70MoCu合金变形性研究

通过不同温度下的拉伸和弯曲试验，研究了70MoCu合金在不同温度下的变形行为。研究结果发现：Mo／Cu系聚合型复相合金的塑性特征及变形规律与常规复相合金存在较大的差别，甚至出现反常的规律。例如Mo70Cu合金由室温到550℃的塑性（延伸率和挠度）随温度的升高反而降低。通过对断口进行观察发现：70MoCu合金的断裂是粘结相Cu的撕裂，Mo—Cu界面的分离，Mo—Mo界面的分离，Mo颗粒的解理断裂等4种断裂模式共同作用的结果，但在不同温度下各断裂模式所起的作用大小不一样。     

Mo-30Cu合金室温变形组织

对Mo-30Cu合金室温拉伸性能进行了研究,并对其断口进行观察分析.通过对Mo-30Cu合金冷轧实验,研究了不同变形量下组织的变化规律.结果表明:Mo-30Cu合金的断裂以Cu相的韧性断裂为主,并伴随着Mo/Cu界面的分离和Mo晶粒的解理断裂.Mo/Cu界面的分离和Mo晶粒的解理断裂是Mo-30Cu合金室温轧制过程中产生裂纹的主要原因.     

铈镧合金室温压缩变形行为

本文以铸态Ce-5wt.％La合金为初始材料,在室温条件下,利用万能力学试验机对其进行压缩变形,并利用光学显微镜和维氏硬度计对压缩变形前后试样的显微组织和显微硬度进行研究.结果表明,Ce-5wt.％La合金的屈服强度和抗压强度分别为46.6 MPa和255.5 MPa,但是却表现出优异的室温塑性,最大真应变达到0.47...     

钼丝断裂行为研究

通过对钼丝生产过程中出现的断口实物样分析，阐明造成钼丝断裂的原因，提出钼丝生产用金属钼棒及其拉拔生产的关键工艺参数控制原理，达到降低钼丝断裂几率，提高综合成材率的目的。     

稀土钼合金组织结构的研究

在TZM钼合金的基础上，通过复合添加稀土Y、Ce的试验，生产出了高温性能优异且工艺易于控制的钼合金。对不同配方稀土钼合金的组织结构进行了深入分析，指出弥散颗粒不仅存在晶界，也可存在于晶内，因此可同时强化晶界和晶粒，但粗大的弥散颗粒和Mo-Ti固溶体对合金性能不利。用化学法富集了合金中的弥散相，通过X射线衍射和能谱综合分析，确定了弥散相的相结构，证实了在合金中稀土元素Y、Ce与Ti、Zr形成Y2O3结构的复合氧化物。Ti在合金中则有三种可能的存在形态：一是形成复合氧化物，二是形成Ti(C,N),三是形成Mo-Ti固溶体。     

脉冲电流对Zn—22%Al合金组织及断裂行为的影响

本文借助于透射电镜和扫描电镜，观察了Ｚｎ－２２％Ａｌ合金超塑变形时，脉冲电流对其组织和断裂行为的影响。研究表明，施加脉冲电流，合金中各部分晶粒变形是不均匀的，局部发生动态回复和动态再结晶，同时保留着纤维状或放射状的变形组织。合金的断裂是通过晶界开裂、扩展、最终断裂，表现出沿晶断裂机制。     

NiAl/Cr(Mo)-Hf 合金的高温变形行为

研究了铸造及热等静压 (HIP)处理后的两种NiAl/Cr(Mo) Hf合金的微观组织 ,分析发现合金主要由NiAl相和Cr(Mo)相以及铪固溶体和Heusler相组成。对合金的高温变形行为和断裂特征进行研究 ,结果表明该合金具有良好的高温压缩性能 ,并运用线性回归方法计算了应力指数n和变形激活能Q。     

93WNiCu合金的高温性能及断裂机理研究

试验选用粉末冶金法制备了93WNiCu合金材料,通过高温拉伸试验、高温线膨胀系数测试,得出材料在700～1300℃的高温力学性能和室温至1300℃的线膨胀系数的变化规律,并研究了温度对93WNiCu合金高温力学性能、线膨胀系数的影响机理。结果表明：93WNiCu合金在常温状态下可以表现出良好的强韧性,但在高温环境下材料的抗拉强度急剧下降,宏观表现为抗拉强度极低,延伸率消失,断裂模式也由微观多种断裂模式转变成强度最低的钨钨界面分离;93WNiCu合金的线膨胀系数随温度的升高而平缓增加,温度的增加降低了钨-粘结相界面强度,使材料的热膨胀对温度越来越敏感;针对93WNiCu合金高温性能不理想的问题,研究从添加微量元素、热处理的角度,给出了提升钨镍铜合金综合性能的建议。     

W/Ti层状复合材料的弯曲断裂行为及其有限元模拟

层状增韧复合材料是提高钨材料韧性的有效方法之一.利用放电等离子体烧结装置在不同温度下连接制备了W/Ti层状复合材料,分析了该复合材料的组织、三点弯曲力学性能和断裂机制,并对其三点弯曲断裂过程进行了有限元模拟.结果表明,Ti韧化层可以有效提高钨材料的韧性,W/Ti层状复合材料的三点弯曲曲线上显示了明显的"伪塑性".W/T...     

