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La (Fe, Si) 13 alloys due to its better magnetocaloric effect in recent years, people of all ages . Under normal circumstances , this alloy is an ingot by arc melting in an inert atmosphere , after prolonged high temperature annealing obtained. Recent studies indicate that , using the rapid quenching can greatly shorten the annealing time of the alloy . However, the rapid quenching process of the phase selection mechanism is unclear. To solve this problem , a (Fe, Si) phase and La ( Fe, Si ) 13 phase in deep over Nucleation in a supercooled liquid was . First , the use of the Spaepen negative entropy model constructed La (Fe, Si) 13 phase of the solid-liquid interface , and calculated structure factor alpha . The specific approach is : First, La (Fe, Si) 13 alloy phase structure were analyzed and the most close-packed surface ; then constructed in the most close-packed surface of the solid-liquid interface ; constructed in accordance with the model permutations rule each step calculated Ordering density and structure factor α, until Ordering density stabilized . The Then, Miedema formula La ( Fe , Si ) 13 melting entropy change ΔSf . On this basis , determine a ( Fe, Si ) phase and La ( Fe, Si ) 13 phase solid-liquid interface σls, and according to the classical nucleation theory on both the nucleation rate calculation . Calculation results for : (1) La (Fe, Si) 13 phase the structure factor of a = 0.417 ; ( 2 ) La ( Fe , Si ) 13 phase melting entropy becomes AsF = 21.27 J / ( mol · K) ; ( 3) La (Fe, Si) 13 phase of the solid-liquid interface can σ = 0.430 J/m2 ; ( 4 ) when the undercooling is larger than 308K , La ( Fe, Si ) 13 phase nucleation rate than a (Fe , Si) phase . Nucleation rate calculation results show that , in small undercooling , La-Fe-Si alloy peritectic phase La ( Fe, Si ) 13 phase because of the nucleation rate lower primary phase in the form of precipitation is very difficult . When the undercooling is large enough ( more than 308K) , La ( Fe, Si ) 13 phase will receive a high nucleation rate , which is likely a primary phase precipitation . A good agreement with the available experimental results .
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