Experimental investigation and thermodynamic calculation of the Al–Fe–P system at low phosphorus contents

Thermodynamic assessment of the Al–P system based on original experimental data

“…fcc ðAlÞ : ðAl; PÞ L 0,(Al) Al,P ¼ À30,000 to À 55,000 a α-P: P 1 red-P: P 1 a Limits according to estimated partition coefficients, the bold value of À 30 kJ is preferred. the diagrams obtained from three more recently published datasets [5,8,9]. The calculated phase diagrams show very similar characteristics with the dominating AlP phase, congruently melting in the relatively narrow temperature range from 2511 to 2557 1C.…”

“…In the following the originally reported data are cited, the data converted to SI units and proper reference states are given in Table 3. This is considered necessary because when these data were cited in the later studies [5,6,9,44,37,38], they were confused by the reference states and units. Wang et al [35] used an oxygen bomb calorimeter and obtained the heat of formation of AlP phase as À 2972 kcal mol À 1 by subtracting the heat of combustion of AlP from the heat of combustion of the aluminum powder and red phosphorus mixture.…”

“…A reliable thermodynamic description of the Al-P system is essential for developing multicomponent Al alloy thermodynamic databases. On the other hand, the Al-P system is also one of the key binary systems for compound semiconductors [4] and steel [5]. Several thermodynamic descriptions of Al-P system have been published in the literature [5][6][7][8][9], however, as will be shown in this work, all of them fail in one or more important aspects.…”

“…The results calculated with that description [9] disagree with any other experimental data on the thermodynamic properties of the liquid and AlP phase. Wu et al [5] published the other recent Calphad description of the Al-P system, and they used the parameters of AlP taken from the SGTE Substances database [15]. Interestingly, we found that the liquid interaction parameters in [5] were taken from the paper [6], while the parameters of AlP phase in the nonpublic SGTE substances database [15] stem from the thermodynamic properties data (Δ f H1 and S o 298 and C p values) of AlP compiled in an older review book [16], also cited by two later review books [17,18].…”

“…However, it produces negative C p values for the AlP phase as will be pointed out in this work. After 1994 two additional thermodynamic descriptions of the Al-P systems were published [5,9]. Tu et al [9] based their thermodynamic modeling of the Al-P system on one experimental data point only, the melting point of the AlP phase at 2530 1C.…”