Effect of incongruent crystallization on glass–liquid transition features of a bulk metal glass

Aji, Daisman P. B.; Johari, G. P.

doi:10.1016/j.tca.2015.07.008

Cited by 6 publications

(1 citation statement)

References 21 publications

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“…Increased interest of industrial enterprises to manufacture of moulding cores and moulds of mixtures based on waterglass binder (WB) is connected with high ecological safety of this material and lack of alternative in the same range of price and technical possibilities [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Production of moulding cores and waterglass mixtures using “dry ice” for steel and iron casting

Leushin¹,

Leushina²,

Balabanov³

et al. 2021

cisisr

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Increased interest of industrial enterprises to manufacture of moulding cores and moulds of mixtures based on waterglass binder is connected with acceptability and high ecological safety of this material. It stipulated more active work for searching technical solutions that can decrease or exclude deficiencies of such technologies as carbon dioxide blowing and thermal effect that are mostly popular at Russian enterprises. Among these deficiencies, the following can be mentioned for example: low setting rates during blowing of waterglass mixtures in the normal temperature conditions as well as the effect of noncontrolled moisture migration in a moulding core of mould body during heating. Their appearances lead to deterioration of operation parameters of core or mould, such as lowering of surface strength, increase of friability, elevation of strength of internal parts of core or mould, what enlarges the risk of their poor knock-out ability from steel and iron castings. Analytical survey of accessible information data was conducted by the authors of this paper; they revealed two directions in searching the solution of the a.m. problem that were supported by overwhelming majority of the researchers. These directions include directed vacuum treatment of technological accessories for increase of control abilities of moisture migration in a body of core or mould, as well as technological additives of different origination in the mixture composition for provision of timely softening of core or mould during knock-out operation out of casting. However, their use does not guarantee always the stable positive effect, thereby this task is still not solved. The authors of this paper concentrated their attention on the problem of development and testing the innovative technology of production of moulding cores and moulds of waterglass mixtures in the conditions of operating enterprise. This technology allows to improve their operating properties and parameters, to lower the mentioned deficiencies and as a result to stabilize the quality of cast metallic billets of steel and iron at the high level. Solving of this task is based on well-known combination of chemical and physical mechanisms of setting of waterglass mixtures together with directed vacuum treatment of technological accessories during acquiring of the required geometrical shape by a moulding core or mould. In this case the following consequent operations tale place: filling of moulding core or moulding box accessories by mixture; its compacting and strengthening via passing of heated setting gas through the mixture from the one side of core or mould with simultaneous its consumption from the other side due to adjustable exhausting. The authors substantiated scientifically and proved experimentally expedience of introduction of small amount of solid carbon dioxide ("dry ice") in the form of particles with preset size and compensation of inevitably occurring undesirable endothermic effect of setting gas heating (air in this case) up to higher temperature in comparison...

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Section: Introductionmentioning

confidence: 99%

Production of moulding cores and waterglass mixtures using “dry ice” for steel and iron casting

Leushin¹,

Leushina²,

Balabanov³

et al. 2021

cisisr

View full text Add to dashboard Cite

show abstract

Evidence of post-polymerization of 110-million-year-old Spanish amber and its consequences for rejuvenation-based interpretation

Johari,

Tombari

2023

Journal of Non-Crystalline Solids

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Decrease in electrical resistivity on depletion of islands of mobility during aging of a bulk metal glass

Aji

Johari

2018

The Journal of Chemical Physics

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The effect of structural relaxation on electrical resistivity, ρ, of strain-free ZrTiCuNiBe bulk metallic glass was studied during isothermal aging at several temperatures, Ts. Since cooling of a liquid metal increases its resistivity ρ, one expects ρ to increase on aging toward ρ at T = T. Instead, ρ decreased non-exponentially with the aging time. The activation energy of aging kinetics is 189 kJ mol, which is higher than the activation energy of the Johari-Goldstein (JG) relaxation. After considering the sample's contraction, phase separation, and crystallization as possible causes of the decrease in ρ, we attribute the decrease to depletion of islands of atomic mobility, soft spots, or static heterogeneity. Vibrations of the atoms in these local (loosely packed) regions and in the region's interfacial area contribute to electron scattering. As these deplete on aging, the contribution decreases and ρ decreases, with a concomitant decrease in macroscopic volume, enthalpy, and entropy (V, H, and S). Local regions of faster mobility also decrease on cooling as V, H, and S of a liquid decrease, but structure fluctuations dominate electron scattering of a liquid metal and ρ increases effectively according to the Ziman-Nagel theory for a homogenously disordered structure. Whether depletion of such local regions initiates the structural relaxation of a glass, or vice versa, may be resolved by finding a glass that physically ages but shows no JG relaxation.

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Effect of incongruent crystallization on glass–liquid transition features of a bulk metal glass

Cited by 6 publications

References 21 publications

Production of moulding cores and waterglass mixtures using “dry ice” for steel and iron casting

Production of moulding cores and waterglass mixtures using “dry ice” for steel and iron casting

Evidence of post-polymerization of 110-million-year-old Spanish amber and its consequences for rejuvenation-based interpretation

Decrease in electrical resistivity on depletion of islands of mobility during aging of a bulk metal glass

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