Features of microstructure and fracture in the transient liquid phase bonded aluminium-based metal matrix composite joints

Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).

Microstructure and Mechanical Properties of as Cast Aluminium Alloy 7075/Basalt Dispersed Metal Matrix Composites

This paper aims to study the effects of short basalt fiber reinforcement on the mechanical properties of cast aluminium alloy 7075 composites containing short basalt fiber of content ranging from 2.5 to 10 percent by weight in steps of 2.5 percent and fabricated using compo-casting technique. The objective is to investigate the process feasibility and resulting material properties such as young’s modulus, ductility, hardness & compression strength. The properties obtained are compared with those of as-cast that were manufactured under the same fabrication conditions. The results of this study revealed that, as the short basalt fiber content was increased, there were significant increases in the ultimate tensile strength, hardness, compressive strength and Young’s modulus, accompanied by a reduction in its ductility. Furthermore, the microstructure & facture studies were carried out using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and hence to link with mechanical properties of the composites.

Influence of surface liquid segregation on corrosion behavior of semi-solid metal high pressure die cast aluminium alloys

The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed in deaerated 3.5%NaCl solution.In separate tests,the open-circuit potential was monitored in aerated 3.5% NaCl for 30 min after immersion.The electrochemical tests show that there is no significant difference in the pitting potential of the wrought alloys and that of the Cu-enriched surfaces of the SSM-HPDC alloys.

Dry Sliding Wear Behaviour of SiC Particles Reinforced Zinc-Aluminium (ZA43) Alloy Metal Matrix Composites

The present paper reveals the wear behaviour of Zinc - Aluminium alloy reinforced with SiC particulate metal matrix composite. The composite is prepared using liquid metallurgy technique. The unlubricated pin-on disc wear test is conducted to find the wear behaviour of the ZA43 alloy based composite. The sliding wear test is conducted for different load, speed and time. The result reveals that wear rates of composite is reduced as reinforcement increases. For the same working conditions wear rate increases with increasing load and with increasing speed. The tested samples are examined by taking micro structure photos and analyzed for the type of wear. Dominating wear types observed are delamination and abrasion.

Experimental Studies of Self Healing Behaviour of Under-Aged Al-Mg-Si Alloys and 60Sn-40Pb Alloy Reinforced Aluminium Metal-Metal Composites

Experimental studies to demonstrate self healing potentials of Al-Mg-Si alloy were undertaken in this research work. Self healing exploring secondary precipitation in the Al-Mg-Si alloy and use of low melting metallic alloy reinforcement (60Sn-40Pb alloy) were used as basis for the investigation. For the precipitation study, the Al-Mg-Si alloy was under-aged at temperature of 160oC for 10 minutes and then subjected to second step ageing treatment at four different temperatures within the range of 25oC and 70oC. In the 60Sn-40Pb alloy reinforced Al-Mg-Si alloy study, the samples were prepared in pre-cracked state and then subjected to healing heat-treatment at 250oC. For all cases tensile test and healing efficiency was used to analyze the results generated. It was observed that a second step thermal ageing at 50oC resulted in peak improvement in tensile strength, yield strength, toughness and percent elongation while ageing above this temperature lead to a drop in the tensile properties in comparison to that of the sample not subjected to a second ageing treatment. Also the use of 60Sn-40Pb alloy as reinforcement in the Al-Mg-Si alloy resulted in a healing efficiency of 91% after pre-cracking and heat-treatment. The satisfactory bonding between the 60Sn-40Pb alloy and the Al-Mg-Si alloy matrix contributed to the high healing efficiency observed.

High-temperature mechanical properties of aluminium alloys reinforced with titanium diboride (TiB_2) particles

The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys （6061 and 7015） at high temperatures were studied. Titanium diboride （TiB2） particles were used as the reinforcement. All the composites were produced by hot extrusion. The tensile properties and fracture characteristics of these materials were investigated at room temperature and at high temperatures to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy. TiB2 particles provide high stability of the alumin- ium alloys （6061 and 7015） in the fabrication process. An improvement in the mechanical behaviour was achieved by adding TiB2 particles as reinforcement in both the aluminium alloys. Adding TiB2 particles reduces the ductility of the aluminium alloys but does not change the microscopic mode of failure, and the fracture surface exhibits a ductile appearance with dimples formed by coalescence.

