1.Why are cast metal sheet ingots hot-rolled first instead of being cold-rolled?Because of cold rolling is to use hot rolled steel coils as the raw material, after acid pickling to remove oxide skin for cold rolling, the finished product is hard roll, because of cold work hardening caused by deformation of continuous cold rolling hard roll strength, increase hardness, toughness and plastic index decreased, so the stamping performance will deteriorate, can only be used for simple deformation of the parts2.What type of heat treatment is given to the rolled metal sheet after hot and“warm” rolling? What is its purpose?轧钢的热处理的类型？轧钢热处理的目的？Heat treatment of the main types are annealing, normalizing, quenching and tempering, solution treatment and aging treatment, cold treatment, chemical treatment, etc.Annealing：The steel is heated to a certain temperature and heat preservation for a period of time, and then make it slowly cooling, called annealing. Steel annealing is a heat the steel to the phase change or part of the phase change temperature, slow cooling after heat preservation heat treatment method. The purpose of annealing is to eliminate tissue defects, improve the organization make composition uniformity and fine grains, increase mechanical properties of the steel, reduce residual stress; Can decrease the hardness at the same time, improve the plasticity and toughness, improve machinability. So before annealing in order to eliminate and improve both the legacy of tissue defects and internal stress, and to prepare for the follow-up process, so the annealing is belong to the intermediate heat treatment, also called heat treatment in advance Normalizing：Normalizing is heated to above the critical temperature of steel, to all into homogeneous austenitic steel, heat treatment and natural cooling in air. It can eliminate hypereutectoid steel mesh cementite, for hyposteel normalizing can refine crystal lattice, improve comprehensive mechanical properties, low requirements for the parts use the normalized instead of the annealing process is more economic.Quenching:Quenching is the steel is heated to above the critical temperature, heat preservation for a period of time, then quickly into the quenching medium, the temperature plummeted, rapid cooling at greater than the critical cooling rate of speed, which is mainly composed of martensite and unbalanced heat treatment method of the organization. Can increase strength and hardness of the steel quenching, but to reduce its plasticity. That is commonly used in quenching hardening agent are: water, oil, caustic soda, and salt solution, etc3.How are metal alloys made by the casting process? (b) Distinguish betweenwrought alloy products and cast alloy products.金属铸造合金的过程是怎样的？区分可锻合金产品和铸造合金产品。

First stage: liquid contraction, the metal liquid from a cooled to near liquidus temperature contraction, when the falling of the liquid surface in the casting.The second stage: solidification shrinkage, the metal solidification, the contraction of the shift from liquid into solidThe third stage: solid shrinkage, i.e., the shrinkage of metal during solidification cooling to room temperature after, this process of contraction is not uniform, because in the process of phase change.Forging belongs to building materials industry, has many USES, from the concept: forging is a metal pressure, through the shape of the plastic deformation shape requirements or suitable compression force. Forgings in the process of manufacturing is to use a hammer or pressure that power. And in the process of casting, change the structure and physical properties of metal particlesAccording to the model of sand mold, material according to your drawings to melt into a liquid, pour the liquid into the sand mould, unpacking after solidification, out from the sand, and the model of object is casting4.Distinguish between elastic and plastic deformation (use schematics).弹性应变和塑性应变的区别Material deformation under the external force, when the external force to cancel, mate rial deformation can disappear and be able to fully recover the original shape of prope rty is called elasticity.This recoverable deformation is called elastic deformation. Plastic deformation is the material - including fluid and solid under certain conditions, deformation under the action of external force, when imposed by external forces to re move or disappear after the object cannot be reinstated a physical phenomenon.5.Define (a) engineering stress and strain, and (b) true stress and strain, (c)Distinguish between tensile/compressive stress (also called normal stress) and shear stress, (d) Distinguish between tensile/compressive strain (also called normal strain) and shear strain.