为研究激光表面微凹坑对AZ31B镁合金耐腐蚀性能的影响,利用光纤激光器在材料表面制备微凹坑阵列。通过扫描显微镜观测微凹坑的形貌、直径和深度,利用双单元电化学工作站测试微凹坑制备前后材料表面的动电位极化曲线。结果表明:微凹坑的直径和深度均随激光功率的增大而增大,微凹坑周围出现烧蚀现象;微凹坑直径与扫描次数无显著相关性,但微凹坑圆度与扫描次数呈正相关性。在相同微凹坑密度下,与未处理试样相比,激光功率为6、10、16 W时试样的自腐蚀电位分别向正移-33、40、26 m V,自腐蚀电流分别减少了91.93%、92.09%、91.19%。激光功率为10 W时具有最好的抗腐蚀性能;在相同激光功率下,与未处理试样相比,微凹坑密度为1.5%、2.5%、5.0%时试样的自腐蚀电位分别向正移21、40、56 m V,自腐蚀电流分别减少了92.22%、92.09%、94.05%。在实验密度范围内,微凹坑密度越高,AZ31B镁合金表面的抗腐蚀性能越好。
A high and stable brake disc friction coefficient is needed for automobile safety, while the coefficient degrades due to elevated temperature during the braking process. There is no better solution except changes in material composition and shape design optimization. In the dynamic strain aging(DSA) temperature regime of gray cast iron, micro-dimples with different dimple depth over diameter and surface area density are fabricated on the material surface by laser peening(LP) which is an LST method. Friction behavior and wear mechanism are investigated to evaluate the effects of surface texturing on the tribological performance of specimens under dry conditions. Through LP impacts assisted by DSA, the friction coefficients of the LPed specimens increase noticeably both at room temperature and elevated temperature in comparison to untreated specimens. Moreover, the coefficient of specimen with dimple depth over diameter of 0.03 and surface area density of 30% is up to 0.351 at room temperature, which dramatically rises up to 1.33 times that of untextured specimen and the value is still up to 0.3305 at 400℃ with an increasing ratio of 35% compared to that of untreated specimen. The surface of textured specimen shows better wear resistance compared to untreated specimen. Wear mechanism includes adhesive wear, abrasive wear and oxidation wear. It is demonstrated that LP assisted by DSA can substantially improve wear resistance, raise the friction coefficient as well as its stability of gray cast iron under elevated temperatures. Heat fade and premature wear can be effectively relieved by this surface modification method.
利用脉宽为8 ns的Nd:YAG脉冲激光对AZ31B镁合金表面进行激光喷丸处理,研究激光喷丸诱导微织构对AZ31B镁合金耐腐蚀性能的影响,进行表面微织构的形貌分析,测量试样表面的动电位极化曲线。结果表明,激光喷丸产生的微织构周围未出现烧蚀现象,其微凹坑的直径和深度随激光能量的增加而增大,随喷丸次数的增加呈现先增大后趋于饱和趋势。与未处理试样相比,在相同微织构间距下,激光能量为1.0 J、1.5 J、2.0 J时试样的自腐蚀电位分别向正移95 m V、123 m V、151 m V,自腐蚀电流密度分别减少36.48%、50.26%、60.42%;在相同激光能量下,微织构间距为1.0 mm、1.5 mm、2.0 mm试样的自腐蚀电位分别向正移145 m V、134 m V、123 m V,自腐蚀电流密度分别减少50.26%、46.19%、44.34%。研究表明激光喷丸诱导的微织构提高了AZ31B镁合金表面的耐腐蚀性,且激光能量越高,喷丸间距越小,抗腐蚀性能越好。
