Effect of Isothermal Solidification Behavior of Al-Si Brazing Filler Layer on the Braze-ability of Al-Alloy to Stainless Steel in the Air

Abstract

In order to clarify such brazing conditions for making sound joints of Al-alloys to stainless steel as to wet the Al-Si brazing filler on the stainless steel before rapid isothermal solidification of the filler, the solidification time is estimated by the numerical analysis and is also measured experimentally. The numerical analysis is conducted for the brazing process of the A1050 pure aluminum base metal and BA4045 aluminum-silicon brazing filler. The analysis contains both the initial dissolution of the base metal by the molten brazing filler and the following isothermal solidification behavior. The movement of the solid-liquid interface is calculated and the total solidification time is estimated. The brazing experiment between the same combination of metals shows the total solidification time is much less than the numerically estimated time. The element analysis by EPMA indicates that the zinc in the flux plays the dominant role in the brazing process. According to the results, the time to solidify the brazing filler layer is 30×10-3 H 2 s, where H is the initial brazing filler layer width in µm. To obtain the brazed joint between the Al alloys and stainless steel, the initial brazing filler layer of at least 30 µm and the holding time of at least 30 s at the brazing temperature are considered to be suitable for the brazing.

In situ silicon particle reinforced ZA27 composites: Part 1 – Microstructures and tensile properties

“…This can be further demonstrated by the isothermal section of Zn-Al-Si alloy at 525uC shown by Fig. 2b, 14,21 in which the A point represents the composite composition. It indicates that the composite has two phases of silicon and liquid at 525uC and silicon is the primary phase.…”

“…Figure 2a presents a phase diagram of Zn-Al-Si alloy at silicon atomic fraction of 0?099 (being equivalent to 6?13 mass% silicon for Zn-27Al alloy (in mass%); 10 vol.-% in the present work is equivalent to 4?76 mass%. Table 1 shows the conversion relationships between the volume percentages and mass percentages of the silicon content in the composites) and the vertical line presents the composition of Zn-27Al (in mass%), 20,21 which shows that the primary phase should be silicon. This can be further demonstrated by the isothermal section of Zn-Al-Si alloy at 525uC shown by Fig.…”