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"THE CONCEPT of energy as a commodity, while not entirely new, is not as widespread as the importance of the idea to this modern world would lead one to expect. The growth in the supply and use of energy over the past years has been tremendous, but our very closeness and familiarity have somewhat distorted the viewpoint, particularly of the younger generation. To many of us who remember the wonderful satisfaction of our first responsibility for directing two horsepower hitched to a farm cart or hay wagon, there still arises a feeling of some awe at the casual flick of the switch with which our sons and daughters summon to their convenience the service of some one hundred or more horsepower.Energy is the vital component of our existence and, no matter what contempt our day-to-day familiarity may •breed, it is wise to .pause from time to time and consider our national energy standing. Have we still capital in the bank? Are our expenditures wisely •conceived and well directed? Is provision being made for the years •ahead for the needs of our children and our children's children?"

Jan 1, 1953

By F. J. Tozer

Canal communication between Lake Erie and Lake Ontario has been one of almost constant enlargement and reconstruction to meet the rapid growth of trade and commerce, and the consequent steady increase in the size of vessels plying the Great Lakes. The original canal was built by the Welland Canal Company. The first sod was turned in 1824 and the first vessel passed through in. 1829. There were 36 lift-locks, built of oak timber, 110 feet long and 22 feet wide, with a depth of water over the sills of 8 feet. The second canal, now known as the 'Old Welland Canal' was built by the Dominion of Canada (1842 to 1850). There were 26 masonry locks, 150 feet long, 26.5 feet wide and with a depth of water over the sills of 9 feet. The walls and banks were raised in 1853 to give a 10-foot draught. The third canal, known as the 'New Welland Canal, built by the Dominion of Canada, was started in June 1874 and the first boat passed through in the spring of 1882. There are 25 masonry lift-locks, 270 feet long, 45 feet wide and with a depth of water over the sills of 12 feet. The walls and banks were raised in 1891 to give a 14-foot draught. This is the canal in use at present.

Jan 1, 1926

By L. V. Kin, V. V. Lodeischikov, A. V. Byvaltsev, IRGIREDMET JSC, O. D. Khmelnitskaya, S. V. Petrov

"Irgiredmet Institute carried out the study on the development of gold recovery technology from refractory ore from a Russian deposit. The ore contained 1.1 g/t Au, 1.5% of pyrite and 2.4% of pyrrhotite. The recovery of gold achieved was 84.7% using gravity with generation of high grade recoverable gold concentrate and gravity middling. In the course of lime treatment, cyanidation of the middling followed by tailings detoxification the consumption of reagents was 13.0 kg/t CaO, 95 kg/t NaCN and 72 kg/t Ca(OCl)2 of the concentrate. This was capital intensive.In order to decrease the consumption of reagents, magnetic separation of the middling of the concentrates from gravity separation was added to this flow sheet. Pyrrotite recovered to magnetic fraction, which did not contain gold in accordance to this advanced flow sheet. The mass yield of pyrite goldbearing non-magnetic fraction decreased down to 1.5 times in relative to gravity middling. The slurry filtration prior to and after cyanidation allowed the organization of cyanide solution recycling.The results of pilot plant tests using the developed flow sheet showed that the content of pyrrhotite in the non-magnetic fraction decreased from 59.1% to 11.3%. The reagents consumption was 12 kg/t CaO, 3 kg/t NaCN and 16 kg/t Ca(OCl)2 of the pyrite concentrate. The total gold recovery using this flow sheet was 83.4%. Due to a decreased consumption of reagents, cost efficiency of the process was achieved. Based on the results of this research, a project design criteria was developed. A processing plant with the annual throughput of 2.6 million tonnes of ore is being designed."

