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利用输出波长为1064 nm的钕玻璃YAG激光器,对2000系铝铜镁航空铝合金进行了激光冲击表面改性试验。用TEM和IFFT方法分析了位错及其运动在铝合金激光冲击表面改性中的作用。结果表明,激光冲击表面改性效果明显,可使表层硬度提高50%以上;残余压应力达到120 MPa以上。激光冲击在基体中诱发大量位错,位错组态主要包括刃型位错、异号位错组和由位错偶构成的螺型位错等。合金中的析出相与基体中的应变位错保持半共格关系,增强了析出相颗粒的强化作用;激光冲击的超高应变率导致基体产生有序连续排列的同号位错形成位错墙,将基体分割为纳米级亚晶粒。激光冲击诱发的复杂位错组态是表层硬度和残余应力提高的内在原因。
Laser surface modification experiments were carried out on 2000 Al-Cu-Al alloy with Neodymium Glass YAG laser with output wavelength of 1064 nm. The effect of dislocation and its motion on the laser surface modification of aluminum alloy was analyzed by TEM and IFFT. The results show that the laser shock surface modification effect is obvious, the surface hardness can be increased by 50% or more; residual compressive stress reaches 120 MPa or more. Laser shock induces a large number of dislocations in the matrix. The dislocation configuration mainly includes edge dislocation, odd-numbered dislocation group and screw dislocation formed by dislocation couple. The precipitated phase in the alloy maintains a semi-coherent relationship with the strain dislocations in the matrix and enhances the strengthening effect of the precipitated phase particles. The ultrahigh strain rate of the laser shock causes the matrix to form ordered dislocation dislocation walls , The matrix is divided into nano-scale sub-grain. The complex dislocation configuration induced by laser shock is the intrinsic reason for the increase of surface hardness and residual stress.