Sheng Li
,
Yu-Zeng Chen
,
Yu-Ke Cao
,
Feng Liu
金属学报(英文版)
doi:10.1007/s40195-016-0367-4
It is well known that, in kinetics, the interaction between dislocations and interstitial solute normally exerts strong solute drag effect on dislocations, leading to strong solution hardening of the metals. However, due to the low mobility of interstitial solute in many metals, thermodynamic aspect of the interaction between dislocations and interstitial solute is often unobservable and omitted. It will be shown in this article by reviewing the H-induced behaviors in metal-H systems, especially the recent progress in Pd-H system that, when the interstitial solute atoms are highly mobile and able to collect in the vicinity of mobile dislocations easily, the scenario will be remarkably different. The interaction between dislocations and these highly mobile interstitial solute atoms, in thermodynamics, will reduce the line energy of dislocations and will facilitate the generation of dislocations, leading to an increase in dislocation density and an enhanced strain hardening of metals upon plastic deformation.
关键词:
Plastic
,
deformation
,
Dislocation
,
Interstitial
,
solute
,
Strengthening
,
mechanism
,
Thermodynamics
Lie ZHAO
,
Fred J. VERMOLEN
,
Jilt SIETSMA
,
Sybr
,
van der ZWAAG
材料科学技术（英）
The present work analyses the total free energy of the material during the martensitic transformation. A general expression for the martensite fraction as a function of temperature is derived, assuming that the nonchemical free energy is proportional to the volume of martensite. This expression indicates that the temperature-dependent martensite fraction can be predicted once the characteristic transformation temperatures and the relation between the chemical free energy and temperature of the martensite and austenite are known. An advantage of this development is that the proposed equation is valid for all types of relations between the chemical free energy and temperature. This simulation is successfully applied to the martensitic transformation upon further cooling of retained austenite in a low-alloyed TRIP steel, in which the relation between chemical free energy and temperature is quadratic and the fraction is determined from a thermo-magnetic measurement.
关键词:
Thermodynamics
,
null
,
null
,
null
Shuigen HUANG
,
Lin LI
,
J.Vleugels
,
O.V.D.Biest
材料科学技术（英）
The phase constitution of a composite consisting of 12 at. pct CeO2-3 at. Pct Y2O3-ZrO2/2.5 wt pct Al2O3 (3Y12Ce2.5Al) was determined by thermodynamic calculation. It is a combination of 36.9 at. pct cubic phase and 63.1 at. pct tetragonal phase at 1450℃. Green compacts were fabricated by cold isostatic pressing with powder synthesized by coating technique, and pressureless sintered at 1450℃. The fracture toughness and Vickers hardness, evaluated by the micro-indentation method, are 2.02 MPa·m1/2 and 11.395 GPa, respectively. The addition of 3 at. pct Y2O3 to 12 at. Pct CeO2-ZrO2 ceramic leads to drastically decrease in toughness compared to composites without yttria stabilizer. No monoclinic phase is detected on the surface of all the ground samples. The high content of cubic phase and lack of phase transformation can be attributed to the low toughness based on the thermodynamic prediction.
