Microstructure and mechanical properties of continuous drive friction welded Ti_(2)AlNb alloy under different rotational rates

Ti_(2)AlNb-based alloy was joined in a continuous drive friction welding machine under different rotational rates(500,1000 and 1500 r/min).The microstructure and mechanical properties of the joints were investigated.It is shown that the weld zone(WZ) is fully composed of recrystallized B2 phase,and the grain size decreases with increasing rotational rate.The thermo-mechanically affected zone(TMAZ) suffers severe deformation during welding,due to which most of original precipitation phase is dissolved and streamlines are present.In the heat affected zone(HAZ),only the fine O phase is dissolved.The as-welded joint produced using 1000 r/min has the best mechanical properties,whose strength and elongation are both close to those of the base metal,while the as-welded joint obtained using 500 r/min exhibits the worst mechanical properties.Post-weld annealing treatment annihilates the deformation microstructure and fine O phase precipitates in the joints,consequently improving the mechanical properties significantly.Decomposed α_(2) phase is a weakness for the mechanical performance of the joint since microcracks are apt to form in it in the tensile test.

Microstructural evolution and mechanical properties of duplex-phase Ti6242 alloy treated by laser shock peening

The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.

退火和变形温度对Ti-Ni-Cr形状记忆合金弹簧低温超弹性的影响

利用拉伸试验研究了350~800℃退火态Ti-50.8Ni-0.3Cr合金弹簧在-20~20℃温度范围变形时的低温超弹性。结果表明,在350~800℃温度范围退火时,随退火温度升高,该合金弹簧对外输出应力先降低再升高,而后趋于稳定。在-20~20℃温度范围变形时,随变形温度升高,该合金弹簧对外输出应力增大。要使该合金弹簧在-20℃下获得残余应变较小的超弹性,可对其进行350~400℃或550~800℃退火处理;要使该合金弹簧在-10~20℃下获得残余应变较小的超弹性,可对其进行350~500℃退火处理;要使该合金弹簧在-20~20℃下获得较大的能耗,可对其进行450~800℃退火处理。随退火温度升高,该合金弹簧的应变恢复率降低;随应力-应变循环次数增加,该合金弹簧的应变恢复率先降低后趋于稳定。预循环训练能明显提高该合金弹簧应变恢复率的稳定性。

退火工艺对Ti-Ni-V形状记忆合金相变和形变行为的影响

利用差示扫描量热仪和拉伸试验研究了400℃×10~120 min和500℃×10~120 min退火态Ti-50.8Ni-0.5V合金的相变行为、拉伸性能和形状记忆行为。结果表明:随退火温度和时间变化,合金的相变类型、R相变温度T_(R)和热滞ΔT_(R)、马氏体相变温度T_(M)和热滞ΔT_(M)、抗拉强度R_(m)、伸长率A、应力诱发马氏体相变临界应力σ_(M)、加载-卸载残余应变ε_(R)和能耗W_(D)的变化规律如下:400和500℃退火态Ti-50.8Ni-0.5V合金皆发生B2→R→B19’/B19’→R→B2(B2-母相,CsCl型结构;R-R相,菱方结构;B19’-马氏体相,单斜结构)型相变;T_(R)^(400℃)>T_(R)^(500℃),T_(M)^(500℃)>T_(M)^(400℃),ΔT_(M)^(400℃)>ΔT_(M)^(500℃)≥ΔT_(R)^(400℃)≈ΔT_(R)^(500℃)≈4℃;R_(m)^(400℃)>R_(m)^(500℃),A^(500℃)>A^(400℃);400℃退火态合金的超弹性(SE)稳定性高于500℃退火态合金。随退火时间延长,T_(R)^(400℃)、T_(R)^(500℃)、T_(M)^(400℃)和T_(M)^(500℃)升高,ΔT_(M)^(400℃)和ΔT_(M)^(500℃)减小,ΔT_(R)^(400℃)和ΔT_(R)^(500℃)在3.5~4.6℃之间变化;400℃退火态合金保持SE,500℃退火态合金由SE向SE+SME(形状记忆效应)转变;σ_(M)^(400℃)和σ_(M)^(500℃)降低;W_(D)^(400℃)和W_(D)^(500℃)增加;ε_(R)^(500℃)先降后升;ε_(R)^(400℃)在0.64%~1.36%之间变化。要使Ti-50.8Ni-0.5V合金获得较高的T_(R),可对其进行400℃退火;要使该合金获得较高的T_(M),可对其进行500℃退火;要使该合金在室温下获得超弹性,可对其进行400℃×10~120 min或500℃×10~60 min退火。

