【摘要】 采用熔化和汽化两种模式对纯镁表面进行了脉冲电子束轰击处理,并在实验和理论基础上用数值方法模拟了温度场、熔化过程及汽化过程的演化。结果表明,在熔化模式下,次表层先熔化和准静态压应力共同作用导致次表层液滴喷发,形成典型的火山口形貌,并产生强的瞬间冲击热应力;在汽化模式下,沸腾在表层一定范围内同时进行,使得表面起伏不平,并产生大量小液滴,在电子束流中,这些小液滴被充上负电,并在电场力的作用下重新返回表面,从而解释了汽化后的特殊表面形貌。汽化量的计算值与实测值也符合较好。更多还原

【Abstract】 The present paper studied the melting and evaporation modes of pure Mg treated by high current pulsed electron beam (HCPEB).Based on experimental investigations,a physical model was proposed to describe the transient thermal process associated with the pulsed beam bombardment,and the melting and evaporation processes were simulated.Under the melting mode,subsurface layer melting and action of quasi-static compressive stress lead to the eruption of small droplets from the subsuface layer,which corresponds to the formation of craters on the surface and results in an intense thermal shock stress.Under the evaporation mode,the boiling occurs simultaneously in a certain depth range,which is the main cause for the increased suface roughness and for the spillage of small droplets from the boiling liquid.These droplets are charged in the electron beam,and some of them are attracted back to the surface by electric field.This mechanism explains the presence of particles on the surface observed on pure Mg treated under the evaporation mode.The calculated evaporation rate is in good agreement with experimental results.更多还原