定义工程应变和应力、真应力应变、区分拉伸/压缩应力和剪切应力、区分拉伸/压缩应变和剪切应变The shape of the curve reaction material under the action of external force of brittleness, plasticity, yield, such as the deformation fracture process.The stress-straincurve is usually referred to as the engineering stress-strain curve.True stress - strain curve, because the area of the sample at any instant in the process of drawing A and gage length L (L = L0 + delta L) are changing frequently, the nominal stress and the nominal strain is calculated on the initial area of A0 and standard of L0.At the exit of specimens under tensile stress, the value of the force imposed by the ratio of the sample of the original cross-sectional area, the unit for the MPaIn the process of compression test, and try them on compression load divided by the value of the original cross-sectional area of the sample unit of MPaDue to external objects (load, temperature, etc.) and deformation, in which any section (shear plane) on both sides of the internal forces, known as "internal".Set of internal force, namely, per unit area of the internal force is called the "stress".Stress can be decomposed into component perpendicular to the section (shear plane), known as "asymmetric" or "method to stress";Tangent to section (shear plane) component is called "shear stress.6.Define the hardness of a metal. (b) How is the hardness of a material determined by ahardness testing machine?定义金属的硬度，金属硬度是怎样测试的？When HB > 450 or sample hours, brinell hardness test and will not be used to switch to rockwel l hardness measurement.It is a diamond cone apex Angle 120 ° or 1.59 and 3.18 mm steel ball d iameter, under certain load down into the material surface under test, the hardness of materials b y indentation depth.7.What are the load used in (a) Rockwell B hardness test, and (b) Rockwell C hardness test?8.What is the difference between Vickers and Knoop hardness tests?I n Vickers hardness test the for used is much lighter than the force used in Rockwell hardness test, The Rockwell hardness test is the considered to be the most routinely used technique to measure the hardness of materials because of its simplicity and because it does not require specific skills in order to perform it.9.Describe the slip mechanism that enables a metal to be plastically deformed withoutfracture.10.Why does slip in metals usually take place on the densest-packed planes?11.Why does slip in metals usually take place in the closest-packed directions?Slip always take place along the atomic density maximum directions （closest-pack ed）and the density on the largest crystal（closest-packed directions），This is due to th e close, close direction between surface spacing between maximum, binding force is wea kest.So the slip plane is the secret of the crystal surface, on the surface of the sliding di rection for the close direction.12.What are the principal slip planes and slip directions for FCC metals? (b) What are theprincipal slip planes and slip directions for BCC metals? (c) What are the principal slip planes and slip directions for HCP metals?13.Describe the deformation twinning process that occurs in some metals when they areplastically deformed.14.What is the difference between the slip and twinning mechanisms of plastic deformation ofmetals?15.What important role does twinning play in the plastic deformation of metalswith regard to deformation of metals by slip?16.Define the critical resolved shear stress for a pure metal single crystal? What happens to themetal from the macroscale point of view and behavior point of view once critical resolved shear stress is exceeded?17.By what mechanism do grain boundaries strengthen metals?18.What is solid-solution strengthening? Describe the two main types, (b) What are twoimportant factors that affect solid-solution hardening?19.What experimental evidence shows that grain boundaries arrest slip in polycrystallinemetals?20.Describe the grain shape changes that occur when a sheet of alloyed copper with anoriginal equiaxed grain structure is cold-rolled with 30 and 50 percent cold reductions, (b) What happens to die dislocation substructure?21.How is the ductility of a metal normally affected by cold working? Why?22.What are the three main metallurgical stages that a sheet of cold-worked metal such asaluminum or copper goes through as it is heated from room temperature to an elevated temperature just below its melting point?23.When a cold-worked metal is heated into the tenperature range whererecrystallization takes place, how are the following affected: (a) internal residualstresses, (6) strength, (c) ductility, and (d) hardness?24.When a cold-worked metal is heated into the temperature range where recoverytakes place, how are the following affected: (a) internal residual stresses, (b)strength, (c) ductility, and (d) hardness?25.Describe what occurs microscopically when a cold-worked sheet of metal suchas aluminum undergoes a recovery heat treatment.26.Describe what occurs microscopically when a cold-worked sheet of metal suchas aluminum undergoes a recrystallization heat treatment.27.What generalizations can be made about the recrystallization temperature withrespect to (a) the degree of deformation, (b) the temperature, (c) the time ofheating at temperature, {d) the final grain size, and (e) the purity of the metal?28.What are five important factors that affect the recrystallization process in metals?29.Why are nanocrystalline materials stronger? Answer based on dislocationactivity.30.(a) Draw a generic engineering stress-strain diagram for a ductile metal andhighlight the key strength points (yield, ultimate, and fracture strength) on thecurve. Schematically, show what happens if you load the specimen just below itsultimate tensile strength point and then unload to zero, (b) Will the specimenbehave differently if you load it again? Explain31.In the rolling process, the selection of the roll material is critical. Based on yourknowledge of both hot and cold rolling, what properties should the roller materialhave?。