Development of a Novel Low-Silver Cu-P Brazing Filler Metal Bearing Sn

The flame brazing of H62 brass using a novel, low-silver Cu-P brazing filler metal was investigated in this study. The effect of the addition of a trace amount of Sn on the microstructure and properties of Cu-7P-1Ag filler metals was analyzed by means of X-ray diffractometer, scanning electron microscopy and energy dispersive spectrometer. The addition of trace Sn led to a decrease in the solidus and liquidus temperatures of Cu-7P-1Ag filler metals. Meanwhile, the spreading performance of the filler metals on a H62 brass substrate was improved. The microstructure of the low-silver, Cu-P brazing filler metal was mainly composed of α-Ag solid solution, α-Cu solid solution and Cu3P; an increase of Sn content led to the transformation of the microstructure of the joints from a block to a lamellar structure. When the Sn content was 0.5 wt. %, the shear strength of the joint at room temperature reached 348 MPa, and the fracture morphologies changed from a cleavage to a quasi-cleavage structure.

MESOPHASE AND GLASS FORMATION IN BINARY SYSTEMS CEASIUM AND BARIUM ALKANOATESMESOPHASE AND GLASS FORMATION IN BINARY SYSTEMS CEASIUM AND BARIUM ALKANOATES

Phase equilibria in binary systems of individually non-mesomorphic components: propionates, isobutyrates, butyrates and valerates of cesium and barium at temperatures from 20 to 400 °C have been investigated by the me­thods of differential thermal analysis and polarization polythermal microscopy. In all systems, the formation of intermediate li­quid-crystalline solutions of smectic modification (type A) was established. The tempe­rature-concentration regions of the formation of ionic liquid crystals and glasses are determined. The studies carried out show that in binary systems of cesium and barium alkanoates interme­diate liquid-crystal solutions are generated due to the latent mesomorphism of the correspon­ding cesium alkanoate and due to the eutectic decrease in liquidus temperatures in the binary systems. The thermal stability of the induced mesophase in the case of systems of the consi­dered type is influenced by the following factors: the degree of ordering of the melt, which correlates with the length of the alkyl chain of the alkanoate anion, and a decrease in the temperatures of the liquidus line relative to the latent clearing temperature. The possible influence of compounds melting congruently or incongruently, formed in binary systems, should also be taken into account. Experimental data indicate the largest temperature-concentration range of the mesophase in the butyrate system, where there are the most favorable conditions for the implementation of intermediate li­quid crystal solutions. Such conditions are the lar­gest decrease in liquidus temperatures in a series of systems relative to the latent clearing point, as well as an additional increase in thermal stability due to the formation of a congruently melting compound of anisometric structure. In the case of the valerate system, a certain increase in anisotropy in comparison with the butyrate system is leveled by high liquidus temperatures; here is the narrowest region of existence of the intermediate mesophase due to its thermal destabilization.

Effect of In and Pr on the Microstructure and Properties of Low-Silver Filler Metal

The novel low-silver 12AgCuZnSn filler metals containing In and Pr were used for flame brazing of copper and 304 stainless steel in this study. The effects of In and Pr content on the melting temperature, wettability, mechanical properties and microstructure of 12AgCuZnSn filler metal were analyzed. The results indicate that the solidus and liquidus temperatures of filler metals decrease with the addition of In. Trace amounts of Pr have little impact on the melting temperature of the low-silver filler metals. In addition, the spreading area of filler metals on copper and 304 stainless steel is improved. The highest shear strength of brazed joint is 427 MPa when the content of In and Pr are 2 wt.% and 0.15 wt.%, respectively. Moreover, it is observed that the trace amount of Pr significantly refines the microstructure of brazed joint matrix. A bright Pr3Cu4Sn4 phase is found in filler metal and brazing seam when the contents of In and Pr are 5 wt.% and 0.5 wt.%, respectively.

Study on Microstructure and Properties of 12Ag–Cu–Zn–Sn Cadmium-Free Filler Metals with Trace in Addition

The effect of different In contents on the melting characteristics, mechanical properties, and microstructure of 12Ag–Cu–Zn–Sn filler metal was investigated in this paper, and flame brazing of 304 stainless steel and copper plates was done using the 12Ag–Cu–Zn–Sn–xIn filler metal. The results indicate that adding appropriate amount of In can evidently decrease the solidus and liquidus temperatures and improve the wettability of the low silver based filler metals. In addition, the shear strength of 304 stainless steel and copper plates joint brazed by 12Ag–Cu–Zn–Sn–1In are satisfactory due to the solution strength effect, and scanning electron microscopy examination of the braze-zone revealed that more relatively sound joints were obtained when brazing was done with 12Ag–Cu–Zn–Sn–xIn filler metal than with Indium free one; its performance is comparable to that of the joint brazed with the 20Ag–Cu–Zn–Sn filler metal, having a remarkable silver-saving effect.

