钛的电阻钎焊技术研究

研究了Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ和Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ金属间化合物合金的热轧组织与性能,结果发现：随着变形量的增加,两种合金第二相Ｔｉ５Ｓｉ３变得细小且趋向于均匀分布。变形量越大,合金的室温四点弯曲程度越大,含Ｔｉ５Ｓｉ３较多的Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ合金的弯曲强度较高。两种合金的室温弯曲断口形貌均为准解理形式,两相界面结合较强。高温拉伸试验表明：随变形量的增大,Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ合金的拉伸强度和塑性都增加。Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ合金由于变形量较大和较高的强化相体积含量,拉伸强度明显较Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ合金的为高,但塑性却大为降低     

铸态MnFeCoCuNix高熵合金的力学性能与断裂机理

采用真空感应熔炼法制备不同Ni含量的MnFeCoCuNix高熵合金。利用X射线衍射仪、扫描电镜以及能谱仪分析材料的相组成和结构,利用万能拉伸试验机测定试样的拉伸性能。结果表明,该高熵合金体系具有双相结构。其中,FCC1相富含Fe和Co,而FCC2相富含Cu和Mn。随着Ni含量的增加,Cu的偏析减少,伴随着FCC2相的减少。在界面强化和固溶强化的共同作用下,抗拉强度先升高后降低,而伸长率略有增加。对MnFeCoCuNi0.5合金进行原位拉伸试验,发现其在拉伸断裂过程中产生明显的颈缩。在初始变形阶段,双相结构中滑移线的形态不同;在变形后期原子的再分布和溶解相的再分离使得表面滑移线更加细长和致密。     

Cryorolling-Induced Texture,Mechanical Properties and Fracture Behavior of Al-Mg-Si Alloys During Cold Deformation

This study investigated the texture, mechanical properties, and fracture behavior during cold working of cryorolled (CR) Al-Mg-Si alloys. An x-ray texture goniometer was used to examine the crystallographic texture, and tensile tests were performed to understand the deformation behavior in more detail. SEM/EBSD/TEM was used to observe the microstructures and fracture morphology of the alloy during cryorolling. The microstructures indicated that a large number of ultrafine grains and dislocations formed after cryorolled. The recrystallization was prohibited due to low temperature during deformation. The ultrafine grains and dislocation strength improved the tensile strength from 279.38 MPa for the room-rolled alloy to 313.98 MPa for the cryorolled alloy; better plasticity (4.6%) was observed in the CR sheet. Ductile and intergranular fractures were observed in the CR sheet deformation from 20 to 90%.     

硫含量对Cu-Ni合金拉伸性能影响的机理分析

对6种不同硫含量的Cu-Ni合金进行了室温拉伸试验。系统地研究了拉伸速率和硫含量对材料屈服强度、拉伸强度、伸长率和断面收缩率的影响。通过扫描电镜、能谱分析和金相组织分析，研究了硫含量对金相组织的影响。分析了Cu-Ni合金中硫析出物的分布、变形及对塑性的影响规律。分析了材料发生断裂的起源和过程及硫含量对塑性影响的根本原因，为后续冷变形过程提供理论依据。     

Microstructure and Mechanical Behavior of CrFeNi2V0.sWx (x=0, 0.25)High-Entropy Alloys

CrFeNi₂V_0.5W_x (x = 0, 0.25) alloys based on these parameters of mixing enthalpy (ΔH_mix), mixing entropy (ΔS_mix), atomic radius difference (δ), valance electron concentration, and electronegativity difference(Δχ) were designed and prepared. The microstructure and room-temperature mechanical behavior of both alloys were investigated. Compressive test results showed that the CrFeNi₂V_0.5W_0.25 alloy had higher yield strength than that of the W-free CrFeNi₂V_0.5 alloy, although they all exhibited quite larger compressive plasticity (ε > 70%). Compression fracture surface of CrFeNi₂V_0.5W_0.25 alloy revealed a ductile fracture in the face-centered cubic (FCC) phase and a brittle-like fracture in the σ phase. Moreover, tensile test results indicated that the CrFeNi₂V_0.5W_0.25 alloy exhibited excellent mechanical property with an ultimate tensile strength of 640 MPa and a high tensile elongation of 15.7%. The tensile deformation mode of the FCC phase in the CrFeNi₂V_0.5W_0.25 alloy is dominated by planar glide, relating to dislocation configurations, high-density dislocations, and dislocation wall. Therefore, dislocation slip plays a significant role in tensile deformation of CrFeNi₂V_0.5W_0.25 high-entropy alloy. The higher strength of CrFeNi₂V_0.5W_0.25 alloy is predominantly due to the solid solution strengthening of W element and σ phase precipitation strengthening. Combination of the higher tensile strength and plasticity suggests that the CrFeNi₂V_0.5W_0.25 alloy can be a promising aerospace material.     

