Showing papers in "Metals technology in 1979"
TL;DR: In this article, an alternative form of the hyperbolic sine relationship is developed for use as a constitutive equation at elevated temperatures, and an optimization technique may be applied to results from torsion tests to determine the constants in this equation and that this method must be more accurate than those presented previously.
Abstract: An alternative form of the hyperbolic sine relationship is developed for use as a constitutive equation at elevated temperatures. It is shown how an optimization technique may be applied to results from torsion tests to determine the constants in this equation and that this method must be more accurate than those presented previously. Experimental results for two aluminium alloys indicate that the activation energy during hot torsion testing is the same as the activation energy for bulk self-diffusion. It is shown that thermal changes occurring during testing affect results significantly.
210 citations
TL;DR: In this article, the influence of composition on the tendency for surface-crack propagation on straightening of continuously cast strand of a commercial C-Mn-Nb-Al grade of steel has been examined and compared with the hotductility behaviour obtained from Gleeble tensile tests, using reduction of area as the measure for hot ductility.
Abstract: The influence of composition on the tendency for surface-crack propagation to occur on straightening of continuously cast strand of a commercial C–Mn–Nb–Al grade of steel has been examined and compared with the hot-ductility behaviour obtained from Gleeble tensile tests, using reduction of area as the measure for hot ductility. The tendency for surface-crack propagation was found to increase with Nb and soluble Al addition and to decrease with a rise in the P level. Hot ductility was also found to be affected in a similar manner by these elements. The results have been interpreted in terms of differences in the effectiveness of the NbCN precipitation in pinning the γ grain boundaries during deformation. From the close agreement between the hot-ductility behaviour as given by the Gleeble tests and the tendency for surface cracks to propagate during straightening of these steels at the exit from the continuous-casting machine, it has been concluded that the Gleeble test can be used with a fair degre...
141 citations
TL;DR: In this article, the operating limits of the three principal process parameters when hardening En8 steel are described and it is shown that the depth of hardening is closely correlated with the parameter P/√D b V. Since the experiments were arranged statistically the reproducibility of hardness traces is also described.
Abstract: A CO2 continuous wave laser producing up to 2 kW continuous power over an area down to 2·0 mm2 was used as a surface heater. The surface hardening of certain steels is possible through a martensitic structure produced by rapid cooling from an elevated temperature, provided the laser power P, beam diameter D b , and transverse speed V are kept within certain limits. Since the heat from a laser all passes into the surface and is not generated internally as with induction heating, thermal distortion is low and depth of hardening is controllable down to very thin layers. In the present paper the operating limits of the three principal process parameters when hardening En8 steel are described and it is shown that the depth of hardening is closely correlated with the parameter P/√D b V. The resulting microstructures are analysed and the upper and lower speed limits for effective hardening discussed. Since the experiments were arranged statistically the reproducibility of hardness traces is also described.
87 citations
TL;DR: In this article, the formation of rolling textures in Cu-30Zn was studied, and the deformation modes which operate at different levels of cold reduction were considered, which has involved a combin...
Abstract: In order to understand the formation of rolling textures in Cu–30Zn it is necessary to consider the deformation modes which operate at different levels of cold reduction. This has involved a combin...
85 citations
TL;DR: In this article, the abrasive wear resistance and fracture toughness of the principal types of alloy white cast iron have been determined in laboratory tests and it was found that low-stress abrasion resistance is con...
Abstract: The abrasive wear resistance and fracture toughness of the principal types of alloy white cast iron have been determined in laboratory tests. It was found that low-stress abrasion resistance is con...
68 citations
TL;DR: In this article, a set of 99·9 %purity copper specimens were deformed by torsion up to €=200 and their mechanical properties were determined from tensile tests.
Abstract: Specimens of 99·9 %purity copper were deformed initially by torsion up to €=200. Their mechanical properties were determined from tensile tests. The extreme values of mechanical properties were observed in a range of strain €=3−200. Changes in microstructure reflecting the mechanicalproperties of the specimens were investigated.
66 citations
TL;DR: In this paper, a new process for producing rapidly chilled metallurgical microstructures under reproducible cooling-rate conditions has been developed, which is accomplished by rapidly traversing a continuou...
