Microstructural and Mechanical-Property Manipulation through Rapid Dendrite Growth and Undercooling in an Fe-based Multinary Alloy

Abstract

Rapid dendrite growth in single- or dual-phase multicomponent alloys can be manipulated to improve the mechanical properties of such metallic materials. Rapid growth of (αFe) dendrites was realized in an undercooled Fe-5Ni-5Mo-5Ge-5Co (wt.%) multinary alloy using the glass fluxing method. The relationship between rapid dendrite growth and the micro-/nano-mechanical properties of the alloy was investigated by analyzing the grain refinement and microstructural evolution resulting from the rapid dendrite growth. It was found that (αFe) dendrites grow sluggishly within a low but wide undercooling range. Once the undercooling exceeds 250 K, the dendritic growth velocity increases steeply until reaching a plateau of 31.8 ms−1. The increase in the alloy Vickers microhardness with increasing dendritic growth velocity results from the hardening effects of increased grain/phase boundaries due to the grain refinement, the more homogeneous distribution of the second phase along the boundaries, and the more uniform distribution of solutes with increased contents inside the grain, as verified also by nanohardness maps. Once the dendritic growth velocity exceeds ~8 ms−1, the rate of Vickers microhardness increase slows down significantly with a further increase in dendritic growth velocity, owing to the microstructural transition of the (αFe) phase from a trunk-dendrite to an equiaxed-grain microstructure.

Phase Field Simulation of Dendritic Solidification of Ti-6Al-4V During Additive Manufacturing Process

“…In additive manufacturing, two main solidification parameters are dendritic arm spacing and microsegregation. The distribution and the spacing of dendritic arms are related to mechanical properties, such as tensile strength and ultimate tensile strength [8][9][10]. Microsegregation, caused by non-equilibrium partition of solute in solid and liquid, affects the texture of dendrites.…”

Dendritic coarsening model for rapid solidification of Ni-superalloy via electrospark deposition

“…The improved properties were directly attributed to the nanostructured coating, which resulted in increased hardness and the formation of lubricating oxides. Ruan et al (2016) showed that decreasing dendrite diameter and secondary dendrite arm spacing both resulted in a microhardness increase, analogous to the Hall-Petch relationship. The presence of cellular dendritic structures in ESD processed materials have been reported for nickel based superalloys by Ebrahimnia et al (2014), which formed parallel to the ESD growth direction with submicron diameters.…”

Experimental and modelling studies for solidification of undercooled Ni–Fe–Si alloys

“…Hence, it is essential to incorporate the solute interactions among all the components to understand the solidification behaviour of multi-component alloys. The measurement of undercooling using experiments can aid in the study of rapid solidification of multi-component systems [3]. The study of recalescence can be carried out by monitoring the thermal and spatial profiles during solidification in the undercooled melt [4].…”