《材料力學(xué)性能》中英文全套PPT課件

《材料力學(xué)性能》中英文全套PPT課件,材料力學(xué)性能,材料,力學(xué)性能,中英文,全套,PPT,課件 Plastic deformation and Strain hardening塑性變形和應(yīng)變硬化NomenclaturePlastic deformation Strain hardeningSlip Resolved shear stressCritical resolved shear stress Austenitic ()IntersectLacquer塑性變形應(yīng)變硬化滑移分切應(yīng)力臨界分切應(yīng)力奧氏體的相交、交叉、橫斷漆、涂漆于使表面光滑術(shù)語(yǔ)Nomenclature 術(shù)語(yǔ)Peculiarity Polycrystalline Periodically Isothermal CrystallographyHexagonal Syngony 特性多晶的周期性地等溫的結(jié)晶學(xué)、晶體學(xué)六角形的，六邊形的晶系The mechanical behaviour of metals and alloys金屬和合金的力學(xué)特性 The mechanical behaviour of metals and alloys is described by the following laws of their resistance to elastic and plastic deformation and fracture.金屬和合金的力學(xué)行為由它們對(duì)彈性和塑性的變形以及斷裂的抵抗性來(lái)描述。The isothermal(等溫的)mechanical behaviour of a metal is determined by four factors:Stress,time,shape,and structure.金屬的等溫力學(xué)行為由四個(gè)因素描述：壓力，時(shí)間，形狀和結(jié)構(gòu)。Peculiarities of Mechanical(力學(xué)的)behaviour金屬力學(xué)特性的特征(i)how high can be periodically or constantly applied loads so that an object could restore its shape and size upon their removal;在金屬發(fā)生形變前最大可以加載多大的周期性或恒定的載荷。(ii)how high is the resistance of an object to plastic flow at a short-term or long-term load applied,what is the rate of variation of the shape and dimensions of the object,and what characteristics and particular conditions of load application determine the course of plastic flow at a desired rate;多大的短期或長(zhǎng)期的力能使物體發(fā)生塑性變形，物體形狀或體積發(fā)生多大的變形。為了達(dá)到某種想要的形變，需要什么樣的條件和載荷。(iii)how large is the force to cause fracture（斷裂）of the object to pieces.多大的力使物體斷裂。More deep analysis of the mechanical behaviour of metals and alloys in the last two or three decades is associated with the development of the theory of dislocations and the description of the phenomena observed on the atomic level and also with improvements in the methods of continuum mechanics.This association between various levels of description of the mechanical behaviour of materials seems to be fruitful.在過(guò)去二三十年間，依靠位錯(cuò)理論，原子級(jí)結(jié)構(gòu)的觀察，連續(xù)體研究的發(fā)展。金屬和合金力學(xué)特性的分析也得到了發(fā)展。這些力學(xué)特性方面的研究很有成果。The mechanical behaviour at the macroscopic level is studied in other courses;we shall deal with the mechanism of plastic flow at the dislocation level.金屬宏觀力學(xué)機(jī)制在其它課程中已經(jīng)討論了。我們這里只研究位錯(cuò)級(jí)的金屬塑性變形機(jī)制。Carbon steel in the elastic region碳素鋼在彈性區(qū)的變化 Linear elasticity and subsequent plasticity比例彈性變形和緊接的塑性變形 Unstable creep in annealed copper銅退火后的蠕變 Plastic deformation塑性變形 The deformation which is independent of time and is retained upon stress release is called plastic deformation.塑性變形是不隨時(shí)間而變化，應(yīng)力去除后仍然保留的形變。Effect of deformation rate on stress-strain curve 變形效應(yīng)對(duì)應(yīng)力應(yīng)變曲線的影響Slip of metal crystalsa Zn,b Cd,c-Sn,d-Bi金屬晶體的滑移 Variation of slip orientation in deformed tungsten single crystal at a different direction of external shear stress 鎢單晶受到不同方向外部切應(yīng)力作用時(shí)滑移方向的變化。Slip of low-carbon steel (polycrystalline)低碳鋼（多晶）的滑移Slip Slip is the displacement of a portion of a crystal relative to another portion with the crystal structure of both portions remaining unchanged.