Analysis of microstructure evolution and precise solid fraction evaluation of A356 aluminum alloy during partial re-melting by a color etching method

Abstract

Spheroidization of Al grains is required for the production of semi-solid slurry either by a partial solidification route or partial re-melting route. In this research, A356 aluminum alloy was deformed and partially re-melted to semi-solid state. A segregation sensitive reagent (Weck's reagent) was used to reveal the inner microstructure of Al grains for the better understanding of the microstructure evolution during partial re-melting. Optical microstructure observation showed that the previously compressed Al dendrites were actually ''fractured'' during heat treatment and such ''fractured'' dendrites contributed to the refinement and spheroidization of Al grains. Further study of this phenomenon indicates that the ''fractures'' are actually migrating high-angle grain boundaries, which was related to the recrystallization that occurred during heat treatment. Moreover, the growth layer of Al grains formed during water quenching is clearly visualized after being etched by Weck's reagent. Consequently, precise evaluation of solid fractions through image analysis was realized by excluding growth layer when measuring the area of solid phase.

Microstructural characterization of aluminum alloys using Weck's reagent, part II: Coloring mechanism

“…Once the temperature of specimen reaches 581°C, specimen was quickly water quenched. The solid fraction of A356 Al alloy at 581°C is about 0.5 according our previous investigation [14].…”

RETRACTED: Mechanical and metallurgical characterizations of AA2014/eggshells/SiC hybrid green metal matrix composite produced at optimum reinforcement parameters

“…Chicken eggshell can be used in commercial products to produce new materials, and it has been highlighted in recent investigation because of its renovation prospective. [6][7][8][9][10] Even though there have been several attempts to use chicken eggshell components for a variety of applications, its chemical composition and accessibility make chicken eggshell a probable source of biofiller-reinforced composites giving additional or improved thermal and mechanical properties. The other advantages of using chicken eggshell are its availability in bulk quantity with lightweight and being economical and environmental friendly.…”

Microstructure Analysis of Quenched Semi-Solid A356 Aluminum Alloy Slurry by Using Weck’s Reagent

“…In order to obtain spherical grains, inducing plastic strain by cold compression before recrystallization and partial melting was adopted. 9,14) The billets were compressed axially by 33% at a room temperature as shown in Fig. 1(a).…”

“…In our previous research, we reported that Weck's reagent is applicable to solve this problem. 9) Weck's reagent was developed by Weck and Leistner in the 1980s. 10) This reagent is a kind of color etchant and can be used to investigate the solute segregation in aluminum alloys.…”

“…Using Weck's reagent to avoid the overestimation can be regard as a modified quantitative metallography. 9,12,13) The microstructure analysis was performed only for the small size specimens, which were cooled at a fixed cooling rate. In order to perform the die-casting for preparing the tensile specimen for future works, much larger size billets were used.…”