Effect of Al Addition to Mg Melt on Microstructure of Mg-Ti Composites in Liquid Metal Dealloying Process

초록

This study investigates the effect of adding Al to Mg molten metal on the microstructural characteristics and hardness of Mg-Ti composites fabricated via a liquid metal dealloying (LMD) process. The addition of Al to the Mg melt significantly reduces the dealloying rate of Cu in a Ti30Cu70 precursor during LMD. The rapid reaction of Al atoms with Ti results in the formation of a Ti3Al phase, which in turn inhibits the spinodal decomposition of Ti and Cu. This inhibition decreases the formation rate of alpha-Mg channels, thereby slowing down the dealloying process of Cu. As a result, as the Al content in the Mg melt increases from 0 to 3 to 6 wt%, the residual Cu content in the composite substantially increases from 0 to 42 wt%. The main phases comprising the composite change from Mg and Ti for the composite using a pure Mg melt to TixCuy, TixAly, and MgxCuy for the composites using Mg-Al melts. The hardnesses of the composites fabricated using the Mg-3Al and Mg-6Al melts are 344 and 354 Hv, respectively, which are more than twice that of the composite fabricated using the pure Mg melt (116 Hv). These results demonstrate that adding small amounts of Al to Mg melt considerably influences the dealloying behavior during LMD as well as the resultant microstructure and mechanical properties of the Mg-Ti composite.

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