Abstract: A new process for producing rapidly chilled metallurgical microstructures under reproducible cooling-rate conditions has been developed. Processing is accomplished by rapidly traversing a continuou...
64 citations
TL;DR: In this article, the effects of deformation on the structure of copper and its low stacking-fault energy alloys are reviewed and it is shown that these may be classified according to the method of examination used.
Abstract: The effects of deformation on the structure of copper and its low stacking-fault energy alloys are reviewed and it is shown that these may be classified according to the method of examination used. In rolled low stacking-fault energy alloys the deformation sequence involves the formation of stacking faults, mechanical twins, and shear bands that are at first restricted to individual grains but subsequently extend from one surface to the opposite surface. Shear bands form at ∼35° to the trace of the rolling plane in longitudinal sections and are composed of very small, slightly elongated crystallites. The twin thickness and crystallite spacing are determined by the stacking-fault energy and decrease as that parameter decreases. In copper the deformation sequence involves the formation of equiaxed cells of dislocations, microbands, clustering of microbands, and shear-band formation. It is shown that measurements of cell thickness as a function of strain in copper are meaningless. Replication and oth...
60 citations
TL;DR: A large number of ferrite-pearlite steels have been examined and measurements made of grain size, pearlite volume fraction, degree of precipitation hardening, and thickness of grain-boundary carbid as discussed by the authors.
Abstract: A large number of ferrite–pearlite steels have been examined and measurements made of grain size, pearlite volume fraction, degree of precipitation hardening, and thickness of grain-boundary carbid...
53 citations
TL;DR: In this paper, continuous and interrupted torsion tests have been conducted in the range of 900°−1000°C at surface strain rates of 0·1−10s−1 on a low-carbon and a Nb-bearing steel.
Abstract: Continuous and interrupted torsion tests have been conducted in the range of 900°−1000°C at surface strain rates of 0·1–10s−1 on a low-carbon and a Nb-bearing steel. During continuous deformation, the strains for recrystallization and for fracture had dependencies on temperature and strain rate that were similar for both steels but were higher and lower, respectively, for the Nb-bearing steel. For both steels, the flow stress depended on temperature and on strain rate according to an Arrhenius and a power-law relationship, respectively, and was consistently higher for the Nb-bearing steel. The interrupted deformations were performed so that in a given test, interruptions were of equal duration being 10, 20, or 40 s at equal strain intervals of either 0·2 or 0·4. The difference in stress at the instant of un loading and upon reloading was measured to assess the amount of static recovery and recrystallization taking place during the interval. At 0·1 S−1 recrystallization took place in the carbon ste...
38 citations
TL;DR: In this paper, the effect of five minor elements (S, Ca, Mg, Y, and Zr) on the hot workability of three solid-solution strengthened, nickel-base superalloys: Inconel 600, Hastelloy-X, and a Ni-Cr-W type alloy (NSC-1) was evaluated from the reduction of area in hot tensile tests using a Gleeble testing machine.
Abstract: Studies have been performed on the effect of five minor elements (S, Ca, Mg, Y, and Zr) on the hot workability of three solid-solution strengthened, nickel-base superalloys: Inconel 600, Hastelloy-X, and a Ni–Cr–W type alloy (NSC-1) for heat-exchanger pipes in high-temperature gas reactors. The hot workability was evaluated from the reduction of area in hot tensile tests using a Gleeble testing machine. Round bar specimens were prepared from near surface portions of alloy ingots melted and cast by vacuum induction melting, vacuum arc remelting, or electroslag remelting. When the sulphur content was increased, a ductility dip appeared for each alloy between 950° and 1150°C; the greater the sulphur content, the deeper the dip. At the same time, the fracture appearance became increasingly intergranular. By adding a small amount of Ca, Mg, Y, or Zr, the hot workability of these alloys changed drastically, and it was found that controlled addition of these minor elements gave a superior hot ductility. ...
TL;DR: The microstructure of the built-up edges of a number of alloys has been examined using both optical and electron microscopy as mentioned in this paper, showing that these were significantly different to those formed in austenitic stainless steel and Cu-40Zn brass.
