Non-Isothermal Melting Kinetics of Pb-61.9Sn-2Al Eutectic-Based Alloy: A Differential Thermal Analysis Study

The non-isothermal melting kinetics of a Pb–61.9 wt% Sn–2 wt% Al ternary alloy were investigated by differential thermal analysis (DTA) at five constant heating rates (? = 10, 15, 20, 25 and 30 °C min^?1). A 40 mg specimen was scanned from ambient to 400 °C under inert atmosphere using ?-Al₂O₃ as the reference material. The melting onset (184.5–190.9 °C) remained in close agreement with the canonical Pb-Sn eutectic of 183 °C, confirming that the 2 wt% Al microaddition does not displace the eutectic temperature. Three complementary model-free kinetic treatments — Kissinger, Ozawa–Flynn–Wall (OFW) and Augis–Bennett — were applied to the main endotherm. The Kissinger and OFW methods yielded mutually consistent apparent activation energies of 138.63 and 139.35 kJ mol^?1 (R² = 0.989 and 0.990) with a relative deviation ? 0.5 %,consistent with the fact that these two model-free treatments are near-identical transforms of the same (?, T_p) dataset; their close agreement therefore reflects internal arithmetic consistency rather than independent cross-validation.  The Augis–Bennett analysis returned a systematically lower value of 73.63 kJ mol^?1 (R² = 0.891), attributable to its inherent sensitivity to the heating-rate-dependent peak width, which broadened nearly threefold (from 18.04 to 50.67 °C) across the experimental range; this broadening is the distinctive thermal signature of the dispersed insoluble Al-rich grains introduced by the microaddition.

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