The size and shape of the primary dendrite tips determine the principal length scale of the microstructure evolving during solidification of alloys. $In\text{−}situ$ x-ray measurements of the tip shape in metals have been unsuccessful so far due to insufficient spatial resolution or high image noise. To overcome these limitations, high-resolution synchrotron radiography and advanced image processing techniques are applied to a thin sample of a solidifying Ga-35wt.%In alloy. Quantitative $in\text{−}situ$ measurements are performed of the growth of dendrite tips during the fast initial transient and the subsequent steady growth period, with tip velocities ranging over almost two orders of magnitude. The value of the dendrite tip shape selection parameter is found to be ${\sigma }^{*}=0.0768$, which suggests an interface energy anisotropy of ${\varepsilon }_4=0.015$ for the present Ga-In alloy. The nonaxisymmetric dendrite tip shape amplitude coefficient is measured to be $A_4\approx 0.004$, which is in excellent agreement with the universal value previously established for dendrites.

Close

PrevNext

View figure in article

• Crystal growth
• Liquid-solid phase transition
• Pattern formation
• Alloys
• Crystalline systems
• Liquid-solid interfaces
• X-ray imaging