稀土元素Er对Ti-6Al-4V-0.5Si合金组织与性能的影响

利用粉末冶金工艺制备了Ti-6Al-4V-0.5Si-xEr(wt%)合金,随后采用OM、XRD、TEM和拉伸试验机等分析手段研究了Er元素含量对固溶时效态(950 ℃×30 min(WQ)+480 ℃×4 h(AQ))试验合金显微组织和性能的影响。结果表明:试验合金经固溶时效处理后均为等轴和片状的双态组织。烧结过程中产生的Er₂O₃氧化物颗粒可以作为形核中心促进α相和β相的析出,起到细化晶粒的作用。随着Er元素含量的增加,晶粒尺寸由10~20 μm细化至5~10 μm。当Er元素含量为1.2%时,试验合金的抗拉强度达到峰值,为930.5 MPa,此时伸长率为9.24%,比未添加Er元素时Ti-6Al-4V-0.5Si合金分别提高了22.3%和10.0%。试验合金的拉伸断口形貌显示有韧窝出现,仅有少量的解理台阶,韧窝的存在可以分散材料断裂时产生的应力,使材料断裂前承受更大的变形。

Effect of rare earth element Er on microstructure and properties of Ti-6Al-4V-0.5Si alloy

Ti-6Al-4V-0.5Si-xEr (wt%) alloy was prepared by powder metallurgy process, and the effect of Er content on the microstructure and properties of the alloys solution-treated+aged (950 ℃×30 min (WQ)+480 ℃×4 h (AQ)) was studied by means of OM, XRD, TEM and tensile testing machine. The results show that the tested alloys are all duplex microstructure with equiaxed and lamellar feature after solution and aging treatment. The Er₂O₃ particles produced in the sintering process can be used as nucleation core to promote the precipitation of α and β phases and play a role in grain refinement. With the increase of Er content, the grain size is refined from 10-20 μm to 5-10 μm. When the Er content is 1.2%, the tensile strength of the tested alloy reaches the peak of 930.5 MPa, and the corresponding elongation is 9.24%, which are 22.3% and 10.0% respectively higher than that of Ti-6Al-4V-0.5Si alloy with no Er addition. The tensile fracture morphologies of the tested alloy show dimples, with only a small amount of cleavage steps. The existence of dimples can disperse the stress generated during the fracture of the material and makes the material withstand greater deformation before fracture.