【摘要】 采用光学显微镜和扫描电子显微镜对球墨铸铁激光表面重熔和淬火的显微组织形成进行详细分析,研究了激光快速加热和冷却过程中的相变特性和原始物相加热状态之间的关系。发现在激光重熔处理后的熔合区附近的过热区,产生了较细小的“巍氏组织”,观察到了在奥氏体晶粒内部直接形核的铁素体。分析了C、Fe原子在石墨和铁素体界面间可以互扩散的条件,证明了C原子向铁素体中的扩散可以在固态中进行,Fe原子向石墨中的溶入只有在形成液相时才能进行,当石墨中扩散一定量的Fe元素之后,冷却时会导致石墨区域的变异。提出铁素体基球墨铸铁激光淬火后的马氏体可能是由过饱和的δ-铁素体直接转变而来的过饱和的α-铁素体（马氏体）,没有中间的γ-奥氏体状态出现的观点。指出球墨铸铁经过激光表面重熔或淬火处理后,由于快速加热和快速冷却,所获得的相应的显微组织细小,重熔后的表面层显微组织为离异共晶白口铸铁显微组织,其物相够成Fe₃C+马氏体的混合组织。重熔后能获得球墨铸铁与白口铸铁的复合材料。更多还原

【Abstract】 Optical Microscope(OM) and Scanning Electronic Microscope(SEM) were used to analyse the microstructure formation of modular cast iron laser surface remehing and laser quenching,and investigated the relation between the phase transition characteris- tic and the condition of the primitive phase heating up in laser fast heating up and cooling process.Found that the Widmanstaten struc- ture were generated in the superheat region after the laser remelting process,and observed the ferrite which were direct shaped nucleus in the anstenite crystal.Analysed the condition of C,Fe atom interdiffuse between the graphite and the ferrite’s interface,testified C atom could diffuse into ferrite in solid state,and Fe atom must diffuse into graphite in liquid stage.Proposed the viewpoint of the mar- tensite might be transited directly from the oversaturationδ-ferrite,and had noγ-austenite appeared.Pointed out that after the fast heating up and cooling,the corresponding microstructure refined,and the surface microstructure were the separate eutectic white cast i- ron,which are composed of Fe3C+martensite.更多还原