摘要
In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.
以AMS 4777粉末为填料,研究瞬时液相连接IN-738LC高温合金的显微组织演变,获得完全等温凝固时间。研究间隙大小和连接时间对接头组织的影响。当间隙大小为40μm时,完全等温凝固时间为45 min。在不完全等温凝固的情况下,连接区的残余液相在非平衡条件下冷却,形成γ-γ共晶相。间隙大小与时间存在非线性关系。随着间隙增大,共晶相变宽。在扩散影响区,发现大量合金元素,其浓度达到峰值,这是由于形成了硼化物和硅化物等金属间化合物。随着间隙增加,所需连接时间增加,合金元素有更多的时间进行扩散和分布至更大区域。因此,合金元素浓度随间隙增加缓慢降低。已有双相模型不能准确预测IN-738LC-AMS 4777-IN738LC瞬时液相连接系统的完全等温凝固时间。
