Ti掺杂对铝钼基合金相稳定性影响及其在钛合金中的应用评价

Effect of Ti Doping on Phase Stability of Al-Mo Based Alloys and Its Application Evaluation in Titanium Alloys

摘要:

钛合金中β稳定元素钼（Mo）通常以AlMo中间合金形式添加，但传统AlMo60合金中存在高熔点、高Mo含量的AlMo3相，易导致钛合金铸锭产生β偏析及硬质夹杂，严重危害构件疲劳性能。本文提出通过Ti掺杂改性AlMo合金，以调控其相组成，降低高熔点富Mo相（AlMo3）的形成风险。采用热力学计算优选AlMoTi合金成分，通过铝热还原法制备AlMo60及AlMo55Ti5合金，利用XRD、SEM、EDS及EBSD等手段表征物相组成与显微组织，并将优选合金应用于TC11钛合金铸锭及棒材的工程化试制。结果表明：Ti掺杂量为5 wt.%时，AlMo55Ti5合金中高熔点AlMo3相完全消失，转变为Al8Mo3及Al6MoTi相，组织均匀性显著提高。将该合金用于3吨级TC11钛合金熔炼，铸锭主成分偏差小、杂质元素可控、无宏观偏析及夹杂缺陷，锻造后棒材力学性能满足且优于标准要求，与使用传统AlMo60的TC11合金性能相当。本研究为高端航空钛合金用中间合金的均质化设计提供了新思路，具有重要的工程应用价值。

Abstract:

Molybdenum (Mo) as a β-stabilizer in titanium alloys is typically added via AlMo master alloys. However, the conventional AlMo60 alloy contains a high-melting, Mo-rich AlMo3 phase, which readily causes β segregation and hard inclusions in titanium alloy ingots, severely deteriorating the fatigue performance of components. This study proposes Ti doping to modify the AlMo alloy, tailoring its phase constitution to reduce the risk of forming the Mo-rich high-melting AlMo3 phase. The optimal AlMoTi alloy composition was determined by thermodynamic calculations. AlMo60 and AlMo55Ti5 alloys were prepared by an aluminothermic reduction method, and their phase constitution and microstructure were analyzed using XRD, SEM, EDS, and EBSD. The optimized alloy was then evaluated in the industrial-scale production of TC11 titanium alloy ingots and bars. The results show that at a Ti doping level of 5 wt.%, the high-melting AlMo3 phase in the AlMo55Ti5 alloy completely disappears, transforming into Al8Mo3 and Al6MoTi phases, along with significantly improved microstructural uniformity. When applied to the melting of a 3?ton TC11 alloy ingot, the main element deviations were small, impurity elements were well controlled, and no macro?segregation or inclusion defects were observed. The mechanical properties of the forged bars met and even exceeded the standard requirements, and were comparable to those of TC11 alloys produced using the conventional AlMo60 master alloy. This study provides a novel strategy for the homogenization design of master alloys for high?end aerospace titanium alloys, with considerable engineering application value.