Effect of low voltage pulsed magnetic field on microstructure and wear behaviour of eutectic Al–Si alloys

Abstract

Effect of discharging frequency of low voltage pulsed magnetic field (LVPMF) on the morphology and size of eutectic Si in eutectic Al–Si (Al–12Si) alloys has been investigated, and some characteristic parameters the characterised the microstructure of the eutectic Si phase were obtained. Dry sliding wear behaviour of eutectic Al–Si alloys without and with LVPMF treatment were also tested using a pin-on-disc wear testing machine, and scanning electron microscopy and energy dispersive spectroscopy X-ray of worn surfaces were carried out to determine the governing mechanisms in the eutectic Al–Si alloys without and with LVPMF treatment. The results show that the eutectic Si became smaller with the increase in discharging frequency. Fine short rod-like or rounded particle-like eutectic silicon with 2·3 μm in length, 0·6 μm in the width, and 3·8 in aspect ratio was formed in eutectic Al–Si alloy treated by 6 Hz LVPMF. The wear resistance of eutectic Al–Si alloys increased with the increase in discharging frequency. The adhesive wear was observed in eutectic Al–Si alloy without LVPMF treatment under normal load of 80 N. However, mainly abrasive was observed in eutectic Al–Si alloy with 6 Hz LVPMF treatment.

Microstructure and properties of A357 aluminium alloy treated by pulsed magnetic field

“…However, the eutectic silicon in the alloy treated by PMF was refined remarkably, and the morphology of eutectic silicon changed into fibrous, as Figure 2(d) depicted. The reasons for the formation of fine primary α-Al and eutectic silicon particles under the action of PMF had been reported elsewhere [18,19,22].…”

“…PMF was started immediately after pouring until the melt completely solidified. The PMF process details were mentioned elsewhere [18,19]. The PMF process parameters were briefly summarised as follows: the discharging voltage was 250 V and the discharging frequency (numbers of per-second discharging) was 10 Hz.…”

“…Results of our previous research showed that the eutectic silicon in eutectic Al-Si alloys was significantly modified under the action of PMF [18,19], and the mechanical properties of eutectic Al-Si alloys were increased [18]. Moreover, PMF process has several advantages [20][21][22] such as low investment, high efficiency, simple equipment, extensive alloy application scope, as well as low pollution due to the noncontact with the melt.…”