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Hot compression deformation behavior of the Cu-0.45Cr-1.0Ni-0.28Si-0.14Co alloy was studied by a thermal-mechanical simulator at strain rates of 0.001–1 s−1 and deformation temperatures of 700–900°C. The microstructure and texture of the copper alloy after the hot compression deformation were investigated. The results showed that the flow behavior of the Cu-Cr-Ni-Si-Co alloy was significantly affected by the deformation temperature and strain rate. The typical dynamic recrystallization (DRX) occurred at high temperatures and low strain rates, while the typical dynamic recovery (DRV) appeared at low temperatures and high strain rates. When the deformation temperature increased from 700°C to 900°C, a transition from copper and S texture to gross texture was found. The value of hot deformation activation energy (Q) was calculated as 330.87 kJ/mol. The optimized hot deformation parameters for the Cu-Cr-Ni-Si-Co alloy were 800–850°C/0.01–0.1 s−1.

A Cu-0.41Mg-0.06Ca (wt.%) alloy was designed and prepared by melting and casting in air atmosphere, followed by equal channel angular pressing (ECAP) process up to 12 passes via Bc route at room temperature. The microstructure and properties of the alloy were investigated by means of hardness test, tensile test, electrical conductivity measurement and electron microscopes observation. After 12 ECAP passes, the initial coarse grains were refined significantly and the average grain sizes decreased to 0.57 μm. The coarse Cu5Ca phase was also fragmented and had the sizes of about 1–3 μm. The Cu-Mg-Ca alloy after 12 ECAP passes showed excellent comprehensive properties, with a yield strength of 619 MPa, an electrical conductivity of 67.86 %IACS and a total elongation of 10.4%. Compared with the Cu-Mg alloy under the same condition, the yield strength of the designed alloy after 12 ECAP passes was improved by 30 MPa and the electrical conductivity increased by 0.63 %IACS accompanied by almost same total elongation. The good comprehensive properties were attributed to the ECAP process and the addition of Ca. The ECAP process provided much high yield strength increments which accounted for more than 80% of the yield strengths after 12 ECAP passes. In addition, the addition of Ca in the Cu-Mg alloy promoted the grain refinement, improved the work hardening ratio, and increased the electrical conductivity.

Magnesium was added into Cu-Cr alloy to overcome the traditional limitations of high-cost and large-scale manufacturing of Cu-Cr alloys and to unveil the acting mechanism of Mg on the microstructure and properties of Cu-Cr alloy. Effect of magnesium on microstructure and properties of Cu-Cr alloy has been investigated by means of hardness test, electrical conductivity measurement, transmission electron microscopy, three-dimension atom probe tomography technique and X-ray diffraction analysis. The precipitation sequence of Cu-Cr-Mg alloy was similar with that of binary Cu-Cr alloy. Additional magnesium in Cu-Cr alloy accelerated the process of precipitates nucleation, restrained the growth of the precipitates by segregating along precipitates surface during aging. This enhanced the stability of the deformation microstructure and improved the mechanical properties of the alloy. Cu-Cr-Mg alloy showed a better comprehensive properties and softening resistance performance than Cu-Cr alloy at elevated temperature. After aged at 480 °C, Cu-Cr-Mg alloy had a tensile strength of 540 MPa and an electrical conductivity of 79.2 %IACS for the peak aging states, and it still maintained a tensile strength of 515 MPa and an electrical conductivity of 80.8 %IACS after 4 h aging.

Objectives Osteoblast deficiency is a key problem in bone tissue engineering, and transplant of mesenchymal stem cells combined with osteoblasts can achieve ideal results. We sought to investigate the in vivo ectopic osteogenesis of adipose-derived mesenchymal stem cells (ADSCs) and osteoblasts (OBs) combined with poly( l -lactic acid) (PLLA)/hydroxyapatite (HAp) nanostructured aerogel scaffolds. Methods We tested a new supercritical fluid-assisted technique for the formation of nanostructured aerogel scaffolds. We obtained PLLA aerogel scaffolds and PLLA/HAp aerogel scaffolds with high level of porosity (>90%), interconnectivity, and mechanical properties (compressive modulus up to 2 kPa). The fibrous nanostructure of these scaffolds was joined to micronic cells of controllable size. ADSCs and OBs were obtained by using an adherent method and an enzymatic digestion method. ADSCs, OBs, and the mixture of ADSCs and OBs (at a ratio of 1:1) were cultured with PLLA/HAp nanostructured aerogel scaffolds, respectively. After 48 hours of in vitro culture, cell-scaffold complexes were subcutaneously implanted into the back of Sprague-Dawley rats in corresponding groups, and PLLA/HAp nanostructured aerogel scaffolds without cells were implanted in a control group. The rats in each group were killed at 8 weeks postoperatively. The macroscopic and histopathological observations were performed to assess the ectopic osteogenesis potential. Results After adipogenic, chondrogenic, and osteogenic induction, ADSCs were positive for Oil Red O, toluidine blue, and alizarin red staining. Results of flow cytometry showed that ADSCs were positive for CD147, CD90, CD105, and CD44, with the rate of positivity being >80%, but negative for CD117, CD34, CD131, and CD45, with the rate of positivity being Conclusions To conclude, ADSCs can promote the ectopic bone formation of OBs in vivo in combination with PLLA/HAp nanostructured aerogel scaffolds.

A novel Cu-Cr-Yb alloy was designed and processed by thermo-mechanical treatment. The microstructure, mechanical and electrical properties were investigated in detail. The results showed that the Cu-Cr-Yb alloy had a higher strength, a better softening resistance and a considerably high electrical conductivity than the Cu-Cr alloy. After 80% cold rolling followed by aging at 500 °C, the peak-aged Cu-Cr-Yb alloy had a Vickers hardness of 160 ± 1 HV, a tensile strength of 465 MPa, an elongation of 21.1% and an electrical conductivity of 89.5 %IACS, respectively. After a long-time aging at 500 °C, the nano-scale Cr-rich precipitates with FCC structure in the Cu-Cr-Yb alloy hardly coarsened. Thermodynamics analysis showed that the Cr-rich precipitates were inclined to nucleate with FCC structure, and the addition of Yb hindered the nucleation of the Cr-rich precipitates.