Abstract: The microstructure of the built-up edges of a number of alloys has been examined using both optical and electron microscopy. The built-up edges of the two ferrific steels examined showed that these were significantly different to those formed in austenitic stainless steel and Cu–40Zn brass. The built-up edge deformation system has been described using three zones: primary shear (1), deformation around the build-up (2), and deformation to form the build-up (3). The ferrific steels exhibited high-strain deformation structures in both zones 2 and 3 with structures similar to those seen in wire drawing and swaging. The stainless steel and Cu–40Zn brass, however, showed equiaxed grains about 0·2μm in size with little or no twinning in zone 3. Zone 2 of these materials showed considerable twinning and the resulting surfaces were markedly less torn than those oftheferritic steels.
TL;DR: In this article, a die-casting system for semisolid Rheocast ferrous alloys is described, which utilizes the thixotropic nature of semi-slurries and uses a softness indicator to determine when the reheated charges are suitable for casting.
Abstract: A die-casting system is described which utilizes the thixotropic nature of semisolid Rheocast slurries. This system has been developed to a pilot-plant scale at the Massachusetts Institute of Technology. This plant comprises a continuous Rheocaster which is used to produce ingot stock, a reheating furnace to reheat individual charges to the semisolid state, a ‘softness indicator’ to determine when the reheated charges are suitable for casting, and a commercial cold-chamber diecasting machine. This paper deals primarily with the structure and properties of Thixocast ferrous alloys. Discussion is given of control of primary particle size, phases, oxide inclusions, and microsegregation in AISI 304, 440C, and other steels. Structure–property relationships are also presented and comparisons made with the properties of conventionally cast and wrought alloys.
TL;DR: In the rolling of sheet and strip in modern mills, deformation takes place mainly in the longitudinal direction as mentioned in this paper, and as the extension increases, there is a deterioration in the transverse and through-thickness toughness parameters, attributable mainly to the plastically deformable inclusions, such as manganese sulphides.
Abstract: In the rolling of sheet and strip in modern mills, deformation takes place mainly in the longitudinal direction. As the extension increases, there is a deterioration in the transverse and through-thickness toughness parameters, attributable mainly to the plastically deformable inclusions, such as manganese sulphides. The form of the inclusion in the wrought product is a function of its morphology in the cast steel and its plasticity. The effect of composition on both factors has been investigated. Increasing the aluminium or sulphur content of the steel promotes the formation of Type II manganese sulphides, which are precipitated as extensive arrays of rods in an interdendritic eutectic distribution, and which deform, as an array, to produce highly elongaled stringers. Mildly deoxidized steels contain globular, isolated, Type I sulphides, which do not form the particularly harmful stringers, but which are still highly deformable. Cerium and calcium additions successfully modified the initial morph...
TL;DR: In this paper, the effects of boron, titanium, and nitrogen contents on the hardenability of bors bearing steels have been studied and a useful guide concerning the limitation of total nitrogen content was derived for the development of titanium-free borspecific steels characterized by a good combination of hardness, machinability and toughness.
Abstract: The effects of boron, titanium, and nitrogen contents on the hardenability of boron-bearing steels have been studied. The boron hardenability factor was found to be a rapidly decreasing function of (total N – N as TiN). Thus, it was confirmed that titanium plays a very important role in retaining the excellent hardenability through its scavenging effect for dissolved nitrogen. From the results of this work, a useful guide concerning the limitation of total nitrogen content was derived for the development of titanium-free boron steels characterized by a good combination of hardenability, machinability, and toughness, especially for heat-treated parts made for heavy equipment.
TL;DR: In this paper, an existing steel was modified to a higher strength level to meet the requirements of airframe structures, achieving a fracture toughness of 156MNm−3/2 at this strength level.
Abstract: An existing steel was modified to a higher strength level to meet the requirements of airframe structures. Factorial-regression analysis of data determined previously helped to determine the interaction effects of the selected alloying elements on mechanical properties. The range of alloying elements required to optimize toughness at the 1586–1724MNm−2 ultimate strength level was subsequently determined by experiment. The developed alloy 0·16C–2Cr–1Mo–10Ni–14Co (AF 1410), attained a fracture toughness K IC = 156MNm−3/2 at this strength level. These properties result from the precipitation of M2C-type alloy carbides in a highly dislocated, lath martensite matrix during aging.
