Effect of Ni addition on the dielectric strength and liquid phase separation of Cu–Cr alloys during the vacuum breakdown

• Alloying of Cr95Ni5 (at.%) can strengthen the dielectric strength of Cr by 130%.
• Cr–Ni alloy powders can improve the dielectric strength of the Cu–Cr–Ni alloys.
• The dielectric strength of commercial Cu55Cr45 contacts is improved by 61%.
• The addition of Ni could restrain the liquid phase separation of the Cu–Cr alloys.

The Cr–Ni and Cu–Cr–Ni alloys were prepared and their dielectric strengths were tested in a vacuum chamber. The experimental results showed that the Cr95Ni5 (at.%) alloy prepared by vacuum arc melting could strengthen the dielectric strength of Cr by 130%, and the addition of the Cr–Ni alloy powders could more obviously improve the dielectric strength of the Cu55Cr45 alloy than that of Ni. The dielectric strength of Cu (Cr95Ni5)(Cu = 55, Cr95Ni5 = 45, at.%) was higher than that of commercial Cu55Cr45 alloys and improved by 61%. The results revealed that the liquid phase separation took place in the Cu–Cr–Ni alloys during the vacuum breakdown. The Ni addition could restrain the liquid phase separation of the Cu–Cr alloys and refine the Cr particles.