WC-Co合金断裂行为行径的观察和分析

结合WC-Co硬质合金工业生产中的质量检测工作,应用OLYMPUSPMG3型光学显微镜和JCXA-733型电子探针显微分析仪的综合功能,较全面地观察和分析了该合金的断裂行为行径,断裂源的走向扩展,裂纹的行径,孔隙、夹杂物成分及周围组织结构。阐述了影响该合金断裂强度的重要结构因素,提出了断裂机理。     

Mo-Si-B三元系复合材料的制备及室温断裂韧性

通过Mo,Si,B三种单质粉末原位合成热压的方法制备了成分为Mo-12Si-8.5B和Mo-28Si-8.5B的Mo-Si-B三元系复合材料.利用金相显微镜、金相偏光镜、X射线衍射技术、扫描电镜等对制备材料的组织进行了分析,研究了退火工艺对其组织的影响,测量了其室温断裂韧性,并对复合材料的增韧机制进行了初步的探讨.     

Deformation and Fracture Behavior of Metallic Glassy Alloys and Glassy-Crystal Composites

The present work demonstrates the deformation behavior of Zr-Cu-Ni-Al bulk glassy alloys and Zr-Ni-Cu-Al-Pd glassy foils as well as Ni-Cu-Ti-Zr bulk crystal-glassy composites. Fracture of Zr₆₀Cu₁₆Ni₁₄Al₁₀ and Zr_64.13Ni_10.12Cu_15.75Al₁₀ bulk glassy alloys is featured by nearly equal fraction areas of cleavage-like and vein-type relief. The observed pattern of alternating cleavage-like and vein-type patterns illustrates a result of dynamically self-organizing shear propagation at the final catastrophic stage. The deformation behavior of Zr_64.13Ni_10.12Cu_15.75Al₁₀ alloy has also been tested at LN₂ temperature. The strength of the sample decreases with temperature, and no clear serrated flow typical for bulk glassy samples tested at room temperature is observed in the case of the samples tested at LN₂ temperature. We also studied the deformation behavior of Zr-Ni-Cu-Al-Pd glassy foils thinned to electron transparency in situ in tension in a transmission electron microscope. We also present a Ni-Cu-Ti-Zr crystal-glassy composite material having a superior strength paired with a considerable ductility exceeding 10 pct. The metastable cP2 crystalline phase promotes a strain-induced martensitic transformation leading to pseudoelastic behavior as well as enhanced plasticity at room temperature. Underlying mechanisms of plastic deformation are discussed in terms of the interplay between the dislocation slip in the crystalline phase and the shear deformation in the glassy matrix.     

组织缺陷对金属铍室温断裂行为的影响规律研究

利用扫描电镜(SEM)、透射电镜(TEM)和电子探针(EPMA)对比分析综合机械性能良好和零延伸率的金属铍材室温拉伸断口形貌和微观组织,研究金属铍室温断裂行为,并着重分析微观组织缺陷对金属铍室温断裂行为的影响规律。结果表明:金属铍室温拉伸断口形貌表现为准解理的断裂特征。解理裂纹形核后,裂纹扩展不受阻挡,表现为完全的脆性,因此铍材有限的延伸率主要来自于微裂纹形核阶段。铍材内部存在的杂质相汇聚区、片状晶体疏松和孔洞等组织缺陷,相当于在铍材内部预制一定尺寸的微裂纹,一旦微裂纹尖端形成,这类缺陷就会成为解理裂纹晶核,使铍本身的屈服过程不能发生,是降低铍材延伸率的主要原因;致密的大颗粒杂质相与基体失配、或在局部区域出现的粗晶粒与周围细晶粒不匹配,均易在铍材内部造成应力集中,也是降低铍材延伸率的原因。另外,当杂质相在晶界形成连续薄膜状晶界组织,导致铍材晶界结合强度降低,引起晶界断裂,造成铍材延伸率降低。     

玻璃铝基复合材料高温压缩变形行为研究

利用Gleeble-1500对玻璃铝基复合材料在温度为573～723K、应变速率为0．01s^-1～10s^-1的条件下进行高温压缩变形行为的研究。结果表明：应变速率和变形温度的变化强烈影响复合材料的流变应力,流变应力随变形速率的提高而增大,随变形温度的升高而降低;玻璃铝基复合材料高温塑性变形时的流变行为可用Zener-Hollomon参数的双曲正弦函数来描述。     

Investigating and Understanding the Cyclic Fatigue,Deformation, and Fracture Behavior of a Novel High Strength Alloy Steel: Influence of Orientation

