Cu-Sn Bronze Research Articles

Optimization of wear-, fracture- and corrosion performance of Vanadis 6 steel through cryogenic treatment and tempering

Vanadis 6 cold work tool steel was vacuum austenitized, room temperature quenched, differently cryogenically treated (-75, -140 and -196 °C for different durations) and double tempered, at temperatures of either 170 or 530 °C. Galling resistance was assessed by pin-on-disc testing of differently treated specimens against CuSn bronze, at wide ranges of sliding velocities and loads. The obtained results show that cryogenic treatments combined with low temperature tempering improves anti-galling performance of the steel. The best tribological properties were obtained when high-temperature tempering was combined with cryogenic treatment at -196 °C, due to the maximum extent of microstructural alteration generated by this kind of treatment. The improvement in wear performance is accompanied with slight but undisputable increase in corrosion resistance of the steel, at almost no affected toughness as compared with the state after conventional heat treatment. In conclusion, the obtained results imply an opportunity to simultaneously improve wear performance, corrosion resistance and toughness of the examined steel, by choosing a proper combination of cryogenic treatment and tempering.

Investigation of Microstructural, Mechanical and Corrosion Properties of Cu-10Sn Bronze Parts Produced by Selective Laser Melting

In this study, the production of full-density Cu-10Sn bronze parts by selective laser melting (SLM) technique and the examination of microstructural, mechanical and corrosion properties were carried out. Cu-10Sn pre-alloyed powders produced by gas atomization technique were shaped using SLM technique within selected parameters and then microstructural properties were determined. Depending on the microstructural properties, the mechanical and corrosion behaviors were determined. The obtained results were compared with similar bronze materials produced by conventional methods. Different characterization techniques were used for microstructural characterization. The microstructure of the Cu-10Sn alloy was observed to consist of dendritic primary α and δ-Cu41Sn11 phases. According to the mechanical test results of the samples produced at densities of 8.75 g cm-3 at room temperature, the yield strength was measured as 420 MPa, the tensile strength was 578 MPa, the elongation was 32 % and the hardness value was 160.3 HV0.2. For the electrochemical experiments, the corrosion rate of the samples was found to be 4.38 mpy. As a result of the productions and experiments, it was determined that the samples produced by the SLM method provide very good mechanical and corrosion properties compared to the literature.

The behavior to cavitation erosion of CuSn12-C bronze structures, as obtained by in-depth heat treatments

CuSn bronze alloys are some of the most used in the casting of freshwater ship propellers. Through in-depth heat treatments, the microstructure and hardness are substantially altered when compared with the initial state of the material after casting. The work highlights the change in the behavior and resistance to the vibrating cavitation erosion of the CuSn12-C bronze microstructures, after being subject to two in-depth heat treatments (hardening at 700ºC, followed by cooling in water, and two hardening treatments at 700ºC, with cooling in water, followed by tempering at 500ºC and 250ºC, with cooling in air). The experimental tests are performed using the vibrating standard piezoelectric crystal assembly, available in the Cavitation Research Laboratory at the Polytechnic University from Timisoara.

The Effect of Sintering Temperature on Wear Resistance of Alloys Produced by Using Hot Isostatic Pressing (HIP) Method

The present study investigated the effect of the temperature, at which a new matrix material was produced via hot isostatic pressing (HIP) method by adding certain rate of Co and Ni elements into CuSn (85/15) bronze alloy, and Co and Ni elements wear resistance of the samples produced. One of major advantages of HIP method is that heat and pressure are applied simultaneously during the sintering process. Thus, all or almost all of the pores are eliminated during the manufacturing and a denser material is obtained. During the study, sintering pressure and sintering time were kept constant as 15 min, and also sintering temperature was selected to be 700 and 800°C as the variable parameter. Sintering process was carried out under vacuum starting from the first burn. The produced samples were then prepared metallographically and SEM and EDS analyses were performed for microstructure examinations. Microhardness of the samples was taken to investigate mechanical behaviors of the samples and they were subjected to wear test. Finally, density test was applied to samples and their experimental and theoretical densities were calculated. In conclusion, it was seen that more homogenous samples were obtained as sintering temperature increased. As Co amount and temperature increased in the study, wear resistance increased.