Microstructure and Thermal Analysis of Metastable Intermetallic Phases in High-Entropy Alloy CoCrFeMo0.85Ni

CoCrFeMoNi high entropy alloys (HEAs) exhibit several promising characteristics for potential applications of high temperature coating. In this study, metastable intermetallic phases and their thermal stability of high-entropy alloy CoCrFeMo0.85Ni were investigated via thermal and microstructural analyses. Solidus and liquidus temperatures of CoCrFeMo0.85Ni were determined by differential thermal analysis as 1323 °C and 1331 °C, respectively. Phase transitions also occur at 800 °C and 1212 °C during heating. Microstructure of alloy exhibits a single-phase face-centred cubic (FCC) matrix embedded with the mixture of (Co, Cr, Fe)-rich tetragonal phase and Mo-rich rhombohedron-like phase. The morphologies of two intermetallics show matrix-based tetragonal phases bordered by Mo-rich rhombohedral precipitates around their perimeter. The experimental results presented in our paper provide key information on the microstructure and thermal stability of our alloy, which will assist in the development of similar thermal spray HEA coatings.

The Solubility of Gd2O3 in K Cl-GdCl3 Melts

The differential scanning calorimetry and the method of cooling curves are used to obtain data on liquidus temperatures of oxide-chloride systems Gd2O3 – K Cl - GdCl3. The solubility of gadolinium oxide in K Cl - GdCl3 melts has been studied. This information can be used for a developing process of the reduction of solid rare-earth oxides into their metals in molten salts.

Investigating mantle melting temperatures on Earth, Mars and the Moon using Al-in-olivine thermometry

<p>Al-in-olivine thermometry, based upon the temperature-dependent solubility of Al in the olivine crystal structure [1], has become a widely adopted method to investigate the crystallisation temperatures of primitive mantle melts on Earth [2]. The thermometer is calibrated using the Al contents of co-existing olivine and spinel: these phases are on or near the liquidus of primitive magmas, so the thermometer should access liquidus temperatures of mantle melts, thereby constraining the minimum mantle melting temperature. CFB-associated primitive melts have average olivine crystallisation temperatures well in excess of MORB, and back-calculation to the potential temperature of their mantle source regions suggests mantle thermal anomalies of several hundred degrees [3].</p><p>Whilst mantle thermal anomalies are moderately well-understood on Earth, relatively little is known about the melting conditions in the mantles of the Moon and Mars that led to the production of Maria basalts and Martian surface basalts and associated volcanic activity. Several samples returned from the Moon and basaltic meteorites from Mars (shergottites) are primitive and rich in both olivine and spinel, so would appear ideal samples for the application of Al-in-olivine thermometry to unravel their respective mantle melting conditions and, more generally, the thermal structures of those planetary interiors. In this study, we present preliminary investigations into a) five Apollo 12 primitive lunar basalts, and b) two olivine-phyric shergottites. We find that pervasive shock features make the trace Al concentrations of shergottitic olivines difficult to use, because high Al concentrations are associated with a fine micron to sub-micron network of K-rich melt veins, suggestive of fluid-mediated melt transport. On the other hand, olivine phenocrysts in all five lunar samples yield clear trends in Al contents and are excellent targets for Al-in-olivine studies. We present preliminary thermal results, as well as a newly-calibrated set of relevant thermodynamic parameters needed for back-calculating lunar melting temperatures. A fully quantitative assessment of lunar maria liquidus temperatures is, however, currently hampered by the limited calibration range of the Al-in-olivine thermometer and the unconstrained effect of high spinel TiO<sub>2</sub> contents on the results.</p><p>[1] Coogan, L. A., Saunders, A. D. & Wilson, R. N. Chem. Geol. <strong>368</strong>, 1–10 (2014).</p><p>[2] Trela, J. et al. Nat. Geosci. <strong>10</strong>, 451–456 (2017).</p><p>[3] Jennings, E. S., Gibson, S. A. & Maclennan, J. Chem. Geol. <strong>529</strong>, 119287 (2019).</p>