激光冲击强化和时效处理对AZ80镁合金形变孪晶及析出相的影响

Effect of Laser Shock Peening and Aging Treatment on Deformation Twins and Precipitates of AZ80 Magnesium Alloy

采用固溶+激光冲击强化(LSP)+时效方法,研究了AZ80镁合金轧板和铸态组织参数(形变孪晶和析出相)和残余应力演变,以及时效处理对其影响。结果表明,固溶+LSP处理后轧板强化层内形成高密度孪晶的形变带,铸态合金高密度形变孪晶产生于晶界附近,均产生于应力集中和高能区域,产生一次或多次孪晶,呈平行或交叉孪晶。时效后连续析出大量的颗粒状β相,其优先于形变带内、孪晶界面或片状孪晶内析出,与晶粒尺寸相关。时效后轧板和铸态冲击表面残余压应力分别为由-100.8 MPa和-68.9 MPa转变为-67.8 MPa和-35.9 MPa,即应力松弛为32.7%和48.7%。LSP次表层硬化效果明显,其时效强化效果较弱。残余压应力及其热稳定性是影响高密度形变孪晶的形成主要因素之一。

In order to study the effect of laser shock processing （LSP） on mechanical properties of magnesium alloys, the tensile stress-strain curves and microstructures of AZ31 and AZ80D-T6 magnesium alloys are investigated by electronic universal tensile machine and with Nd： glass laser with the wavelength of 1064 nm and pulse width of 20 ns. The results show that after LSP, the tensile strength of AZ80-T6 and AZ31 alloys are increased by 4.6% and 15.7%, the surface hardness are increased by 22.7% and 31.8%, respectively. The strengthening effect of LSP on AZ31 is more significant than AZ80D-T6. The LSP generates high value residual compressive stress and high-density twins as well as the lamellar or short columnar or dynamic precipitation b phases. The grains are refined and the ultrafine grains are formed. The effect of pre - aged β precipitates on LSP strengthening effect and tensile fracture characteristics are discussed.