COMPUTER NUMERICAL SIMULATION OF MECHANICAL PROPERTIES OF TUNGSTEN HEAVY ALLOYS

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｕｎｇｓｔｅｎｈｅａｖｙａｌｏｙｓａｒｅｄｕａｌｐｈａｓｅｃｏｍｐｏｓｉｔｅｓｐｒｏｄｕｃｅｄｂｙｌｉｑｕｉｄｐｈａｓｅｓｉｎｔｅｒｉｎｇｏｆａｍｉｘｔｕｒｅｏｆ８０％～９７％ｔｕｎｇｓｔｅｎａｎｄａｓｍａｌａｍｏｕｎｔ...     

Distribution of Phosphorus and Its Effects on Precipitation Behaviors and Tensile Properties of IN718C Cast Superalloy

The effect of phosphorus on the precipitations of γ",γ' and δ phases and associated tensile properties in IN718C alloy are investigated in this study.It is revealed that P atoms are dissolved in the grain interior to a relatively high degree and hence influence the precipitation behaviors in the grain interior and improve the tensile strength of IN718C alloy.γ" and γ' phases did not precipitate in the alloy without P addition during air cooling,while γ" and γ' phases precipitated in the grain interior during air cooling in the alloys with P addition,and the amounts of γ" and γ' phases increased with increasing P content.Therefore,the Vickers micro-hardness in the as-cast state increased gradually with increasing P content.In double-aging state,the sizes of γ" and γ' phases in the alloys with P addition were larger than that in the alloy without P addition,while the sizes were invariable when the P content(wt%)was higher than 0.015.Therefore,the micro-hardness and tensile strength of IN718C alloy treated by double aging increased first and then kept invariable with increasing P content.The precipitations of δ phases both in the grain interior and on grain boundaries were inhibited by P markedly.The inhibitory effect of P on δ phase enhanced gradually with increasing content of P,but the plasticity increased first and then decreased.What is more,the crack tended to propagate into the matrix around the particles(Laves phases and NbC carbides)in the alloys without P addition at the beginning of the tensile fracture,while it tended to propagate along the interfaces between the matrix and those particles in the alloys with P addition,which resulted from the synthetical effect of P on γ" γ' and δ phases.     

95W-3.5Ni-1.5Fe合金高温性能、组织及断裂机制

研究了95W-3.5Ni-1.5Fe合金在400～1100℃范围内的高温拉伸力学性能及其断口特征,并分析了其断裂机制.结果表明:合金的抗拉强度及屈服强度均随温度升高而降低,延伸率和断面收缩率随温度升高呈现先增加后降低的关系,600℃时延伸率和断面收缩率达到最大值.对其断口分析结果表明:在400～600℃范围内,由于钨相发生了塑脆转变,钨颗粒塑性提高使得两相协调变形能力增强,合金塑性提高.而当温度升高到700℃以上,粘结相发生动态再结晶软化,钨相和粘结相界面结合强度大幅度下降,外加应力不能由粘接相传递到钨颗粒,其两相协调变形能力变差,导致合金强韧性急剧下降.     

GH690合金拉伸变形行为的温度敏感性

通过拉伸试验研究了GH690合金从298～623K的变形行为,用光学显微镜、扫描电镜和透射电镜观察了变形组织。结果表明,合金在298K拉伸时能够通过孪生协调变形,生成的形变孪晶阻碍了位错的滑移,从而使合金获得了较高的加工硬化速率,导致合金的强度和塑性较高。随着形变温度的升高,合金通过孪生协调变形的能力降低,变形机制由孪生转变为滑移,滑移产生的加工硬化效应小于孪生,因此合金的强度和塑性随之降低。     

铸态Mg-2Zn-1.5Cu合金组织及力学性能

利用金相显微镜、扫描电镜、透射电镜、XRD物相分析以及力学性能测试等手段,研究了Mg-2Zn-1.5Cu(at%)合金的显微组织及力学性能。结果表明:铸态合金存在较为明显的元素偏析,主要的第二相为MgCuZn相;合金的力学性能随着温度的提高而不断降低,塑性变化幅度要明显高于强度,合金的断裂方式也由低温时的沿晶断裂转变为高温时的穿晶断裂;在相同温度下,随着应力的提升,合金的稳态蠕变速率提高,蠕变机制由晶界控制转变为晶界及位错共同控制;在相同的应力下,随着温度的提升,合金的稳态蠕变速率存在数量级的提升,蠕变激活能由130kJ/mol降低到36.4 kJ/mol;在200℃,45 MPa时,出现加速蠕变阶段,发生蠕变断裂,断口存在明显的穿晶断裂特征,基体中有大量的沿基面运动的位错,部分位错发生攀移,MgZnCu相具有减缓蠕变变形的作用。     

