Experimental evidence of liquid feeding during solidification of a steel

Abstract

Sufficient liquid feeding under constrained solidification conditions like, those experienced in welding and casting, is vital to avoid solidification cracking. We present the results of unique in-situ experimental observations of liquid feeding in a solidifying steel melt pool. Liquid feeding was observed in the inter-cellular regions during the terminal stage of solidification. An average liquid flow speed of 450-500 µm s −1 was found. A pressure difference of the order of 10 4 Pa is calculated to cause the liquid flow. The rate of solidification shrinkage and the rate of deformation were found to be less than the rate of liquid feeding.

Study of Solidification Cracking Susceptibility during Laser Welding in an Advanced High Strength Automotive Steel

“…If the deformation exceeds a certain threshold, separation of the dendrites at the grain boundary can occur. At the terminal stage of solidification, such an opening cannot be compensated by the remaining liquid due to both low permeability and a high solid fraction [5,6]. As a result, solidification cracking occurs.…”

Hot Tearing of 9Cr3Co3W Heat-Resistant Steel during Solidification

“…If the liquid feeding in the inter-dendritic region of the mushy zone is insufficient to compensate for the shrinkage and cumulative deformation of the mushy zone, then the pressure drops below a certain cavitation pressure, voids form and eventually coalesce to form a crack. Agarwal et al [14] observed the solidification process of dual-phase steel in-situ by using a high-temperature laser scanning confocal microscope. Liquid feeding was observed in the inter-cellular regions during the terminal stage of solidification.…”

Investigation of grain growth and microstructural evolution in electron beam melting additive manufacturing process

“…Furthermore, a higher solute concentration at a GB decreases the permeability of the surrounding mushy zone, which retards liquid feeding. This is particularly detrimental for the already crack prone divergent GBs as liquid feeding alleviates strains associated with solidification shrinkage [145,281]. It is, therefore, evident that microsegregation of solutes to divergent GBs promotes cracking.…”

“…(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) consists of two additional contributions, the rate of solidification shrinkage (ROS) and the rate of deformation (ROD). A detailed explanation of these terms is provided in [281]. The ROS is defined as…”

“…(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) become 61.53 × (1 + 1/𝑐𝑜𝑠𝜃) and 626.96 × 𝑡𝑎𝑛𝜃, respectively. The liquid feeding velocity in the feeding term is derived for an average PDAS value of 4.0 µm and a liquid channel length of 42 µm obtained from meso-scale simulations to be in the order of 10 -3 m/s [281] as shown here:…”