Conditions for partial and complete crystallization suppression upon quenching from liquid state
For bulk-amorphizing alloys Мg65Сu25Y10 and Zr41,2 Тi13,8Сu12,5Ni10Ве22,5, the thickness and cooling rate of melt layers is calculated, which ensure the formation of X-ray amorphous structures typical for metallic glasses ( lC, vC ), and truly amorphous states without inclusions of «frozen-in crystallization centers» (lc*, vc* ). Correlation of the calculated values lC, vC with the known experimental estimates is C Cachieved. It is shown that both studied alloys demonstrate a predisposition to complete suppression of crystallization processes at physically correct values of the parameters lc* and vc* (10 μm; 1,3·107 K/s and 550 μm; 2,7·103 K/s for alloys based on Mg and Zr, respectively). It is concluded that the most significant factors controlling the tendency of materials to noncrystalline solidification are the decrease in the frequency of non-stationary nucleation with the increase in the rate of QLS, as well as relatively low <1018 m-3 s-1) maximum values of the rate of stationary crystallization centers formation.