The role of Sn on the long-term atmospheric corrosion of binary Cu-Sn bronze alloys in architecture

The role of Sn on the atmospheric corrosion performance of binary Cu-Sn bronze alloys (4–6 wt.% Sn) compared with Cu metal used in outdoor architecture is elucidated in terms of microstructure, native surface oxide composition, patina evolution, corrosion rates, appearance and metal release. Results are presented for non-exposed surfaces and surfaces exposed at different urban and marine sites in Europe up to 5 years and based on multi-analytical findings from microscopic, spectroscopic, electrochemical and chemical investigations. Alloying influenced the corrosion, aesthetic appearance and patina evolution, differently for urban and marine sites, whereas no effects were observed on the release pattern.

Patina enrichment with SnO2 and its effect on soluble Cu cation release and passivity of high-purity Cu-Sn bronze in artificial perspiration

The antimicrobial function of Cu surfaces can be linked to soluble Cu release from corrosion. However, direct replacement of high-touch surfaces with Cu-based alloys is limited by knowledge gaps regarding how alloying directly relates to corrosion. A systematic approach to determine the role of Sn as a solute element and the minimum alloy content for passivation has been lacking. High-purity arc-melted binary alloys of Cu-Sn with specific additions of 0.1, 1, 5, and 10 wt% Sn were compared to pure Cu and Sn. The role and amount of Sn in corrosion products (patina) formed on the alloy surface as a function of alloying was interrogated in artificial perspiration. The fate and identity of the solute (Sn) and solvent (Cu) elements following corrosion, as soluble ions or insoluble corrosion products, was investigated. Alloy patinas became increasingly enriched in Sn corrosion products identified as SnO2 with increasing Sn content in the alloy. The critical alloy content for complete SnO2 layer coverage were theoretically quantified through a model based on interfacial surface energy. The predicted minimum solute content for a complete conformal inner layer of SnO2 was 1 wt% Sn whereas experimentally complete coverage was achieved only at 10 wt% Sn. Differences between theory and experiment are discussed.

The effect of sintering temperature on microstructure and mechanical properties of alloys produced by using hot isostatic pressing method

In this study, a new matrix material was produced via HIP (Hot Isostatic Pressing) method by adding Cobalt and Nikel elements to CuSn (85/15) bronze alloy at certain ratios and the effect of sintering temperature during the production was examined. One of the biggest advantages of the HIP method is that the heat and pressure are applied at the same time during sintering process. Thus, all or almost all of the gaps during the production were removed and a more dense material was obtained. During the operation, it was kept constant that the sintering pressure was 30 MPa and the sintering time was 15 min, and the sintering temperature was selected as the variable parameter between 700 °C and 800 °C. The sintering process was carried out under the vacuum condition after the moment of first combustion. The produced samples were then metallographically prepared and SEM and EDS analyses were carried out for microstructure studies. Microhardness was taken from the samples and three-point bending test was carried out in order to examine the mechanical behaviors of the samples. Finally the density test was applied to the samples and their experimental and theoretical densities were calculated. As a result, it was observed that more homogeneous samples were obtained by increasing the sintering temperature.

The Effect of Bottom Ash Additions on the Properties of Sintered Bronze-Graphite Composites

The aim of this research was to study the effect of bottom ash additions to a bronze-graphite composite on the sintering behavior, as well as on the resultant physical, mechanical and tribological properties. The composites were produced by a powder metallurgy technique from prealloyed Cu-10Sn bronze powder, graphite powder and milled bottom ash powder. The compositions studied were Cu-10Sn bronze with constant 5 wt.% graphite, and 0-20 wt.% bottom ash. Samples were die compacted under 795 MPa and sintered at 850 oC for 30 minutes in an open atmosphere furnace. It was found that the sintered density of the composites decreased with increasing amounts of bottom ash. The hardness of the samples increased with bottom ash additions and reached a maximum at 5 wt.% and decreased with further additions. The frictional properties were studied using a ball-on-disc test at ambient temperature. It was found that both the friction coefficient and the wear rate were increased with increasing amounts of bottom ash.

Effect of Compaction Pressure and Sintering Time on the Properties of Sintered Cu-10Sn Bronze

Bronze-based composite materials are well known for use as friction materials. They are produced by powder metallurgy techniques from bronze powder, which acts as a matrix, and various friction modifying additives. The objective of this work was to study the effect of compaction pressure and sintering time on the properties of the unmodified bronze matrix. The bronze powder used was prealloyed with a composition of Cu-10Sn. The specimens were pressed by uniaxial die compaction with pressures of 282 to 339 MPa. The sintering experiments were conducted in an alumina tube furnace at 800 °C with sintering times of 30, 45, and 60 min under a vacuum pressure of 2.25x10-2 Torr. From the results, it was found that the density of the samples increased with increasing compaction pressure. A microstructural examination of the samples for the different sintering times showed them to look very similar. Finally, the highest sintered density of 7.30 g/cm3 was obtained at 800 °C for 60 min.

