Structure and properties of mechanically alloyed composite material from waste of high purity aluminium production

Abstract

The present investigation has been based on the study of an opportunity of production dispersion strengthened composite material from waste of high purity aluminium production. Such waste represents an alloy with the following chemical composition: 50–60%Al, 25–35%Cu, ～10%Fe and 5–10%Si. The alloy Al–25Cu–10Fe–10Si with a chemical composition typical for industrial anodic sludge has been milled in a high energy planetary mill. The change in morphology and properties of granules of this material during mechanical alloying is estimated. For an assessment of some operational characteristics, a consolidated sample is obtained. The compact sample of the material possesses a high level of hardness, both at room and at higher temperatures, low level of thermal expansion coefficient and high level of wear resistance.     

Comparison of static and dynamic methods for measuring stiffness of high modulus steels and metal composites

The accurate measurement of modulus is not an issue specific to high modulus steels, but is still a challenge for the wider engineering and materials community. Inherently, the measurements should not offer significant problems, but results from a series of interlaboratory validation exercises and data on representative high modulus steels are included to illustrate some of the practical issues associated with the static and dynamic techniques. Dynamic methods probably offer the potential for the most accurate measurements due to the simple geometry and test set-up. Results show that a well set up test could be expected to give modulus values with an uncertainty of ±1–2%. Comparable levels can be achieved from the tensile test, but only through the use of a separate and dedicated test, where loading is carried out below the elastic limit, using averaging strain measurement, careful alignment and robust data analysis procedures.

La mesure précise du module d’élasticité n’est pas un problème spécifique aux aciers à module d’élasticité élevé, mais c’est quand même un défi pour la grande communauté d’ingénierie et des matériaux. Fondamentalement, les mesures ne devraient pas offrir de problèmes importants, mais on inclut les résultats d’une série d’exercices de validation entre laboratoires et les données d’aciers représentatifs à module d’élasticité élevé pour illustrer certains des problèmes pratiques associés aux techniques statiques et dynamiques. Il est probable que les méthodes dynamiques offrent le potentiel de mesures les plus précises grâce à la géométrie et au montage d’essai simples. Les résultats montrent qu’on peut s’attendre à ce qu’un essai bien monté donne des valeurs du module d’élasticité avec une incertitude de ±1–2%. On peut obtenir des niveaux comparables pour l’essai de traction, mais seulement au moyen de l’utilisation d’un essai séparé et dédié, où la mise sous contrainte est effectuée sous la limite d’élasticité, en utilisant la mesure moyenne de la déformation, un alignement diligent et des procédures robustes d’analyse de données.     

Effect of nano-SiC content on mechanical properties of SiC/2014Al composites fabricated by powder metallurgy combined with hot extrusion

Nano-SiC particulates (n-SiC_p) reinforced 2014Al matrix composites with different reinforcement volume fractions (0, 0.25, 0.5 and 1?vol.-%) were fabricated by powder metallurgy combined with hot extrusion. The effect of volume fraction of n-SiC_p on mechanical properties of composites was studied at both ambient and elevated temperatures. The increase of n-SiC_p content led to an increase in yield strength (YS) and ultimate tensile strength (UTS) and a slight decrease in elongation which is much better than the composites reinforced with micro-SiC_p. The 0.5?vol.-% n-SiC_p/2014Al composite observed the highest YS and UTS of ～378 and ～573?MPa at room temperature and of ～303 and ～409?MPa at 473?K. The enhancement of the properties is suggested to be induced by uniformly dispersed and well-bonded n-SiC_p reinforcements as well as the age-hardening effect of the more and finer precipitates.     

Mo对TiC/316L不锈钢复合材料组织和性能的影响

为了提高TiC/316L不锈钢复合材料的力学性能,在TiC/316L复合粉末中添加不同质量分数的Mo元素,采用粉末冶金法制备TiC/316L不锈钢复合材料.通过对复合材料的显微组织分析,拉伸、摩擦磨损等力学性能的测试,研究Mo含量对复合材料的组织和性能的影响.结果表明,Mo的添加有利于复合材料的组织均匀化,从而提高复合...     

