基于不同α/β团簇式比例的Ti-Al-V合金的铸态组织和力学性能

Microstructure and Mechanical Properties of As-Cast Ti-Al-V Alloys with Different Proportion ofα/βClusters

在课题组前期工作基础上,设计并铜模吸铸了满足α-{[Al-Ti_(12)](AlTi_(2))}_(17-n)+β-{[Al-Ti_(14)](V_(2)Ti)}n团簇式的合金系列,通过改变β相团簇式的个数n,获得组织覆盖α到β的Ti-(3.19~7.45)Al-(0~12.03)V系列合金,进而表征了铸态组织和室温拉伸力学性能。结果表明,随着n增加,铸态组织由单一α(α'马氏体)经双相态直到单相β,α'马氏体形态由板条状逐渐转变为细片状和针状,当n=5时开始出现β相,n=8时α'马氏体数量最多且呈针状,当n=12时α相完全消失,形成单一β相。相应地,合金强度呈先上升而后下降的趋势,塑性变化趋势则相反,这源自细小针状α'马氏体提升强度而降低塑性的作用。当n=8时,合金的强度达到最大(比Ti-6Al-4V提高了90 MPa),抗拉强度约为1019 MPa、屈服强度约为867 MPa、延伸率与Ti-6Al-4V持平(约为4%),尤其是比强度和比硬度均优于Ti-6Al-4V,达到了230 kN·m/kg和0.76 GPa·cm^(3)/g,分别提升了9%和5%。

The dual-cluster composition formula of the widely-usedα+βTi-6Al-4V andα-{[Al-Ti_(12)](AlTi_(2))}12+β-{[Al-Ti_(14)](V2Ti)}5,reported in our previous work,indicates that all Ti alloys are composed ofαandβunits.In this study,Ti-(3.19-7.45)Al-(0-12.03)V(mass fraction,%)alloys are designed following composition formula of[Al-Ti12](AlTi2)}17-n+β-{[Al-Ti14](V2Ti)}n by changing n value(number ofβcluster units).The alloys as prepared by copper mould suction-casting cover microstructures ranging from pureαto pureβ.In the as-cast state,as the n value increases,the microstructure changes from singleαphase(α'martensite),viaα+βdual-phase,and finally to singleβphase.The morphology ofα'martensite gradually changes from plate-like to lamellar and needle-like.Ti-6Al-4V alloy corresponds to n=5,whereβphase begins to appear.When n=8,needle-likeα'martensite shows the highest content.When n=12,αphase disappears completely and is replaced byβphase.Correspondingly,the strength of the alloys increases first and then decreases,while the plasticity changes inversely,due to the presence of fine-needleα'martensite.Among all the compositions,Ti-5.28Al-6.14V alloy(n=8)shows the highest strength(about 90 MPa higher than Ti-6Al-4V),with tensile strength of 1019 MPa,yield strength of 867 MPa.Its specific strength and hardness of 230 kN·m/kg and 0.76 GPa·cm^(3)/g increased by 9%and 5%,respectively,are both superior to Ti-6Al-4V.