摘要
研究了离心铸造汽车排气阀用Ti-48Al-0．7B-xNb(x=0,3,5,8;原子分数,％)合金的组织和力学性能．结果表明,不同Nb含量合金均由α2+γ两相组成,不存在β相．添加Nb后,合金的晶粒尺寸受凝固前沿B产生附加的成分过冷和硼化物钉扎晶界两方面的作用．合金的片层间距λ与晶粒尺寸d-1／2符合线性关系．O含量和Nb含量影响合金的断裂强度,晶粒尺寸是影响合金塑性的主要因素．Ti-48Al-0．7B-5Nb合金的晶粒尺寸最小,综合性能最佳(σb=399．6 MPa,δ=0．26％)．
Ti-48Al-0.7B-xNb （x=0, 3, 5, 8; atomic fraction, %） alloys were centrifugal cast into car exhaust valves and their microstructures and mechanical properties were studied. The results indicate that all the cast alloys possessed the fully lamellar α2＋γ structure, and has no β phase. The grain sizes of the alloys with different Nb contents are related to the additive composition supercooling induced by boron at the solidification front area and the grain boundary pinned by the precipitated borides during the solidification process. The interlamellar spacing （λ） has a linear relationship with grain size d^-1/2. The σb of the alloy is affected by oxygen and niobium contents and the 5 is directly dominated by the grain size. The Ti-48Al-0.7B-5Nb alloy has the most refined grain size and the optimum combined mechanical property （σb=399.6 MPa, δ=0.26%）.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第5期482-486,共5页
Acta Metallurgica Sinica