Jan 1, 2016

By K. Becerra, D. G. Almond, T. D. Maru

"Nkomati Nickel Mine in South Africa processes one of the world’s hardest ores in a 375k TPM autogenous grinding circuit. The plant employs an unconventional processing circuit, comprising a primary autogenous mill (AG or FAG) and pebble crushing circuit followed by a secondary hybrid pebble/ball mill and classification cyclone cluster.Advanced Process Control (APC) or Expert Control is now generally accepted as an advantage in most modern high capacity concentrator grinding circuits. This paper reviews the installation of model predictive control at Nkomati and examines the results and benefits of installation in an autogenous mill during plant ramp-up. The paper also demonstrates how predefining process control objectives together with good plant and supplier cooperation can achieve a robust and reliable APC implementation on a very short site program.The results conclusively demonstrate operational and economic benefits during circuit operation with the advanced process control system ON. Production performance and circuit stability were significantly better than during manual control."

Jan 1, 2012

By R. C. Fernandes, F. L. Santos

Aluminum alloys in particular, have certain limitations when subjected to welding process. This is mainly present because aluminum alloys have high thermal conductivity, high contraction in solidification and high hydrogen solubility. Taking this into account, the FSW process has great potential for this application, since it is autogenous, held without metal melting and without the use of slags or shielding gases. From this concept, the aim of this study is to evaluate the joining of thin sheets of aluminum alloy 3105 H26 with 0.7 mm of thickness. To performing of the tests, some parameters were analyzed, such as: tool penetration in the sheets, attack angle, the type of welding tool and penetration control mode (position or force). The results indicated that the force control mode is most suitable for thin sheets, and the transient state at the beginning of welding was the most critical part to control the welding quality.

Jan 1, 2015

By Jaeheon Lee, Junmo Ahn, Isabel F. Barton

"Newmont’s Mike prospect, currently undeveloped, is a blind Cu-Au(-Zn) deposit on the Carlin Trend, containing >8.5 M oz. Au, 1027 M lbs. Cu, and 809 M lbs. Zn as Carlin-type gold and polymetallic Cu-Zn minerals in Paleozoic lower-plate carbonates and shales. This project was undertaken 1) to examine the effectiveness of different lixiviants for leaching the Mike supergene Cu-Au ores via bottle roll tests, and 2) to determine what ore minerals resist dissolution in each leaching agent by comparing the mineralogy and chemistry of head and tail samples. Sulfuric and sulfurous acids were used to leach copper and cyanide was used to leach gold. Thiourea, glycine, and other lixiviants were used to leach both base metals and precious metal. QEMSCAN and SEM study of six samples of different ore types and grades indicate that the Au occurs as varieties of native gold, including auricupride and electrum. Major Cu minerals are native Cu, cuprite, malachite, chrysocolla, and conichalcite (Ca-Cu arsenate), with locally significant Cu in jarosite and goethite. Gangue mineralogy is dominated by quartz, sericite, chlorite, alunite, smectite and kaolinite, K-feldspar, and iron oxides (sensu lato). Results of bottle roll tests and leach residue mineralogy will be presented and discussed at the conference.INTRODUCTION Resource and Geologic Setting The Mike deposit is a large, blind Cu-Au(-Zn) deposit in the Maggie Creek district of the Carlin Trend of Nevada, USA, near the Gold Quarry mine (Figure 1). The mineral inventory, based on drilling, is 8.568 Moz. Au, 1027 M lbs. Cu, and 809 M lbs. Zn at average grades of 0.72 g/t Au, 0.34 wt% Cu, and 2.13 wt% Zn (inventory for a cone at $400/oz Au and $0.80/lb Cu by Norby and Orobona, 2002)."

