Experimental investigation of microsegregation in low frequency electromagnetic casting 7075 aluminum alloy

Abstract

7075 aluminum alloy ingots were prepared by the process of low frequency electromagnetic casting (low frequency electromagnetic casting = LFEC) and conventional direct chill (direct chill = DC) casting, respectively. The effects of low frequency electromagnetic field on microsegregation were investigated from eutectic analysis and electro probe microanalysis (EPMA). It was found that the amount of the eutectic, which was composed of a-Al (aluminum phase), T phase and MgZn 2 was decreased markedly. In contrast, the solute concentration profiles which depend on solid fraction were increased to a certain extent with the presence of low frequency electromagnetic field. The effective distribution coefficient k e was calculated, and the values of k e for solutes in the LFEC sample were bigger than those in the DC sample. The LFEC process alleviated the microsegregation in 7075 aluminum alloy.Keywords: aluminum alloy / low frequency electromagnetic casting (LFEC) / microsegregation / effective distribution coefficient / Schlüsselwörter: Aluminiumlegierung / niederfrequentes elektromagnetisches Gießen / Mikroseigerungen / effektiver Verteilungskoeffizient /

Effect of Low-Frequency Electromagnetic Casting on Micro-Structure and Macro-Segregation of 5A90 Alloy Ingots

“…The solutes in grains were discharged from grains to the liquid through the interface [15]. The amount of alloying elements that were solid solved in the solid grains increased and the amount that were discharged from grains to the liquid was reduced because the cooling rate of solidification was intensified and part of the energy needed for lattice distortion from the solute atom solid solved in the matrix was supplemented by LFEC [16], which resulted in an increase in the effective distribution coefficients of the alloying elements and the starting value of solutes meant the improvement of micro-segregation [17]. The most potential nuclei were activated by the application of the low-frequency electromagnetic field, which increased the amount of new grains and refined grains so that the amount of solutes discharged from grains to the liquid decreased because of a decrease in the small size of the grains.…”

Low Frequency Electromagnetic Casting of 2195 Aluminum–Lithium Alloy and Its Effects on Microstructure and Mechanical Properties

“…For 2195 alloy, the refinement of grain causes the increase of grain boundaries, which not only acts as obstacles to dislocation motion [15], but also benefits nucleation for the precipitates during aging treatment [16]. The mechanism of grain refinement under low frequency electromagnetic field has been systematically and extensively investigated in previous research [13,16]. In LFEC treatment, the melt in the sump was acted upon by the Lorenz forces produced by the interaction of the induced current and electromagnetic field.…”

“…The flow and temperature distribution of melt in the sump are improved by LFEC. In recent years, we have seen a growing interest in the production of magnesium alloy and aluminum alloys by LFEC owing to a series of characteristics and advantages, such as refined microstructure, improved surface quality of ingots, improved macrosegregation, eliminating cracks and increased intra-granular solid solubility of alloy elements [11][12][13][14], which are all the key aspects to prepare the high quality aluminum-lithium alloy ingots. But, so far, there are few reports on the casting technology of aluminum-lithium alloys.…”

Micro-Structure and Mechanical Properties of 2A97 Al-Li Alloy Cast by Low-Frequency Electromagnetic Casting

“…The mechanism of grain refinement under low-frequency electromagnetic field has been systematically and extensively investigated [9][10][11][12]. In this treatment, the melt in the sump was subjected to Lorenz forces caused by the interaction of the induced current and magnetic field [20].…”

“…With the development of this process, it continues to gain popularity in the preparation of aluminum alloys. The numerous advantages of this process, which include refined micro-structures [10,11], improved surface quality of ingots, enhanced solid solubility of alloying elements within grain interiors [12], and improved macro-segregation and eliminating cracks [13], could improve the metallurgical quality of Al-Li alloys effectively.…”