The influence of solid solution treatments on the dissolution of carbides precipitates,the grain size,and the hardness of high strength low expansion alloy were investigated through XRD analysis,microstructure observations,and theoretical computation.It was seen that most primary Mo2C type carbide band dissolved in a temperature range of 1 100-1 150 ℃.When the temperature was over 1 200 ℃,the grain size increased remarkably,which led to the reduction of hardness. The influence of solid solution treatments on the dissolution of carbides precipitates, the grain size, and the hardness of high strength low expansion alloys were investigated through XRD analysis, microstructure observations, and theoretical computation. It was seen that most primary Mo2C type carbide band dissolved in a temperature range of 1 100-1 150 ° C.When the temperature was over 1 200 ° C., the grain size increased remarkably, which led to the reduction of hardness.