Early stages of tin bronze corrosion in neutral aqueous chloride media: Electrochemical and FTIR investigations

The corrosion behavior of tin bronze alloy equivalent to a Punic one was investigated in aqueous 0.5 M chloride electrolyte using potentiodynamic measurements. The electrochemical results showed selective dissolution of the major alloy component reflecting a decuprification process. FTIR characterization of the patina anodic layers showed the presence of various dehydrated and hydrated tin compounds with a few copper species suggesting the patina type I formation on the Cu10Sn bronze alloy. A kinetic model for the Cu10Sn bronze alloy dissolution in the chloride solution was developed. The reaction order with respect to chloride content was determined for the Cl− halide concentration domains. The low order value (about 0.22) was attributed to the Cl− adsorption intermediate step. The high reaction order value (about 2) reflected two determining steps of cuprous chloride complex formation. Two behaviors for the material were evidenced when varying the temperature. The values of the activation energy Ea, activation enthalpy ΔH* and activation entropy ΔS* were calculated and discussed.

Effect of nickel content on hardness and wear behaviour of surface modified functionally graded Cu-Sn bronze alloy

The effect of nickel content on the hardness, wear properties and microstructure of surface modified Cu-10Sn bronze alloy was investigated in this study. Gas tungsten arc (GTA) was used as the heat source for the surface modification process. Nickel with varying coating thicknesses was applied on the bronze substrate and the surface modification was done. Hardness and wear rate of the modified layer were measured using a microhardness tester and a pin-on-disc wear tester, respectively. The Ni concentration profiling was done using EDAX. A layered functionally graded bronze alloy was obtained after the surface modification process. A fine grained microstructure was observed in the modified layer. The hardness as well as wear resistance was found to improve as a result of nickel addition. The coefficient of friction remains constant irrespective of the hardness. The results of this study are comparable to those of previous works.

An Investigation on the Effect of Process Parameters on Microstructure, Hardness and Wear Properties of Surface Modified Cu-Sn Bronze Alloy

An investigation was carried out to understand the effect of process variables on the microstructure, hardness and wear properties of surface modified Cu-10Sn bronze alloy. The surface modification was carried out using Gas Tungsten Arc (GTA) as the heat source. Hardness and wear rate of the modified layer were measured using a microhardness tester and a Pin-On-Disc wear tester, respectively. A uniformly distributed fine grained microstructure was observed in the modified layer. The hardness and wear resistance of the modified layer were improved when compared with that of as cast sample. The coefficient of friction is found to be a constant and is not a function of hardness. The results of this study are comparable to those of previous works.

The Effect of Sn Content on the Properties of Surface Refined Cu-Sn Bronze Alloys

An investigation was carried out to assess the effect of the Sn content on the microstructure, hardness and wear properties of surface refined Cu-Sn bronze alloys. The surface refining was carried out using the Gas Tungsten Arc (GTA) as heat source. Alloys of various compositions, (4, 6, 8, 10, 12 wt% Sn) were melted in a melting furnace under an argon atmosphere and cast into sand moulds in the form of rods. Microstructural evaluation of the as-cast, refined and homogenized specimens were conducted using an optical microscope. The Vicker's Hardness Tester was used to measure the hardness of the modified layer and the wear testing was conducted using DUCOM Pin-On-Disc wear testing machine as per ASTM G99 standard under dry sliding condition in air. The microstructure of the modified layer showed a refined grain structure as compared to the coarse dendritic structure observed in the as cast sample. The homogenized specimen showed that there was no formation of any non-equilibrium phase due to rapid cooling. It was found that the hardness of the modified layer increases when the Sn content was increased from 4-12%. The wear rate decreases linearly with the Sn content. The Coefficient of Friction was found to remain constant irrespective of the hardness. The results of this study using GTA as heat source are comparable to those of previous works in which laser and e-beam heat sources were used.

A 3D FIB Investigation of Dynamic Recrystallization in a Cu-Sn Bronze

A combination of electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques were used to obtain 3D EBSD data in an investigation of dynamic recrystallization in a Cu-2%Sn bronze alloy. The results of this investigation show the origin of the nucleation sites for dynamic recrystallization and also elucidates the orientation relationship of the recrystallized grains to the deformed, prior grains and between the dynamically recrystallized grains.

