拉伸高速铣削对TC4钛合金疲劳性能的影响

Fatigue Resistance Improvement of TC4 Titanium Alloy with High Speed Milling Under Stretching Fixation

提出采用拉伸高速铣削新方法来提高钛合金等难加工材料的疲劳性能。进行了TC4钛合金的拉伸高速干铣削试验，拉伸装夹应力从O～327MPa，铣削速度从190～570m／min，其他加工条件保持不变。对铣削件进行低周疲劳试验，建立疲劳裂纹监测系统对疲劳裂纹进行在位停机拍摄，并用JSM-7001F型场发射扫描电镜对疲劳断口进行观察。结果表明在高速铣削中采用拉伸装夹能使试件疲劳寿命提高8％～16％，这归因于拉伸铣削形成了更为有利的表层残余压应力层，延长了疲劳裂纹萌生寿命。

High speed milling under stretching fixation （SF-HSM） is proposed as a new method of anti-fatigue machining of difficult-cut-material, such as titanium alloy. High speed dry milling experiment of TC4 titanium alloy under stretching fixation is implemented, under the condition of the stretching stress ranged from 0 to 327 MPa and the milling speed ranged from 190 to 570 m/min, while other machining parameters are kept to be constant. Low-cycle fatigue test is carried out while the fatigue crack is in-situ observed with a fatigue crack monitoring system during periodical shutdown of the fatigue machine, and the fatigue fracture is observed on JSM-7001F field-emission scanning electron microscope. Experimental result shows that stretching fixation in high speed milling causes an 8%-16% growth of the fatigue life, and it is attributed to high residual compressive stress induced by SF-HSM, thus increasing fatigue crack initiation life.