Solid-solid phase transition via the liquid in a Pd₄₃Cu₂₇Ni₁₀P₂₀ bulk metallic glass under conventional conditions

The microscopic mechanism of solid-solid phase transitions is a long-standing fundamental issue in materials science. Here we directly report the experimental evidence of the existence of an intermediate liquid during the solid-solid phase transition in a bulk Pd₄₃Cu₂₇Ni₁₀P₂₀ alloy by in situ high temperature high energy X-ray diffraction, combined with the differential scanning calorimetry at slow heating rates down to 5 K/min. We elucidate that this intermediate liquid is attributed to the melting of the low-melting-point crystalline phases, rather than induced by the elastic stress energy along the interface proposed in literatures. This could also be a general feature in multicomponent alloys if a low-melting-point crystalline phase is formed together with other crystalline phases during heating. All results obtained here are scientifically sound and provide new insight into the phase transition theory, which will trigger more studies on the microscopic mechanism of solid-solid phase transition via an intermediate liquid.