轧制变形量对GNPs/Ti复合材料组织与性能的影响

本文采用放电等离子烧结技术(SPS)和热轧制备了石墨烯/钛基复合材料(GNPs/Ti)。重点研究了轧制变形量对GNPs/Ti复合材料的显微组织及力学性能的影响规律。采用扫描电镜观察不同变形量后的显微组织,结果显示,随着轧制变形量的增加,基体晶粒长径比增大,石墨烯取向性提高。拉伸结果表明,GNPs/Ti复合材料的抗拉强度和断后伸长率随着变形量的增加而增加,最大抗拉强度达到680MPa,相比纯钛提高了33%。采用轧制工艺可以使GNPs/Ti复合材料孔洞减少、GNPs分布具有取向性,从而提高材料的力学性能。     

轧制变形量对GNPs/Ti复合材料组织与性能的影响（英文）

采用放电等离子烧结技术(SPS)和热轧制备了石墨烯/钛基复合材料(GNPs/Ti)。重点研究了轧制变形量对GNPs/Ti复合材料的显微组织及力学性能的影响规律。采用扫描电镜观察不同变形量后的显微组织,结果显示,随着轧制变形量的增加,基体晶粒长径比增大,石墨烯取向性提高。拉伸结果表明,GNPs/Ti复合材料的抗拉强度和断后伸长率随着变形量的增加而增加,在变形60%时,最大抗拉强度达到680 MPa,相比纯钛提高了33%。采用轧制工艺可以使GNPs/Ti复合材料孔洞减少、GNPs分布具有取向性,从而提高材料的力学性能。     

等温锻造过程中变形量对TiBw/Ti60复合材料显微组织和力学性能演变的影响(英文)

为了研究TiB晶须增强Ti60复合材料在热压缩过程中变形程度对微观结构和力学性能的影响，在1030℃，应变速率为1×10^-2 s^-1，变形量为30%、50%和70%的条件下分别进行等温锻造。研究结果表明，随着应变的增加，大角度晶界(HAGBs)的比例在70%变形量时显著上升到71.47%。由于材料再结晶效率的提高，αs晶粒的织构成分逐渐成为主导织构成分。TiB能够促进再结晶晶粒的形核并且阻碍晶粒长大。经过等温锻造，复合材料在室温和600℃下的力学性能均有所提高，在50%变形量时锻造试样具有最佳的拉伸强度和伸长率。在拉伸试验过程中TiB晶须承受周围基体传递的载荷，从而材料表现出强化效果。     

放电等离子烧结TiB/Ti-1.5Fe-2.25Mo复合材料的微观组织与力学性能

采用放电等离子烧结技术原位合成了TiB增强Ti?1.5Fe?2.25Mo复合材料,研究了烧结温度对复合材料微观组织和力学性能的影响规律。结果表明,随着烧结温度的升高,钛合金中 TiB 晶须的长细比迅速减小;然而,复合材料的相对密度及TiB的体积含量随着烧结温度的升高而不断增大。由于TiB晶须长细比的减小会导致复合材料强度的降低,而复合材料的相对密度及TiB体积含量的增大又会带来复合材料强度的增加,因此,在这两种因素的共同作用下,最终导致 TiB/Ti?1.5Fe?2.25Mo复合材料的弯曲强度随着烧结温度的升高而缓慢增大。在烧结温度为1150°C 时,TiB/Ti?1.5Fe?2.25Mo复合材料具有最大的弯曲强度1596 MPa。     

增强相含量对原位(TiB+TiC)增强钛基复合材料组织与性能的影响

采用放电等离子烧结法制备了(TiC+TiB)/TC4复合材料，并研究了TiC和TiB增强相含量对钛基复合材料物相组成、微观结构和力学性能的影响。采用SPS温度为1 100℃原位合成制备出(TiC+TiB)/TC4复合材料，TiCp和TiBw呈准连续的网状结构分布在晶界处。样品按照TiC∶TiB为1∶1的比例来制备出增强相体积分数为x%(x=0、1、2.5、5、7.5)增强钛基复合材料。在增强相的体积分数为2.5%时复合材料的屈服强度、抗压强度最高，分别为1 264和1 803 MPa,工程应变由基体合金的30%增加至39.4%。     