Jan 1, 2017

By J. L. Bowlby

Introduction In the following discussion, boiler-feed and mine waters will be considered from the point of view of the problems arising from the chemical nature of the mineral and gaseous impurities they contain. The theories underlying some of these problems will be reviewed for the purpose of getting a clearer concept of the problems themselves. Certain terms of a chemical nature, necessary to the discussion, will be explained on the assumption that they are not generally familiar to mining engineers. Finally, an attempt will be made to correlate theory and practice, with the abject of establishing certain limits to factors relevant to the problems, and to show that these limits are justified by practical experience. The general problems occasioned by the presence of mineral and gaseous impurities in boiler-feed and mine waters are: (1) Scale formation and corrosion in boiler systems. (2) Corrosion of mine pumps and pump fittings. These will be discussed separately. Boiler Scale Typical analyses of waters available for use in steam power-plants are given in the accompanying Table (Table I). All analytical data are expressed in grains per Imperial gallon. The bicarbonates of calcium and magnesium in the raw waters are shown as normal carbonates in the Table. Substances in the first five rows constitute the encrusting solids. All the waters listed in Table I would be classified as 'very good' in the schedule of classification for boiler waters adopted by the American Association of Railway Chemists in 1887. In spite of this classification, however, the waters contain sufficient encrusting solids to cause serious scale trouble after prolonged evaporation.

Jan 1, 1934

By G. D. Bateson

"The Low NOx/SOx (LNS) Burner is a technology which, in pilot-scale tests, significantly reduces acid rain-forming emissions from the burning of coal. The precursors of acid rain are nitrous oxides (NO) and sulphur dioxide (SO:;) . TransAlta is currently planning two demonstration projects.Esso Resources Canada and TransAlta are undertaking a project to demonstrate how coal can be burned cleanly for steam raising in heavy oil operations by using TransAlta's LNS Burner on a steam generator at Esso's Cold Lake Production Project. The $10.7 million project started up in mid-J990, with testing to be completed in mid-I99J. The province of Alberta and Western Economic Diversification Canada, along with other private industry, are contributing funding to the project.The other demonstration project that has been selected for funding under the United States Department of Energy's Innovative Clean Coal Technology Program is a retrofit of LNS Burners to a 33 MW cyclone unit at Southern Illinois Power Cooperative's Marion generating plant. The US$13.6 million project is scheduled for completion 18 months after final funding arrangements are made.TransAlta believes that these demonstrations will lead to the development of a commercial ""clean coal"" technology. Other demonstration projects being planned will further broaden the base of applications.IntroductionTransAlta has recognized an increasing concern worldwide for the environment, and in particular the acid rain problem. Increasing public concern and the need to meet either current or possibly more stringent emission regulations have prompted them to explore various emission reducing technologies - despite the low sulphur content of its coal.The flue gas desulphurization (FOD) and selective catalytic reduction (SCR) technology currently available to reduce sulphur and nitrous oxides from coal burning power plants is very costly. Having to incorporate FGD technology, or ""scrubbers"", greatly adds to the cost of producing power. Having to add such high costs to electric customers' bills is something TransAlta is striving to avoid.There are many research programs now underway which are evaluating ways to provide electricity from coal in a clean manner. TransAlta has been observing or participating in a variety of these programs. However, there is one new technology which the company has identified as having the potential to control acid rain causing emissions at a fraction of the cost of conventional systems. That technology is called Low NOx/SOx, Burner - or LNS Burner."

Jan 1, 1990

By A. A. el-Geassy, A. A. el-Tawil, Hesham M. Ahmed, Bo Bjorkman

The Iron and steel industry is one of the most intensive energy consuming processes. The majority of iron making processes is now directed towards the uses of fossil-based energy sources like coke, coal and oil. Recently, emphasis has been paid to replace part of fossil- based energy sources with renewable biomass-derived reducing agents. In the present work, the possibility of the effective use of woody biomass in carbon-iron oxide composites was investigated. Wood powder was carbonized in N2 atmosphere at 300 up to 450oC. The carbon content in the produced bio-char increased with temperature. The porosity of the char arises from maintaining the cellular structure inherent in wood biomass increases with temperature. The reduction behavior of four iron oxide-bio char composites having different fixed carbon content were carried out non-isothermally up to 1200oC in Ar atmosphere using thermogravimetric anlyser (TGA). Quadruple mass spectroscopy (QMS) was also adopted to measure the CO, CO2 concentrations in the off gases resulted during reduction process. The effect of volatile matter on the reduction of iron oxide was intensively studied. The different phases developed in the reduced product were identified by X-ray diffraction (XRD). The reduction of composites was found to proceed in a stepwise manner (Fe2O3?Fe3O4?FexO?Fe).

