【摘要】 通过扫描电镜、透射电镜和小角散射研究了Cu-20Ni-20Mn合金在573~698 K温度下的时效析出行为,确定不连续析出和连续析出之间的相互作用。结果表明:当时效温度低于623 K,沉淀相析出主要以不连续析出为主导。时效温度大于673 K时,沉淀相析出则主要由连续析出和不连续析出共同控制。时效过程中,沉淀相优先在晶界形核长大,形成由Ni Mn相和贫溶质原子基体组成的片层状不连续析出胞状组织。然而连续析出沉淀相的存在会抑制不连续胞状组织的长大,当沉淀相直径约大于5 nm时,将能有效阻碍不连续析出胞状组织界面前沿的迁移。利用Aaronson-Liu模型估算出不连续析出的晶界化学扩散混合积sδDb,进一步通过Arrhenius方程分析得出不连续析出胞状组织的激活能为77.3~110.9 kJ/mol。界面激活能要远低于Ni、Mn元素在Cu中扩散所需的激活能,表明沉淀相易于在晶界处形核析出。更多还原

【Abstract】 The discontinuous and continuous precipitation behavior,and the interaction between them during the aging process in a Cu-20 Ni-20 Mn alloy have been investigated in the temperature range 573~698 K by scanning electron microscope(SEM),transmission electron microscopy(TEM) and small-angle X-ray scattering(SAXS).The results show that discontinuous precipitation is the predominant mechanism at 623 K and below,whereas both discontinuous and continuous precipitations occur when the temperature is higher than 673 K.The discontinuous precipitations with a lamellar mixed structure,consisting of alternate lamellae of matrix and Ni Mn phase,nucleate and grow preferentially on grain boundaries during the aging process.Continuous precipitations can either partially or completely inhibit the growth of discontinuous precipitation colonies.Obvious inhibition action on the migration of reaction front of discontinuous precipitation colonies are found by experimental results,owing to the continuous precipitates when their diameters reach up to about 5 nm or larger.The grain boundary chemical diffusion triple product sδDb is calculated according to an Aaronson-Liu model.In addition,the activation energy for discontinuous precipitation is determined to be between 77.3 and 110.9 kJ/mol based on Arrhenius equation,well below the activation energy for volume-bulk diffusion of Ni and Mn in Cu-rich alloy,indicating that discontinuous precipitation is easy to occur in grain boundaries.更多还原