利用XRD、SEM和TEM等手段分析了TC16钛合金辊模拉丝变形过程中的相组成和显微组织的变化情况,并对不同应变的辊模拉丝变形丝材进行了室温拉伸性能与显微硬度测试。结果表明,在辊模拉丝变形过程中,TC16钛合金丝材主要由α相和β相组成,部分β相发生应力诱发α''马氏体相变;随着辊模拉丝真应变的增加,TC16钛合金丝材的显微组织明显细化,当真应变达到2.14时,横截面和纵截面中的α相和β相纤维状组织厚度均约为0.3 μm,两相衍射斑点已经近似环状,表明两相显微组织也明显细化;随着辊模拉丝真应变的增加,TC16钛合金丝材的抗拉强度和显微硬度大幅提高,当真应变达到2.14时,TC16钛合金丝材的显微硬度由初始的266 HV提高到365 HV。

Grain refinement is a challenging topic to improve mechanical properties of metallic materials, especially for titanium alloys which show great potential in aerospace and medical implants areas due to the low density and good corrosion resistance. However, severe plastic deformation (SPD) technologies which have been commonly used in laboratory in smaller scale are difficult to be realized in industrial. Considerable researches are therefore paying attention to the development of new technologies for improvement of grain refinement at relatively lower strains. In this work, the dual phase TC16 titanium alloy showing excellent room temperature ductility was investigated with emphasis on the feasibility of producing ultrafine grains by roller die drawing at room temperature. The techniques of XRD, SEM, TEM, Vickers hardness test and tensile test were employed to analyze the phase constitutes, microstructure evolutions and preliminary mechanical properties of the alloy deformed at different conditions. Results reveal that TC16 titanium alloy mainly consists of α and β phases after roller die drawing at room temperature, and a small quantity of stress-induced α" martensite can be additionally identified inside β grains. The grain sizes of α phase and β phase decrease with strain increasing, which result to enhanced tensile strength and Vickers hardness. Indeed, the fibrous morphology of both α phase and β phase with 0.3 μm in thickness and a high value of 365 HV in Vickers hardness were revealed at the applied true strain of 2.14. Ultra-fine grains evidenced by a near-ring SAED spots were therefore achieved in the present case.