增材制造高体积陶瓷增强马氏体钢缺陷抑制与机理研究

Defects Suppression and Mechanism in Additive Manufacturing High-volume SiC Reinforced Maraging Steel

随着航空航天和交通运输等领域对材料性能的要求日益严格,高体积分数陶瓷增强金属复合材料成为一种发展需求。基于激光增材制造原位成型多组分材料的优势,采用选区激光熔化(SLM)制备了15%Si C(体积分数)陶瓷增强马氏体时效钢(MS)复合材料(MMC)。着重针对Si C与金属基体之间的相容性和开裂问题,从多个方面研究了SLM成型过程中的裂纹缺陷抑制措施,包括激光重熔、预热基板、设计支撑与成型方向;提高基体预热温度能够显著减少裂纹数量。同时,研究了SiC陶瓷对微观组织、相结构与相转变和硬度的影响及其与开裂的联系。MMC微观组织为带状组织和粗化的树枝晶组织,还存在富Si元素区域。MS中主要为马氏体相,添加Si C促进了奥氏体转变,使得MMC中主要为奥氏体相,树枝晶间仍可发现少量马氏体相。树枝晶主要为大角度晶界,表明MMC中形成了大量的位错。此外,加入高体积分数Si C后,基体材料的硬度得到明显提升。

With the increasingly stringent requirements of aerospace and transportation on high-performance materials,high-volume fraction ceramic reinforced metal matrix composites(MMCs)have become a developing trend.Taking the advantages of laser additive manufacturing in-situ processing multi-component materials,15 vol.%SiC ceramic reinforced maraging steel(MS)MMCs are prepared by selective laser melting(SLM).Facing the compatibility and cracking problems raised between SiC and metal matrix,great efforts on the defect’s suppression during SLM process are taken from various aspects,including laser remelting,substrate preheating,design of support and build directions;among which substrate preheating suppressed cracking significantly.In addition,the effects of SiC on microstructure,phase structure and transition,and hardness are investigated,which could potentially associate with cracking.The microstructure of MMC is strip and coarse cellular structures,with Si-rich regions.The addition of SiC promotes the transformation of martensite in MS to austenite in MMC,since MMC consists of majority austenite and a small amount of martensite distributed between dendrites.Notably,most of these dendrites are high-angle grain boundaries,indicating that a large number of dislocations are formed in MMC.Furthermore,the high-volume SiC increases the hardness of the MS matrix significantly.