Melting Point Of Zinc Research Articles

Liquid metal induced embrittlement of a nitrided clutch shell of a motorbike

Abstract The failure mechanism of a clutch shell made from SPCC nitrided steel was analyzed. The component sustained multiple brittle fractures during assembly. Under SEM examination, the fracture surface was found to have facet and cleavage grain appearance. It was predicted that the cleavage fractures started from sites of intergranular fractures. XRD results showed that the nitriding layer contained Fe 3 N (60 wt.%) and Fe 4 N (40 wt.%). It is noted that Fe 3 N is more brittle than Fe 4 N. An impact test was carried out to compare the impact resistance of the failed and normal components. EDS analysis was also carried out, and it was found that the fracture surface contained zinc, which was not an element specified for the SPCC steel or the nitriding salt. As the salt bath nitriding process operated at a temperature higher than the melting point of zinc, failure was most likely due to liquid metal zinc induced embrittlement, as a result of localized salt bath material contamination with zinc.

Evolution of microstructures of galvanised and galvannealed coatings formed in 0·2 wt-% aluminium–zinc bath

The present investigation examines the evolution of the microstructures of galvanised steel during the galvannealing process with a special reference to the formation and breakdown behaviour of aluminium rich inhibition layer at the substrate/coating interface. The interstitial free steel was galvanised in a molten zinc bath with 0·2 wt-% aluminium content. The bath temperature and strip entry temperatures were 460 and 480°C respectively. Aluminium of 0·2 wt-% was chosen to retard the formation of iron–zinc intermetallic compounds in the coating. The as dipped galvanised interstitial free steel was annealed above the melting point of zinc in a salt bath at 480°C for a period ranging from 1 to 60 s. After annealing, the as galvanised coatings exhibited microstructural changes as a function of test time. The present work highlights the possible mechanisms of nucleation of iron–zinc intermetallic compounds during galvannealing treatment of steel galvanised in aluminium containing zinc bath.

Use of Zinc-Alloys for Low Temperature Soldering of Zinc Coated Steels

Zinc coated steels are nowadays used for different applications as for example for household appliances, automotive or offtakes. Due to the boiling temperature of zinc (907°C), which is lower than the steel melting point, the welding of zinc coated steel sheets presents many difficulties. As a result of the violent evaporation of zinc, pores in the weld seam are present after solidification and the zinc coating near the weld is damaged. Brazing of zinc coated steels with CuSi-alloys offers some advantages, as the joining temperature is about 950-1000°C. Nevertheless the high melting point of these filler materials requires very restricted process strategies and damaging of the zinc coating near the brazing seam can’t be avoided. Although laser-, plasma- and MIG-joining with CuSi and CuAl are performed nowadays. ZnAl-alloys are characterized through low melting temperature, which are comparable to the melting point of zinc, so that the damaging of the zinc coating can be reduced. In this paper investigations carried out with ZnAl-materials for joining zinc coated steel sheets as DC04ZE75/75 and DX56Z (thickness 0,9 mm) are reported. First investigations were performed by resistance spot soldering and show that using low temperature melting materials leads to a lower damaging of the zinc coating. Further the process reliability of laser soldering with ZnAl-alloys and a Nd:YAG as well as a diode laser is reported and confirms the suitability of these alloys for a damaging free joining zinc coated steels. The low surface tension leads to a wide bearing section, so that advantageous properties are expected. The mechanical properties of edge welds are evaluated in this paper through tensile tests as well.

Desorption of hydrogen from blowing agents used for foaming metals

Hydrogen desorption from TiH 2, ZrH 2, and MgH 2 was studied by thermal desorption spectroscopy (TDS), differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Loose hydride powders as well as powder compacts of zinc and various hydrides were studied. It was found that during the powder compaction process free surfaces on the hydride powder particles were created. As a consequence, the desorption temperature of the hydride in the precursor was lowered in comparison to loose powder exposed to air. Foam expansion of zinc was highest for TiH 2 which also exhibits the highest desorption rate at the melting point of zinc, followed by ZrH 2 and MgH 2 which decompose at lower temperatures and are therefore less effective for foaming. The desorption kinetics of Al and AlSi7 compacts containing TiH 2 were also studied for matters of comparison. The much lower foam expansions compared to Zn foams could be explained by higher hydrogen losses at temperatures below the melting point of Al and AlSi7.