In this paper, the results of a recent study aimed at understanding the influence of orientation on high cycle fatigue properties and final fracture behavior of alloy steel Pyrowear 53 is presented and discussed. This alloy steel has noticeably improved strength, ductility, and toughness properties compared to other competing high strength alloy steels having a near similar chemical composition and processing history. Test specimens of this alloy steel were precision machined and conformed to the specifications detailed in the ASTM standards for tension testing and stress‐controlled cyclic fatigue tests. Test specimens were prepared from both the longitudinal and transverse orientations of the as‐provided alloy steel bar stock. The machined test specimens were deformed in cyclic fatigue over a range of maximum stress and under conditions of fully reversed loading, i.e., at a load ratio of ?1, and the number of cycles‐to‐failure recorded. The specific influence of orientation on cyclic fatigue life of this alloy steel is presented. The fatigue fracture surfaces were examined in a scanning electron microscope to establish the macroscopic fracture mode and to characterize the intrinsic features on the fatigue fracture surfaces. The conjoint influence of microstructure, orientation, nature of loading, and maximum stress on cyclic fatigue life is discussed.     

Mechanical Properties and Fracture Behavior of Cu-Co-Be Alloy after Plastic Deformation and Heat Treatment

Mechanical properties and fracture behavior of Cu-0.84Co-0.23 Be alloy after plastic deformation and heat treatment were comparatively investigated.Severe plastic deformation by hot extrusion and cold drawing was adopted to induce large plastic strain of Cu-0.84Co-0.23 Be alloy.The tensile strength and elongation are up to 476.6 MPa and 18%,respectively.The fractured surface consists of deep dimples and micro-voids.Due to the formation of supersaturated solid solution on the Cu matrix by solution treatment at 950℃for 1h,the tensile strength decreased to271.9 MPa,while the elongation increased to 42%.The fracture morphology is parabolic dimple.Furthermore,the tensile strength increased significantly to 580.2 MPa after aging at 480℃ for 4h.During the aging process,a large number of precipitates formed and distributed on the Cu matrix.The fracture feature of aged specimens with low elongation(4.6%) exhibits an obvious brittle intergranular fracture.It is confirmed that the mechanical properties and fracture behavior are dominated by the microstructure characteristics of Cu-0.84Co-0.23 Be alloy after plastic deformation and heat treatment.In addition,the fracture behavior at 450 ℃ of aged Cu-0.84Co-0.23 Be alloy was also studied.The tensile strength and elongation are 383.6 MPa and 11.2%,respectively.The fractured morphologies are mainly candy-shaped with partial parabolic dimples and equiaxed dimples.The fracture mode is multi-mixed mechanism that brittle intergranular fracture plays a dominant role and ductile fracture is secondary.     

高体积分数SiC_P/Al复合材料断裂性能及其机理研究

对高体积分数SiCP/Al复合材料的硬度、抗拉强度及断裂韧性进行了实验研究。结果表明,随SiC颗粒体积分数的增加,该复合材料的维氏硬度为单调增大;而抗拉强度和断裂韧性均呈先升后降的变化规律,并在体积分数为55%时达到最大值。     

粉末冶金法制备Wp/AZ91镁基复合材料的热变形行为分析

通过对粉末冶金法制备Wp/AZ91镁基复合材料的热变形行为分析,发现该复合材料非常敏感于应变速率.随应变速率升高,真应力-真应变曲线特征从“平缓”型向“锯齿”型转变,材料热变形软化特征增强.材料的软化作用一方面来自基体合金自身的再结晶软化,另一方面来自第二相的强化所引发的再结晶软化.通过微观组织观察发现低应变速率下,材料内析出相呈板条状,而高应变速率下,材料内析出相呈细小短棒状和棱柱状弥散析出,强化作用明显,一方面使晶体内产生大量高畸变能区域从而为再结晶形核提供驱动力,有利于再结晶行为.另一方面也有利于再结晶晶粒的均匀长大,从而有利于再结晶软化.因此高应变速率下材料的软化率更高.     

Roll-Bonded Tri-Layered Mg/Al/Stainless Steel Clad Composites and their Deformation and Fracture Behavior

The deformation and fracture behaviors of roll-bonded tri-layered Mg/Al/stainless steel (SST) composite plates were studied. Brittle interfacial reaction compounds were observed at the Mg/Al interface upon annealing at and above 573 K (300 °C), whereas no visible interfacial reaction compounds were observed at Al/SST interfaces even after annealing up to 673 K (400 °C). The strength of the tri-layered Mg/Al/SST clad plates is in close agreement with those calculated from the strength data of the separated Mg, Al, and ST layers using the rule of mixture. The fracture strain components of the tri-layered clad in the absence of brittle interfacial intermetallic layer far exceed those calculated based on the fracture strain data of separated Mg, Al, and SST sheets. The enhanced ductility of the clad composites is due to the suppression of the localized deformation in a metallic layer by other metallic layers caused by the mutual constraint imposed by an adjacent layer. On the other hand, the fracture strain was found to be reduced in the presence of intermetallic layers between the metallic substrates. Cracks perpendicular to the stress axis were observed in the intermetallic compound layer between Mg and Al, inducing the localized slip in the vicinity of intermetallic cracks and premature fracture of the Mg alloy layer.