Precipitated Phase of Titanium Alloy with Adding Nd Elements

通过粉末冶金方法(冷等静压-真空烧结)制备钛合金Ti-6Al-4V-2Cr-1Nd, 经过固溶-时效热处理后, 利用光学显微镜(OM)、; X射线衍射仪(XRD)和透射电镜(TEM)分析合金的微观组织、 物相的组成及析出相的形核特点, 研究添加稀土元素Nd对析出相的影响。; 实验结果表明,在添加1%Nd(质量分数)元素后, 钛合金组织得到了明显细化;通过合金细化成核理论分析发现, 添加稀土元素Nd后,; 固溶时效中Nd_2O_3可以作为形核的基础, 促进形核, 所以稀土Nd元素可以有效促进非均匀形核, 主要析出相Nd_2O_3有利于晶粒的细化,; 是有效的形核剂;在高分辨透射电镜下对离子减薄后的试样进行观察,通过对合金的形貌和析出物进行傅里叶变换(FFT)和反傅里叶变换(IFFT)分析,; 得到清晰的原子排列图, 发现析出相Nd_2O_3与基体alpha-Ti之间存在平行相界面, 经分析为半共格界面。Titanium alloy Ti-6Al-4V-2Cr-1Nd prepared by powder metallurgy method; (cold isostatic pressing and vacuum sintering) was researched. The; microstructure, phase composition and precipitated phase nucleation; process were analyzed by optical microscope (OM), X-ray diffraction; (XRD) and transmission electron microscope (TEM) after solution and; aging treatment. The effect of adding rare earth element Nd to the; titanium alloy on its precipitated phase was studied. The experimental; results showed that the microstructure refinement effect was obvious; after adding rare earth element 1%Nd (mass fraction); based on the; analysis of alloy refining nucleation theory, it was found that after; adding Nd, Nd_2O_3 could serve as the basis of nucleation because of its; high energy, promoting nucleation, there fore Nd could promote the; heterogeneous nucleation effectively, the main precipitation phase; Nd_2O_3 was beneficial to refining crystalline grains and it was; effective nucleating agents. Through high resolution observation of ion; thinning sample, and the morphology of the alloy precipitates were; analyzed by fast Fourier transform (FFT) and inverse fast Fourier; transformation (IFFT). It was found that there was parallel interface; between precipitated phase Nd_2O_3 and matrix alpha-Ti, and it was; semi-coherent interface shown by analysis.河南省重大科技专项项

Effects of Nd element addition on microstructure and mechanical properties of Ti-6Al-4V-2Cr alloy

本试验采用冷等静压法及粉末冶金法制备钛合金,消除了成分偏析对合金性能的影响。在Ti-6Al-4V-2Cr中加入稀土Nd元素并进行热处理,运用光学; 显微镜、XRD和TEM对其组织和性能进行观察和分析。通过观察发现合金的组织为均匀的alpha +; beta相。运用XRD和TEM观察发现,晶界和晶内均有Nd_2O_3析出物,Nd_2O_3的出现细化了晶粒,提高了形核率,降低了晶粒尺寸。运用精; 密万能试验机进行了力学性能测试,当Nd元素含量为1%时,合金的综合力学性能最好,合金的抗拉强度提高了10.7%,伸长率提高了49.1%。The Ti-6Al-4V-2Cr-xNd alloys were prepared by the cold isostatic; pressing method and powder metallurgy with addition of Nd element,the; effect of composition segregation on properties of the titanium alloy; was eliminated,and microstructure and the properties of the alloy after; heat treatment were studied by means of optical microscope,XRD and TEM.; The results show that the microstructure of the Ti-6Al-4V-2Cr-xNd is; composed of homogeneous alpha + beta phase. Nd_2O_3 precipitates are; observed in the grain boundaries and in the grains by XRD and TEM,and it; can refine the grains,increase the nucleation rate and decrease the; grain size. The optimal mechanical properties of the alloy are obtained; when the Nd content is 1%,and the tensile strength and elongation of the; alloy increase by 10.7% and 49.1%,respectively.军工863项目; 国防973支持项

Effects of Nd element addition on microstructure refinement of Ti-6Al-4V-2Cr alloy

采用冷等静压–真空烧结法制备Ti-6Al-4V-2Cr-1Nd合金,然后进行固溶及时效热处理,通过实验与最小错配度理论计算,研究Nd元素对该合金组织细化的影响,并分析细化机理。结果表明,添加1%(质量分数)的稀土元素Nd后,析出相Nd2O3能有效促进晶粒细化。二维错配度的计算结果证明析出相Nd2O3是有效的形核剂,可促进非均匀形核,增加形核率,从而使晶粒细化。通过对合金试样薄区进行高分辨率观察,发现另一种絮状的、非常细小的、弥散分布的Nd2Ti4O11相,由于其界面错配度较低,也可作为非均匀形核的核心,促进形核,起到细化晶粒的作用。Titanium alloy Ti-6Al-4V-2Cr-1Nd is made by the cold isostatic pressing and vacuum sintering, then the solution and aging heat treatment was carried on the prepared of titanium alloy, the effect of Nd elements on the microstructure refinement and the refinement mechanism were researched and analyzed through the experiment and theory calculation of minimum mismatch degree. The results show that the main precipitation phase Nd_2O_3 can effectively promote the grain refinement after adding rare earth element 1% Nd(mass fraction). The two-dimensional mismatch degree calculation results proved that the precipitated phase Nd2O3 is the effective nucleating agents that can promote the heterogeneous nucleation and increase the nucleation rate, thus promote the grain refinement. Through the high resolution observation of thin area in the sample, another precipitated phase Nd2Ti4O11 is found, which is flocculent, dispersed and very small. Because of the low degree of interface mismatch, Nd2Ti4O11 can also be used as the core of heterogeneous nucleation and promote nucleation, which means it can also play a role in grain refinement.河南省重大科技专项(102105000007