TC17钛合金激光冲击温强化机制的研究

Strengthening Mechanism of TC17 Titanium Alloy Warm Laser Shock Peening

目的提高材料在交变载荷和高温下的疲劳性能,稳定材料的位错结构,增加位错的钉扎效果,使激光诱导的残余压应力更加稳定,有效地抑制强化效果的高温失稳。方法通过提高温度发生动态应变时效(DSA),并与激光冲击温强化(WLSP)结合,使得材料表面形成更深的残余应力层和纳米级沉淀相。对TC17钛合金温控激光冲击强化后的显微硬度、残余应力等性能进行了初步探索。结果经200℃的WLSP后,TC17钛合金的显微硬度可达385HV,相比未强化时提高了18.48%,相比于室温的LSP提高了4.62%。深度方向的残余压应力幅值呈现先增大后减小的趋势,200℃时残余应力达到-236 MPa,相比于常温强化提高了14.56%。观察微观组织发现,位错结构的稳定性和位错密度得到提高。结论激光冲击温强化(WLSP)技术提高了材料表面残余压应力层的高温稳定性,有利于抑制疲劳裂纹的萌生和扩展,有效地提高了高温条件下残余应力和表面强度的稳定性。该技术操作相对简单,无污染,残余应力高温维稳效果显著。

The work aims to improve fatigue properties of materials under alternating load and at high temperature, stabilize dislocation structure of materials. The pinning effect of dislocation was significantly enhanced, laser induced residual compressive stress was more stable, and high temperature instability of peening effect was effectively inhibited. Deeper residual stress layer and nanoscale precipitated phase were generated on the surface of materials by combining dynamic strain aging（DSA）（due to temperature rise） and warm laser shock peening（WLSP）, which leaded to deeper residual stress layer and nanoscale precipitate. After WLSP at 200 ℃, microhardness of TC17 titanium alloy could reach 385 HV, increased by 18.48% compared with that of original alloy, and 4.62% compared with that of alloy receiving LSP at room temperature. Residual compressive stress amplitude in depth direction first increased and then decreased, residual stress reached-236 MPa at 200 ℃, increased by 14.56%, compared with that receiving peening at normal temperature. Microstructure observation results showed that both stability and dislocation density of the dislocation structure were improved. High-temperature stability of residual compressive stress layer on the surface of materials is enhanced by WLSP technology, initiation and expansion inhibition of fatigue cracks are facilitated, stability of residual stress and surface strength at high temperature is effective improved. Warm laser shock peeningtechnology is relatively easily operated, pollution-free, and plays a significant role in maintaining stability of residual stress at high temperature.