Ti含量对氩弧熔覆CoCrFeNiCuTi_(x)高熵合金涂层组织及性能的影响

采用氩弧熔覆技术在Q235钢基体表面制备了CoCrFeNiCuTi_(x)(x表示摩尔比值,x=0、0.3、0.5、0.8和1)高熵合金涂层,研究了Ti含量对CoCrFeNiCuTi_(x)高熵合金微观结构和力学性能的影响。结果表明,不同Ti含量的CoCrFeNiCuTi_(x)高熵合金均为FCC单相固溶体。CoCrFeNiCu合金的微观组织为柱状晶结构。随着Ti的加入,微观组织中开始出现析出相,且Ti含量越高,析出相越多。同时Ti的加入明显提高了合金的显微硬度,当Ti的摩尔比为1时,涂层的截面显微硬度值达到最高值439.54 HV0.1。Ti对CoCrFeNiCuTi_(x)高熵合金的耐磨性具有显著影响,CoCrFeNiCuTi合金表现出最好的耐磨性。随着Ti含量的升高,合金的磨损机理由黏着磨损转化成黏着磨损与氧化磨损并存。

基于ICP的Ar等离子体干法刻蚀Ti/Ni/Ag薄膜

在电感耦合等离子体(ICP)刻蚀工艺中,选择合适的刻蚀条件对Ti/Ni/Ag薄膜的刻蚀至关重要。使用氩气(Ar)作为刻蚀气体,研究了射频偏压功率、气体体积流量、腔体压强、刻蚀时间等多个参数对功率芯片背面Ti/Ni/Ag薄膜刻蚀深度的影响,并优化刻蚀工艺参数。实验结果表明,调节射频偏压功率和Ar体积流量可以显著影响刻蚀速率,进而对薄膜的微结构进行有效调控。通过优化工艺参数,在射频偏压功率300 W、Ar体积流量40 cm^(3)/min、腔体压强1.2 Pa、刻蚀时间50 min下,芯片Ti/Ni/Ag薄膜的刻蚀深度达到283.25μm,有效提升了刻蚀效率和刻蚀精度。

Ni-Al辅助微波自蔓延烧结制备Ti_(3)SiC_(2)基金刚石复合材料工艺研究

为降低金刚石磨削工具的制造成本和能耗,探寻一种在低能耗下实现高性能陶瓷结合剂金刚石磨具的制备工艺,同时研究助燃剂Si和金刚石粒度等因素对样品物相组成、显微形貌和磨削性能的影响。采用Ti、Si、石墨粉和金刚石磨料作为原料,经冷压成型至生胚,通过Ni-Al辅助在微波场加热诱发Ti-Si-C体系发生自蔓延高温合成(SHS)反应以制备Ti_(3)SiC_(2)基金刚石复合材料。结果表明,高热值Ni-Al合金辅助可以缩短样品的烧结时间,还可以将诱发SHS反应的温度点控制在金刚石石墨化温度以下。在Ar保护气氛下,Ti-Si-C体系发生SHS反应,可生成Ti_(3)SiC_(2)、TiC和Ti5Si3等3种物相。随Si含量升高,Ti_(3)SiC_(2)相先增多后减少,当n(Ti):n(Si):n(C)=3∶1.1∶2时,复合材料的磨削性能最佳,磨耗比最高可达286.53。分析不同原料配比下的试样磨耗比差异的产生机制,认为基体组织中存在微小且分布均匀的气孔结构,在磨削时可产生大区域的平整磨削面,易于发挥金刚石磨料的磨削效果,有利于提升复合材料样品的磨削性能。

Rh_(n)Ni_(n)合金团簇尺寸对Rh_(n)Ni_(n)/TiO_(2)催化合成气制乙醇性能的影响

本工作采用密度泛函理论(DFT)和微观动力学方法研究了不同Rh-Ni合金团簇尺寸的Rh_(n)Ni_(n)/TiO_(2)(n=1、2、3、4)催化剂上的合成气制乙醇反应。结果表明,Rh_(1)Ni_(1)/TiO_(2)和Rh_(3)Ni_(3)/TiO_(2)能够显著促进CO活化转化及C−C链的形成,并抑制甲烷的生成。其中,Rh_(1)Ni_(1)/TiO_(2)表现出最高的乙醇生成活性和相对选择性。电子性质分析表明,在Rh_(1)Ni_(1)/TiO_(2)催化剂上,合金团簇上Ni原子及载体上Ti和O原子向Rh原子转移的电荷最多,合金团簇上Rh-Ni间相互作用最强,且合金团簇与TiO_(2)载体间的相互作用也最强,其催化活性最高。在525 K下,从头算分子动力学模拟(AIMD)模拟显示Rh_(1)Ni_(1)/TiO_(2)催化剂具有较高的热稳定性。