Jan 1, 2015

By N. Morrison, I. Holl, R. Welyhorsky, A. Hempstock

ABSTRACT: The Victor diamond mine is located in the James Bay lowlands, 90 km west of the First Nations village of Attawapiskat. The project was the first of its kind in northern Ontario. The process plant was designed to produce a 95 to 98% by weight diamond concentrate through three stages of comminution, dense medium separation, and proprietary X-ray technology for final recovery. The plant was commissioned over a period of six months, commencing prior to substantial completion of construction. Through effective planning of the commissioning phase, the Victor mine start-up was safely completed nine months ahead of schedule.

Jan 1, 2011

By L. M. Pidgeon

Abstract The production of metallic calcium, by reduction of lime with aluminium, was investigated. Using a modified form of the effusion method, the vapour pressure of calcium above the reaction: 4CaO + 2Al ~ 3Ca + CaO.AI203 was determined and found to vary from 1.0 to 1.3 mm. Hg from 1,150° to l,200°C. From the magnitudes of the various thermodynamic quantities involved, together with a consideration of the known chemical characteristics of the reaction, it was suggested that the reaction proceeded by reduction of lime with aluminium vapour. INTRODUCTION The conventional production of metals by reduction of their ores by carbon (or carbon monoxide) may be represented by the equilibrium: MO+ R [] RO+ M . . . . . . . . . .(1) where MO represents the metal oxide, and R the reducing agent (carbon or carbon monoxide). The free energy change ?F° associated with the reaction is given by -?F° = RTlnKp . . . . . . . . ... . (2) where R is the gas constant, T the absolute temperature, and KP the equilibrium constant. It should be noted that ?F° represents ? the standard free energy gained by the system and hence -?F° is the free energy gained by the surroundings - and that as ?F° increases K must decrease, and conversely. For metals above manganese in the electromotive series, the ?F° associated with reaction would quantity and from it can be seen that this corresponds to a small fraction for K. The equilibrium pressure of the oxide of carbon represented by RO is then too near its concentration in the furnace gases for the reaction to proceed in an internally fired furnace. For the practical reduction of such metals, fuel fired furnaces are inadequate. Electric furnaces may be used to give higher temperatures with lower concentration of carbon oxides and the reaction may still proceed. However, for many metals such as calcium and aluminium the formation of stable carbides or acetylides may prevent production of the metal by this reaction. In this case, either electrolytic methods must be used, orrecourse must be had to reducing agents other than carbon. It is the latter method which is under consideration here.

Jan 1, 1948

By Michel Grenier, Robert Scott, Mahendra Gangal, Andrew Dasys

This research project which took place at Brunswick Mining and Smelting's Brunswick mine, was undertaken to assess the ability of new diesel engine technology to meet current and anticipated underground worker exposure limits to diesel exhaust contaminants. Concentrations of CO, CO2 NO, NO2 SO2 and respirable combustible dust (RCD) were measured in a remote mine area where a haulage truck was operating under simulated duty cycles. The 26 ton haulage truck was equipped with a 300 hp, electronically controlled engine. Fresh air was supplied to the area as per the MSHA certification document for this particular engine. Results showed that while the vehicle operated in a normal and realistic duty cycle, the concentrations of contaminants remained well below the ACGIH guidelines for the threshold limit values (TLV)for exposure. While operating at 630/0 of maximum horsepower (26 tons of ore in the dump), the time-weighted average exhaust gases concentrations (CO, CO2 NO, NO2 and SO2) never exceeded 150/0 of their respective TL Vs. ReD concentrations in this instance were measured at 0.59 mg/mJ or 39.30/0 of the exposure limit suggested by the Canadian ad hoc Diesel Committee. The Air Quality Index was 1.55 or 520/0 of the maximum suggested value for exposure.

