LOW MELTING NICKEL-MANGANESE-SILICON BASED BRAZE FILLER METALS FOR HEAT EXCHANGER APPLICATIONS

Ni-Mn-Si based braze filler alloys or metals which may be nickel-rich, manganese-rich, or silicon-rich braze filler alloys, have unexpectedly narrow melting temperature ranges, low solidus and low liquidus temperatures, as determined by Differential Scanning calorimetry (DSC), while exhibiting good wetting, and spreading, without deleterious significant boride formation into the base metal, and can be brazed at lower temperatures. The nickel rich alloys contain 58 wt % to 70 wt % nickel, the manganese-rich alloys contain 55 wt % to 62 wt % manganese, and the silicon-rich alloys contain 25 wt % to 29 wt % silicon. Copper with or without boron to partly replace nickel may be employed without any substantial increase of the melting point, or to reduce the melting point. The braze filler alloys have sufficient brazability to withstand high temperature conditions for thin-walled aeronautical and other heat exchangers.