复合场对TiB2/AZ31复合材料组织和性能的影响

利用熔体内高温自蔓延反应制备了TiB2/AZ31复合材料,通过金相、扫描电镜、力学性能测试等技术考察了复合场对镁基复合材料铸态、均匀化态和轧制态微观组织和力学性能的影响。结果表明,TiB2/AZ31复合材料施加复合场后,α-Mg基体得到了显著的细化,铸态组织中的骨骼状β-Mg17Al12相渐渐向层片状共晶组织转变,并且使TiB2颗粒团簇的尺寸明显减小,均匀的分布于基体中。由于TiB2颗粒和复合场的引入,复合材料轧制态组织中切变带变得更窄更密集,TiB2颗粒团簇在流变应力作用下有少许的破碎,并沿着轧制变形流线分布。另外,复合材料的力学性能得到了明显改善,其中抗拉强度、屈服强度和延伸率分别达到351 MPa,315 MPa和7.7%。     

新型网状增强体分布的原位自生TiB_w/Ti6Al4V复合材料的热变形行为(英文)

通过原位自生反应热压法制备出TiB晶须增强Ti6Al4V(TC4)合金基复合材料(TiBw/Ti64)。通过热压缩实验研究这种新型复合材料的高温变形行为,变形温度区间为900~1100°C,变形应变速率区间为0.001~10s1。结果显示,该复合材料的流变应力随变形温度的升高与应变速率的降低而降低。当应变速率达到10s1时,出现了非连续屈服与流变失稳现象,特别是在β相区变形时,这种现象更加明显。根据应力—应变曲线上获得的峰值流变应力,分别获得了α+β双相区与单一β相区的流变应力方程。根据流变应力方程,获得了α+β双相区塑性变形激活能为822.3kJ/mol,单一β相区塑性变形激活能为209.4kJ/mol。增强体网状组织结构与基体组织结构变形形态较大程度上取决于变形区域与变形参数。     

Ti-BN粉末冶金原位制备Ti(N)-TiBw复合材料

本文以纯Ti粉末和BN粉末为原料,采用放电等离子烧结技术(SPS)通过原位反应制备了Ti(N)-TiBw复合材料,研究了退火温度对Ti(N)-TiBw复合材料显微组织演化和力学性能的影响。结果表明:在1000 ℃进行烧结时,Ti与BN发生原位反应生成了TiBw和N固溶复合增强钛基复合材料。TiBw以针状形式呈网络状分布于一次颗粒边界处,随着热处理温度的升高,TiBw的长径比先增大后减小,在1100 ℃时达到最大值。而在1100 ℃以上退火处理时,TiBw逐渐发生粗化,微观形貌从针状变成短棒状,其对基体的钉扎效果明显减弱,Ti基体晶粒尺寸逐渐粗化,TiBw的形貌演变遵循Ostwald熟化机制。随着热处理温度的升高,材料的强度先提高后降低,在1000 ℃达到最大值,为908 MPa。材料强度的提升归因于晶粒细化、TiBw载荷传递和O/N的固溶强化。     

非连续TiB+TiC颗粒增强钛基复合材料的剧烈塑性变形行为

针对TiB+TiC陶瓷颗粒增强钛合金提出一种新的强塑性变形方法,即将等径弯曲通道变形应用到非连续增强钛基复合材料中。本文采用通道夹角Φ=120°成功地实现了(TiB+TiC)/Ti6Al4V钛基复合材料1~4道次B_c路径的ECAP变形,研究了剧烈塑性变形对微观组织演化和力学性能的影响。结果表明,剧烈塑性变形可以实现TiB纤维和TiC颗粒的细化,以及基体晶粒的细化;随着挤压次数的增加,基体中偏聚的TiB细长纤维和TiC大颗粒也随着挤压道次的增加也逐渐趋于均匀化,力学性能也得到了提高,抗拉强度能够提高至1205MPa,延伸率与挤压1道次相比也得到了明显提高。     

铸态(TiB+TiC)/Ti1100复合材料高温拉伸性能及蠕变行为EI北大核心CSCD

通过XRD、SEM、TEM等表征手段研究(TiB+TiC)/Ti1100复合材料的铸态显微组织、高温拉伸性能和高温蠕变行为。结果表明:(TiB+TiC)/Ti1100复合材料具有典型的网篮组织,通过B_(4)C、C和Ti的反应原位生成了晶须状的Ti B和等轴状的TiC。随着温度的升高,(TiB+TiC)/Ti1100复合材料的极限抗拉强度从766 MPa降低至511 MPa。在实验范围内,(TiB+TiC)/Ti1100复合材料的稳态蠕变速率随温度和应力的升高而降低。根据对相关数据的计算,(TiB+TiC)/Ti1100复合材料的应力指数和激活能分别为3.75和269.5 kJ/mol。结合蠕变后的变形区域组织,可以确定该材料的蠕变过程主要受位错滑移控制。α/β界面是位错滑移的主要障碍,同时TiB、TiC和硅化物也阻碍着位错的运动。β-Ti的大量溶解导致硅化物的形成,并降低了α/β界面对位错的阻碍效果。增强相特别是TiB可以通过承载作用,降低基体中的应力集中从而抑制β-Ti的溶解。     

