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Powder Bed Fusion is a promising metal additive manufacturing technology based on layer by layer powder spreading, and particle uniformity has a great influence on the forming quality. By Discrete Element Method, the interaction and movement between particles were studied during powder spreading, including powder jamming, rebound, splash, eddy and empty powder area. Additionally, five kinds of powder spreading schemes were explored, and the new process of one-way reciprocating with tri-splint blade was designed to change the motion state of powder spreading from "blade pushing powder" to "blade holding powder". The results showed that by adjusting the spacing between the blade and the working platform, the optimized powder spreading process decreased the defects such as powder splash and empty powder, and achieve the uniform powder bed of aluminum alloy powder.

The electronic structure, cohesive energy and interfacial energy of ferrite (100)/NbC (100) and TiC (100)/NbC (100) interfaces have been investigated by the first-principles calculation. Moreover, the heterogeneous nuclei mechanism of NbC particle was also analyzed. The results showed that the stacking sequences have a great influence on the cohesive energy and equilibrium interfacial separation of the above-mentioned interfaces. Compared with C-terminated interfaces, the cohesive energy of Nb-terminated ones is lower while the equilibrium interface distance is larger. Among the two C-terminated interface structures, the interfacial energy between the NbC and ferrite is 4.54 J/m2, which is larger than that of NbC/TiC interface (1.80 J/m2). Therefore, NbC particles prefer heterogeneous nucleation on TiC particles surface rather than the ferrite matrix, which agrees well with the experimental result.

The nucleation potential of transition metal (TM) carbides formed in steel can be predicted by the behavior of iron adsorption on their surface. Therefore, Fe adsorption on the (001) surface of (A1-xmx)C (A = Nb, Ti, m = Mo, V) was investigated by the first-principles method to reveal the initialization of Fe nucleation. The Mulliken population and partial density of state (PDOS) were also calculated and analyzed in this work. The results show that Fe adsorption depends on the composition and configuration of the composite carbides. The adsorption energy (Wads) of Fe on most of (A1-xmx)C is larger than that of Fe on pure TiC or NbC. The maximum Wads is found for Fe on (Nb0.5Mo0.5)C complex carbide, indicating that this carbide has the high nucleation capacity at early stage. The Fe adsorption could be improved by the segregation of Cr and Mn atoms on the surfaces of (Nb0.5Mo0.5)C and (Ti0.5Mo0.5)C. The PDOS analysis of (Cr, Mn)-doped systems further explains the strong interactions between Fe and Cr or Mn atoms.

Nine Cu(I)-cyanide metal–organic frameworks (MOFs), namely, [Cu4(CN)2(4-bpt)2]n (1), {[Cu3(CN)2(4-bpt)]·H2O}n (2), [Cu2(CN)(3-bpt)]n (3), [Cu2(CN)2(3-Hptz)]n (4), [Cu3(CN)2(3-ptz)]n (5), [Cu7(CN)7(3-tpt)2]n (6), {[Cu9(CN)9(btb)2]·btb}n (7), [Cu2(CN)2(4-azpy)]n (8), and [Cu3(CN)3(bpp)]n (9) (4/3-Hbpt = 3,5-bis(4/3-pyridyl)-1,2,4-triazole; 3-Hptz = 3-pyridyl-tetrazole; 3-tpt = 2,4,6-tris(3-pyridyl)-1,3,5-triazine; btb = 1,4-bis(1,2,4-triazol-4-yl)benzene; 4-azpy = 4,4′-azobispyridine; bpp = 1,3-bis(4-pyridyl)propane), were synthesized under hydrothermal conditions and structurally characterized. The 4-bpt, 3-bpt, and 3-Hptz ligands in 1–4 were in situ generated by cycloaddition reactions. Their structural features vary from two-dimensional (2D) (3), three-dimensional (3D) (4, 5, 6), 3D 2-fold interpenetration (1, 2, 8), to 3D 3-fold interpenetration (7, 9). Complex 1 is an intriguing 3D metal–organic framework (MOF) with a nanosized rectangular channel. Complex 3 exhibits a chiral 2D double-layered network ...

