Abstract: By using FeNiCrSiB amorphous alloy as filler metal,the dissimilar steel pipes of T91and T23 were welded through transient liquid phase(TLP) bonding under the protection of argon atmosphere.The weld joints were rapidly aged at 700℃ for different times.The changes of the microstructures and mechanical properties of the weld joints after ageing were analyzed.The results show that the aged T91/T23 TLP joint can meet the requirements of mechanical properties,and the strength of the weld joint is higher than that of the side of T23 base metal.With increasing the ageing time,the main alloying elements(Fe,Ni,Cr) in the weld joint are diffused,and a continuous concentration gradient is formed.These microstructural changes can improve the uniformity of microstructure and composition of the joint and enhance the impact toughness and mechanical property stability of the weld joint during service.