Porous Al Alloys by Local Melting and Diffusion of Metal Powders

ABSTRACTA novel method exploiting local melt and diffusion induced porosity is described for producing porous Al alloys. Aluminum powder and zinc powder were blended and cold-compacted to a near net shape. A porous AI-Zn alloy component was then formed by annealing the material above the melting point of zinc but below the solidus temperature of the alloy. Pores were generated by the diffusion of molten Zn into the solid Al grains. The pore structure is shown to be determined by the volume fraction, distribution, and size of the Zn powders in the powder mixture, and by time and temperature of the annealing heat treatment. The pores can be further expanded by incorporating small amounts of titanium hydride into the powder blend and conducting the annealing treatment above the decomposition temperature of the titanium hydride (T>447°C). Porosity levels of 45 vol.% have been achieved to date. This processing approach appears amenable to the production of sandwich panels with a gradient porosity core and fully dense face sheets, and is applicable to other solid solution systems.

Improvement in the Corrosion Resistance of Zinc-plated Steel by Electrodeposition of Magnesium from a Molten Salt.

Electrodeposition of magnesium on zinc-plated steel from a molten salt electrolyte was investigated in order to improve its corrosion resistance. The 55 mol%LiCl-39 mol%KCl-5 mol%MgCl2-1 mol%CsCl molten salt was used for the electrodeposition of magnesium on zinc-plated steel. The primary crystallization temperature of the salt is 574 K, which is 119 K lower than the melting point of zinc. The molten salt gave homogeneous electrodeposition of magnesium on a zinc-plated steel at 653 K. The magnesium electrodeposited diffused into the zinc layer of the zinc-plated steel during electrolysis. In 5 mass%NaCl aqueous solution at room temperature, the magnesium-deposited zinc-plated steel did not form red rust for 41 days whereas the zinc-plated steel formed red rust after 10 days. The red rust, which was formed at 41 days on the magnesium deposited zinc-plated steel, had localized for further 21 days without expanding. This fact suggests that the magnesium-deposited zinc-plated steel have a self healing ability. Moreover, in a salt spray test at 308 K, the time of generation of red rust for the magnesium-deposited zinc-plated steel was 10 times longer than for the conventional zinc-plated steel.

The effect of perpendicular electric fields on the orientation of zinc oxide crystals during the oxidation of zinc thin films

The effect of direct current (d.c.) electric fields on the crystal orientation of zinc oxide thin films was investigated. Evaporated zinc thin films were oxidized in air under the application of perpendicular electric fields (detached electrodes) at different temperatures. The application of positive fields at 550 °C improved thec-axis orientations up to 1000 V cm−1. Further increase in field strength caused thec-axis orientations to decline to their original values (no applied field). The application of negative normal fields at 550 °C deteriorated thec-axis orientations up to 800 V cm−1. Thec-axis orientations improved to their original values by increasing the field strength to greater than 800 V cm−1. The crystal size remained unchanged, but the surface morphology was affected by the application of the electric fields at temperatures above the melting point of zinc. No significant change in optical properties was detected for samples that were subjected to electric fields. Whenever thec-axis orientation improved, crystals on the film surface became rounded and a more ordered microstructure was observed. On the other hand, the deterioration ofc-axis orientation was manifested by the increase in the number of whisker-shaped crystal needles on the surface of the ZnO thin films.

Combustion of some zinc-fuelled binary pyrotechnic systems

Combustion studies of several binary pyrotechnic systems using zinc as fuel and one of the oxidants: PbO 2, Pb 3O 4, PbO, BaO 2, SrO 2 or KMnO 4, are reported. Combustion was very sensitive to compaction, and only mixtures of Zn PbO 2 , Zn Pb 3 O 4 and Zn KMnO 4 sustained combustion when compacted. In all of the systems studied, the temperatures measured during passage of the combustion front past an imbedded thermocouple rapidly rose above the melting point of zinc. Burning rates were recorded for the Zn PbO 2 system compacted under 50 MPa, and the Zn KMnO 4 system under 50, 100 and 150 MPa. Thermochemical and kinetic data were determined where possible. Combustion mechanisms are suggested, involving condensed phase, diffusion-controlled reactions and gas-phase reactions occurring in parallel. Analysis of residues shows that ZnO is the major product in the Zn PbO 2 and Zn Pb 3 O 4 systems, and that mixed zinc oxides are possibly the major products of the Zn KMnO 4 , Zn BaO 2 and Zn SrO 2 systems.

Ａｌ‐Ｍｇ合金の超音波併用ろう接 超音波併用アルミニウムのろう接（第三報）

It is said that the aluminum alloys with the content of magnesium more than approximately 0.5 mass% is difficult to be brazed and soldered. In this study, we attempted to solder the aluminum alloys, such as A5052 and A5056, which contain magnesium more than 2.5 mass% with the aid of ultrasonic vibration. The joining was performed in the air using no flux and a zinc plate as a filler metal.Those alloys were able to be soldered at the temperarures between the eutectic point in Al-Zn binary system and the melting point of zinc. The tensile strength of a joint decreased with increasing the applying time of ultrasonic vibration over 1 sec and the vibration amplitude over approximately 50 km. The Mg amount segregated to a faying surface and the tensile strength of a joint decreased with increasing the heating rate to the joining temperature.

