Effect of Mg composition on sintering behaviors and mechanical properties of Al-Cu-Mg alloy

Al-3Cu-Mg alloy was fabricated by the powder metallurgy(P/M) processes. Air-atomized powders of each alloying element were blended with various Mg contents(0.5%, 1.5%, and 2.5%, mass fraction). The compaction pressure was selected to achieve the elastic deformation, local plastic deformation, and plastic deformation of powders, respectively, and the sintering temperatures for each composition were determined, where the liquid phase sintering of Cu is dominant. The microstructural analysis of sintered materials was performed using optical microscope(OM) and scanning electron microscope(SEM) to investigate the sintering behaviors and fracture characteristics. The transverse rupture strength(TRS) of sintered materials decreased with greater Mg content(Al-3Cu-2.5Mg). However, Al-3Cu-0.5Mg alloy exhibited moderate TRS but higher specific strength than Al-3Cu without Mg addition.

Effects of fabrication methods on deformability and microstructure of Mg-Zn-Zr wrought alloy

The effects of fabrication processing methods on the workability of Mg-Zn-Zr wrought magnesium alloy(ZK60A) were investigated based on the microstructure and inherent internal defects. Three different billets, semi-continuously cast, semi-continuously cast and subsequently extruded, and die-cast, were fabricated and uniaxially compressed at elevated temperatures and two different strain rates to determine the deformation capabilities. The grain structure of the billets was investigated using electron backscatter diffraction(EBSD) and transmission electron microscopy(TEM). The internal defects were inspected by an X-ray scanner. The enhanced deformability was observed in semi-continuously cast billet compared to the one fabricated by conventional die-casting, and the subsequent extrusion further improved the deformability.

Fluorine doping for improved thermoelectric properties of spark plasma sintered bismuth telluride

Bismuth-telluride(Bi_(2)Te_(3))is considered to have the best thermoelectric properties at room temperature(ca.300 K).Thus,synthesis and improvement of Bi_(2)Te_(3)and its derivatives quickly and cost-effectively at favorite temperatures are of interests.Recently,doping fluorine(F)into electronic materials(e.g.,FTO)has gained attention;however,it is not applied to Bi_(2)Te_(3)till now.Here,our synthesis of F-doped Bi_(2)Te_(3)for thermoelectric application is introduced using spark plasma sintering(SPS)for Bi_(2)Te_(3)preparation and reactive ion etching(RIE,with SF_6 gas)for F-doping.The exposure time of SF_6 plasma is adjusted to evaluate F-doping effect on the thermoelectric properties of the samples.During characterizations,the increased electrical conductivity and the improved Seebeck coefficient of F-doped Bi_(2)Te_(3)are observed.Through spectroscopic studies and DFT calculations,the main mechanism behind that improvement is unveiled.It also emphasizes the essential role of the F-doping(optimum treatment time of 40 s)in increasing the carrier concentrations as well as electrical conductivity.With increasing measurement temperature(300-510 K),F-doping raises the figure of merit of electron rich Bi_(2)Te_(3)from 1.0 to 1.11(peaked at 390 K).