Interfacial models of SiC/ZrB2 composite coating were studied by first-principles calculations based on density functional theory (DFT). The cubic SiC and hexagonal ZrB2 were selected in our work, and twelve types of SiC (111)/ZrB2 (0001) interface structures were investigated in consideration of four different terminations and three stacking sequences. The cohesive energy (Wad), interfacial energy (γint), and electronic structure of the SiC/ZrB2 interfaces were all calculated. The results show that the ZrB2 (0001) surface with 9 layers exhibits bulk-like interior characteristic. Among the interfaces of C/Zr terminated hcp-stacked (CZH), Si/Zr terminated hcp-stacked (SZH), C/B terminated center-stacked (CBC) and Si/B terminated center-stacked (SBT), the CZH interface has the largest Wad (6.28 J/m2) and thus is of the best stability. Over the range of zirconium chemical potential, the γint of CZH, SZH, CBC and SBT interfaces are −0.31–2.50 J/m2, 1.07–3.88 J/m2, 2.85–5.66 J/m2 and 2.32–5.13 J/m2, respectively. The calculated electronic properties reveal that, the CZH, CBC and SBT interfaces mainly contain covalent bonding, while the SZH one primarily consists of metallic bonding.

The segregation behavior of alloying elements X (X=Zr, V, Cr, Mn, Mo, W, Nb, Y) on the ferrite (100)/TiC(100) interface has been investigated using first principles method, and the work of separation and interface energy of ferrite/TiC interfaces alloyed by these elements were also analyzed. The results indicated that all these alloying additives except Y were thermodynamically favorable because of the negative segregation energy, showing that they have the tendency to segregate to the ferrite/TiC interface. When the Fe atom in the ferrite/TiC interface is replaced by Y, Zr, or Nb, the adhesive strength of the interface will be weakened due to the lower separation work, larger interfacial energy, and weaker electron effects. However, the introduction of Cr, Mo, W, Mn and V will improve the stability of the ferrite/TiC interface through strong interaction between these elements and C, and Cr-doped interface is the most stable structure. Therefore, the Cr, Mo, W, Mn and V in ferrite side of the interface can effectively promote ferrite heterogeneous nucleation on TiC surface to form fine ferrite grain.

Three Cu(I)-cyanide coordination polymers based on trigonal 1,3,5-tris(1H-imidazol-1-yl)benzene (tib) ligand, namely [Cu 3 (CN) 3 (tib)] n ( 1 ), [Cu 4 (CN) 4 (tib)] n ( 2 ), and [Cu 2 (CN) 2 (tib)] n ( 3 ), have been prepared and characterized by elemental analysis, IR, PXRD, thermogravimetry and single-crystal X-ray diffraction analysis. Complex 1 displays a 3D metal-organic framework with nanosized pores. Complex 2 is a 3D coordination polymer assembled by three μ 2 -cyanides and a μ 3 -cyanide with a very short Cu(I)···Cu(I) metal bond(2.5206 A). Complex 3 is a 2D coordination polymer constructing from 1D Cu(I)-cyanide zigzag chain and bidentate tib spacer. Three Cu(I) complexes are thermally stable up to 250–350 °C. Complexes 1 – 3 show similar orange emission band at 602 nm originating from LMCT mechanism.

In order to eliminating the banded structure in SAE8620H gear steel,an isothermal annealing process and its mechanism has been studied in this paper. Results showed that isothermal annealing process can effectively eliminate banded structure in SAE8620H gear steel.With isothermal temperature 640°C-a certain low temperature indeed high undercooling,and for high nucleation at this temperature resulting in the decrease of nucleation rate difference in all areas,banded structure level decreased to 1 level.When isothermal temperature decreased to 610°C and 590°C,although the undercooling is so high that various regions began to nucleate at the same time,the transition temperature is so low that alloy elements in the regions previously occupied by pearlite bands diffuse faster than other regions,thus proeutectoid ferrite grains in these regions grow faster,regenerating the banded structure .