The range of zinc coatings

SummaryOver 40 million tonnes of steel are coated with zinc or zinc alloys each year. The most important technique is hot dip galvanizing, which can be applied either to un fabricated sheet or wire, to tube (in automatic plants) or to fabricated articles. Other methods of applying zinc include spraying of the molten metal, sherardizing (involving heat below the melting point of zinc), electroplating, mechanical coating and a wide range of zinc rich paints and products in which zinc dust or flake are added to organic or inorganic media.The combination of metallic zinc coatings with paint, powder or plastics overcoats is both important and expanding because the combined (‘duplex’) coating has a greater life than a simple summation of the lives of the coating layers taken individually.

Equilibrium structural transitions of solid-liquid interfaces in zinc based alloys

The equilibrium roughening transition of basal planes of solid zinc in contact with its molten alloys with Bi, In. Pb and Sn has been studied by analyzing the shape of small liquid droplets inside solid zinc grains. We found that this transition exists in all the systems studied: for Zn-In and Zn-Sn alloys, this transition takes place well below the melting point of zinc, while for Zn-Bi and Zn-Pb the roughening temperature is located exactly at the monotectic temperature. These results are discussed by using a simple, solid-fluid, zeroth-order monolayer model.

Prevention of pitting corrosion of aluminum by zinc diffusion cladding

A new process called zinc diffusion cladding was developed which shows an effect similar to that of the conventional sacrificial claddings and it is easily applied to various aluminum shapes.The process consists of the following two stages:(1) A thin zinc film is deposited on aluminum surfaces from alkaline zincate solutions by chemical substitution.(2) Zinc is diffused into the basic alloy.Distribution of zinc solute in the cladding, which affects the pitting corrosion, depended upon the amount of zinc in the deposit as well as time and temperature for diffusion. The amount of zinc was increased with the rise of solution temperature and the increase of dipping time. When the temperature for diffusion was lower, the thickness of effective layer was decreased, which reduced the life of clad. Whereas, when the temperature for diffusion was higher than the melting point of zinc, the sacrificial protection was also decreased owing to a smoother gradient of zinc concentration in the diffusion clad.Therefore, it was concluded that the depth of pitting corrosion was restricted by the diffusion cladding at 350400°C for 224 hrs. in a similar way to that of the conventional sacrificial claddings.

Compression Strength of Zinc/Zinc Oxide Composites at Temperatures above the Melting Point of Zinc

AbstractTwo types of zinc-base composite have been studied, one containing networks of zinc oxide and the other particles of zinc oxide dispersed within the metal matrix. The composites containing zinc-oxide networks possessed mechanical strength at above the melting point of zinc; those containing discontinuous dispersoids had no measurable strength at such temperatures. These results tend to confirm an earlier suggestion that commercial sintered aluminium powder products (SAP) contain a continuous network of alumina dispersed throughout the aluminium matrix.

特殊亜鉛滲透法について（第1報）純鉄上のZn鍍金

It was found that the special zinc-cementation method proposed by the present authors has both merits of the so-called galvanizing and sherardizing. The method is to pack the iron in the powder composed of 3∼10%Zn, 97∼90%Al2O3 or MgO and to heat it to above the melting point of zinc, 500∼600°C, for less than an hour. The authors postulate that the coating is formed by the gaseous penetration as well as by the solid diffusion of zinc into the iron. The effects of zinc content in the powder (from 3% to 90%Zn), heating time (from 1 hr to 5 hr), and heating temperature (from 450°C to 850°C) on the nature of coatings were studied : the greater part of the coating, the outer portion, is a layer consisting of zinc solid solution containing a small amount of iron, and the inner layer is ζ phase based on FeZn13, δ1 phase based on FeZn7, or Γ phase based on FeZn3 as the heating temperature is raised. The thickness of the coating is 0.05 mm to 0.1 mm on heating at the temperature range of 450°C∼600°C for an hour. The cohesion of the coating was studied by dropping a 1.3 kg weight from 10 cm height fifty times repeatedly on the coated articles and measuring the weight change. The corrosion of these articles in the NaCl solution and in the air were also examined, and the result was compared with that of the galvanized or the sherardized articles. The durability of the formers were superior to that of the others.Merits in this special method are as follows :— (1) The treating time becomes shorter than that of sherardizing, since heating temperature is at above the melting point of zinc.(2) This method may be applied for the machine articles finished, without seriously changing their dimentions.(3) The uniformity and evenness of the coating were obtained.(4) There is no fear of the powder coking,in spite of heating at above the melting point of zinc,since little zinc is contained in the powder, and can be used repeatedly by adding a small amount of fresh zinc.

