Investigation of the mechanical behavior of a two-phase Mg-Ni compound during fast compression

The paper presents the results of using a pressing process well known in metallurgy as forging. However, here the Fast Forging process is used as a new way to synthesize materials having e.g. a high hydrogen sorption capacity. Firstly, the method allows delivering a final consolidated product from the initial Mg and Ni powdered elements during pressing. Secondly, it enables a phase transformation, i.e. synthesizing the Mg2Ni binary phase from the initial Mg-Ni mixture of powders, which is a unique result. It is established that the key point in the formation of the binary phase in a sample is the temperature of the Fast Forging. The temperature increase (below the level of the eutectic transition) leads to an almost full consumption of free Ni and the resulting presence of the Mg2Ni phase in the material without melting the work piece. In order to determine the optimal deformation conditions with the goal to obtain a maximum Mg2Ni phase content in the sample, a 2D calculation model of the cell is built with an arbitrary distribution of different-sized Ni particles among the Mg ones. The numerical simulation of the adiabatic compression of the cell up to an average strain of 80-90 % shows that except for preheating the sample chamber, it is necessary to account for the rise of еру sample’s temperature created with the hammer impact during the Fast Forging. It is found that when increasing the initial temperature from 20 °C to 400 °C, the contribution of the additional heat during the intense plastic deformation decreases progressively. The numerical simulation results of the temperature increase within the contact zone of the two types Mg and Ni particles are presented. The deformation fields are determined in the used 2D model cell, which makes it possible to evaluate the system’s mechanical behavior during the Fast Forging process. The calculation results are found in an excellent agreement with the experimental ones.