Junmei Guo

Platinum group metals (PGMs) are strategic metals, and recycling PGMs in spent automobile exhaust catalysts (SACs) is a key path to alleviate the contradiction between resource supply and demand. This paper proposes a new Cu-Ni capture process and conducts research on the recovery of PGMs from SACs. Through the binary phase diagram analysis of Cu, Ni and PGMs and the thermodynamic calculation of the system reduction reaction, the feasibility of this technology was theoretically confirmed. Experimental results show that under the conditions of a temperature of 1450 °C, a holding time of 90 min, a Cu-Ni ratio of 1:1, and a basicity of 0.58, the recovery rates of Pt, Pd, and Rh reached 99.2%, 99.34%, and 98.48% respectively. Combined with orthogonal experiments, it was verified that temperature is the most influential factor on the recovery rate, and the four-stage capture mechanism of “initial diffusion—droplet aggregation—sedimentation and wetting—slag–metal separation” was clarified. This process reduces the melting temperature and provides new technology for green and efficient recycling of PGMs.

Precious metal electrical contact materials are pivotal in microelectronic devices due to their excellent chemical stability and electrical properties. Their practical application is hindered by the strength, contact resistance, and high cost. Multi‐principal elements alloys (MPEAs) provide the possibility to develop cost‐effective materials with enhanced mechanical properties. To address this, a novel precious metal MPEA, PdAgCuAuPtZn alloy, is designed, which exhibits significant solid solution strengthening and aging strengthening effects. The ultimate tensile strength increases from 747 MPa in the solution state to 1126 MPa in the aged state, while resistivity remains low. This study presents the first systematic investigation into the strengthening mechanisms of precious metal MPEAs using nanoindentation technology. These findings indicate that the aging strengthening of the alloy is attributed to spinodal decomposition (SD) and chemical short‐range order (CSRO) in the matrix. Furthermore, the precipitation structure with Cu‐rich and Ag‐rich phases gradually replaces the matrix, primarily accounting for aging softening. Additionally, it is discovered that precipitation structure can be strengthened by CSRO formed in the Cu‐rich phase, thus providing an innovative strengthening in PdAgCuAuPtZn alloy. These results will be beneficial to both deeply understanding the aging behaviors of PdAgCuAuPtZn alloys and designing high‐performance precious metal MPEAs.

Limited research has been undertaken regarding the homogeneity of CoCrPtB alloy billets. A CoCrPtB alloy was processed through casting and vacuum hot pressing. This investigation delved into the interconnection between the secondary dendrite arm spacing (SDAS) in the as-hot-pressed samples and their corresponding attributes, specifically Vickers hardness and magnetic properties. Systematic sampling was conducted on the cross-sectional layer and longitudinal surface. Upon examination of the cross-sectional layer proximate to the uppermost region of the hot casting, a discernible parabolic trend was observed for the SDAS that exhibited a gradual increment from the peripheral regions toward the central area along the width. Simultaneously, the fraction of the dendrite phase displayed a consistent linear decline, attaining its peak value at the central portion of the billet. Conversely, on the longitudinal surface, SDAS and the fraction of the dendrite phase remained fairly uniform within the same column sampling regions. However, a notable divergence was identified in the central section, characterized by an augmented SDAS and diminished dendrite phase content. This inherent microstructural inhomogeneity within the CoCrPtB alloy engendered discernible disparities in material properties.

In this study, pure copper’s hot deformation behavior was studied through isothermal compression tests at deformation temperatures of 350~750 °C with strain rates of 0.01~5 s⁻¹ on a Gleeble-3500 isothermal simulator. Metallographic observation and microhardness measurement were carried out of the hot compressed specimens. By analyzing the true stress–strain curves of pure copper under various deformation conditions during the hot deformation process, the constitutive equation was established based on the strain-compensated Arrhenius model. On the basis of the dynamic material model proposed by Prasad, the hot-processing maps were acquired under different strains. Meanwhile, the effect of deformation temperature and strain rate on the microstructure characteristics was studied by observing the hot-compressed microstructure. The results demonstrate that the flow stress of pure copper has positive strain rate sensitivity and negative temperature correlation. The average hardness value of pure copper has no obvious change trend with the strain rate. The flow stress can be predicted with excellent accuracy via the Arrhenius model based on strain compensation. The suitable deforming process parameters for pure copper were determined to be at a deformation temperature range of 700~750 °C and strain rate range of 0.1~1 s⁻¹.