低价氯化钛浆料直接电化学还原制备钛铝合金新工艺研究

A new process for preparing Ti-Al alloys from low-valance titanium chlorides slurry by direct electrochemical reduction

针对低价氯化钛(LTC)浆料熔盐电解制备钛铝合金存在的电化学行为研究不系统、合金产品的高温抗氧化特性不明晰等问题,采用电化学工作站、示差热重分析仪等手段对LTC浆料在熔盐体系中电化学行为及合金产品的高温抗氧化特性进行研究。结果表明,LTC浆料在熔盐体系中可直接电化学还原制备Ti-Al合金,且为逐级还原的历程:Ti^(3+)→Ti^(2+),Al^(3+)→Al,Ti^(3+)/Al^(3+)→Ti-Al合金和Ti^(2+)→Ti;随着熔盐体系中Ti^(3+)离子浓度的增加,钛铝合金的组成变化规律为:Al/Al_(3)Ti→Al_(3)Ti_(2)/Al_(5)Ti_(2)→AlTi/Al_(0.64)Ti_(0.36)→Al_(0.64)Ti_(0.36)/AlTi_(3)→AlTi_(3)→AlTi_(3)/Ti→Ti,产品形貌变化规律为:粗枝晶→细枝晶→细球状结构→粗球状团聚体→细球状团聚体→细球多孔状→多孔状结构。钛铝合金中随着铝含量和产品致密性的增加,合金的抗高温氧化性能逐渐增强,Al_(0.64)Ti_(0.36)/AlTi_(3)合金经高温熔炼后呈Al含量更高的α_(2)/γ和γ组织,使其高温抗氧化性能优于商用Ti_(48)Al_(2)Cr_(2)Nb。钛铝合金产品高温氧化历程为:Ti-Al合金→铝酸钛→金红石/氧化铝,并且形成的氧化物层可有效防止钛铝合金的进一步氧化。

Owing to the lack of systematic research on electrochemical behaviors and unclear high-temperature oxidation resistance characteristics of Ti-Al alloys prepared from low-valence titanium chlorides slurry by the electrochemical reduction in molten salt,the electrochemical workstation and differential thermal gravimetric analyzer were used to study the electrochemical behavior of LTC slurry in the molten salt system and the high-temperature oxidation resistance characteristics of alloy products.The results show that LTC slurry can be directly electrochemically reduced to Ti-Al alloys,following a step-by-step reduction process:Ti^(3+)→Ti^(2+),Al^(3+)→Al,Ti^(3+)/Al^(3+)→Ti-Al alloys,and Ti^(2+)→Ti.As the concentration of Ti^(3+)ions in molten salts increases,the composition of Ti-Al alloys changes as follows:Al/Al3Ti→Al3Ti_(2)/Al_(5)Ti_(2)→AlTi/Al_(0.64)Ti_(0.36)→Al_(0.64)Ti_(0.36)/AlTi_(3)→AlTi_(3)→AlTi_(3)/Ti→Ti.The variation law of product morphology is as follows:coarse dendrite→fine dendrite→fine spherical structure→coarse spherical aggregate→fine spherical aggregate→fine spherical porous structure→porous structure.With the increase of aluminum content and product density in Ti-Al alloys,the high-temperature oxidation resistance gradually enhances.After high-temperature melting,Al_(0.64)Ti_(0.36)/AlTi_(3) alloy showsα2 andγphase structures with a higher Al content,and its high-temperature oxidation resistance is superior to commercial Ti48Al2Cr2Nb.The high-temperature oxidation process of Ti-Al alloys is as follows:Ti-Al alloys→titanium aluminate→rutile/alumina,and the formed oxide layer can effectively prevent further oxidation.