Microstructure and mechanical properties of SiC particles reinforced Mg–8Al–1Sn magnesium matrix composites fabricated by powder metallurgy

The new type of Mg–8Al–1Sn (AT81) magnesium matrix composites reinforced with different volume fractions (5, 10, 15, 20, 25 and 30 vol.-%) of SiC particles (average size of 10 μm) was fabricated by powder metallurgy. With the increasing volume fraction of SiC particles (SiC_p), the particles gradually show more homogeneous distribution. Compared with the AT81 alloy, the yield strength (YS) and ultimate compressive strength of the SiC_p/AT81 composites are improved simultaneously. With the increasing SiC_p from 0 to 30 vol.-%, the YS and ultimate compressive strength increase from 69 to 239 MPa and 286 to 385 MPa respectively, while the corresponding fracture strain (ε) decreases from 19·3 to 4·8%. The improvement of the YS and ultimate compressive strength of the SiC_p/AT81 composites benefits from the more homogeneous microstructure due to the increase in the SiC particles.     

Influence of crystallographic texture and microstructure on elastic modulus of steels

In this paper the effects of crystallographic texture and microstructure on the elastic modulus of different grades of steel have been collected from the available literature and put in one place. It is expected that this will help researchers in their understanding of both the fundamental and the practical aspects of the different grades of steel used for various purposes.

Dans cet article, on a recueilli à partir de la littérature disponible et rassemblé en un seul lieu les effets de la texture cristallographique et de la microstructure sur le module l’élasticité de différentes nuances d’acier. On s’attend à ce que cela aide les chercheurs dans leur compréhension tant des aspects fondamentaux que pratiques des différentes nuances d’acier utilisées à diverses fins.     

碳纳米管增强铝基复合材料的力学和物理性能

采用磁力搅拌与放电等离子烧结技术制备了碳纳米管(CNT)增强铝基复合材料.对试样进行了扫描电镜和透射电镜表征,测试了试样的力学性能、摩擦性能、电学性能和热学性能.当碳纳米管在试样中的质量分数为1%时,可在铝基体中均匀分布且CNT/Al界面结合良好,此时试样的抗拉强度和硬度较纯A1分别提高了29.4%和15.8%.在获得最佳力学性能强化和最佳减磨效果的同时.试样电导率较纯Al仅降低8.0%.碳纳米管可提高基体的热导率.但强化效果不明显.     

原位合成SiC对铝基复合材料微观组织和力学性能的影响

以铝粉、硅粉、石墨粉为原料, 通过冷压真空烧结原位合成了含不同质量分数SiC颗粒的SiC/Al-18Si复合材料。利用X射线衍射仪, 扫描电子显微镜和能谱分析仪等设备手段表征了铝基复合材料的相组成和微观结构, 研究了原位合成SiC对复合材料微观结构、抗弯强度和显微硬度的影响, 分析了复合材料力学性能的变化规律。结果表明: 复合材料的基体相为Al相, 第二相为Si相和SiC相; 原位合成的SiC颗粒弥散细小的分布在Al基体中, 其颗粒尺寸主要分布在0.2~2.8 μm, 具有亚微米、微米级的多尺度特性; 随着SiC质量分数的不断增加, 复合材料的显微硬度增大, 同时颗粒的平均尺寸仅由0.81 μm增大到1.13 μm, 但仍均匀分布, 正是这种尺寸稳定性, 使得SiC/Al-18Si复合材料硬度远大于Al-18Si; 当SiC质量分数为30%时, 材料的显微硬度最高, 达到HV 134, 相较于Al-18Si提高了88%。     

Effects of chromium sources on the microstructure and properties of TiC-steel composites

The composites of low alloy steel reinforced with TiC particles (36?wt-%) were prepared by conventional powder metallurgy process in this paper. The chromium in the steel matrix was provided by pure chromium powder (PCP), low carbon ferrochrome powder, medium carbon ferrochrome powder (MCFP) and high carbon ferrochrome powder. The SEM was used to observe the particle morphology and microstructure. Density, hardness and transverse rupture strength (TRS) of the samples were tested. The results show that the composite prepared with the PCP as a chromium source has low hardness and TRS and the composites prepared with different ferrochrome powders have higher hardness and TRS. The microstructures of the samples prepared with different chromium sources have some differences and provide the differences in mechanical properties and fracture morphology. The sample prepared with the MCFP as chromium source has the highest comprehensive performance after tempering: hardness 70 HRC and TRS 1752?MPa.     

TMCP工艺对Si—Mn系贝氏体钢组织与性能的影响

研究了轧后中温缓慢冷却与中温等温两种不同的热机械控制工艺(thermomechanical control process,TMCP)对硅锰系贝氏体钢的组织与性能的影响.通过拉伸试验机测试试验钢的力学性能,利用扫描电子显微镜、电子背散射衍射等分析手段对试验钢进行显微组织结构分析,并利用X射线衍射测定残余奥氏体含量.结果表明:随着轧后连续缓慢冷却开始温度的升高,贝氏体钢的抗拉强度、硬度及拉伸应变硬化指数n值有所提高,伸长率和冲击韧性降低,屈强比先降低后升高.随着轧后等温时间的延长,贝氏体钢的抗拉强度与屈强比先降低后升高,伸长率及冲击韧性先升高后降低.相对于等温制度,连续缓慢冷却可得到更好的综合力学性能,强塑积明显高于前者,伸长率比前者高20%以上.     

