Study On Preparation Of Ti-Al Alloy Powder By Mechanical Alloying And Its Properties

Ti-Al alloys are usually applied to the engine of aviation, aerospace and automobile for their light weight, excellent properties of high temperature, oxidation resistance and creep resistance. While the Ti-Al alloys produced by casting technology are always with complex preparation process, low compressive strength which usually between250-600MPa, and also low indoor temperature compressibility which varies between0.3%-4%To solve this problem, when preparing Ti-Al alloys, this research adopted mechanical alloying method which can avoid complex solidification process and had easy process conditions. This method is expected to improve compressive strength and room temperature compression rate of Ti-Al alloys. Methods were as follow: using high-energy ball mill to manufacture mechanical alloying powders of Ti-48at%Al, and then applying Pressing, sintering technology to prepare Ti-48at%Al alloy materials. In this study, the ball mill process of mechanical alloying and pressure molding and sintering parameters were systematically studied, and the influence from other materials to Ti-48at%Al powders and materials was also discussed.Primarily, the influence from high-energy ball mill process parameters to Ti-48at%Al powders was studied. We respectively studied rotational speed, milling time, ball/powder-weight ratio and additive amount of process control agent. Researches show that the best parameters of ball milling process are the rotational speed of1100rpm, milling time of3h, ball/powder-weight ratio of20:1, and additive amount of2%. The phase evolution progress can be described by:Ti+Al�'Ti (Al)、 TiAl、TiAl3、Ti3Al�'TiAl3、Ti3Al�'amorphous state. According to Miedema model, we calculated that when T=300K, the Gibbs free energy of TiAl, TiAl3, Ti3Al and amorphous free energy, and the Gibbs free energy difference is that TiAl�'>9.24KJ/mol Ti3Al�'2.68KJ/molTiAl3�'334278KJ/mol非晶态。 Secondly, the influence from pressing process and sintering process to Ti-48at%Al material properties was studied. Researches show that the best pressing parameters are that molding pressing of35MPa, the holding time of10min. The best sintering parameters are that sintering temperature of950℃, holding time of1h. The performances of Ti-48at%Al material Prepared using the best parameters are that Vickers hardness can be660HV, the compressive strength can be310MPa, and compression rate can be2.2%.Finally, the influence of Ni, Cu, and CNTs for Ti-48at%Al powders and materials was also discussed, Researches show that Ni, Cu, CNTs could increase D50of Ti-48at%Al powders and also reduce the material density. Ni element accelerated the process of mechanical alloying powders of Ti-48at%Al, and compressive strength was increased to739MPa, the compression rate was increased to2.9%, and the hardness was up to698HV. Cu element made the compression ratio increased to4.64%, the compressive strength increased to520MPa, and hardness was up to745HV. CNTs made its compressive strength drop to168MPa, and hardness was decreased to596HV.