Effect of rare earth Ce on microstructure and properties of Zn-22Al filler metal

The effects of the rare earth Ce on the resistivity, melting temperature,spreadability,microstructure of Zn- 22Al filler metal and shear strength of brazed joints were studied.The results indicated that the addition of Ce has little effect on the resistivity and the melting temperature of the filler metal.But with the addition of Ce,the spreadability is significantly improved, the microstructure is refined obviously.It has been found that Ce can improve the shear strength of Cu/Al joint notablely.When the content of Ce is 0.05%,the spread area of filler metal on Al and Cu substrates reached maximum values,respectively, which are 21.4% and 11.6% higher than those of Zn-22Al alloy respectively.Moreover,the shear strength of Cu/Al joint brazed with Zn-22Al-0.05Ce reaches the peak value of 91.3 MPa,which is improved by 30.3% compared with the joint brazed with Zn-22Al alloy.However,with the addition of excessive amount of Ce,some brittle Ce-bearing phases appear in the microstructure and their sizes increase,and the spreadability of filler metal and shear strength of Cu/Al joint deteriorate significantly.