热冲压钢Al-Si镀层形貌动态演化及形变开裂特征

Dynamic morphology evolution and deformation cracking characteristics of Al-Si coating on hot stamping steel

对热冲压钢Al-Si镀层在加热和高温拉伸阶段的表面形貌动态演化过程进行了观测,分析了形变条件下Al-Si镀层的裂纹形貌与开裂特征。结果表明,在奥氏体化加热过程中,不同熔点的合金相在镀层内逐步形成,使镀层经历了从固态到液态最终再到固态的转变过程,并导致镀层表面形貌的改变。加热后的Al-Si镀层内以Fe2Al5相为主,导致镀层表现为整体脆性,其开裂行为对拉伸变形极其敏感。在形变过程中,镀层内产生多条垂直于拉伸方向的裂纹,且裂纹宽度随应变量的增加持续增大,最终产生的界面裂纹导致镀层与基体的剥离。

The dynamic evolution process of surface morphology of Al-Si coating on hot stamping steel during heating and hot tensile stages was observed.The crack morphology and cracking characteristics of Al-Si coating under deformation condition were analyzed.The results show that during austenization heating process,alloy phases with different melting points are formed gradually in the coating,which makes the coating undergo a transformation process from solid state to liquid state and finally to solid state,and results in the change of surface morphology of coating.The dominant phase in the heated coating is Fe2 Al5,which leads the coating to show overall brittleness and its cracking behavior is extremely sensitive to the tensile deformation.During the deformation process,many cracks perpendicular to tensile direction occur in the coating,the crack width increases continuously with the increase of strain amount,and the interfacial crack generated eventually leads to the debonding of coating from substrate.