Jan 1, 1994

By D. G. Almond

Nkomati Nickel Mine in South Africa processes one of the world?s hardest ores in a 375k TPM autogenous grinding circuit. The plant employs an unconventional processing circuit, comprising a primary autogenous mill (AG or FAG) and pebble crushing circuit followed by a secondary hybrid pebble/ball mill and classification cyclone cluster. Advanced Process Control (APC) or Expert Control is now generally accepted as an advantage in most modern high capacity concentrator grinding circuits. This paper reviews the installation of model predictive control at Nkomati and examines the results and benefits of installation in an autogenous mill during plant ramp-up. The paper also demonstrates how predefining process control objectives together with good plant and supplier cooperation can achieve a robust and reliable APC implementation on a very short site program. The results conclusively demonstrate operational and economic benefits during circuit operation with the advanced process control system ON. Production performance and circuit stability were significantly better than during manual control.

Jan 1, 2012

By X. Cao, A. Birur, R. R. Chromik, J. Cuddy, P. Wanjara, J. Gholipour Baradari, T. Shariff

In this study, 3.1 mm thick Ti-5553 (Ti-5Al-5V-5Mo-3Cr) butt joints were autogenously welded using a 4 kW continuous wave Nd:YAG laser. The effect of welding speed and defocusing distance on the weld quality was investigated in terms of the surface morphology, welding defects, microstructure and hardness. Welds with full penetration were achieved at a defocusing distance ranging from -1 mm to 0 mm and welding speeds from 2.25 to 6.0 m/min. Underfill and porosity were the two main defects most frequently observed but within the optimum process window these defects could be maintained to meet aerospace specification tolerances. The fusion zone (FZ) consisted entirely of retained beta with a refined dendritic morphology. Compared to the bimodal alpha (a) + beta (ß) microstructure of the base metal (BM), the dissolution of the a phase was observed in the heat affected zone (HAZ), which led to an 11 % decrease in hardness from the BM to the FZ. To determine the tensile properties of the welded samples, an automated 3D deformation measurement system was used to measure the local strain in the weld region. The yield strength (YS) and ultimate tensile strength (UTS) increased with increasing welding speed with a highest joint efficiency of 75 % being achieved, albeit with a concomitant reduction in the ductility.

Jan 1, 2010

By A. Grimod

Rockfall drapery systems are commonly used as a simple, fast and cheap measure against the rock falling trajectories affecting very steep slopes. The system basically consists of a steel mesh, which is held on the top edge with a longitudinal cable fixed by means of a suitable number of anchors. The effect of this kind of intervention is to control the falls of the rocks, which are driven toward the bottom with slow velocity, or are stabilized on place. It can be used on any kind of slope to protect sensitive target in the mining industry, roads and railways, and inhabited areas. The falling blocks, typically smaller than 0.6 - 1.0 m in diameter, pile up into a trench (or into a ?pocket of mesh?) at the bottom. In comparison to other types of rockfall interventions, the simple drapery is cheaper, and its maintenance is easier, but on the other hand it cannot be considered the remedy for shallow instabilities, because it can only mitigate the effect of the falling trajectories. The design of simple draperies requires the analysis of several factors like the slope features (height, gradient, morphology), the geological and dynamic features (nature of the ground or rock, type of instability, erosion problem, blocks size), the environmental condition (presence of vegetation, aesthetical problem), the installation problem (accesses to the slope, safety for the workers, safety for the surrounding areas) and finally the performance required (temporary or permanent intervention, required maintenance, cost). Finally the most problematic design-step is the choice of the suitable mesh, the top longitudinal cable, and the top anchors type. Because of the highly variable nature of rockfall behaviour these structures cannot be standardized, but they have to be analyzed and designed for each case. Maccaferri has developed a new software application (MacRO 2) has a practical tool to define the mesh and the related supporting structure composed by up-slope cable and anchors. The software, based on the approach proposed by Muhunthan B. et al. (2005), allows designers to verify the top longitudinal cable, the anchors, and the mesh drapery, and to plan for maintenance procedures. Even if the method seems quite simple and rough, it is effective and lets the designer correctly foresee the materials and the geometrical features to be used on the interventions. This paper analyses the condition for the simple drapery installation, the main steps for the calculations, and it will present a case study in a U.S. mine. Nevertheless, even if the software allows a quick and simple calculation approach, onsite observations are always recommended in order to achieve a good design, with the ultimate goal of protecting property and human lives.

