电子束快速成形TC18钛合金柱状晶组织的拉伸性能

采用电子束快速成形方法,获得了一种TC18钛合金的柱状晶组织,研究了热处理工艺对该类组织析出相和拉伸性能的影响。结果表明,在740～830℃温度范围内固溶、在550℃时效处理,随着固溶温度的升高,快速成形样品沿柱状晶方向的强度呈上升趋势,塑性呈下降趋势;在830℃固溶处理后,在550～650℃时效温度范围内,随着时效温度的升高,沿柱状晶方向的强度呈下降趋势,而塑性呈上升趋势;拉伸性能随热处理工艺的变化主要取决于热处理过程中产生的二次α相;发现了延性韧窝和沿晶+准解理两种不同类型的断口形貌,并对其形成原因进行了分析。

Tensile properties of rapidly solidified TC18 titanium alloy with columnar crystal structure by electron-beam deposition

Columnar crystal structure of TC18 titanium alloy was obtained by electron beam deposition method.Tensile properties and microstructure of the differently heat-treated TC18 alloy with columnar structure was investigated.The results show that both tensile and yield strength of the alloy in direction parallel to the length of the columnar grains increase with increasing solution temperature from 740 to 830 ℃ followed by 550 ℃×4 h aging treatment,at the expense of ductility.After solution treating at 830 ℃ followed by air cooling,ageing experimental results obtained at temperatures from 550-650 ℃ show that yield and tensile strength of the alloy parallel to the columnar grain length direction decrease with increasing ageing temperature.Fracture surface observation by SEM shows two failure modes,ductile and intergranular + quasi-cleavage,for tensile test,which may account for the scatter of tensile ductility data found under specific heat treatment conditions and the formation mechanisms of the two fractures was analyzed.