The effect of Mg content and milling time on the solid solubility and microstructure of Ti–Mg alloys processed by mechanical milling

This research presents a high energy ball milling method for producing supersaturated solutions of the Ti100-xMgx (x = 10, 15, 20) composite powders containing a process control agent (PCA) under an argon atmosphere at an ambient temperature. The microstructure of the Ti–Mg solid solution during milling was analyzed by scanning electron microscope, and an X-Ray diffraction. A particle size analyzer was employed to investigate the average particle size at different milling times (12 h, 20 h, 32 h). After milling for 32 h of Ti100-xMgx (x = 10, 15, 20) composite powders, the solid solubility of the Mg in Ti reached about 0.5 wt.%, 1.14 wt.%, and 1.92 wt.%, respectively. It was found that the crystallite size of the milled powder decreased by increasing the milling time and reached the value of 4–11 nm after 32 h of milling. Moreover, the addition of the process control agent after 12 h and 20 h significantly reduced the agglomeration by cold welding. As a result, the average particle size of the dispersed composite powder Ti100-xMgx (x = 10, 15, 20) was refined to about 1 μm which indicated that the Ti controlled the final size as being a major alloying element. The maximum value of the density of green compacts was found to be 2.69 g/cm3 for Ti–10Mg.