In this study, industrial trial production of the microstructure evolutions and resultant mechanical properties and finite element model of the temperature variation in the cryogenic temperature rebar subjected to the TempCore processes were presented. The microstructure of tested steel rebar is composed of ferrite, pearlite and bainite when the cooling rate is less than or equal to 5 ℃/s. The pearlite disappears when the cooling rate is 10 ℃/s, and the microstructure is composed of granular bainite and a small amount of ferrite. The microstructure consists of martensite and bainite at cooling rate of 20 ℃/s. Compared with the tested steel rebar with water flow rate of 450 m3/h, the tested steel rebar with water flow rate of 100 m3/h has an optimum mechanical strength and a higher uniform elongation at room temperature, and has a higher NSR(notch sensitivity ratio) at - 165 ℃. The uniform elongation is 7.3% at room temperature and NSR is 1.14 at -165 ℃. The ductile-brittle transition temperature of the tested steel rebar with water flow of 100 m3/h is about - 30 ℃, while which of 450 m3/h is 0 ℃. The impact energy of the tested steel bar with water flow of 100 m3/h is 2~3 times that of 450 m3/h at or below 0 ℃, which is mainly due to its ultrafine acicular ferrite and bainite containing high dislocation density and sub-grains.

An attractive cryogenic near-zero thermal expansion (ZTE) behavior was achieved in the Mn₃Cu_0.5Ge_0.5N_0.78C_0.22 compound, spanning a broad temperature window of 120 K (5 K to 125 K) with an average coefficient of thermal expansion (CTE) of α = 0.68 × 10⁻⁶ K⁻¹. Furthermore, the effect of sintering temperature and holding time on thermal expansion and magnetic properties were investigated. Two distinct magnetic phase transitions are evident in the magnetization–temperature (M-T) curve of Mn₃Cu_0.5Ge_0.5N_0.78C_0.22, which precede the near-ZTE behavior. These two antiferromagnetic (AFM)-like ordering transitions are hypothesized to play a pivotal role in governing the ZTE behavior, as they induce two episodes of negative thermal expansion (NTE). The realization of ZTE behavior is thus attributed to the counterbalance of these two NTE contributions, which can be effectively tuned by varying the carbon content or optimizing the sintering process parameters. Collectively, these results demonstrate significant potential for the design of diverse cryogenic functional materials.

The magnetic transition, thermal property, and the distance of Mn–Mn of Mn₃Ga_0.3Sn_0.7N compound with the Sn element substitution of Ga in Mn₃GaN compounds were investigated. Magnetic measurements indicate that the existence of spin glass system at high temperature (502 K) in Mn₃Ga_0.3Sn_0.7N compound may be attributed to competing antiferromagnetic (AFM) and ferromagnetic (FM) interactions due to the doped Sn inducing ferromagnetic orders in Mn₃GaN and the partially random Sn substitute Ga at a corner site of the lattice. It is not clear how much role the pure Sn power, which is not doped into Ga site completely, played in inducing the magnetic characteristic. This finding will be helpful to reveal the mechanism of the antiperovskites’ intriguing physics properties and to develop more smart materials.

Microwave sintering enabled the efficient fabrication of bulk Mn₃Cu_0.5Ge_0.5N_0.9C_0.1 NTE materials in 3–5 h, versus 2 to 8 days for conventional methods. The microwave approach demonstrated high efficiency and energy savings. By adjusting temperature and dwell time, the NTE operating range can be shifted to lower temperatures. Under the optimized condition of 800 °C for 4 h, the resulting bulk material achieved an NTE coefficient of −20.56 × 10⁻⁶ K⁻¹ over a temperature interval ΔT of 88 K (from 159 K to 247 K), along with favorable densification and high hardness. The demonstrated processing efficiency, microstructural control, and tunable NTE properties establish a solid foundation for potential industrial scale-up.

In this paper, the crystal structure and electronic properties of Mn₃Ga_{1- x}Sn_xN(x=0, 0.25, 0.5, 0.75, 1) have been studied based on density functional theory. Results showed that the lattice constants of the Mn₃Ga_1-xSn_xN compounds increase with the increase of Sn doping concentration. As the doping amount of Sn increases, the 3d orbitals of Mn and the 5p orbitals of Sn hybridize when the doping amount of Sn is 50%, the distance of Mn-Mn nearest neighbor atoms is maximum due to lattice distortion, which affects the interaction of Mn-Mn moment in the nearest neighbor in the Γ_5g antiferromagnetic structure, resulting in the minimum average magnetic moment of Mn ion.