熔速对高填充比06Cr18Ni11Ti电渣重熔铸锭凝固过程的影响

以06Cr18Ni11Ti钢高填充比电渣重熔铸锭为研究对象,通过建立瞬态电渣重熔过程的多相多物理场耦合模型,探究了熔速对电渣重熔过程中电磁、传热、流动及凝固行为的影响。结果表明,不同熔速下的电流路径基本一致,且存在明显的集肤效应,结晶器内部温度呈抛物线形分布,且温度梯度较大。随着熔速从5 kg/min增至7 kg/min,电流密度、洛伦兹力和焦耳热分别增加了16.2%、37.7%和63.3%;渣池最高温度从1902 K上升至2058 K;渣池内存在两对方向相反的涡旋,结晶器内的流动随熔速增大变得更加剧烈;在本文研究条件下,提高熔速会导致熔池深度增大、铸锭局部凝固时间延长;当熔速为5 kg/min时,局部凝固时间最短,熔池深度在结晶器直径的1/2~1/3,有助于保证铸锭良好的致密性和结晶质量。

Ti/SnO_(2)-Sb-Ni电极电化学氧化去除水中BIT

1,2-苯并异噻唑啉-3-酮(BIT)是一种新型广谱工业杀菌剂,因其强杀菌能力而难以直接通过传统生化法处理,电化学氧化是一种有效的预处理方法。通过实验对比不同典型阳极对BIT去除率的影响;以锑镍共掺杂钛基二氧化锡电极(Ti/SnO_(2)-Sb-Ni)为阳极电化学氧化BIT,考察BIT电化学氧化过程中不同初始BIT浓度、初始pH、电流密度和硫酸钠浓度等操作参数对BIT去除率的影响,结合紫外-可见吸收光谱和荧光光谱分析,探究BIT降解过程中的结构变化。结果表明:相较于商业电极,Ti/SnO_(2)-Sb-Ni电极可高效电化学氧化BIT及其产物,消除其生物毒性;Ti/SnO_(2)-Sb-Ni电极电化学氧化BIT过程中,最佳电流密度为15 mA/cm^(2),pH和初始硫酸钠浓度对BIT降解影响较小,最佳BIT初始浓度15 mg/L,BIT降解过程中杂环先被破坏,苯环再被破坏。

冷轧Ti-50.8Ni-0.4V形状记忆合金相变和超弹性研究

利用金相显微镜、示差量热分析法和拉伸试验对比研究了冷轧和退火态Ti-50.8Ni-0.4V合金的相变及超弹性。结果表明:退火处理对冷轧合金的相变和超弹性(SE)特性具有显著的影响。具有大量位错塞积的冷轧态合金表现为线性SE,而退火态合金呈非线性SE,350~550℃退火态合金表现为两步相变(A→R→M/M→R→A),形状回复率Rr达到96%,具有优异SE特性。600℃和650℃退火态合金发生完全再结晶,随温度的升高R相逐渐消失,其相变分别为(A→R→M)/(M→A)和(A→M)/(M→A),形状回复率Rr值<29%,其SE特性明显变差。

Enhanced wear resistance,antibacterial performance,and biocompatibility using nanotubes containing nano-Ag and bioceramics in vitro

A good Ti-based joint implant should prevent stress shielding and achieve good bioactivity and anti-infection performance.To meet these requirements,the low-elastic-modulus alloy—Ti–35Nb–2Ta–3Zr—was used as the substrate,and functional coatings that contained bioceramics and Ag ions were prepared for coating on TiO_(2)nanotubes(diameter:(80±20)nm and(150±40)nm)using anodization,deposition,and spin-coating methods.The effects of the bioceramics(nano-β-tricalcium phosphate,microhydroxyapatite(micro-HA),and meso-CaSiO_(3))and Ag nanoparticles(size:(50±20)nm)on the antibacterial activity and the tribocorrosion,corrosion,and early in vitro osteogenic behaviors of the nanotubes were investigated.The tribocorrosion and corrosion results showed that the wear rate and corrosive rate were highly dependent on the features of the nanotube surface.Micro-HA showed great wear resistance with a wear rate of(1.26±0.06)×10^(−3)mm^(3)/(N·m)due to adhesive and abrasivewear.Meso-CaSiO_(3)showed enhanced cell adhesion,proliferation,and alkaline phosphatase activity.The coatings that contained nano-Ag exhibited good antibacterial activity with an antibacterial rate of≥89.5%against Escherichia coli.These findings indicate that hybrid coatings may have the potential to accelerate osteogenesis.