By adding Mn into SAE8620 gear steel, the effect of Mn on the microstructure and hardness of steel treated by quenching and partitioning process is investigated in this research. Microstructure is observed. Hardness is measured, after that it is converted into tensile strength. And the content of austenite is determined by X-ray diffraction analysis. It is found that higher content of Mn increases the content of martensite and reduces that of blocky ferrite and also leads to higher hardness of steel. In addition, XRD pattern shows obvious existence and enhancement of retained austenite.

Material cutting properties can be judged by turning temperature and chip shape. A new method that can measure turning temperature more accurately was discussed in this paper. Compared with the traditional method, results show that turning temperature can be accurately measured through a new method in turning process. Turning temperature become stable and will not jump after 20s later. In addition, the higher the hardness, the higher the energy is needed, leading to the higher turning temperature. The average turning temperature of the quenched specimen, normalized specimen and annealed specimen measured through the new method is 100°C,70°Cand 60°C, respectively. And the chip morphologies of quenched specimen, normalized specimen and annealed specimen are irregular band chips, spiral debris chips and C-shaped chips, respectively.

Hydrothermal reactions of AgNO3, K3[Fe(CN)6] with N-heterocyclic ligands afforded three novel Ag(I)–cyanide coordination polymers, [Ag2(CN)2(tpt)]n (1), {[Ag(CN)(bpe)0.5][Ag(CN)]}n (2) and [Ag(CN)(btmb)0.5]n (3) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine, bpe = 1,2-bis(4-pyridyl)ethane, btmb = 1,2-bis(1,2,4-triazol-1-ylmethyl)benzene). In complex 1, two Ag(CN) linear chains are bridged by bidentate tpt ligand to form a ladder-like structure, which are further connected by Ag Ag metal bond to generate a 2D polymeric network. Complex 2 is an interesting 3D supramolecular architecture assembled by 2D [Ag1(CN)(bpe)0.5]n network and linear [Ag2(CN)]n chain combined by strong Ag Ag metal bond. Complex 3 is a 1D ladder-like double-chain polymer constructed from Ag–cyanide linear chains and btmb spacer, which is further extended to a 2D supramolecular network by Ag–Ag weak interaction. The Ag–Ag metal interactions play important roles in the construction of three coordination polymers. Complexes 1 and 2 are respectively thermally stable at 300 and 180 °C. Complexes 1 and 3 emit strong blue luminescence.

A numerical model of recrystallization taking the deformation and the inhomogeneous distribution of stored energy into account were proposed in this paper. Here the deformed microstructure is obtained by a lattice deformation model and the microstructure evolution during recrystallization is simulated by a multi-state free energy phase field method. According to the characteristics of the different deformation zone and the inhomogeneous distribution of the stored energy, the weight factor reflected the distribution of the stored energy in the deformed zones is introduced in this work. As for the density of dislocation, the stored energy in the grain boundary and the triple junctions are double and 2.5 times higher than that within the grain, respectively. We utilize the multi-state free energy function to simulate the recrystallization process of the 0.11C-0.21Si-1.40Mn-0.04Nb steel. The results of simulation match very well with the experiments in the 0.11C-0.21Si-1.40Mn-0.04Nb steel. Therefore, through these models, it provides an excellent resolution to the problem that the deformation and nucleation affection on the process of the recrystallization. It is confirmed that recrystallization simulation depending on the lattice deformation model and taking the inhomogeneous distribution of the store energy into account can be successfully proposed to simulate practical situation.

Hydrogen content in pure aluminum melting was increased through inserting fresh branches and measured by decompression solidification method and density method. Resistivity of pure aluminum casting was measured by means of the electrical resistance method, and physical model of resistivity measuring method was established. Combined with experimental data, the mathematical relationship between resistivity of pure aluminum casting and hydrogen content was derived. To further verify the feasibility of resistivity measurement model on the hydrogen content in aluminum melting, this paper also has carried on the hydrogen evolution experiment.