Effects of rolling deformation on microstructure and mechanical properties of network structured TiBw/Ti composites

TiB whiskers reinforced pure Ti (TiB_w/Ti) composites with a novel network microstructure were successfully fabricated by reaction hot pressing (RHP). TiB whiskers are in situ synthesized around the large pure Ti matrix particles, and subsequently formed into TiB_w network structure. The novel TiB_w/Ti composites with a network microstructure exhibit a superior combination of mechanical properties. In order to further improve the mechanical properties and guide the subsequent plastic forming, the rolling deformation behavior of the novel composites was investigated. The results show that the strength of the novel TiB_w/Ti composites can be effectively enhanced by rolling deformation due to the matrix deformation strengthening effect, and increased with increasing the rolling reduction. The strength of 8.5%TiB_w/Ti (volume fraction) composite is significantly increased from 842 MPa to 1030 MPa by rolling deformation. It is certain that the TiB whiskers are gradually broken with increasing the rolling reduction, which is harmful to the mechanical properties of the composites.     

Microstructure and mechanical properties of Al-TiB2/TiC in situ composites improved via hot rolling

A kind of Al-TiB₂/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum. In order to improve the distribution of the particles and mechanical properties of the composites, subsequent hot rolling with increasing reduction was carried out. The microstructure evolution of the composites was characterized using field emission scanning electron microscopy (FESEM) and the mechanical properties were studied through tensile tests and microhardness measurement. It is found that both the microstructure uniformity and mechanical properties of the composites are significantly improved with increasing rolling reduction. The ultimate tensile strength and microhardness of the composites with 90% rolling reduction reach 185.9 MPa and HV 59.8, respectively, 140% and 35% higher than those of as-cast ones. Furthermore, the strengthening mechanism of the composite was analyzed based on the fracture morphologies.     

Mechanical properties of Ti-6Al-4V/TiB composites with randomly oriented and aligned TiB reinforcements

In situ Ti-6Al-4V/TiB discontinuously reinforced composites, containing 20 and 40% of TiB whiskers by volume, were produced by blending Ti, Al/V, and TiB₂ powders. The consolidated powder blends were annealed to transform the TiB₂ particles to TiB. The microstructural evolution of the composite was studied as a function of heat treatment duration at 1100, 1200, 1300 and 1400 °C. The mechanical properties of Ti-6Al-4V/TiB composites were established in tension and compression at room temperature and 300 °C, and by resonant ultrasound spectroscopy (RUS), for the two volume fractions of TiB, and for randomly oriented and aligned arrays of TiB whiskers. The average Young’s modulus of the composite with 20% of randomly oriented TiB whiskers was 153 GPa, compared to 109 GPa for unreinforced Ti-6Al-4V. The average Young’s modulus of composites with 20 and 40% of aligned TiB whiskers was measured along the extrusion axis as 169 and 205 GPa, respectively. The stiffness of TiB whiskers was determined from bulk measurements with the Halpin-Tsai equation to be 482 GPa. Yield and ultimate strengths near 1200 MPa were measured. The strength and ductility of the materials were limited in the present study by non-optimal matrix microstructure and inadequate particulate distribution, and approaches for properties improvements are provided.     

Hybrid effect of TiBw and TiCp on tensile properties of in situ titanium matrix composites

In order to study the hybrid effect of in situ TiB whisker (TiBw) and TiC particle (TiCp) on the tensile properties of titanium matrix composites (TMCs), TMCs with various TiBw/TiCp volume ratios of 4:1, 1:1 and 1:4 were prepared by reactive hot pressing of blended powders of Ti, B₄C, and graphite. Room tensile testing results exhibited that the composite with TiBw/TiCp volume ratio of 1:1 experienced an increase in the ultimate tensile strength of 25 and 50%, respectively, over the composite with ratio of 4:1 (based on Ti–B₄C) and pure Ti. The hybrid strengthening effect still existed at elevated temperature but it was not as obvious as that of room-temperature. Meanwhile, the ductility of the composites was decreased with decreasing TiBw content. The results suggest that the hybrid effect exists both at room and at elevated temperatures and it should be taken into account to prepare TMCs with good mechanical properties.     

