新锆合金不同热处理条件下第二相结构及成分变化研究

Study on the Structure and Composition Changes of Second Phase Particle of New Zirconium Alloy Under Different Heat Treatment Conditions

锆合金中的第二相是影响其力学性能和耐腐蚀性能的主要因素,开展国产新锆合金不同温度环境中的第二相研究对事故等特殊工况下的服役性能预测具有非常重要的意义。通过加热锆合金样品至500,700,900℃,并保温1 h,随后采用不同冷却速率进行降温,并用TEM对第二相结构及元素组成进行分析,结果表明:900℃时,样品中第二相结构均为体心正方结构Zr2Fe;500℃和700℃时,样品第二相为密堆六方结构Zr(FeCrNb)2和面心立方结构Zr3Fe。Zr-Nb-Fe-Cr第二相在不同温度析出都是以密堆六方结构的ZrCr2为基本骨架,由Nb,Fe替换Cr得到。第二相中Fe和Cr的原子个数比随着温度的升高而不断增加。冷却速率越快时,Fe来不及充分扩散,将形成少部分面心立方结构Zr3Fe。

The second phase in zirconium alloy is the main factor affecting its mechanical properties and corrosion resistance.It is of great significance to carry out the study of the second phase of domestic new zirconium alloys in different temperature environments for the prediction of service performance under special conditions such as accidents.In this paper,the zirconium alloy samples are heated to 500℃,700℃and 900℃for 1 h,and then cooling at different cooling rates.The crystal structure and elements of the second phase are analyzed by TEM.The results show that the second phase structures of samples at 900℃are BCT-Zr 2Fe.The second phases of samples at 500℃and 700℃are dense hexagonal structure HCP-Zr(FeCrNb)2 and face-centered cubic structure FCC-Zr 3Fe.The second phase precipitation of Zr-Nb-Fe-Cr at different temperatures takes ZrCr 2 with HCP structure as the basic skeleton,and it is obtained by replacing Cr with Nb and Fe.The x(Fe)/x(Cr)of the second phase increases continuously with the increase of temperature.The faster the cooling rate is,the less time the Fe can fully diffuse,and a small fraction of FCC-Zr 3Fe will be formed.