THEORETICAL CALCULATION OF SPECIFIC INTERFACIALENERGY OF SEMICOHERENT INTERFACE BETWEEN MICROALLOY CARBONITRIDES AND AUSTENITE

According to the misfitting dislocation theory,a method of theoretical calculation was devel- oped for the specific energy of the semicoherent interface between microalloy carbonitrides and austenite matrix.The calculating formulae were derived and the results were satisfactorily applied on the research works.

Coherent and semicoherent α/β interfaces in titanium: structure, thermodynamics, migration

Theα/βinterface is central to the microstructure and mechanical properties of titanium alloys.We investigate the structure,thermodynamics and migration of the coherent and semicoherent Tiα/βinterfaces as a function of temperature and misfit strain via molecular dynamics(MD)simulations,thermodynamic integration and an accurate,DFT-trained Deep Potential.The structure of an equilibrium semicoherent interface consists of an array of steps,an array of misfit dislocations,and coherent terraces.Analysis determines the dislocation and step(disconnection)array structure and habit plane.The MD simulations show the detailed interface morphology dictated by intersecting disconnection arrays.The steps are shown to facilitateα/βinterface migration,while the misfit dislocations lead to interface drag;the drag mechanism is different depending on the direction of interface migration.These results are used to predict the nature ofαphase nucleation on cooling through theα-βphase transition.

THEORETIC CALCULATION OF SPECIFIC ENERGY OF SEMICOHERENT INTERFACE BETWEEN MICROALLOY CARBONITRIDE AND FERRITE

In some research of microalloy steel, such as the precipitation behaviour and the precipitation strengthening of microalloy carbonitride (M(CN)phase)in ferrite, it is essential to know the accurate value of the interfacial energy between M(CN )phase and ferrite. However, this energy cannot be directly measured because the average size of M(CN) particle is only 2-10 nm, thus the deepgoing researches concerned are seriously limited.

Preparation and Microstructural Analysis of Ti_2AlC/TiAl(Nb) Composite

By using the spark plasma sintering process, Ti2AlC/TiAlcomposite with the addition of Niobium （Nb） was prepared in-situ and the microstructure of Ti2AlC/TiAl （Nb） composite was investigated by means of transmission electron microscopy （TEM） and high-resolution electron microscopy （HREM）. The results indicate that new-formed Ti2AIC particles disperse with a high degree of uniformity and well combine with the matrix. In the area of phase interface the d-spaces of Ti2AlC （100） and TiAI （110） were measured as 0.2648 nm and 0.2991 nm,respectively. The atom arrangement beside the interface was only partly corresponding, existing in semicoherent state. On the contrary, in the area of grain interface the d-spaces of TiAl （100） and TiAl （110） were measured as 0.2462 nm and 0.2631 nm,respectively and the atom arrangement beside the interface was almost corresponding, existing in coherent state.

Achieving grain refinement ofα-Al and Si modification simultaneously by La-B-Sr addition in Al-10Si alloys

As-cast Al-Si alloys always face low ductility because of coarseα-Al grains and large lamellar eutectic Si.Although B-containing refiners and Sr modifiers could refine theα-Al grains and eutectic Si respec-tively,simultaneous addition leads to an invalid effect of Sr because B-containing refiner has a poison-ing effect(PE)on Sr modifier in the Al-10Si-B-Sr alloys.The present work achieves both refinement ofα-Al grains and modification of Si merely by the addition of 500 ppm La in Al-10Si-0.02B-0.015Sr alloy,which greatly enhances the ductility and tensile strength.Sr-B interaction in the Al-10Si-0.02B-0.015Sr melt results in a consumption of Sr by forming Sr-B intermetallic compound.CALPHAD-type calculations reveal that Sr concentration in liquid before eutectic reaction becomes a key parameter to estimate the alloying modification effect.The addition of La forms LaB 6 and thereby releases Sr to protect the Sr modification effect.First-principles calculations illustrate that both Sr and La are benefi-cial to the formation of twin boundaries in Si particles due to their negative formation energy of twin boundaries.The formed LaB 6 has a semicoherent interface withα-Al with the orientation relationship of[110]_(LaB6)//[110]_(Al) and(111)_(LaB6)//(111)_(Al),demonstrating that LaB 6 is an efficient nucleation site forα-Al,which contributes to the refinement ofα-Al in the Al-10Si-0.05La-0.02B-0.015Sr alloy.Our findings re-veal the micro-mechanism of refinement during the solidification process and develop an effective and simple way to obtain high-performance Al alloys.

具有O–Fe–Se配位键的半共格异质界面工程提高电池型超级电容器阳极的容量和倍率

低容量和低倍率限制了电池型超级电容阳极材料的大规模应用.本文通过构建一种具有半共格异质界面特性的Fe_(2)O_(3)/FeSe_(2)纳米结构作为先进的阳极材料来解决这一瓶颈.系列表征和第一性原理计算表明,这种特殊的异质界面不仅能自发产生较强的内建电场,从而提高电子传递速率和OH^(-)离子的吸附能力;还可使得活性物质与OH^(-)之间发生更多的氧化还原反应,并且使该反应体系更容易进行.基于上述优势,所制备出的阳极材料的最大比容量为199.2 mA h g^(-1)(1 A g^(-1)),并且在10 A g^(-1)下仍能保持105.8 mA h g^(-1),同时,经历5000次循环后,其比容量可维持初始值的90.2%.此外,以Fe_(2)O_(3)/FeSe_(2)作为阳极组装的非对称超级电容器在0.8 kW kg^(-1)时的能量密度为52.55 Wh kg^(-1),即使经历15,000次循环,该器件还能维持初始容量的91.2%.我们的工作为设计大容量和高倍率性能的电池型超级电容器阳极材料提供了一种创新性的策略,有望推动过渡金属化合物在储能系统中的大规模应用.