The Analysis of Deformability, Structure and Properties of AZ61 Cast Magnesium Alloy in a New Hammer Forging Process for Aircraft Mounts

This article presents the analysis of the deformability, structure and properties of the AZ61 cast magnesium alloy on the example of a new forging process of aircraft mount forgings. It was assumed that their production process would be based on drop forging on a die hammer. Two geometries of preforms, differing in forging degree, were used as the billet for the forging process. It was assumed that using a cast, unformed preform positively affects the deformability of hard-deformable magnesium alloys and flow kinematics during their forging and reduces the number of operations necessary to obtain the correct product. Numerical analysis of the proposed new technology was carried out using DEFORM 3D v.11, a commercial program dedicated to analyzing metal forming processes. The simulations were performed in the conditions of spatial strain, considering the full thermomechanical analysis. The obtained results of numerical tests confirmed the possibility of forming the forgings of aviation mounts from the AZ61 cast magnesium alloy with the proposed technology. They also allowed us to obtain information about the kinematics of the material flow during forming and process parameters, such as strain intensity distribution, temperatures, Cockcroft–Latham criterion and forming energy. The proposed forging process on a die hammer was verified in industrial conditions. The manufactured forgings of aircraft mounts made of AZ61 magnesium alloy were subjected to qualitative tests in terms of their structure, conductivity and mechanical properties.

Microstructure and Corrosion of Cast Magnesium Alloy ZK60 in NaCl Solution

In this work, the effects of the microstructure and phase constitution of cast magnesium alloy ZK60 (Mg-5.8Zn-0.57Zr, element concentration in wt.%) on the corrosion behavior in aqueous NaCl (0.1 mol dm−3) were investigated by weight-loss measurements, hydrogen evolution tests, and electrochemical techniques. The alloy was found to be composed of α-Mg matrix, with large second-phase particles of MgZn2 deposited along grain boundaries and a Zr-rich region in the central area of the grains. The large second-phase particles and the Zr-rich regions were more stable than the Mg matrix, resulting in a strong micro-galvanic effect. A filiform corrosion was found. It originated from the second-phase particles in the grain boundary regions in the early corrosion period. The filaments gradually occupied most areas of the alloy surface, and the general corrosion rate decreased significantly. Corrosion pits were developed under filaments. The pit growth rate decreased over time; however, it was about eight times larger than the general corrosion rate. A schematic model is presented to illustrate the corrosion mechanism.