(長安大學 材料科學與工程學院，西安 710064)
摘 要: 采用掃描電鏡和電子背散射衍射等研究了激光重熔Inconel 718合金微觀組織和顯微硬度在不同熱處理工藝與超聲沖擊強化(UIT)作用下的演化規(guī)律。結果表明：原始態(tài)重熔區(qū)(FZ)組織主要由γ枝晶干和Laves相組成；經(jīng)固溶處理(SHT)后，Laves相大量溶解，元素偏析減弱，顯微硬度降低；固溶+雙時效處理(SDA)后，γ′和γ″強化相大量析出，顯微硬度顯著提升；而直接進行雙時效處理(DA)時，由于時效溫度不足以溶解Laves相，F(xiàn)Z形貌與原始態(tài)非常類似，但強化相γ′和γ″充分析出，使FZ顯微硬度明顯升高。之后，對原始態(tài)(AR)試樣及熱處理態(tài)試樣表面進行UIT處理后，試樣表層均出現(xiàn)嚴重塑性變形和壓應力，位錯密度顯著增加，并產(chǎn)生了不同深度的硬化層。相比于AR和SHT樣品，UIT處理對SDA和DA樣品產(chǎn)生的強化效果減弱，這與γ′和γ″強化相的位錯強烈交互作用有關。
關鍵字: 激光重熔；Inconel 718高溫合金；熱處理；超聲沖擊強化
（School of Materials Science and Engineering, Chang''an University, Xi’an 710064, China）
Abstract:The effect of heat treatment and ultrasonic impact treatment (UIT) on the evolution of microstructure and microhardness of laser remelted Inconel 718 superalloy was studied by optical microscopy, scanning electron microscopy and electron backscatter diffraction techniques. The results show that the fusion zone (FZ) of as-received (AR) sample is mainly composed of γ dendrite core and interdendritic Laves phase. After solution heat treatment (SHT), the majority of Laves phase dissolves and the element segregation weakens, the microhardness reduce. After the solution + double aging treatment (SDA), a large number of γ′ and γ″ strengthening phases precipitate, significantly improve the microhardness. In addition, the direct double aging treatment (DA) sample are similar with the SDA sample in microstructural morphology, which is associated with the undissolved Laves phases due to the relatively low aging temperature. Simultaneously, the γ′ and γ″ strengthening phases are completely precipitated after aging, resulting in a significant microhardness increment comparable to that of SDA sample. After UIT treatment, severe plastic deformation together with compressive stress and high-density dislocations is produced near the surface of the four samples but the obtained hardening layers ranged indistinct depths. The strengthening effect of UIT on the SDA and DA samples is not as significant as the AR and SHT samples, which is mainly due to the strong interaction between γ′/γ″ strengthening phases and dislocations.
Key words: laser remelting; Inconel 718 superalloy; heat treatment; ultrasonic impact treatment
