Study On The Effect Of The Ferromagnetic Shape Memory Alloy Particles On The Arcing Performance Of Contact Material

The performance of electrical contact plays an important role on the life and reliabilityof the relay. With the development of automotive electrical system and demands of highreliability in automatic control, the popular contact material become little competitive sinceit has a poor arc blowout, many efforts have been made to obtain high-performance contactmaterial. The ferromagnetic shape memory alloys is a kind of new functional material,having phase transformation strain and decalescence properties, which was added tocontacts expect to extinguish the arc.In this paper, the silver-based contact materials adding ferromagnetic shape memoryalloys were prepared and the effect of the ferromagnetic shape memory alloys on the arcingperformance of contact material were discussed. The ferromagnetic shape memory alloyswere prepared by the arc melting，then the metal buttons were sealed into vacuum quartzampoules and annealed at900°C for72hours, followed by ice-water quenching. Themartensitic transformation temperature of Ni50+xMn25Ga25-x(x=4,5,6,7,8),Ni50Mn25+xGa25-x(x=9,10.5,13.5,12,15) and Mn50Ni50-xSnx(x=2,3,4,5) were determinedby DSC. The crystal structure were conducted on X-Ray diffractometer. The results suggestthe martensite structure for these alloys and the martensitic transformation temperaturemeet the requirements (more than200℃).With the powder metallurgy method, the above mentioned alloys were compound withsilver respectively. The ratio of the alloy to the whole materials was10%.The obtainedcontact materials have high density, high hardness and low resistivity. The contacts weretested in DC42V,8A and light load conditions, The electrical life test results show that thecontact were not sticking after50000times and100000times; Pits and projectionsappeared on the anode and cathode surfaces; The mass transferred from anode to cathode；The addition of alloy has a certain effect on arc suppression, and with the increase ofmartensite phase transformation temperature, the inhibition of arcing improved to a certainextent. In addition, the melting point of the alloy also have evident influences on arcingability, The materials with low melting point evaporation prone to erosion, crack, while thematerial with high melting point can inhibit molten silver flow, reduce material loss,strengthen contact welding resistance.