2018-15年金属学及热处理(上)复习题(1).docx

ReviewLFill in correct multiple choices(1) Critical radius of solidification (ACD )a. The minimum size that must be formed by atoms clustering together in the liquid before the solid particle isstable and begins to grow; b. The minimum size that the total free-energy begins to increase; c.Theminimum size that the bulk of the material remains liquid without a small crystal solid; d.The minimum sizethat the total free-energy will be positive.(2) The dendrite segregation formed during the nonequilibrium solidification of a binary phase system (ACD )a. The closer to the diagram edges when the composition, the much severer of the dendrite segregation; b. Thefaster of the cooling, the less of the dendrite segregation; c. The stronger of the components diffusionability, the less of the dendrite segregation; d.The larger of the distance between liquid-solid line, the muchseverer of the dendrite segregation.(3) Superlattice (order phase) ( BD )A. is a short-range ordered solid solution; B. is a long-range ordered superlattice; C. is a solute segregation inlocal region; D. is a intermetallic compounds.(4) Reciprocal lattice ( BC )A. is a real crystal lattice; B. is a abstract lattice whom is transformed from real crystal lattice by mathematicalmethod; C. the reciprocal vector h k 1* is parallel to real crystal plane normal vector |h k 1; D. the modulusof reciprocal vector |h k 1* is equal to the plane distance of real crystal plane (h k 1).(5) Crystalline materials (ABC )A are substances which are of regular appearance ; B. are substances whose inner articles arrange regularly; C. aresubstances which have positive resistance-temperature coefficient; D. are substances which conduct current.(6) The factors which influencing solubility of substitutional solid solution are ( ABCD )A. atomic size and electronegative; B. electron concentration and crystal structure ; C. temperature and pressure;D. all of above.The atomic radius ( ABD )A. increases as the coordinative number increasing. C- keeps in constant;C. varies as temperature and pressureD. is influenced by the atomic bond and alloy elements.(8) During the process of solidification ( C )A. the larger of the critical radius, the easier of the nucleation; B. the larger of the critical nucleus work, the easier ofthe nucleation; C. the larger of the supercooling, the easier of the nucleation; D. the homogeneous nucleating ismuch easier than the heterogeneous nucleating.(9) Ternary system phase diagrams ( D )A. the level rule could be applied on the vertical sections; B. the three-phase region are the straight line triangles; C. it iscurve-line quad for fbur-phase reaction plane; D. four-phase reaction is processed isothermally.(10) Diffusion on the metals ( AB )A. its driving force is chemical potential gradient; B. diffusion mechanisms are mainly interstitial and vacancymechanism; C. high-diffusivity path is mainly inner-grain path; D. the diffusion coefficient decreases as temperatureincreasing.(11) Solid solution ABCA. is a substance whose structure is the same as its component; B. is a substance with much higher strength andhardness than that of the pure solvate component; C. they often appear on the two edge of a phase diagram; D. is asubstance that is presented with only two component.(12) Allotropy(ACD)A. is a characteristic of an element being able to exist in more than one crystal structure depending on temperature andpressure; B. the volume and structure does not change when allotropy phase transforms; C. the volume and structurechange when allotropy phase transforms; D. the driving force of the allotropy transformation is the decrease of thefree-energy.2. Judgement ( V for Right and X for incorrect)1、 > A proper inoculatant could enhance the nucleating rate that grain must be refined in any solidified process. ( X )2、 A larger solubility must be got when a binary alloy made of elements whose radius are close. ( X )3、 The equilibrium constitutional structures are "cementite and perlite” when super-eutectoid steel was cooled to roomtemperature.( J)4、The much close to 50% of a constitutional composition in binary isomorphous system, the much severer of the segregation in alloys.( J )5、There must be net-cementite when super-eutectoid steel was cooled to room temperature X )3. Explain the concepts of the following:自己查意思。(1) composition cooling 成份过冷(2) Homogeneous nucleation and heterogeneous nucleation 均质形核和异质形核(3) Compound 化合物(4) Solid solution 固溶体(5) allotropy同素异形体(6) anisotropy 各向异性(7) crystalline 晶体(8) activation energy in diffusion 扩散激活能(9) driving force in diffusion.扩散驱动力(10) Chill zone, columnar zone and equiaxed zone 细晶区，柱状晶区，等轴晶区(11) critical radius 临界半径(12) inoculants 孕育剂2. Fe-FesC metastable phase diagram 答案制作中。需要时间找记忆(1) recite Fe-Fe3c metastable phase diagram (including composition > temperature> phases and s