Microstructural evolution of Cu/W nano-multilayers filler metal during thermal treatment

• Published in: Vacuum 2022-06, Vol.200, p.111007, Article 111007
• Main Authors: Li, Hong, Xing, Zeng-cheng, Li, Bo-jin, Liu, Xu-sheng, Lehmert, Benjamin, Matthias, Manka, Li, Zhuo-xin, Tillmann, Wolfgang
• Format: Article
• Language: English
• Subjects: Annealing; Cu/W nano-multilayers; Microstructure evolution; Thermal stability
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/j.vacuum.2022.111007

Copper/Tungsten (Cu/W) nano-multilayers show potential for application as novel low-temperature brazing filler metals. Therefore, researchers are interested in understanding phase stability and microstructural evolution of the nano-multilayers during thermal treatment. A repetition of 50 alternating nanolayers of Cu and W with individual thicknesses of 10 nm were prepared by magnetron-sputtering on silicon substrates. The structural evolution of Cu/W nano-multilayers (NMLs) within the temperature range 400 °C–800 °C was monitored using real-time in-situ XRD, SEM, TEM, SAXS, DSC and in-house XRD system. The results showed that the melting point of Cu/W nano-multilayers determined using DSC was 793.694 °C was remarkably lower than the melting point of bulk Cu(1083 °C) and W (3140 °C). After annealing at 400 °C for 30 min, the surface of the NMLs exhibited more copper grains, with significant coarsening of the copper grains. The layered structure of the Cu/W NMLs was unaffected after annealed at 400 °C. When annealed at 600 °C for 30 min, some Cu particles migrated into the W layers along the internal interface leading to cracks which partially collapsed the original stratified structure. The nano-multilayered structure was completely destroyed when annealed at 800 °C. Further, the in-situ XRD results showed that the copper grains grew substantially, while the tungsten size remained unchanged with increasing temperature. •Magnetron-sputtering deposition of Cu/W nano-multilayers.•Real-time in-situ XRD investigation of the microstructural evolution during thermal treatment.•Possible application of nano-multilayers filler metal for lower brazing temperature of Titanium to steel.