Explosion Cladding of CuSn Bronze to Malleable Iron

Process of cladding CuSn bronze on malleable cast iron was studied. Characteristics of welded materials are described. Preparation of welded materials is outlined. Selection of suitable explosive is discussed. Design of welding assembly is illustrated. Welding parameters and conditions are given. Bimetals were fabricated. The quality of fabricated bimetals was inspected by ultrasonic defectoscopy, strains were measured with a 3D scanner and the microstructure was studied by optical microscopy and EDX microanalysis.

Study on the Growth of Nb<sub>3</sub>Sn Superconductor in Cu(Sn)/Nb Diffusion Couple

Nb3Sn growth following the bronze technique, (i.e. by interdiffusion between Cu(Sn) alloy (bronze) and Nb) is one of the important methodologies to produce this superconductor. In this study, we have addressed the confusion over the growth rate of the Nb3Sn phase. Furthermore, a possible explanation for the corrugated layer in the multifilamentary structure is discussed. Kirkendall marker experiments were conducted to study the relative mobilities of the species, which also explained the reason for finding pores in the product phase layer. Based on the parabolic growth constant at different temperatures, the activation energy for the growth is determined. We have further explained the dramatic increase in the growth rate of the product phase by changing just one atomic percentage of Sn in the Cu-Sn bronze alloy.

Microstructure and mechanical properties of Ti6Al4V/Cu-10Sn bronze diffusion-bonded joint

The microstructures and mechanical properties of Ti6Al4V/Cu-10Sn bronze diffusion-bonded joint were studied via scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS). Diffusion bonding of Ti6Al4V to Cu-10Sn bronze was investigated at different holding time. Four obvious interfacial layers were observed in the joint. It is revealed that the bonding joint has high shear strength up to 102 MPa bonded at 830 °C, bonding pressure 10 MPa and bonding time 15 min. Shear test results show that the fracture takes place between the reaction layer and the Cu-10Sn bronze substrate, and the shear strength is strongly related to the formation of Cu-Ti-Sn intermetallic compounds.

A 3D EBSD Investigation of Dynamic Recrystallisation in a Cu-Sn Bronze

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Grain Growth, Morphology, and Composition Profiles in Industrial ${\hbox{Nb}}_{3}{\hbox{Sn}}$ Wires

The A15 formation process in Nb3Sn wires has been revisited. The progress of the reaction was studied by a careful FE-SEM study after a series of heat treatments at various temperatures and times. It was found that in the very early stage of the reaction, the Sn flow is high and a very thin layer of equiaxed A15 grains is formed at the interface between Nb and the Cu-Sn bronze. Beyond the very first layer with equiaxed grains, the grains form with a columnar shape. With further progress of the A15 layer and the continuous flow of Sn through the already formed layers, a decomposition of the columnar grains to equiaxed grains was observed. By TEM/EDX, we have confirmed our earlier observation of a radial Sn gradient in the filaments. The equiaxed regions have a sufficiently high critical field to carry supercurrents at high magnetic fields, in contrast to the columnar regions, where the B values are lower, thus their contribution to the current transport at the higher fields is limited. We have also studied internal Sn wires and found equiaxed grains only, with a Sn content through the A15 layer reaching from 22 at.% to values close to 25 at.%.

急加熱処理による内部拡散法Ｎｂ３Ｓｎ線の高Ｊｃ化

We tried to improve Jc-B properties for the multifilamentary Nb3Sn wires made by internal-tin-diffusion method. As a trial to improve Jc value under magnetic fields, two kinds of heat treatments were investigated. In conventional heat treatment (step heating) some phases of Cu-Sn bronze were synthesized at first by diffusing internal Sn below 600°C and then Nb3Sn filaments were formed at 675°C for 160h. In the new heat treatment Nb3Sn filaments were formed by rapidly putting the wire into furnace kept at 675°C (rapid heating). The Jc's in high fields of both heat-treated wires were measured at 4.2K. As a result the Jc value at 12T for the rapid-heated wire was higher than that for the step-heated wire. The superconducting transition width of the rapid-heated wire was narrower. The Nb/Sn composition ratio of the rapid-heated wire was nearer to the stoichiometry than those of the step-heated wire. It was suggested that internal Sn was diffused more smoothly to Nb filaments by this rapid heating.