Laser processing effects on Ti−45Nb alloy surface,corrosive and biocompatible properties

The Ti−45Nb(wt.%)alloy properties were investigated in relation to its potential biomedical use.Laser surface modification was utilized to improve its performance in biological systems.As a result of the laser treatment,(Ti,Nb)O scale was formed and various morphological features appeared on the alloy surface.The electrochemical behavior of Ti−45Nb alloy in simulated body conditions was evaluated and showed that the alloy was highly resistant to corrosion deterioration regardless of additional laser surface modification treatment.Nevertheless,the improved corrosion resistance after laser treatment was evident(the corrosion current density of the alloy before laser irradiation was 2.84×10^(−8)A/cm^(2),while that after laser treatment with 5 mJ was 0.65×10^(−8)A/cm^(2))and ascribed to the rapid formation of a complex and passivating bi-modal surface oxide layer.Alloy cytotoxicity and effects of the Ti−45Nb alloy laser surface modification on the MRC-5 cell viability,morphology,and proliferation were also investigated.The Ti−45Nb alloy showed no cytotoxic effect.Moreover,cells showed improved viability and adherence to the alloy surface after the laser irradiation treatment.The highest average cell viability of 115.37%was attained for the alloy laser-irradiated with 15 mJ.Results showed that the laser surface modification can be successfully utilized to significantly improve alloy performance in a biological environment.

Effect of hot isostatic pressing processing parameters on microstructure and properties of Ti60 high temperature titanium alloy

Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.

多孔Ti/SnO_(2)-Sb-Ni电极的制备及电催化产臭氧性能研究

采用溶胶凝胶法制备了多孔Ti/SnO_(2)-Sb-Ni电极,并研究了所制备电极的电催化产臭氧性能。采用SEM与XRD等方法对电极涂层的表面形貌及结构进行了表征;考察了不同电极基体条件对电催化产臭氧性能的影响。实验结果表明:多孔Ti/SnO_(2)-Sb-Ni电极表面呈现为密集粗糙颗粒状结构;当电极涂层中Sn∶Sb∶Ni摩尔比为500∶8∶5、泡沫钛基体孔径为20μm时,制备出的电极有最佳的电催化产臭氧性能。多孔Ti/SnO_(2)-Sb-Ni电极可为新型电化学生成臭氧技术的研究和应用提供支撑。

First-principles calculations of Ni–(Co)–Mn–Cu–Ti all-d-metal Heusler alloy on martensitic transformation,mechanical and magnetic properties

The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125,0.25,0.375,y=0.625)]alloys were systematically studied by the first-principles calculations.For the formation energy,the martensite is smaller than the austenite,the Ni–(Co)–Mn–Cu–Ti alloys studied in this work can undergo martensitic transformation.The austenite and non-modulated (NM) martensite always present antiferromagnetic state in the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) (y<0.625) alloys.When y=0.625 in the Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) series,the austenite presents ferromagnetic state while the NM martensite shows antiferromagnetic state.Cu doping can decrease the thermal hysteresis and anisotropy of the Ni–(Co)–Mn–Ti alloy.Increasing Mn and decreasing Ti content can improve the shear resistance and normal stress resistance,but reduce the toughness in the Ni–Mn–Cu–Ti alloy.And the ductility of the Co–Cu co-doping alloy is inferior to that of the Ni–Mn–Cu–Ti and Ni–Co–Mn–Ti alloys.The electronic density of states was studied to reveal the essence of the mechanical and magnetic properties.

