TC16鈦合金輥模拉絲過程中的顯微組織和力學性能

TC16鈦合金輥模拉絲過程中的顯微組織和力學性能Microstructure and Mechanical Properties of TC16 Titanium Alloy by Room Temperature Roller Die Drawing

利用XRD、SEM和TEM等手段分析了TC16鈦合金輥模拉絲變形過程中的相組成和顯微組織的變化情況,并對不同應變的輥模拉絲變形絲材進行了室溫拉伸性能與顯微硬度測試。結果表明,在輥模拉絲變形過程中,TC16鈦合金絲材主要由α相和β相組成,部分β相發生應力誘發α''馬氏體相變;隨著輥模拉絲真應變的增加,TC16鈦合金絲材的顯微組織明顯細化,當真應變達到2.14時,橫截面和縱截面中的α相和β相纖維狀組織厚度均約為0.3 μm,兩相衍射斑點已經近似環狀,表明兩相顯微組織也明顯細化;隨著輥模拉絲真應變的增加,TC16鈦合金絲材的抗拉強度和顯微硬度大幅提高,當真應變達到2.14時,TC16鈦合金絲材的顯微硬度由初始的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.

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