Effects of degree of deformation on the microstructure,mechanical properties and texture of hybrid-reinforced titanium matrix composites

Titanium matrix composites reinforced by TiB whiskers and La₂O₃ particles are synthesized in a consumable vacuum arc remelting furnace by an in situ technique based on the reaction between Ti, LaB₆ and oxygen in the raw material. The titanium matrix composites are hot rolled with degrees of deformation of 60%, 80%, 90% and 95%. The effects of the hot rolling degree of deformation on the mechanical properties of the composites are investigated by experiment and modeling. In particular, the variation in the inclination of the TiB whiskers during rolling is quantified in the model. The results show that, with increasing degree of deformation, the mechanical properties of composites are improved. Modeling of the mechanical properties reveals that grain refinement and TiB whisker rotation during rolling contribute to the improvement in the yield strength of the titanium matrix composites. Electron backscatter diffraction and transmission electron microscopy observations are used to study the texture of the composites. It is found that the orientation relationships between Ti matrix and TiB whiskers are [1 1 ?2 0]_Ti || [0 1 0]_TiB, (0 0 0 1)_Ti || (0 0 1)_TiB and (1 ?1 0 0)_Ti || (1 0 0)_TiB. TiB whiskers rotate in the rolling direction (RD) with increasing degree of deformation, which results in a higher intensity [1 1 ?2 0]_Ti || RD fiber due to the special orientation relationship between TiB and the Ti matrix.     

电弧熔炼Ti6Al4V/B4C复合材料微观组织与力学性能

采用真空电弧熔炼技术制备了不同含量B₄C的Ti6Al4V/B₄C钛基复合材料,并采用光学显微镜、扫描电子显微镜、显微硬度计、静态压缩及拉伸测试等对其微观组织及力学性能进行了表征分析. 结果表明,电弧熔炼过程B₄C与钛基体原位反应生成TiB,TiC及TiB₂相,TiB呈现一维生长晶须状,TiC呈现颗粒状,在B₄C质量分数为10%时生成块状TiB₂,并可能会形成特殊的中空棱柱状结构Ti(B_xC_y)聚合物. 原位反应生成的TiB₂可显著提高钛基复合材料的显微硬度. 当B₄C质量分数为0.5%时,钛基复合材料原位反应生成的连续网状、均匀分布的TiB和TiC试样具有最优力学性能,试样最大抗压强度值达到1 990 MPa,最大压缩应变为35.5%,压缩性能超过熔炼钛合金,抗拉强度达到1 034 MPa,与熔炼钛合金材料相比提高近24%,但塑性有所降低,并随着B₄C含量增加,抗拉强度逐渐下降,其断裂方式由韧性断裂转变为脆性断裂.     

原位自生TiB2/Al复合材料的组织与力学性能

采用钛盐与硼盐反应法成功制备原位自生TiB2/纯Al复合材料。利用扫描电子显微镜、透射电子显微镜和拉伸试验机研究不同粒子含量(质量分数为1%、2%和3%)对复合材料组织和力学性能的影响。结果表明:原位生成的TiB2粒子有矩形、近圆形和六边形三种形貌,尺寸为200~500 nm;粒子与Al基体界面洁净无反应层。随着粒子含量的增加,复合材料的强度随之升高,而伸长率则随之降低;当TiB2含量为3%时,屈服强度和抗拉强度分别达到78.1 MPa和102 MPa,相比于纯Al分别提高58%和43%,而伸长率降至32.5%,下降了24%。断口分析表明:随着TiB2粒子含量的增加,粒子团聚机率增加,在拉伸过程中,裂纹在粒子团聚处萌生并扩展,导致材料的塑性降低。     

原位合成TiC和TiB增强钛基复合材料的微观结构与力学性能

利用钛与Ｂ４Ｃ之间的自蔓延高温合成反应经普通的熔钐工艺原位合成制备了ＴｉＣ、ＴｉＢ增强的钛基复合材料。光学金相、ＥＰＭＡ、ＴＥＭ和Ｘ射线衍射的研究结果表明：存在匠两种不同形状的增强体,即短纤维状ＴｉＢ晶须和等轴、近似等轴状ＴｉＣ粒子。ＴｉＢ、Ｔｉ基体界面洁净,没有明显的界面反应,而ＴｉＣ、Ｔｉ基体界面有非化学配比的ＴｉＣ过度层存在。由于增强体承受载荷,基体合金晶粒细化以及高密度位错的存在,制备钛基