Thermal Vibrations and Atomic Structure of Zinc Crystals at 100° and 298°K

The diffuse scattering of x-rays from single crystals of zinc has been investigated over a greater range of angles of scattering than in previous experiments. As a result of this more extended study, the root-mean-square displacements of the crystal atoms at $T=100$\ifmmode^\circ\else\textdegree\fi{}K are 0.098 and 0.050A for orientation angles of 0\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{}, respectively. At the melting point of zinc it is likely that the root-mean-square displacement in a given direction is not more than 8 percent of the axial distance in the same direction. The atomic structure factors at a scattering angle of 90\ifmmode^\circ\else\textdegree\fi{} are somewhat larger than would be expected on quantum-theoretical grounds. At large scattering angles the curves of the intensity of the scattered rays approach each other irrespective of temperature or orientation, the intensity approaching that of x-rays scattered from a gas of zinc atoms.

Societies and Academies

LONDON Institute of Metals (Annual General Meeting), March 7. G. A. HANKXNTS and C. W. ALDOUS: Minimum dimensions of test samples for Brinell and diamond pyramid hardness tests. The metals investigated include copper, brass, aluminium and steel. A width of test-specimen of 4 £ times the diameter of the impression is satisfactory for accurate Brinell tests. For Brinell tests, the limiting value of the ratio of thickness of test sample to depth of impression for accurate results appears to be a characteristic of the test material; a value of the ratio of 6 is required for mild steel, about 15 for copper and more than 20 for spring steej. For diamond pyramid hardness tests a limiting value of the ratio of test-sample thickness to impression diagonal of 1J gives results which are practically independent of test-sample thickness except with soft copper and soft brass. I. G. SLATER: Note on the influence of gases in an 8 per cent copper-aluminium alloy on normal and inverse segregation. In a sand-cast ingot, 3 in. in diameter by 3 in., segregation is inverse with very gassy melts but normal with degassed melts. GILBERT RIGG: The diffusion of zinc and iron at temperatures below the melting point of zinc. When clean rolled zinc sheet is heated in close contact with clean iron, diffusion commences at below 300 ° C. and is fairly rapid at above 380 ° C.; it proceeds by the formation of cones of diffusion products, which spread out from isolated points where the contact between the metals is most perfect, and gradually penetrate into the zinc and across its surface. Two well-defined layers of diffusion products are formed, a thin layer of constant thickness (about 0-08 mm.) containing about 17 per cent iron being next to the iron, and a thicker layer containing 0-11 per cent iron outside this. On continued heating, the thin layer moves towards the zinc, being continuously converted into the zinc-rich layer; this would seem to indicate that the principal diffusion constituent is the iron. H. G. GOUGH, H. L. Cox and D. G. SOPWITH: A study of the influence of the intercrystalline boundary on fatigue characteristics. With the object of studying the process of fatigue in relation to crystalline boundaries, tests under alternating torsional stresses have been made on three specimens of aluminium each consisting of two crystals. The distribution of slip bands showed that the effect of the boundaries on the distribution of stress was extremely slight, each crystal of each specimen behaving as if it alone composed the whole specimen. It appears that the presence of intercrystalline boundaries may considerably strengthen the constituent crystals against fatigue; but that the effect of the boundaries on the distribution or even on the amount of slip is very small. It is probable that the major effect of the boundary may lie in some restriction of strain that it imposes. C. E. PEARSON: The viscous properties of extruded eutectic alloys of lead-tin and bismuth-tin. Elongations up to 2,000 per cent have been obtained in tensile tests employing prolonged loading. An apparatus designed to maintain a constant stress on the test-piece during extension shows that deformation takes place at a uniform rate which is greatest in freshly extruded rods and decreases with age pr on annealing. The viscosity is not that of simple liquids, but resembles that shown by some disperse systems in which the viscosity coefficient is a function of the stress causing flow. The locus of viscous flow is found to be at the inter-crystalline boundaries. E. W. FELL: A note on some formulae concerning viscous and plastic flow in soft metals. In particular, the flow of the metal in a prolonged ball-hardness test is compared with the flow in tensile test-pieces under a constant stress per unit area of cross-section. A. PORTE VIN and P. BASTIEN: Castability of ternary alloys. The ability of a molten metal or alloy to fill a mould completely is termed ‘castability’; it can be determined by ascertaining the length of a spiral cast-iron mould filled by the metal under predetermined casting conditions. The castability of a pure metal is a linear function of the difference between the pouring temperature 6 and the melting point F; the slopes of the castability (Q?F) curves vary with the viscosity of the metal. The castability of binary alloys varies with the solidification range and with the mode of crystallisation, being greater when polyhedral crystals separate than when the primary crystals are dendritic. Maximum castability occurs with the eutectic composition and minimum at the limit of solid solubility. The castability of ternary alloys generally varies inversely with the primary solidification range.