TL;DR: In this paper, an examination has been made of alumina formed during the deoxidation of iron-oxygen alloys by aluminium, and also of the fracture of the alumina during mechanical working.
Abstract: An examination has been made of alumina formed during the deoxidation of iron–oxygen alloys by aluminium, and also of the fracture of the alumina during mechanical working. The morphology of alumina is controlled largely by the supersaturation of the melt, high supersaturation giving dendritic alumina while low supersaturation gives liquid mixed oxides which react to form alumina and spinel reaction rims. The morphology of the alumina formed direct from the melt is controlled largely by the dissolved oxygen content which, in turn, controls the alumina/melt surface energy. Spheroidization and sintering of the dendritic alumina occurs as the dissolved oxygen of the melt decreases until dense, sintered alumina aggregates are formed. During deformation, the alumina becomes fractured and disseminated into stringers. Dendritic alumina fractures by breaking off the dendrite arms, while the polycrystalline alumina aggregates fracture intergranularly. Mechanisms are suggested for the formation of the vario...
TL;DR: The surface composition of swarfs from leaded Cu-40Zn has been determined by Auger electron spectroscopy and ion etching as a function of bulk-lead content and machining conditions as discussed by the authors.
Abstract: The surface composition of swarfs from leaded Cu-40Zn has been determined by Auger electron spectroscopy and ion etching as a function of bulk-lead content and machining conditions. The lead additive is distributed at the swart surface as a continuous thinfilm of monatomic thickness and as varying proportions of thick (p.m) lead striations along the cutting direction. The surface lead concentration of the chip is much higher than in the bulk metal. There is also a strong enrichment of zinc at the swart surface. It is considered that the lead surface layers are formed by a process of extrusion of lead owing to the high compressive forces which are developed during cutting. One complete lead monatomic layer is formed at bulk contents≥ 0·88 wt-% and this is associated with the absence of a secondary-shear zone, pointing to the lubrication of the tool/swarfinterface by the lead. A lead content in excess of 2·76 wt-% reduces power consumption, produces discontinuous chips, and is sufficient to maintain...
TL;DR: In this article, the effects of alloy composition and of heat treatment on the high-temperature creep resistance of some α-alloys of the Ti-Al-Zr-Mo-Si system related to the IMI 685 Ti-alloy composition were investigated.
Abstract: An investigation has been made of the effects of alloy composition and of heat treatment on the high-temperature creep resistance of some α-alloys of the Ti–Al–Zr–Mo–Si system related to the IMI 685 Ti-alloy composition (Ti–6Al–5Zr–0·5Mo–0·25Si wt-%). At least two mechanisms are rate controlling in the temperature range 660–860 K. At low temperatures in this range the creep exhibits nearly a thermal characteristics, the rate being only slightly dependent on temperature and characterized by very low apparent activation energy values ∆Hap and by some anomalous values of stress exponent n. The behaviour is attributed to a drag creep mechanism. The high values of ∆Hap and n observed for creep at higher temperatures are attributed to microstructural changes which occur during the tests. Stress-assisted precipitation occurs on dislocations during creep and it is proposed that the creep rate is limited by the rate at which the dislocations can break away from the precipitates.
TL;DR: In this article, an investigation has been conducted into the contribution made by nitrogen and nitrogen plus carbon to the properties of non-alloy steel treated at 570 °C and it is shown that both the fatigue properties of the diffusion zone and the tribological and corrosion properties of surface compound layer are independent of the carbon content.
Abstract: An investigation has been conducted into the contribution made by nitrogen and nitrogen plus carbon to the properties of non-alloy steel treated at 570 °C. It is shown that both the fatigue properties of the diffusion zone and the tribological and corrosion properties of the surface compound layer are independent of the carbon content. Recommendations are made on how such processes may be conducted and controlled in practice, and examples are shown of how the property improvements associated with these treatments have been exploited in the design and manufacture of non-alloy steel automobile components.
TL;DR: In this paper, the importance of determining the temperature at varying strains and strain rates during the twisting of a torsion specimen is emphasized and it is argued that previous analyses are inadequate.