Effect of fusion welding processes on tensile properties of armor grade, high thickness, non-heat treatable aluminium alloy joints

AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the best suitable process among the fusion welding processes such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) by evaluating the tensile properties of AA5059 aluminium alloy joints. The fracture path was identified by mapping the low hardness distribution profile (LHDP) across the weld cross section under tensile loading. Optical and scanning electron microscopies were used to characterize the microstructural features of the welded joints at various zones. It is evident from the results that GTAW joints showed superior tensile properties compared to GMAW joints and this is primarily owing to the presence of finer grains in the weld metal zone (WMZ) and narrow heat-affected zone (HAZ). The lower heat input associated with the GTAW process effectively reduced the size of the WMZ and HAZ compared to GMAW process. Lower heat input of GTAW process results in faster cooling rate which hinders the grain growth and reduces the evaporation of magnesium in weld metal compared to GMAW joints. The fracture surface of GTAW joint consists of more dimples than GMAW joints which is an indication that the GTAW joint possess improved ductility than GMAW joint.

The effect of zinc coating during joining aluminium to zinc-coated steel by welding-brazing process

An optical sensing system was constructed to study the coating when joining ahtminium alloy to zinc-coated steel by MIG welding-brazing process. The results showed that the coating fused to form a liquid zinc film on surface during process. The Al-Si filler metal reacted with the liquid zinc film to improve the spreadability of filler metal and thus a new method was established to join aluminium alloy and uncoated steel by depositing a mixed layer on steel surface.

Production of High Purity Metals: A Review on Zone Refining Process

Purification is a primary application of zone melting, in which the improvement of efficiency, production yield and minimum achievable impurity level are always the research focus due to the increasing demand for high purity metals. This paper has systematically outlined the whole development of related research on zone refining of metals including basic theories, variants of zone refining, parametric optimization, numerical models, and high purity analytical methods. The collection of this information could be of good value to improve the refining efficiency and the production of high purity metals by zone refining.

Cavitation-erosion mechanism of laser cladded SiC particle reinforced metal matrix composite

With 2 kW continuous wave Nd-YAG laser, SiC ceramic powder was laser-cladded on the AA6061 aluminium alloy surface. Within the range of process parameters investigated, the parameters were optimized to produce the SiC_p reinforced metal matrix composites(MMC) modified layer on AA6061 alloy surface. After being treated, the modified layer is crack-free, porosity-free, and has good metallurgical bond with the substrate. The microstructure and chemical composition of the modified layer were analyzed by such detection devices as scanning electronic microscope(SEM-EDX) and X-ray diffractometer(XRD). The performance of electrochemical corrosion and cavitation erosion and their mechanism were estimated by the microhardness tester, potentiostat and (ultrasonic-)(induced) cavitation device.

Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties of Aluminum Metal Matrix Composites

The wide choice of materials, today’s engineers are posed with a big challenge for the right selection of a material and as well as the right selection of a manufacturing process for an application. Aluminium Metal Matrix Composites is a relatively new material among all the engineering materials. It has proved its position in automobile, aerospace, and many other engineering applications due its wear resistance properties and due to its substantial hardness. One of the most important criteria is forgeability by which the workability of the material can be determined. The nature of distribution of reinforcing phase in the matrix greatly influenced the properties of Aluminum Metal Matrix Composites. The forgeability of Aluminum Metal Matrix Composites, which are produced by powder metallurgy method, are greatly depends on the size and percentage of reinforcement materials, compacting load, sintering temperature and soaking time etc. In this present work, the forgeability of Aluminum Metal Matrix Composites reinforced with silicon carbide (400 meshes) has investigated. A comparison have been made with different types of Aluminum Silicon Carbide Metal Matrix Composite materials contains 0%5%,10%,15%&20% by weight of silicon carbide. The mechanical properties like hardness of the different composites have also investigated. It is observed that the forgeabilty of the composites decreases with increasing the wt% of SiC but the mechanical properties like hardness enhanced on increasing the wt% of SiC.

TIME-RESOLVED IMPEDANCE RESPONSE OF GUILLOTINEDALUMINIUM UNDER GALVANOSTATIC POLARISATION

Transient repassivation of freshly generated aluminiutn surface is monitored by using time-resolved frequency response spectroscopy. Information relating to the anodic film formation as well as the cathodic evolution of hydrogen on the metal surace is obtained as function of repassivation time and applied constant current. Pronounced effects of anodic and cathodic applied curmnts on the time-resolved impedance spectroscopy support a previous model which suggests that the low frequtncy RC time constants are due to the anodic film growth and the high Asquency one to the cathodic charpetrensfer or clectron transfer process occuwtng simultaneously on the electrode surace.