Microstructures,tensile properties and serrated flow of AlxCrMnFeCoNi high entropy alloys

Microstructures and mechanical properties of dual-phase Al_xCrMnFeCoNi (x=0.4, 0.5, 0.6, at.%) alloys were investigated. Thermomechanical processing leads to a microstructural evolution from cast dendritic structures to equiaxed ones, consisting of face-centered cubic (fcc) and body-centered cubic (bcc) phases in the two states. The volume fraction of bcc phase increases and the size of fcc grain decreases with increasing Al content, resulting in remarkably improved tensile strength. Specifically, the serrated flow occurring at the medium temperatures varies from type A+B to B+C or C as the testing temperature increases. The average serration amplitude of these Al-containing alloys is larger than that of CoCrFeNiMn alloy due to the enhanced pinning effect. The early small strain produces low-density of dislocation arrays and bowed dislocations in fcc grains while the dislocation climb and shearing mechanism dominate inside bcc grains. The cross-slip and kinks of dislocations are frequently observed and high-density-tangled dislocations lead to dislocation cells after plastic deformation with a high strain.     

Effects of Cu addition on microstructure and mechanical properties of as-cast Mg-6Zn magnesium alloy

The application of Mg-Zn binary alloys is restricted due to their developed dendritic microstructure and poor mechanical properties. In this study, an alloying method was used to improve the mechanical properties of Mg-Zn alloy. The Mg-6Zn magnesium alloys microalloyed with varying Cu content(0, 0.8, 1.5, 2.0 and 2.5wt.%) were fabricated by permanent mould casting, and the effects of Cu content on the microstructure and mechanical properties of as-cast Mg-6Zn alloys were studied using OM, SEM, XRD and tensile tests at room temperature. The obtained results show that the addition of Cu not only can refine the grains effectively, but also can modify the eutectic morphology and improve the mechanical properties of the alloys. The main phases of the studied alloys include α-Mg, MgZn_2, Mg_2Cu and CuMgZn. When the content of Cu exceeds 0.8wt.%, Mg_2Cu phase appears. Meanwhile, the eutectic morphology is modified into dendritic shape or lamellar structure, which has an adverse effect on the tensile properties. Furthermore, among the investigated alloys, the alloy containing 0.8% Cu shows an optimalultimate tensile strength of 196 MPa, while the alloy with 1.5wt.% Cu obtains an excellent elongation of 7.22%. The experimental alloys under different Cu contents show distinguishing fracture behaviors: the fracture of the alloy with 0.8wt.% Cu reveals a mixed mode of inter-granular and quasi-cleavage, while in other investigated alloys, the fracture behaviors are dominated by cleavage fracture.     

不同固溶状态Mg-10Gd-3Y-1.2Zn-0.5Zr合金的力学性能及断裂行为研究

通过在Mg-10Gd-3Y-0.5Zr合金中添加少量Zn制备出一种新型Mg-10Gd-3Y-1.2Zn-0.5Zr合金,并利用扫描电子显微镜、拉伸试验机分析研究Mg合金不同状态下的显微组织、力学性能及断裂行为。结果表明：Mg-10Gd-3Y-1.2Zn -0.5Zr合金在不同的时效状态下,铸态塑性差,T4态塑性好,T6态塑性优于铸态但劣于T4态,且所有样品都是脆性解理断裂为主,晶界和层状相界面比化合物界面结合牢固。通过比较3个不同温度下T6态的力学性能,发现提高固溶温度能提高合金的强度,但延伸率会略降。并且Zn促进层状相生长,但是对基体塑性提高作用有限。     

Correlation between tensile and indentation behavior of particle-reinforced metal matrix composites: an experimental and numerical study

The correlation between tensile and indentation behavior in particle-reinforced metal matrix composites (MMCs) was examined. The model composite system consists of a Al–Cu–Mg alloy matrix reinforced with SiC particles. The effects of particle size, particle volume fraction, and matrix aging characteristics on the interrelationship between tensile strength and macro-hardness were investigated. Experimental data indicated that, contrary to what has been documented for a variety of monolithic metals and alloys, a simple relationship between hardness and tensile strength does not exist for MMCs. While processing-induced particle fracture greatly reduces the tensile strength, it does not significantly affect the deformation under indentation loading. Even in composites where processing-induced fracture was nonexistent (due to relatively small particle size), no unique correspondence between tensile strength and hardness was observed. At very low matrix strengths, the composites exhibited similar tensile strengths but the hardness increased with increasing particle concentration. Fractographic analyses showed that particle fracture caused by tensile testing is independent of matrix strength. The lack of unique strength–hardness correlation is not due to the particle fracture-induced weakening during the tensile test. It is proposed that, under indentation loading, enhanced matrix flow that contributes to a localized increase in particle concentration directly below the indenter results in a significant overestimation of the overall composite strength by the hardness test. Micromechanical modeling using the finite element method was used to illustrate the proposed mechanisms under indentation loading and to justify the experimental findings.     

