Abstract
Based on the general[Mo]equivalent criterion and d-electron orbital theory,a new ultrahigh-strength βtitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V,TB17)for industrial ap-plications was developed.An ingot of five tons was successfully melted by thrice vacuum consumable arc melting.The microstructure and elements partitioning of different conditions were investigated system-atically.The results suggest that the hierarchical structures of micro-scale first α phase(αf),nano-scale secondary α phase(αs),and ultrafine FCC substructures can be tailored by solution plus aging(STA)heat treatment.The lateral and epitaxial growth of αf phase promotes the HCP-α to FCC substructure transfor-mation with the help of elements partitioning during the aging process.Moreover,the element V,gener-ally regarded as β stabilizer,is found to mainly concentrate in the Al-rich αf phase in this study probably due to its relatively lower content and the strong bonding energy of Al-V.The hierarchical structure has a strong interaction with dislocations,which contributes to achieve a superhigh strength of 1376 MPa.In addition,the plastic strain is partitioned in the multi-scale precipitates(such as the α and FCC sub-structures)and β matrix,resulting in a considerable plasticity.TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test.It can be deduced that both dislocation slipping and twinning mechanisms are present in this alloy.Therefore,TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight.
基金项目
financial support from13th five-year planequipment pre-research project of China(41422010501)
NETL
NSTL
维普
万方数据