Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560℃ for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180℃. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420℃, and then increased;the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180℃ rolling water-quenched alloy were also improved by the presence ofβ″phase. Above 420℃, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.

Electrochemical behavior of tungsten in(NaCl–KCl–NaF–WO_3)molten salt

Abstract The electrochemical reaction mechanism and electrocrystaUization process of tungsten in the NaCl- KCl-NaF-WO3 molten salt were investigated at 973 K （700℃） by means of cyclic voltammetry, chronopotentiometry, and chronoamperometry techniques. The results show that the electrochemical reaction process of tungsten in the NaCl-KCl-NaF-WO3 molten salt system is a quasireversible process mix-controlled by ion diffusion rate and electron transport rate. Tungsten ion in this system is reduced to W（0） in two steps. The electrocrystallization process of tungsten is found to be an instantaneous, hemispheroid three-dimensional nucleation process and the tungsten ion diffusion coefficient of 2.361 × 10^-4 cm2.s^-1 is obtained at experimental conditions.

Evaluation of casting fluidity and filling capacity of Zr-based amorphous metal melts

Understanding the flow characteristics of amorphous metal melts is important for casting and molding processes.Fluidity of Zr-based amorphous metal melts was determined by using a self-designed apparatus.Phase analysis demonstrated that the fluidity test samples were fuUy amorphous structure.The onset crystallization temperature significantly moved toward high temperature with the increases of casting temperature,which improved the glass-forming ability and thermal stability of Zr-based amorphous metal.Fluidity test results demonstrated that the fluidity length increased monotonically with the increases of temperature,pressure,and runner diameter.By identifying the types and quantities of the defect in castings,it could conclude that smooth filling processes occurred under appropriate conditions.Experimental results indicated that the flow behavior of the Zr-based amorphous metal melts strongly depended on the casting temperature and equivalent thickness.Constitutive equation based on Newton's law of heat exchange and Rayleigh rule was established to'evaluate the fluidity of Zr-based amorphous metal melts.Theoretical calculations and experimental tests were basically coincided with each other.The determined optimal casting temperatures and equivalent thicknesses were adopted to successfully fabricate a series of fully shaped castings through gravity casting.