Precipitation and coarsening kinetics of H-phase in NiTiHf high temperature shape memory alloy  

作　　者：A.Shuitcev Y.Ren B.Sun G.V.Markova L.Li Y.X.Tong Y.F.Zheng 

机构地区：[1]Institute of Materials Processing and Intelligent Manufacturing,College of Materials Science and Chemical Engineering,Harbin Engineering University,Harbin 150001,China [2]Center of Testing and Analysis,College of Materials Science and Chemical Engineering,Harbin Engineering University,Harbin 150001,China [3]Physics of Metal and Material Science Department,Tula State University,Tula 300012,Russian Federation [4]School of Materials Science and Engineering,Peking University,Beijing 100871,China

出　　处：《Journal of Materials Science & Technology》2022年第19期90-101,共12页材料科学技术（英文版）

基　　金：supported by the National Natural Sci-ence Foundation of China(Nos.52050410340 and 51971072);the Fundamental Research Funds for the Central University(No.3072021CFJ1002).

摘　　要：Precipitate hardening is the most easiest and effective way to enhance strain recovery properties in NiTiHf high-temperature shape memory alloys.This paper discusses the precipitation,coarsening and age hardening of H-phase precipitates in Ni_(50)Ti_(30)Hf_(20)alloy during isothermal aging at temperatures between 450℃and 650℃for time to 75 h.The H-phase mean size and volume fraction were determined using transmission electron microscopy.Precipitation kinetics was analyzed using the Johnson-Mehl-Avrami-Kolmogorov equation and an Arrhenius type law.From these analyses,a Time-Temperature-Transformation diagram was constructed.The evolution of H-phase size suggests classical matrix diffusion limited Lifshitz-Slyozov-Wagner coarsening for all considered temperatures.The coarsening rate constants of H-phase precipitation have been determined using a modified coarsening rate equation for nondilute solutions.Critical size of H-phase precipitates for breaking down the precipitate/matrix interface coherency was estimated through a combination of age hardening and precipitate size evolution data.Moreover,time-temperature-hardness diagram was constructed from the precipitation and coarsening kinetics and age hardening of H-phase precipitates in Ni_(50)Ti_(30)Hf_(20)alloy.

关 键 词：High temperature shape memory alloys NiTiHf Time-temperature-transformation diagram Coarsening kinetics H-phase 

分 类 号：TG139.6[一般工业技术—材料科学与工程]