铸态V-5Cr-5Ti合金在退火过程中的第二相行为研究

Research of the secondary phase behavior during annealing of as-cast V-5Cr-5Ti alloy

摘要:

采用XRD、OM、SEM和TEM对铸态V-5Cr-5Ti合金退火处理后组织结构进行分析。研究表明：在退火过程中，随着退火温度升高，铸态V-5Cr-5Ti合金第二相发生分解、扩散、聚集。第二相形貌由层状组成树枝状第二相转变成针状组成团聚状第二相。随着时间的推移，针状第二相尺寸发生了粗-细长-短粗的转变。1100℃?h退火处理后V-5Cr-5Ti合金的晶格常数为0.30362 nm，Ti原子与间隙原子（C、N、O等）结合形成更稳定的第二相，降低V-5Cr-5Ti合金晶格的膨胀。1100℃?h退火处理后V-5Cr-5Ti合金组织中存在三种类型的第二相，（1）条状第二相，宽度约为80~100nm，长度为几个μm，化学式记为V2-CO。（2）针状第二相，具有FCC结构，晶格常数为0.4193~0.4256nm，该第二相在晶内或平行或垂直排列。（3）椭圆状第二相，具有FCC结构，晶格常数为0.4203~0.4268nm。铸态V-5Cr-5Ti合金退火过程中，树枝状第二相首先发生分解、扩散，随后合金元素脱溶沉淀，形成以针状第二相为特征的团聚状第二相。该第二相是以Ti、V元素为主，Cr元素为辅，具有FCC结构的、稳定的碳-氧-氮化物，化学式记为(TiV)-CON。

Abstract:

The microstructure of as-cast V-5Cr-5Ti alloy during annealing was analyzed by XRD、OM、SEM and TEM. The results show，with increasing annealing temperature,V-5Cr-5Ti alloy secondary phase of as cast V-5Cr-5Ti alloy decompose, diffuse and aggregate. The dendritic phase made by lamellar secondary phase is turn into reunion phase made by acicular secondary phase. The shape of acicular secondary phase changes coarse- elongated - tubby over time. The lattice parameters of V-5Cr-5Ti alloy after 1100℃?h annealing is 0.30362 nm, Ti and interstitial (C, N, O etc.) are combined to form more stable secondary phase, reduce the expansion of V-5Cr-5Ti alloy lattice.There are three kinds of the secondary phase in V-5Cr-5Ti alloy after 1100℃?h annealing:1) Strip secondary phase, chemical formula can be expressed as V2(CO); 2) Acicular secondary phase, has FCC structure, the lattice parameter is 0.4193~0.4256nm; 3) Elliptical-shaped secondary phase, has FCC structure, the lattice parameter is 0.4203~0.4268nm; In the process of annealing, The dendritic phase decompose and diffuse firstly, then the alloy matrix will precipitate due to alloy element desolution and separate out the reunite phases, witch is the Characteristic of acicular secondary phase. Finally, the secondary phase is chromium-alloyed stabilized precipitations of titanium-vanadium oxycarbonitride with FCC structure, which chemical formula can be expressed as (TiV)(CON).