Effect of Ti content on microstructures and mechanical properties of cast Al-2Li-2Cu-0.5Mg alloy

Ti is regarded as one of the promising grain refiners in cast Al-Li-Cu alloys,but few research works have been done on its independent role.In this study,the effect of Ti on the microstructure evolution and mechanical properties of cast Al-2Li-2Cu-0.5Mg base alloy was investigated.The results revealed that the grains can be prominently refined with the increase of Ti addition.After adding Ti,high density TiB_(2)-Al_(3)Ti composite particles with a low lattice misfit form as heterogeneous nucleation sites for the α-Al matrix.δ’(Al3Li) and T_(1)(Al_(2)CuLi) precipitates that provide enhanced strength are dominated in the alloys after T6 aging treatment.The average size of both δ’ and half-width of δ’-precipitation free zone(PFZ) decreases gradually with the increase of Ti content.This is because the higher binding energy between Ti atoms and vacancies limits the diffusion efficiency of Li atoms,and thus results in a higher ductility.Additionally,no nano-sized Al_(3)Ti or core-shell structure of Al_(3)(Li,Ti) particles are found.The tensile property test results indicate that the Al-2Li-2Cu-0.5Mg alloy achieves optimal properties after aging at 175 °C for 32 h when 0.15wt.% Ti is added.It exhibits a yield strength of 352±5 MPa,an ultimate tensile strength of 423±6 MPa,and an elongation of(3±0.4)%.These findings are expected to offer a reliable theoretical guidance for the industrial composition design of the Al-Li-Cu series cast alloys.

Effect of Ni content on the weldability of middle-chromium hyperpure ferritic stainless steels 00Cr21Ti

Excellent weldability substantially contributes to the intrinsic quality of steels,while appropriate chemical composition plays a primary role in the essential weldability of steels.The poor weldability of ferritic stainless steels could be improved through modification with minor alloy elements while minimally increasing the cost.Therefore,studying the effect of minor alloy elements on the weldability of steels is of considerable importance.In this study,several steels of middle-chromium hyperpure ferritic stainless 00Cr21Ti with different Ni content(0.3%,0.5%,0.8%,and 1.0%)were developed,and their weldabilities of butt joint samples welded using the metal inert gas welding process,including the influence of welded joints on the microstructure,tensile performance,corrosion resistance,and fatigue property,were investigated.Results show that the steels with w(Ni)≥0.8%exhibit excellent mechanical properties compared with those with low-Ni content steels,further,their impact toughness at normal atmospheric temperature meets the industrial application standard and the fatigue property is similar to that of 304 austenitic stainless steel.Moreover,results show that the corrosion resistance of all the samples is almost at the same level.The results acquired in this study are supposed to be useful for the optimization of the chemical composition of stainless steels aiming to improve weldability.

06Cr18Ni11Ti管坯探伤与晶间腐蚀不合原因分析及改进措施

针对06Cr18Ni11Ti管坯探伤不合以及晶间腐蚀不合问题,采用光学显微镜和扫描电子显微镜对缺陷进行了检测和分析。结果表明:造成探伤不合与腐蚀开裂的原因是相同的,都是因为管坯中存在大量0.4~0.6 mm大尺寸链状TiN夹杂物团簇。通过控制Ti合金化过程中Ti含量、Al含量、炉渣成分,降低浇注温度,提高快锻机单道次压下量,有利于提高探伤、晶间腐蚀的合格率。

时效处理对Ni-Ti-La合金微结构、相变及力学性能的影响

时效处理是调节合金微结构,影响合金性能的有效方法。用实验的方法分析了Ni-Ti-La合金的微结构,研究了合金的相变行为,测定了合金的维氏硬度。实验结果表明,用La元素替代Ni元素形成的Ti_(50)Ni_(49.5)La_(0.5)合金,经时效处理后合金由NiTi基体、NiLa沉淀相和Ti_(2)Ni沉淀相组成,并且沉淀相的数量随着时效温度升高而减少,合金在加热和冷却的过程中均为一步相变B2↔B19',合金相变开始温度随时效温度的升高而增大,合金的硬度随时效温度的升高而增大。用La元素替代Ti元素形成的Ti_(49.5)Ni_(50)La_(0.5)合金,经时效处理后合金由NiTi基体、NiLa沉淀相组成,并且沉淀相的数量随时效温度的升高而增加,合金在加热和冷却的过程中呈现一步相变B2↔B19',相变开始温度随时效温度的升高而增大,合金的维氏硬度随时效温度的升高而减小。时效处理对Ti_(50)Ni_(49.5)La_(0.5)合金和Ti_(49.5)Ni_(50)La_(0.5)合金的微结构产生了影响,进而影响了合金的相变行为和力学性能。