Estimation of critical cooling rates for glass formation in bulk metallic glasses through non-isothermal thermal analysis

Abstract

Critical cooling rate (Rc) for glass formation has been calculated from an integrated transformation curve, constructed by combining continuous cooling transformation (CCT) and continuous heating transformation (CHT) curves. The CCT and CHT curves were calculated from experimental measurements on cooling rate dependence of solidification onset temperature using classical nucleation kinetics and heating rate dependence of crystallization onset temperature using Kissinger method, respectively. The critical cooling rate was calculated from the intersection point of the two curves, corresponding to an apparent nose point in the integrated transformation curve. The calculated critical cooling rates were in good agreement with those measured for five different bulk glass forming alloys of Ca-Mg-Zn, Pd-Ni-Cu-P, Zr-Ti-Cu-Ni-Be and Mg-Cu-Y alloys.

Heating and cooling rate dependence of the parameters representing the glass forming ability in bulk metallic glasses

“…Under extremely slow cooling condition, T s will merge to T L . With the decrease of the heating rate, T x will move more closely to T g , since the degree of heating rate dependence of T x is larger than that of T g , generally [24,25]. Therefore, under the condition of extremely slow cooling and heating, the parameter T x /T s will be close to T g /T L which is known as reduced glass transition parameter, T rg .…”

“…Since T rx values from a CCHT curve will be different depending on the cooling rate used to measure T s , it is needed to investigate the effect of heating/cooling rate on the previously suggested parameters, DT x , T rg and c. In general, it is expected that DT x increases in proportional to heating rate since the heating-rate dependence of T x is generally larger than that of T g [24,25]. The heating rate dependence of T rg and c is mainly originated from the heating-rate dependence of T x and T g , since T L is materialÕs thermodynamic property.…”

“…Details on the extension of Kissinger method and CHT curves are well documented elsewhere [4,19,22,23,25]. Once the CHT curve is fixed, T rx parameter can be obtained by measuring T s under specific cooling rate, as schematically shown in Fig.…”

A new approach for determining the critical cooling rates of nucleation in glass‐forming liquids

“…There is a critical cooling rate, , above which glass can form due to the arrest of structural disorder of the liquid. Using differential thermal analysis (DTA) or differential scanning calorimetry (DSC), it is possible to estimate under interval‐by‐interval cooling or dynamic cooling conditions . The nose‐like temperature‐time transformation (TTT) diagram is most widely employed to determine from the time required to form a given volume fraction of crystals during an isothermal treatment at various temperatures .…”

“…Using differential thermal analysis (DTA) or differential scanning calorimetry (DSC), it is possible to estimate q à c under interval-by-interval cooling or dynamic cooling conditions. [1][2][3][4] The nose-like temperature-time transformation (TTT) diagram is most widely employed to determine q à c from the time required to form a given volume fraction of crystals during an isothermal treatment at various temperatures. 5,6 However, this diagram is experimentally difficult to be made, especially for some liquids with a strong trend to crystallization.…”