关键词:
Thermodynamics
,
null
,
null
丁戊辰
,
李微雪
催化学报
doi:10.1016/S1872-2067(14)60165-0
采用第一性原理计算考察了阴离子(硼、碳、氮、氟、磷、硫)掺杂的二氧化钛(包括锐钛矿相和金红石相)。芯位移计算结果表明,在氮掺杂的TiO2中,间隙掺杂类型的N的1s能级在XPS能谱上峰的位置要比替代掺杂的能级高,类似的结果也在硼、碳、磷和硫掺杂的TiO2上发现。然而对于F掺杂的TiO2,替代掺杂的峰位置比间隙掺杂的高,且与TiO2的晶相无关。还对阴离子掺杂的TiO2进行了热力学研究。结果表明,替换掺杂的形成焓高于间隙掺杂的,因此替代掺杂的TiO2的制备需要苛刻的条件,而间隙掺杂TiO2的制备只需温和的湿化学条件。
关键词:
二氧化钛
,
芯位移
,
X射线光电子能谱
,
阴离子
,
替换掺杂
,
间隙掺杂
,
密度泛函理论
,
热力学性质
S.N. Hosseini
材料科学技术（英）
The nanostructured CoAl intermetallic compound was produced by mechanical alloying (MA) of the Co50Al50 elemental powder mixture in a planetary high energy ball mill. The ordered B2-CoAl structure with the grain size of about 6 nm was formed via a gradual reaction after 10 h of MA. A thermodynamic analysis of the process was also done. The results showed that the intermetallic compound of CoAl had the minimum Gibbs free energy compared to solid solution and amorphous states indicating the initial MA product was the most stable phase in the Co-Al system which was changed to a partially disordered structure with a steady long-range order of 0.82 at further milling. This amount of disordering caused the enthalpy of final product to show an increase of about 5.1 kJ·mol-1. Calculation of enthalpy related to the triple defect formation revealed that the enthalpy required for Al anti-sites formation was about 3 times greater than that for Co anti-sites formation.
关键词:
Intermetallics
Bin ZHAO
,
Kuiwei GENG
,
Fei ZENG
,
Feng PAN
材料科学技术（英）
The Ni80Nb20 films were prepared by ion beam assisted deposition (IBAD) with various Ar+ ion energies. A phase evolution of fcc→amorphous→Ni+Nb→Ni+hcp was observed with the increasing of ion beam energy from 2 keV to 8 keV. When bombarded by Ar+ ions of 8 keV during deposition, a new crystalline phase with hcp structure was obtained, of which the lattice parameters are a=0.286 nm and c=0.483 nm, different from those of the similar A3B-type hcp phase previously reported. The experimental results were discussed in terms of thermodynamics and restricted kinetic conditions in the far-from-equilibrium process of IBAD. The formation of hcp phase may also be related to the valence electron effect.
关键词:
Hcp phase
,
null
,
null
,
null
,
null
Xiaobo LI
金属学报(英文版)
The characteristic crystal model is applied to the study of phase stability and thermodynamics in substitutional bcc-based Ta-W alloys. The basic principle and method of alloy thermodynamics which is described by the characteristic crystal model is introduced in detail. The Gibbs energy of various phases including both disordered and ordered phases of the Ta-W system are evaluated. The phase diagram of Ta-W alloys is assessed and predicted. The results are in good agreement with experiments and better than that of first principle.
关键词:
Ta-W alloys
,
phase diagram
,
characteristic crystal model
,
thermodynamics
,
phase stability
Ximiao PAN
,
Zhanpeng JIN
材料科学技术（英）
The phase equilibrium relations of the ternary Ni-Cr-Zr system at 900°C have been investigated by means of diffusion triple and electron probe microanalysis (EMPA) techniques. A series of tie lines and triangles have been determined, and the corresponding tentative isothermal section is presented based on the current information.
关键词:
Nickel
,
null
,
null
,
null
S.N. Hosseini
材料科学技术（英）
The nanostructured CoAl intermetallic compound was produced by mechanical alloying (MA) of the Co50Al50 elemental powder mixture in a planetary high energy ball mill. The ordered B2-CoAl structure with the grain size of about 6 nm was formed via a gradual reaction after 10 h of MA. A thermodynamic analysis of the process was also done. The results showed that the intermetallic compound of CoAl had the minimum Gibbs free energy compared to solid solution and amorphous states indicating the initial MA product was the most stable phase in the Co-Al system which was changed to a partially disordered structure with a steady long-range order of 0.82 at further milling. This amount of disordering caused the enthalpy of final product to show an increase of about 5.1 kJ·mol-1. Calculation of enthalpy related to the triple defect formation revealed that the enthalpy required for Al anti-sites formation was about 3 times greater than that for Co anti-sites formation.
关键词:
Intermetallics
