Effect of magnesium in breaking the correlation between reaction speed and intensity in the fabrication of TiAl3 intermetallics

•Broke the correlation between reaction speed and intensity.•The diffusion speed of magnesium consistent with the moving speed of liquidus.•Magnesium and aluminum form eutectic liquid phase in regional area. When TiAl3 intermetallics were fabricated by the reactive synthesis of titanium and aluminum powder, the correlation between the speed and intensity of the reaction was stable. The magnesium-addition method with the addition of trace magnesium broke this correlation for the first time. Magnesium controlled the reaction in three stages in different ways: the initial melting and reaction area, the dynamic equilibrium formed by the diffusion rate consistent with the liquidus, and the high flowability eutectic liquid phase. The diffusion state of magnesium in each stage and the eutectic liquid phase formed with aluminum were the critical factors.