Aug 1, 2013

By D. M. Morrison

"The most important factor in Canadian mining is not the operating cost of current projects but the availability of capital for future projects. The future of mining at depth will be producing ore from the top of the orebody working downward with very effective, tightly controlled mining methods, i.e. either selective mining or bulk mining with well controlled dilution and fragmentation. The key characteristics of future mines will be smaller access excavations, more effective ground support, very precise blasting techniques and more efficient and reliable materials handling systems. Equipment will be smaller and designed for high efficiency and low maintenance, reducing both the capital and operating cost. This means there will be fewer scoops, more continuous mucking machines and conveyor belts, both lateral and vertical.Orepass failures have become accepted and the resultant redevelopment and retramming has become common. The capital investment in so-called permanent ore passes and crusher stations becomes questionable, particularly when crushers are only necessary for less than 10% of the ore going through the system. The best way to solve the chronic instability of ore passes is, as with all of the stability problems at depth, by reducing the excavation size rather than increasing ground support. Smaller access drifts would reduce the capital cost and increase the rate of development as well as reduce the amount of waste to be handled, reducing the ground support and the ventilation requirements. Large drifts and ore passes are essential only for the equipment needed to handle large pieces of ore and the productivity of scoops is very expensive when the requirements for ventilation and large access drifts are taken into account. The key issue is the fragmentation generated by primary blasting.The future of mining in Canada will depend on simple and robust technology geared to the environment in which it will have to operate. Its survival will depend on some-thing much more fundamental and difficult to accomplish than a technological advance — it will require a dramatic change in the way the mining process is managed, how work is organized, how effort is rewarded and how costs are measured — a complete change in mind-set."

Jan 1, 1996

By Nordau R. Goodman

"IntroductionTHE HISTORY of Nova Scotia's gypsum industry goes back about two hundred years. The extensive deposits found in the Windsor formation, which is Lower Carboniferous, were the first discovered in North America and were known to the earliest .settlers. There has been a steady increase in production from these beds, except for minor setbacks in years of wars and depressions, but at the same time there has been a decrease in the number of operating quarries. This decrease reflects the change from the days of horse-and-cart recovery to the modern, large-scale, highly mechanized operations. In the beginning, almost any outcrop could •supply the tonnage requirements and the most •convenient were selected, but the millions of tons needed to meet present-day needs are not easily found.Despite the size and importance of the Nova Scotian deposits there has been little detailed geological work. Sir Charles Lyell, in 1843 ( 10), established that the beds are Lower Carboniferous and this was confirmed by Sir William Dawson (3) a .few years later. Both Lyell and Dawson agreed the calcium sulphate beds were an original part of a bedded series .but did not consider they resulted from a concentration of sea water. Lyell reached the conclusion that the gypsum was related to volcanic action in the form of heated vapours or hot springs. Dawson believed it was formed by the action •of sulphuric acid on calcium carbonate. The acid, derived from the oxidation •of iron pyrites which was abundant in the older formations, was carried by rivers into basins which were rich in shells."

