预扭转及退火热处理对TA2拉伸力学性能的影响

Influence of Pre-torsion and Annealing Heat Treatment on the Tensile Mechanical Properties of TA2

研究了预扭转和退火热处理对TA2拉伸力学性能的影响。结果表明,预扭转可显著增强TA2的拉伸屈服强度和极限强度,在一定范围内屈服强度随预扭转角增加而增大,当预扭转角超过一定值(6π)时,屈服强度急剧下降;极限强度随预扭转角增大一直呈上升趋势;延伸率随预扭转角的增加逐渐降低。预扭转后TA2不同温度(350～750℃)下的退火热处理试验表明,随着退火温度的提高,TA2强度逐渐降低,650℃时其强度已降低至母材初始值;延伸率随退火温度的升高而逐渐升高,但不能完全恢复至母材初始值。观察断口发现,随着预扭转角增加断口韧窝逐渐变小、变浅,预扭转为8π时出现了河流发散状的解理条纹。金相组织表明,预扭转后产生的大量孪晶和形变组织是导致TA2强度增大的主要原因。

The effects of pre-torsion and annealing heat treatment on the tensile mechanical properties of TA2 were studied. According to tensile test results, the pre-torsion can significantly enhance the tensile yield strength and ultimate strength of TA2. The yield strength increases with the increase of pre-torsion angle in a certain range, and drops sharply when the pre-torsion angle exceeds a certain value(6π). The ultimate strength increases all the time with the pre-torsion angle increasing. The elongation decreases with the increase of pre-torsion angle. Subsequent annealing heat treatment tests of pre-torsion TA2 at different temperatures(350~750 °C) show that the strength gradually decreases with the increase of annealing temperature. When the temperature is 650 °C, the strength has been reduced to the initial value of parent metal. The elongation increases with the increase of temperature, but it cannot recover to its initial value of parent material. The observation of fracture surface shows that dimple gets smaller and shallower with the increase of pre-torsion, and there are lots of cleavage striation characterized by river pattern when pre-torsion angle is 8π. The observation of SEM shows that twins and deformation tissues after the pre-rotation is the main reason for the increase of TA2 strength.