Bo Cui

This paper presents a comprehensive investigation into the influence of manganese on the microstructural characteristics and properties of Cu–12.0Al–4.0Ni–xMn high‐temperature shape memory alloys. The study reveals that the matrix structure of these alloys is primarily composed of both 18R and 2H martensitic phases, with a notable increase in the proportion of the 18R phase as the Mn content rises. Notably, the addition of Mn significantly enhances the thermal stability of the Cu–12.0Al–4.0Ni alloy system. Upon examining the alloys with varying Mn contents, it is observed that when the Mn content is less than 1.5 wt%, the phase transformation temperatures exhibit considerable fluctuations during thermal cycling. In contrast, when the Mn content reaches or exceeds 1.5 wt%, the Cu–12.0Al–4.0Ni–xMn alloy demonstrates commendable thermal stability even after 50 thermal cycles. Furthermore, among the studied compositions, the Cu–12.0Al–4.0Ni–1.5Mn alloy exhibits optimal plasticity of 12.8% and shape memory effect of 6.4%.

PbSe-based thermoelectric materials exhibit promising ZT values at medium temperature, but its near-room-temperature thermoelectric properties are overlooked, thus restricting its average ZT (ZT_ave) value at low-medium temperatures. Here, a high ZT_ave of 0.90 at low temperature (300–573 K) is reported in n-type PbSe-based thermoelectric material (Pb_1.02Se_0.72Te_0.20S_0.08−0.3%Cu), resulting in a large ZT_ave of 0.96 at low-medium temperatures (300–773 K). This high thermoelectric performance stems from its ultralow lattice thermal conductivity caused by dense dislocations through heavy Te/S alloying and Cu interstitial doping. The dislocation density evaluated by modified Williamson-Hall method reaches up to 5.4 × 10¹⁶ m⁻² in Pb_1.02Se_0.72Te_0.20S_0.08−0.3%Cu. Moreover, the microstructure observation further uncloses two kinds of dislocations, namely screw and edge dislocations, with several to hundreds of nanometers scale in length. These dislocations in lattice can strongly intensify phonon scattering to minimize the lattice thermal conductivity and simultaneously maintain high carrier transport. As a result, with the reduced lattice thermal conductivity and optimized power factor in Pb_1.02Se_0.72Te_0.20S_0.08−0.3%Cu, its near-room-temperature thermoelectric performance is largely enhanced and exceeds previous PbSe-based thermoelectric materials.

The microstructure and mechanical properties of pure W, sintered and swaged W-1.5ZrO₂ composites after 1.5 × 10¹⁵ Au⁺/cm² radiation at room temperature were characterized to investigate the impact of the ZrO₂ phase on the irradiation resistance mechanism of tungsten materials. It can be concluded that the ZrO₂ phase near the surface consists of two irradiation damage layers, including an amorphous layer and polycrystallization regions after radiation. With the addition of the ZrO₂ phase, the total density and average size of dislocation loops, obviously, decrease, attributed to the reason that many more glissile 1/2 loops migrate to annihilate preferentially at precipitate interfaces with a higher sink strength of 7.8 × 10¹⁴ m⁻²_. The swaged W-1.5ZrO₂ alloys have a high enough density of precipitate interfaces and grain boundaries to absorb large numbers of irradiated dislocations. This leads to the smallest irradiation hardening change in hardness of 4.52 Gpa, which is far superior to pure W materials. This work has a collection of experiments and conclusions that are of crucial importance to the materials and nuclear communities.

The effects of rare earth element Sm on the microstructure, mechanical properties, and shape memory effect of the high temperature shape memory alloy, Cu-13.0Al-4.0Ni-xSm (x = 0, 0.2 and 0.5) (wt.%), are studied in this work. The results show that the Sm addition reduces the grain size of the Cu-13.0Al-4.0Ni alloy from millimeters to hundreds of microns. The microstructure of the Cu-13.0Al-4.0Ni-xSm alloys are composed of 18R and a face-centered cubic Sm-rich phase at room temperature. In addition, because the addition of the Sm element enhances the fine-grain strengthening effect, the mechanical properties and the shape memory effect of the Cu-13.0Al-4.0Ni alloy were greatly improved. When x = 0.5, the compressive fracture stress and the compressive fracture strain increased from 580 MPa, 10.5% to 1021 MPa, 14.8%, respectively. When the pre-strain is 10%, a reversible strain of 6.3% can be obtained for the Cu-13.0Al-4.0Ni-0.2Sm alloy.