Effect of Trace Addition of Ag on the Precipitation Behavior of Al-Mg-Cu Alloy

Effect of Ag addition on the age-hardening response and precipitate microstructure of the Al-3.0Mg-1.0Cu (wt%) alloy has been investigated by micro Vickers hardness and transmission electron microscopy (TEM). The alloy compositions located in the (α+S+T) phase field of the Al-Mg-Cu phase diagram are known to be effective to harden in two stages separated by a distinct and often prolonged hardness plateau. The first stage of hardening occurs very rapidly (e.g. within 60 s at 443 K) and contributes to increase the hardness as much as 50% of the total age-hardening. Trace addition of Ag changes the age hardening response of the Al-3.0Mg-1.0Cu alloy dramatically. In the Ag-added alloy, the hardness change during the first stage of hardening is larger and the plateau stage is shortened as a result of the fast arrival at the second stage of hardness. The microstructure at the plateau stage of hardening for the Al-3.0Mg-1.0Cu alloy exhibits no clear evidence of any precipitates contributing to the first rapid hardening. On the other hand, lath-shaped S phase was observed at the peak hardness. In the Ag-added alloy, fine distributed precipitates were obtained from the beginning of age-hardening

Effect of pre-deformation on age-hardening behaviors in an Al-Mg-Cu alloy

The effects of 3%–50% pre-deformation following solution heat treatment on the age hardening of an Al-3Mg-1Cu alloy have been investigated by Vickers microhardness measurement, tensile tests, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. Pre-deformation has a strong effect on subsequent age-hardening behavior. The precipitation was accelerated, hardness peaks appeared earlier, formation of clusters was inhibited, and a larger fraction of precipitates was observed along the dislocation lines. The contribution of the precipitates to the hardness was evaluated by dissolution tests. It was found that pre-deformation followed by artificial aging resulted in a good strength-elongation balance. The results are significant for the development of combined mechanical deformation and heat treatment processes.publishedVersio

In Vitro Corrosion Properties of Mg Matrix In Situ Composites Fabricated by Spark Plasma Sintering

Mg matrix in situ composites were fabricated from Mg and ZnO powder by a spark plasma sintering method. The composition and microstructure of the sintered samples were characterized. Corrosion properties of fabricated composites were evaluated by immersion and by electrochemical tests using Hanks’ solution. The results showed that the formation of in situ products improved significantly the corrosion resistance of the fabricated composites compared with pure Mg; Mg-10 wt % ZnO composites especially exhibited the lowest corrosion rate. In addition, an energy-dispersive X-ray (EDX) analysis showed that calcium phosphate formed as a corrosion product on the surface of Mg-10 wt % ZnO composites, while Mg(OH)_2 appeared as a corrosion product on the surface of Mg-20 wt % ZnO composite. The findings suggested Mg-10 wt % ZnO composite as a potential candidate for temporary implant application