Cu含量对Zn20Sn钎料力学性能的影响

对非真空熔炼的Zn20SnxCu钎料合金进行了抗拉强度和伸长率的测定,结果表明:随着Cu含量增加,Zn20SnxCu钎料合金抗拉强度逐渐增大,伸长率逐渐降低;当w(Cu)8％时,Zn20Sn8Cu合金的抗拉强度为229.9 MPa,较基体钎料提高了1.86倍,这主要与形成ε-CuZn5金属间化合物的数量和形态有关,且钎...     

Microstructure and tensile properties of low cost titanium alloys at different cooling rate

Titanium and titanium alloys have several advantages, but the cost of titanium alloys is very expensive compared with the traditional metal materials. This article introduces two new low-cost titanium alloys Ti-2.1Cr-1.3Fe (TCF alloy) and Ti-3Al-2.1Cr-1.3Fe (TACF alloy). In this study, we used Cr-Fe master alloy as one of the raw materials to develop the two new alloys. We introduce the microstructure and tensile properties of the two new alloys from β solution treated with different cooling methods. Optica...     

原位晶态相增强Mg-Cu-Dy非晶基块状复合材料

采用铜模喷铸法制备出直径为3 mm的原位Mg晶态相增强块状Mg70Cu17Dy13非晶基复合材料,对Mg-Cu-Dy类合金的力学性能和变形行为进行研究。结果表明,Mg70Cu17Dy13非晶基复合材料受压时产生加工硬化并获得最大抗压强度为702.38 MPa和塑性变形率为0.81%。这缘于其中Mg相有效的承载能力、塑性变形能力及Mg相对剪切带及裂纹扩展的有效抑制作用,可从其剪切变形、断裂方式和断裂面上密集的熔滴及凸凹不平得到证实     

Effect of Long-Term Thermal Exposures on Tensile Behaviors of K416B Nickel-Based Superalloy

The effect of long-term thermal exposure on the tensile behavior of a high W content nickel-based superalloy K416B was investigated. The microstructure and the deformation characteristics were observed by scanning electron microscopy and transmission electron microscopy, and the phase transformation of the alloy during long-term thermal exposure was analyzed by X-ray diffraction patterns and differential thermal analysis. Results showed that after thermal exposure at 1000 °C, the MC carbides in the K416B alloy decomposed into M₆C. During tensile deformation, dislocations slipping in γ matrix crossed over the M₆C by Orowan bowing mechanism. With the increase of thermal exposure time, the secondary M₆C reduced greatly the yield strength of the alloy at room temperature. Meanwhile, the continuous distribution of the secondary M₆C with great brittleness in the grain boundary could become the main source of crack, which might change the fracture characteristic of the alloy from trans-granular to intergranular.     

Re及温度对单晶镍基合金晶格常数及错配度的影响

通过对不同状态及不同Re含量单晶镍基合金进行高、低温X射线衍射谱线测定及组织形貌观察,研究Re含量及温度对单晶镍基合金中γ、γ′两相晶格常数及错配度的影响。结果表明:铸态合金中γ、γ′两相有较大的晶格常数及错配度;经完全热处理后,立方γ′相以共格方式嵌镶在γ基体中,合金中两相的晶格常数及错配度略有减小;长期时效使γ′相粗化后,两相之间出现界面位错,使合金中两相的晶格常数及错配度绝对值增加。随Re含量增加,合金中γ、γ′两相在室温的晶格常数增大,错配度的绝对值减小。与γ′相相比,γ基体相有较大的膨胀系数,因此,随温度提高,合金中两相晶格错配度的绝对值增大。     

高强度铝青铜合金锻造失效分析

采用扫描电镜对高强度铝青铜合金在锻造过程中出现的断裂现象进行了显微组织观察和失效分析。通过宏观断口分析和显微组织观察,发现合金中出现了角度为45°的裂纹和一些断裂区域。分析表明,高强度铝青铜合金在锻造过程中出现的断裂现象,主要是由于变形应力超过了合金的抗拉强度和合金中的K相形成了断裂的裂纹源,致使其发生了脆性断裂。