Effect of C/Ti ratio on the compressive properties and wear properties of the 50 vol.-% submicron-sized TiCx/2014Al composites fabricated by combustion synthesis and hot press consolidation

In this study, in situ 50?vol.-% TiC_x/2014Al composites with different C/Ti molar ratios (0.6, 0.7, 0.8, 0.9 and 1) were successfully produced by the method of combustion synthesis and hot press consolidation. The microstructure and the mechanical properties of the composites were investigated. Microstructure characterisation of the TiC_x/2014Al composites showed relatively uniform distribution of the TiC_x particles with the particle size in the range of 200–900?nm. With the increase of the C/Ti molar ratio, the yield strength (σ_0.2) and the ultimate compression strength (σ_UCS) increased first then decreased, and the fracture strain (ε_f) increased. The σ_0.2, σ_UCS and the abrasive wear resistance of the 50?vol.-% TiC_x/2014Al composites reached the highest value when the value of the C/Ti molar ratio comes to 0.8. The σ_0.2, σ_UCS and ε_f of the 50?vol.-% TiC_x/2014Al composites with the C/Ti molar ratio of 0.8 are 1094?MPa, 1454 and 6.13%, respectively.     

12%SiCp/Al复合材料制备工艺及力学性能研究

对碳化硅颗粒进行表面氧化酸洗处理，采用粉末冶金加热挤压工艺制备了12％SiCp／Al（体积分数）复合材料。利用金相显微镜和电镜对微观组织进行了观测，拉伸试验测试复合材料的力学性能。试验结果表明：SiC颗粒在铝基体中分布比较均匀；T6热处理条件下12％SiCp／Al复合材料的屈服强度和抗拉强度分别约为472．4MPa、525．7MPa，伸长率为6．5％，弹性模量为92．7GPa。     

Evolution of the microstructure and mechanical properties of Mg-matrix in situ composites during spark plasma sintering

Biomedical Mg-matrix in situ composites were fabricated from Mg and ZnO powder via ball mixing and spark plasma sintering. XRD analysis indicated that in situ reactions occurred during sintering process producing MgO, Zn and Mg–Zn intermetallic compounds. The formation of in situ products strongly contributed to the enhancement of the strength and the ductility of the fabricated composites compared with pure Mg. Specifically, the highest strength at 380?MPa was observed in the Mg-20 wt-% ZnO composite, and the highest failure strain at 12.9% was achieved in the Mg-5 wt-% composite compared with the 156?MPa strength and the 10.2% failure strain of pure Mg. In addition, the strengths of as-produced composites are as double as that of cortical bones. With these superior mechanical properties, the fabricated composites are considered as very potential candidate for biomedical load-bearing applications.     

Experimental investigation into microstructure,metallurgy and mechanical properties of AISI 422 stainless steel weldments produced using fibre laser welding direct forming

In this study, the Taguchi design method was used to determine the optimal parameters for the fibre laser welding direct forming (FLWDF) of AISI 422 stainless steel (SS) weldments for use in the repair of the tenons in steam turbine blades. Experiments were then conducted to investigate the microstructural characteristics and mechanical properties of the weldments. Our results show that the fusion zone of the AISI 422 SS weldments possesses a grain structure of significantly higher refinement than does the original AISI 422 SS. Moreover, tempering at 700°C for 2?h was found to enhance the hardness as well as the impact toughness of the weldments. Finally, mock-up trials of tenon repair were performed using the optimal FLWDF parameters. Our results reveal that the repaired tenons are able to withstand a tensile load of 30?kN in as-welded condition and up to 55?kN following tempering at 700°C for 2?h.     

涂覆颗粒增强耐热铝基复合材料的力学及摩擦磨损性能

研究了经真空热压、热挤压工艺制备的涂覆颗粒(化学涂层工艺)增强Al-Fe-V-Si耐热铝合金基复合材料在不同温度下的力学性能与摩擦磨损性能.实验结果表明:涤覆后的SiC_p与基体结合更加牢固,涂覆层(Ni)的加入降低了材料内部颗粒(SiC_p)与基体(Al-Fe-V-Si)之间的孔隙,10％SiC(Ni)/Al-Fe-V-Si(0812)复合材料在室温的断裂强度分别比基体和10％SiC_p/Al-Fe-V-Si(0812)复合材料增加了62.15％和2.82％,在400℃时分别增加了55.3％和28.6％.复合材料耐磨性能比增强体未涂覆复合材料大大提高,在载荷50N,转速0.63 m/s的工况下,经增强体涂覆的铝基复合材料在300℃时为以磨粒磨损为主的磨损机制;高于350℃时,为以粘着磨损为主的磨损机制.     

