生长速度对定向凝固Ti-46Al-2Cr-2Nb合金领先相及微观组织的影响  

EFFECTS OF GROWTH RATE ON PRIMARY PHASE AND MICROSTRUCTURES OF DIRECTIONALLY SOLIDIFIED Ti-46Al-2Cr-2Nb ALLOY

作　　者：张元[1] 刘国怀[1] 李新中[1] 陈瑞润[1] 苏彦庆[1] 郭景杰[1] 傅恒志[1] 

机构地区：[1]哈尔滨工业大学材料科学与工程学院,哈尔滨150001

出　　处：《金属学报》2013年第11期1374-1380,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51071062;51274077和51271068;国家重点基础研究发展计划项目2011CB605504;中央高校基本科研业务费专项资金项目HIT.NSRIF.2013002资助~~

摘　　要：采用Birdgman定向凝固系统,在恒定的温度梯度和宽的生长速度范围(υ=10—120μm/s),对Ti-46Al-2Cr-2Nb合金进行了定向凝固实验,并对合金的领先相类型、一次枝晶间距(λ_1)、二次枝晶间距(λ_2)和片层间距(λ_e)进行分析.结果表明,随着生长速度的增加,试样的领先相由β相转变为α相;通过计算领先相界面温度,发现基于最高界面温度判据的相选择模型能对Ti-46A1-2Cr-2Nb合金领先相随生长速度υ的转变趋势进行预测;λ_1随υ的变化规律受领先相转变影响不大,满足λ_1=700.6υ^(-0.24)关系;但λ_2随υ的变化规律受领先相转变影响较大,当领先相为β和α时,分别满足λ_2=44.0υ^(-0.10)和λ_2=57.3υ^(-0.23)关系;λ_e与υ之间满足λ_e=16.4υ^(-0.76)关系,不受领先相转变的影响.与TiAl二元合金相比,提高生长速度更有利于Ti-46Al-2Cr-2Nb合金片层细化.TiAl alloys with fully lamellar structure has been intensively studied for excellent fracture toughness and creep properties. Directional solidification is an effective way to control the lamellar structure. Thus it is important to investigate the effect of solidification parameters on the structure of TiAl alloys during directional solidification. In this work, microstructures of directionally solidifiedTi-46Al-2Cr-2Nb （atomic fraction, %） alloy has been investigated throughBridgman-type directional solidification experiment at constant temperaturegradient and wide range of growth rates （v=10-120 μm/s）. The type of primary phase,the primary dendritic arm spacing （λ1）, the secondary dendritic arm spacing （λ2） and the lamellar spacing （λe） are investigated. It is found that： the primary phase of the specimenstransformed from β phase to α phase with the increase of growth rates; the transformation trend of primary phases with growth rates can be predicted by the phase selection model based on the highest interface temperature criterion. λ1, λ2, andλe all decrease with the increasing of v. The relationship between λ1 and v is not affected by the transformation of primary phases, which follows λ1=700.6v-0.24 relationship. However the relationship between λ2 and v is associated with the type of primary phases, λ2 and v followsλ2=44.0v-0.10 relationship when β is the primary phases, while follows λ2=57.3v-0.23 relationship when the primary phase has transformed to α phase. The relationship between λe and v can be expressed by λe=16.4v-0.76.Compared with TiAl binary alloys, lamellar spacing is more effectively refined by increasing the growth rates in Ti-46Al-2Cr-2Nb alloy.

关 键 词：TIAL合金 定向凝固 领先相 微观组织 

分 类 号：TG146.2[一般工业技术—材料科学与工程]