基于α''组织设计适于激光立体成形的新型高塑性Ti-4.13Al-9.36V合金

A Novel Ti-4.13Al-9.36V Alloy of High Ductility Designed on Base ofα’’-Microstructure for Laser Solid Forming

为了提高Ti-6Al-4V合金的加工硬化率和塑性,基于其团簇成分式12[Al-Ti_(12)](AlTi_(2))+5[Al-Ti_(14)](V2Ti)设计成分式为4[Al-Ti_(12)](AlTi_(2))+12[Al-Ti_(14)](V2Ti)的(Ti-4.13Al-9.36V,%)合金,采用激光立体成形工艺制备Ti-4.13Al-9.36V和Ti-6.05Al-3.94V(对比合金),研究了沉积态和固溶温度对其显微组织和力学性能的影响。结果表明,沉积态Ti-4.13Al-9.36V和Ti-6.05Al-3.94V合金的显微组织均由基体外延生长的初生β柱状晶和晶内细小的网篮α板条组成。Ti-6.05Al-3.94V合金的初生β柱状晶的宽度约为770μm,α板条的宽度约为0.71μm;而Ti-4.13Al-9.36V合金的初生β柱状晶的宽度显著减小到606μm,α板条的宽度约为0.48μm。经920℃固溶-淬火处理后Ti-6.05Al-3.94V样品的显微组织为α’+α相,其室温拉伸屈服强度约为893 MPa,抗拉强度约为1071 MPa,延伸率约为3%。经750℃固溶-淬火处理后Ti-4.13Al-9.36V样品的显微组织为α’’+α相,与α’马氏体相比,应力诱发的α’’马氏体能显著地提高合金的加工硬化能力,其室温拉伸屈服强度约为383 MPa,抗拉强度约为989 MPa,延伸率达到了17%。这表明,根据团簇理论模型调控α’’+α的显微组织能有效提高激光立体成形Ti合金的加工硬化能力和塑性。

Ti-6Al-4V alloy is widely used in laser solid forming,however,low work-hardening ability and ductility limit its industrial applications.In this paper,a novel Ti-4.13Al-9.36V(%)alloy with cluster composition of 4[Al-Ti_(12)](AlTi_(2))+12[Al-Ti_(14)](V2Ti)was designed based on the cluster composition formula 12[Al-Ti_(12)](AlTi_(2))+5[Al-Ti_(14)](V2Ti)of Ti-6Al-4V.Samples of two alloys Ti-4.13Al-9.36V and Ti-6.05Al-3.94V(set as contrast alloy)were prepared by laser solid forming and followed by heat treatment.Then the microstructure and mechanical properties of the as-deposited and solution treated alloys were investigated.The results show that the microstructure of the as-deposited alloys Ti-4.13Al-9.36V and Ti-6.05Al-3.94V consists of columnar prior-βgrains,which grow epitaxial from the substrate along the deposition direction.A basket-weaveα-laths existed in the inner prior-βgrains.The width of prior-βgrains and the width ofα-laths of Ti-4.13Al-9.36V alloy are ca 606μm and 0.48μm,in the contrast,those of Ti-6.05Al-3.94V alloy are ca 770μm and 0.71μm,respectively.Further,after the Ti-6.05Al-3.94V subjected to post solution treatment at 920°C for 2 h followed by water cooling,its microstructure consists of phasesα'+α,and the corresponding yield strength,ultimate tensile strength and ductility to failure were ca 893 MPa,1071 MPa and 3%,respectively.However,when the Ti-4.13Al-9.36V subjected to post solution treatment at 750°C for 2 h followed by water cooling,its microstructure consists of phasesα''+α,and the related yield strength,ultimate tensile strength and ductility to failure were ca 383 MPa,989 MPa and 17%,respectively.This may be ascribed to that the stress-inducedα''-phase could significantly improve the work-hardening ability compared withα'-phase.The work-hardening ability and ductility of the Ti-alloy used for laser solid forming could be significantly improved by adjusting the microstructure with phasesα''+αvia clusterplus-glue atom model.