Abstract: The importance of determining the specimen temperature at varying strains and strain rates during the twisting of a torsion specimen is emphasized and it is argued that previous analyses are inadequate. A three-dimensional finite-diflerence model is developed and a method of obtaining an ‘average’ temperature rise is presented. It is shown that significant temperature profiles are set up during torsion testing and that axial conduction cannot be assumed to be zero. The assumption of a laminar boundary layer is acceptable. Results are presented for two aluminium alloys.
TL;DR: In this article, the effects of solution-treatment temperature, cooling rate after solution treatment, aging treatment, and composition (i.e. molybdenum and silicon contents) on the microstructure and mechanical properties of some α-alloys of the Ti-Al-Zr-Mo-Si system related to IMI 685 Ti-alloy composition were investigated.
Abstract: An investigation has been made of the effects of (a) solution-treatment temperature, (b) cooling rate after solution treatment, (c) aging treatment, and (d) composition (i.e. molybdenum and silicon contents) on the microstructure and mechanical properties of some α-alloys of the Ti–Al–Zr–Mo–Si system related to IMI 685 Ti-alloy composition (Ti–6Al-5Zr–0·5Mo–0·25Si wt-%). β-solution treatment following quenching produces martensitic structures which are accompanied by small amounts of retained β-phase in the molybdenum-containing alloys. Increasing the β-solution treatment temperature does not significantly affect the martensite plate size but increases the original β-grain size, without altering markedly the strength. Reducing the cooling rate after the solution treatment increases the amount of retained β-phase and changes the microstructure from a martensitic- to a basket-weave-type morphology. The strengths of these alloys are enhanced by dynamic strain aging (DSA) in the range ∼700–850K, and ...
TL;DR: The effects of trace amounts of Pb, Sn, Se, Te, and Tl on the creep and stressrupture properties of Nimonic 105 at 815°C have been investigated as mentioned in this paper.
Abstract: The effects of trace amounts of Pb, Sn, Se, Te, and Tl on the creep and stressrupture properties of Nimonic 105 at 815°C have been investigated. The work confirmed that with the exception of Sn, all the elements have a deleterious effect when present in a sufficient amount. The most harmful impurities were Te and Pb. A generally more sensitive indication of the presence of harmful amounts of impurity was obtained with notched specimens. Optical metallography established that the deleterious effects were associated with greatly increased intergranular cavitation which became evident at an early stage of creep life when impurities were present. Auger electron spectroscopy showed that about one monolayer of lead was present on a cavitated grain boundary in a creep-tested specimen containing 34 ppm of Pb.
TL;DR: In this article, the authors investigated the ballistic penetration behavior of a high-strength aluminium alloy, 7001 T6, and found that targets of the alloy were found to fail in two modes, discing or plugging, depending on the orientation of the target in relation to the extrusion direction of the round bar from which it was cut.
Abstract: The ballistic penetration behaviour of a high-strength aluminium alloy, 7001 T6, was investigated and targets of the alloy were found to fail in two modes, discing or plugging, depending on the orientation of the target in relation to the extrusion direction of the round bar from which it was cut. The dependence of failure mode on orientation was related to poor fracture toughness in planes containing intermetallic stringers which were aligned parallel to the extrusion direction. A model for discing failure was developed which allows the penetration resistance of the plates to be calculated from the target strength properties. It is possible to prevent both the discing and the plugging failure modes by the use of steel back-up plates in contact with the rear of the target.
TL;DR: In this paper, a series of submerged-arc welds in C-Mn steels produced at interpass temperatures of 60° and 250°C have been studied in the as-welded and stress-relieved conditions.
Abstract: A series of multipass submerged-arc welds in C–Mn steels produced at interpass temperatures of 60° and 250°C have been studied in the as-welded and stress-relieved conditions. For those welds containing 0·08%C and less than 1·0%Mn stress relieving at 625°C causes an increase in the critical crack-opening displacement (COD) transition temperature, owing to the formation of brittle grain-boundary carbide networks. To explain this carbide development a carbon-concentration profile model, which depends on the extent of the transformation of austenite to pro-eutectoid ferrite is proposed. The results are compared with earlier work on steels containing 0·08%C and more than 1·0%Mn in which stress relieving produced a decrease in the critical COD transition temperature.