碳纳米管增强Cu基和Al基复合材料界面改性

在碳纳米管(carbon nanotubes,CNTs)增强Cu基和Al基复合材料的制备中,界面改性是提高复合材料性能的重要方法。金属基体和碳纳米管间的有效界面结合直接影响了复合材料中界面的载荷传递、导电以及导热性能,从而影响复合材料性能。本文综述了近几年碳纳米管增强Cu基和Al基复合材料界面改性的工艺方法,讨论了界面改性工艺对碳纳米管增强Cu基和Al基复合材料界面结构和性能的影响。     

Effect of compacting pressure on microstructure and mechanical properties of carbide cutting tools

Abstract

The effects of compaction pressure on properties of carbide cutting tools containing 80·5 wt-%WC, 5 wt-%TiC, 5 wt-%TaC–NbC and 9·5 wt-%Co were studied. These tools were formed by powder metallurgy with different compacting pressures ranging from 77 to 231 MPa (5–15 tons in^?2) and sintered in a vacuum furnace at a constant sintering temperature (1450°C) and at a constant heating and cooling rate of 5°C min^?1. Green and bulk densities, shrinkage and hardness of the produced compacts were measured. Tool cutting performance has been assessed based on machining a medium alloyed steel workpiece under different cutting conditions and measuring the tool flank wear and the workpiece surface roughness. The microstructure of the compacts was metallographically examined using scanning electron microscopy. The results have revealed that both densities and hardness figures increase with increasing compaction pressures, while shrinkage decreases. Cutting performance has not demonstrated a substantial improvement of the tool's performance and life due to the increasing compacting pressure of these tools.     

Effect of reheating temperature on the microstructure and tensile properties of SiCP/2024Al composite prepared by powder thixoforming

Powder thixoforming, a novel method for preparing and forming particle-reinforced metal-matrix composites has been proposed, and the effect of reheating temperature on the microstructure and tensile properties of a thixoforged SiC_p/2024 Al-based composite was investigated. The results indicated that the temperature influences the liquid amount and microstructure compactness and the subsequent solidification behaviour during thixoforging. The best comprehensive tensile properties, ultimate tensile strength of 361?MPa, yield strength of 271?MPa and elongation of 4.2%, were obtained under reheating for 70?min at 898?K, which were 24 and 29% higher and 57% lower than those of 2024 Al matrix alloy thixoforged under the same conditions, respectively. The fracture mode of the composite varies from a mixture of intergranular and transgranular mechanisms to transgranular mechanism and intergranular mechanism as the temperature increases.     

MWCNTs特征对MWCNTs/Al复合材料组织及性能的影响

采用粉末冶金法制备多壁碳纳米管(MWCNTs)增强铝(Al)基复合材料(MWCNTs/Al),研究MWCNTs的特征对MWCNTs/Al复合材料显微组织结构及性能的影响。采用X线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和拉伸实验对复合材料进行性能测试。结果表明:经过球磨混合的复合粉末中没有碳化铝(Al_4C_3)相,通过烧结和热挤压后出现Al_4C_3相。与长碳纳米管(L-MWCNTs)和短碳纳米管(S-MWCNTs)相比,镀镍碳纳米管(Ni-MWCNTs)在复合材料中分散更均匀,与Al基体的结合性更好,所得到的复合材料硬度和抗拉强度较高,抗拉强度可达到247 MPa,是纯Al的4倍。     

Study on microstructure and mechanical properties of spark plasma sintered Alumix 431 powder

Spark plasma sintering (SPS) has been used to successfully densify a 7075 aluminium alloy obtained from Alumix 431 powder. Sintering experiments were conducted at the temperature of 450 and 500°C for 2.5, 5 and 10?min. All the presented results confirm the excellent sinterability of Alumix 431 powder in vacuum during the SPS process and clearly show the effect of sintering temperatures and holding times on the densification, microstructure and mechanical properties of the obtained sintered compacts. The best results of hardness (1412?±?39?MPa), tensile strength (345?±?15?MPa) and compressive strength (618?±?4?MPa) were obtained by the compacts sintered at 500°C for 5 min.