The effect of silicon content on the microstructure and creep behavior in die-cast magnesium AS alloys

Abstract

The effect of increasing levels of silicon on the microstructure and creep properties of high-pressure die-cast Mg-Al-Si (AS) alloys has been investigated. The morphology of the Mg 2 Si phase in die-cast AS alloys was found to be a function of the silicon content. The Mg 2 Si particles in castings with up to 1.14 wt pct Si have a Chinese script morphology. For AS21 alloys with silicon contents greater than 1.4 wt pct Si (greater than the ␣-Mg 2 Si binary eutectic point), some Mg 2 Si particles have a coarse "blocky" shape. Increasing the silicon content above the eutectic level results in an increase in the number of coarse faceted Mg 2 Si particles in the microstructure. Creep rates at 100 hours were found to decrease with increasing silicon content in AS-type alloys. The decrease in creep rate was most dramatic for silicon contents up to 1.1 wt pct. Further additions of silicon of up to 2.64 wt pct also resulted in significant decreases in creep rate.

Effect of holding temperature on microstructure of an AS91 alloy during semisolid isothermal heat treatment

“…In general, the Mg 2 Si phases in Mg-Al-Si-based alloys are prone to forming coarse Chinese script shape under low solidification rate [21,22]. Therefore, under the permanent mould casting of this paper, the Mg 2 Si phases in the AS91 alloy exhibit typical Chinese script shaped morphology.…”

Quantitative characterization of Mg17Al12 phase and grain size in HPDC AZ91 magnesium alloy

“…This plot also explains that the ␤-PP are more in number and finer in the surface compared to the centre of the casting. In general, it is stated by researchers [14,[26][27][28] that the ␤-PP are finer and high in area fraction in the surface compared to the centre of the pressure die castings. However, the present quantitative description about the area fraction of the ␤ phase from the surface to centre shows a contradictory conclusion compared to the general understanding.…”

The effect of aluminium content on the eutectic morphology of high pressure die cast magnesium–aluminium alloys

“…The microstructure observed for each alloy composition was obtained from 6 mm diameter creep test bars made by high pressure die casting. The casting process and the casting geometry have been described in detail elsewhere [12].…”