TL;DR: The role of lead in free-machining brass has been studied by calculating the temperatures formed in the primary and secondary shear zones of chip formation and by examining, in a scanning electron microscope, the structure of chips from cutting experiments.
Abstract: The role of lead in free-machining brass has been studied by calculating the temperatures formed in the primary and secondary shear zones of chip formation and by examining, in a scanning electron microscope, the structure of chips from cutting experiments. The calculations show that the temperatures in the primary zone do not exceed 200°C for workpiece speeds up to 200mmin−l. The discontinuous chip segments are formed as ductile fracture occurs along a shear instability in the primary zone. Scanning electron microscopical observations of the cuplets on the free surface of the chips suggest that voids occur at the lead inclusions so that the void–sheet mechanism of crack propagation gives rise to the discontinuous chip. A possible cause of void initiation at the lead inclusions is discussed. In the chip/tool contact region the major function of the lead is to provide layers of low shear strength within the secondary shear zone. Lead is also drawn out of the many voids to be deposited on the tool ...
TL;DR: In this paper, the enthalpies of vaporization and sublimation of these metals were estimated from the temperature dependence of the ion-current intensity values, by applying the combined effusion vaporization from a Knudsen cell and mass spectrometry sensing techniques the thermodynamic properties of liquid Cu-Ag solutions were investigated.
Abstract: By applying the combined effusion vaporization from a Knudsen cell and mass spectrometry sensing techniques the thermodynamic properties of liquid Cu–Ag solutions were investigated. The method of measuring the intensity of the 63CU29 and 107Ag47 ion currents J is described. The enthalpies of vaporization and of sublimation of these metals were estimated from the temperature dependence of the ion-current intensity values. The investigation of the Cu–Ag system was carried out over the range 1350–1550 K for ten selected compositions covering the complete concentration range of the system explored. The obtained dependence of J+63 CU 29/J+107 Ag 47 on temperature served to determine the activity and the coefficients of Cu and Ag activity by means of the modified Gibbs–Duhem equation. The partial thermodynamic functions of Cu and Ag in the solutions examined were also determined. These experimental values are compared With the data obtained by other authors.
TL;DR: In this paper, a brief account of work which has been done in the Institute of Metals Working and Physical Metallurgy, Academy of Mining and Metallurgy on mechanisms of plastic deformation, dislocation structures, and properties of Cu and α-brasses is given.
Abstract: The main aim in the paper is to give a brief account of work which has been done in the Institute of Metals Working and Physical Metallurgy, Academy of Mining and Metallurgy, on mechanisms of plastic deformation, dislocation structures, and properties of Cu and α-brasses. The investigations were carried out to determine how stacking-fault energy (SFE), temperature, and strain influence the thermally activated processes olplastic deformation. The work included different tests which were performed over a wide range of temperature and strain rates; these indicated the conditions at which deformation has an athermal character or becomes thermally activated. It was shown that dynamic recovery processes are responsible for differences in flow stress at different temperatures and strain rates and that SFE controls the intensity of these processes.
TL;DR: In this paper, a TIG weld deliberately made to maximize grain refinement was shown to have very high resistance to reheat cracking even though of relatively low purity, and it was concluded that by appropriate choice of welding process, grain refinement can be maximized in both weld metal and heat-afrected zone, and consequently can be prevented.
Abstract: In multipass submerged-arc welds deposited from 2· 25 Cr–Mo wires of controlled difference in purity, the reheat-cracking susceptibility was only slightly dependent on the residual-element content. When the wires were used to deposit tungsten inert gas (TIG) welds, the effect of residual elements remained small, but the extent of grain refinement was significantly increased and the reheat-cracking resistance consequently improved. A TIG weld deliberately made to maximize grain refinement was of very high resistance to reheat cracking even though of relatively low purity. Hence, it is concluded that by appropriate choice of welding process, grain refinement can be maximized in both weld metal and heat-afrected zone, and reheat cracking in low-alloy power-plant steels consequently can be prevented. Special measures to reduce the residual-element content below the levels generally obtained in current low-alloy steelmaking practice, therefore, should be unnecessary.