsAnD propertIes of synthesIZeD DIAMonD crystAls purpose. To analyze how the structural transformations in the cast iron metal matrix near graphite inclusions influence the features of synthesis of metastable diamond crystal on diamond polycrystals (substrate) synthesized by shockwaves.Methodology. In experiments, we used the laserinduced detonation of explosive charges to create a flat shockwave front and employed chemical, microstructural, spectral and Xray phase analyzes. In particular, the features of chemical element distribu tion in cast iron phases, dislocation density in a solid solution, crystal lattice parameters, and others were studied.findings. It has been shown that solidphase autoepitaxy is a physically justified, experimentally proved and stably reproduc ible phenomenon. The accelerated transfer of carbon atoms to the surfaces of metastable diamond growing crystals in the kinetic mode is facilitated by a number of factors that cannot be quantified by numerically evaluated parameters. These include, first of all, the microstructure of the growing medium (cast iron matrix), carbon source, temperature and deformation fields that ensure transformation of polymorphic graphite to diamond with emerging gradient stress fields at the stages of forging, exposure to shock waves and thermal cycling. Defect redistribution in the crystal structure of the metal matrix and graphite inclusions plays a certain role at the mesoscale. It has been found that saturation with microstructural defects brings higher physicochemical activity to the system in the whole. originality. For the first time in world practice, diamond single crystals have been synthesized that contain the inclusions of polycrystalline diamond particles of shockwave origin inside the single crystal shell; this may indicate a general discreteness of natural diamond formation.practical value. The growth of single metastable crystal on polycrystalline diamond of shock wave synthesis is the most favor able in case of using austenitic gray cast iron with foliate graphite inclusions. The experimentally proved diamond growth in a solid medium under pressure and temperature within the range of graphite stability can be used to develop new lowenergy tech nologies for the synthesis of metastable diamond single crystals.

Profiled Detonation Waves in the Technologies of Explosion Treatment of Metals

“…2. Scheme of initiating a light-sensitive explosive composite by laser radiation: laser beam (1), diaphragm (2), laser beam after diaphragm (3), diverging lens (4), scattered laser beam (5), LSEC layer (6), explosive charge or the processed material (7). V. N. Viliunov, 1984, and others.…”

Compound physical and mechanical effects stimulating metastable diamond formation

“…The authors of [61,84,85] suggested that relic diamond particles could be found in other bodies of the Solar Sys tem, e. g. meteorites [86]. This idea was later (1987) proved in the research [1].…”

“…Exposure to a shock wave occurs with simultaneous heat ing of carboncontaining alloys [59], additional thermalme chanical [60] and thermal cycling treatment of alloys [61] ei ther before or after shockwave treatment. In addition to the above methods, electromagnetic treatment of a solid carbon containing medium after synthesis in highpressure chambers was used [63,64].…”

On the mechanism of ionization of atoms at compression of a substance by front of the converging shock wave

“…The method for forming a plane detonation wave is reliable. Evidence is a number of positive experimental results obtained during the formation of plane shock waves in the material under study directly by a plane detonation wave front at an angle of 0° relative to the surface of the material facing the striker [33,34], or by a detonation wave front sliding at an angle of 90° to the generatrix of the cylinder surface [35], or by the impact of a fl at plate accelerated by the products of the PEC explosion [36], including in problems of studying the nature of the fl ow of matter behind the front of the bow shock [37].…”