A Review on Prerequisites of a Set-Up for Particle Detection by Ultrasonic Waves in Aluminium Melts

In many applications in aluminium industry, the number of inclusion-critical products increases and the quality of those products depend on the inclusion concentration and size. In order to improve the quality of aluminium products and the effectiveness of the processes, a reliable and cheaper on-line detection method is needed. Ultrasonic detection has been used in steel industry, but relatively rare in aluminium industry, although it would theoretically allow for an online non-intrusive detection of the cleanliness of the melt. In this work, the current information on ultrasonic inclusion detection was gathered and recommendations were provided on the Prerequisites for a set-up for ultrasonic detection of non-metallic inclusions in aluminium as a contribution on previous works. It has been concluded that ultrasonic waves seem promising, and should be experimented more on an industrial level to have a clear view on the potentials of the method.

Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing-An experimental study and analytical approach

High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.

水下EGaIn对7075铝合金的脆化机理研究

用EGaIn涂覆7075铝合金表面,并进行液态金属脆化研究,探究在大气与水两种环境下腐蚀脆化对铝合金微观结构、力学性能的影响规律。结果表明:与大气相比,在水下样品的腐蚀速率和力学性能弱化程度更高,其抗拉强度、伸长率和弹性模量分别降低了37.5%、57.7%和44.2%。对断口形貌和腐蚀产物表征发现,EGaIn在7075铝合金内部沿晶界扩散,促进了铝和水反应。铝水反应与液态金属扩散脆化协同作用,使水下EGaIn对7075铝合金的拉伸性能削弱程度更高,证明水是液态金属脆化的重要影响因素。

欧标铝塑复合带屏蔽综合护套的生产工艺探讨

通过对比双面铝塑复合带和单面铝塑复合带的纵包工艺,对单面铝塑复合带的纵包工艺进行讨论,并对热熔胶的性能选型进行分析,解决了铝塑复合带生产过程中的质量问题,发现单面铝塑复合带不仅可用作综合防水护层,也可起到金属屏蔽的作用,从而降低电缆成本。

金属型低压铸造铝合金裂纹分析及改进

从宏观特征、微观形貌、成分性能及金相组织等方面,分析了金属型低压铸造铸铝件的铸造裂纹特征。对裂纹进行了原因分析,并通过制定针对性改进措施,从源头彻底解决了铸造裂纹,大大提高了产品的铸造成品率。

7050铝合金大型锻件微裂纹原因分析

7050铝合金具有优异的力学性能,适用于制造具有高强度、高断裂韧性及耐应力和剥落腐蚀要求的主承力零件。锻件制造工艺难度高,工序复杂,在制造过程中会产生各种缺陷,如夹渣、气孔、裂纹等,严重降低了产品的合格率。对微裂纹缺陷进行观察和分析,结果表明:微裂纹产生的根本原因是铝锆中间合金未充分溶解产生了金属夹杂,该裂纹在锻造过程中进一步扩展。在7050铝合金生产中,当铝锆中间合金析出相(Al3Zr)的粒子粗大、分布不均时,凝固组织就会产生缺陷,其产生金属夹杂聚集缺陷主要是由于铝锆中间合金的大尺寸析出物(Al3Zr)的遗传。为了获得粒子细小、均匀分布的Al3Zr,应使用搅拌器搅拌,使用超声波对金属液进行处理,加快凝固的冷却速度。在原材料检验工序,加严超声探伤检查标准,增加高倍组织检查,避免带初始微裂纹缺陷的原料投入生产,造成产品报废。

聚合氯化铝在某矿区选矿废水深度治理中的研究及应用

近年来,聚合氯化铝在工业废水治理过程中应用逐渐广泛,但在有色金属选矿废水中砷及氟化物的治理案例较少,尤其是针对选矿废水中低浓度砷及氟化物的治理应用相对较少,本研究运用聚合氯化铝针对于选矿废水中的中低浓度砷及氟化物,通过实验室小试、工业试验,得出聚合氯化铝对低浓度有色金属选矿废水中砷及氟化物的治理效果显著,并通过连续运行跟踪,研究工艺的可行性、稳定性、经济性。

中等应变率下泡沫铝的吸能特性

进行了不同密度、高度和压缩方向下泡沫铝的准静态压缩试验和中等应变率下(<100 s-1)的冲 击试验,研究了具有不同密度的闭孔泡沫铝在准静态压缩和冲击工况下的吸能特性．结果表明,泡沫铝是一 种近似的各向同性结构,具有较高的单位质量吸能特性,是一种较好的吸能材料．在准静态和中等应变率冲 击条件下,泡沫铝对应变率不敏感,其应力一应变关系与应变率关系不大．不同的泡沫铝,其平台应力与密 度之间的关系不同,在研究其性能时,必须测量应力-应变关系．泡沫铝的致密区对其吸能特性有很大的 影响．