Jan 1, 1954

"10.1. IntroductionAs discussed by Westland (1981), the six platinum-group elements (PGE) belong to the Group VIII transition metals, to which iron, nickel and cobalt also belong. The chemical similarity between these nine metals accounts for the fact that they tend to be concentrated together as a result of geological processes. These processes started to effect the distribution of these metals at the very beginning of the earth's history.The first line in Table 1 gives the concentration of nickel and certain other Group VIII transition metals in carbonaceous chondrites, those meteorites with a composition that is believed to reflect best the composition of our planetary system apart from hydrogen and helium. The second line is the estimated concentration of the same elements in the earth as a whole. It is seen that these two estimates are quite similar, the earth being perhaps 2 to 3 times richer in these particular metals than the planetary system as a whole. The reason for this is not fully understood, but it may be due to the earth being formed by the accumulation and capture of a greater proportion of iron (and therefore siderophile-rich) than stoney (and therefore siderophile-poor) planetesimals than the planetary system itself.The third line in Table 1 is the average composition of the crust of the earth. With the exception of iron, all of the Group VIII transition elements are rare in the crust, present at concentrations of It tOO to Itt ,000 of that of the bulk earth. This is because the outstanding chemical characteristic of this group of elements is their siderophile nature; that is, their tendency to alloy with metallic iron. Because of this, once the earth became molten very early in its life history, these elements dissolved in the molten iron present at this stage and were removed from the outer accessible parts as this dense liquid sank to the centre of the earth to form the core. Although iron was the main instrument of concentration of the Group VIII metals, its much greater over-all abundance and its ability to combine with oxygen more easily than the others in the group means that significant amounts still remain in the oxidized portions of the earth.The fact that most of the Group VIII metals are available to use in workable concentrations at all is that they are 5 to 30 times more concentrated in the earth's mantle than the crust, as shown in line 4 of Table I. There has been a constant, if slow, interchange of matter between the mantle and the overlying crust throughout most of the earth's history and, under certain circumstances, this interchange has given rise to economic concentrations of metals."

Jan 1, 1979

By K. Purazrang, P. Musavi Garavi, P. Sh. Naseri, P. Abachi

The fracture behavior of high strength Al7050 alloy was investigated at room and elevated temperatures using small size, V-notched tear (called Kahn specimen) and compact tension, CT, specimens, respectively.To study the elastic-plastic behavior of the alloy, the tensile test was also performed on the sub-sized cylindrical tension test specimen. The microstructure of the alloy was examined using optical- and scanning electron- microscopy. The rupture mechanisms and crack path were also studied by examination of specimens' fracture surfaces using SEM. The microstructure examination revealed equiaxed grains and some elongated grains in rolling direction, with the areas of partial re-crystallized grains where coarse intermetallic particles are mostly found.In general, fracture surfaces were indicative of dimpled ductile type. Considering the fractographs of tensile specimens, the void growth mechanism is also dominant in fracture of these specimens. Nevertheless, in some regions, smooth areas can be observed due to the friction during rupture process. The results of mechanical tests at RT made the evaluation of tear strength to 0.2 % tensile yield strength ratio, as a measure of notch toughness, available. According to elevated temperature, 150°C, test results and plots of log da/dt vs. log KI , the crack propagation behavior over discrete ranges of crack growth rates could be assumed linear and then be obeyed as a power law equation in the form of da/dt = A (KI)n .

Jan 1, 2015

By Guojun Wang, Zejun Chen, Wenchang Liu

Al/Mg/Ti laminated metal composite sheet (LMCS) can combine the merits of each of metal components, and obtain excellent performances. It incorporates the advantages of high strength, light weight, easy melt and atomization, and good space adaptability to substitute for the bumper Al sheet of Whipple shield structure for space debris shield. The Al/Mg/Ti LMCS was fabricated by hot roll bonding technology in a certain sequence. The manufacturing process and parameters were analyzed and studied, including the first rolling reduction, roll boding temperature and stacking structure of each metal. The microstructure of dissimilar metals and bonding interface were characterized and analyzed. The optimized manufacturing procedures and parameters were presented based on the microstructure and mechanical properties of LMCS. The research results offer some guides and references for controlling the shape of bonding interface, optimizing the annealing process, improving the mechanical properties of Al/Mg/Ti LMCS.

Jan 1, 2015