滑移是晶體的一部分移動(dòng)到另一部分的位置，并且在移動(dòng)過(guò)程兩部分晶體的結(jié)構(gòu)保持不變。a-undeformed 未變形 b-elastically deformed 彈性變形 c-elastically and plastically deformed,彈性和塑性變形 d-plastically deformation in which slip has taken place 塑性變形滑移發(fā)生 AB slip plane 滑移面Slip planes in three typical lattice of metal crystals(Slip plains usually have the closest packing of atoms)三種典型金屬晶體結(jié)構(gòu)的滑移面（滑移面通常也是原子密排面）Three possible slip directions in-Fe;the shortest direction is preferable 在-Fe中三個(gè)可能的滑移方向，是其中最優(yōu)滑移方向。Microstructure of austenitic Cr-Ni-Mo steel deformed 25%(a.)and 50%(b.)奧氏體Cr-Ni-Mo鋼變形25%或50%時(shí)的微觀結(jié)構(gòu)Strain bands of low-carbon steel低碳鋼的應(yīng)變帶 Stretched grains in low-carbon steel低碳鋼中的被拉伸晶粒Crystallography of slip in single crystals單晶的晶體滑移體系 Fracture of zinc single crystal鋅單晶體的斷裂 In cubic syngony crystals this situation is impossible,i.e.the ultimate strength in tension cannot be attained earlier than plastic flow begins.在立方晶系晶體中，這種情況（上圖中的脆性斷裂）是不可能的。例如：只有當(dāng)晶體發(fā)生塑性變形時(shí)才可能達(dá)到最大的拉應(yīng)力。For instance,in f.c.c.crystals where the four systems of 111 planes intersect one another,it is impossible to orientate the crystal relative to the tensile or compressive axis so that the shear stress be zero in all these planes.At least one of the plane systems turns out to be orientated for favourable slip.With f.c.c.metals(aluminium,copper,lead,gold,silver)subjected to tension or compression,fracture is always preceded by a plastic deformation.例如：在面心立方晶體中，111 四個(gè)滑移體系相互作用，所以它不可能使晶體轉(zhuǎn)到一個(gè)方向使其只受拉應(yīng)力和壓應(yīng)力，使這些面上的剪切應(yīng)力為0；但其中至少有一個(gè)滑移體系會(huì)成為最優(yōu)滑移體系。對(duì)fcc金屬晶體（鋁銅鉛金銀）而言受拉應(yīng)力、或壓應(yīng)力，在斷裂之前通常已經(jīng)發(fā)生塑性變形。B.c.c.crystals have no planes with such a dense packing of atoms as the basal planes in c.p.h.crystals or octahedral planes in f.c.c.crystals.For instance,the 110 planes in b.c.c.crystals,though they are characterized by the closest packing of atoms,differ in this parameter only slightly from other families of planes in that lattice.體心立方晶體沒(méi)有像六方晶體的底面和面心晶體那樣的院子密排面（這里的密排面指的是和其它晶面有顯著區(qū)別的面）。例如：體心立方晶體中的111 面。盡管它們稱(chēng)為最密面，但只和晶體中其它的滑移面有微量區(qū)別。The most essential structural feature of b.c.c.crystals,which can influence the course of slip,is the existence of a family of close-packed directions,cube diagonals（對(duì)角線）.These directions play even a greater part in slip than the close-packed directions in hexagonal or face-centered cubic crystals.體心立方晶體最基本的特征，對(duì)滑移有影響的是，其有一系列密排方向，體對(duì)角線。在滑移時(shí)其起到的作用比六方和面心立方晶體中的密排方向更大。In b.c.c.crystals,however,the direction of preferable slip can be found in several families of planes:in a-iron,for instance,it is found in 110,112 and 123.In that case,slip occurs simultaneously in a number of families of planes,in the example discussed,in two or even three families;in the general case,it is impossible to predict reliably which of the slip planes in b.c.c.metals will be operative.On the other hand,these metals have a larger number of intersecting systems of probable slip planes than c.p.h.metals and for that reason they are more plastic than the latter.在體心立方晶體中，方向?qū)?yīng)于幾種不同的滑移面相互構(gòu)成不同的滑移系。例如在a鋼中有，110,112 和 123晶面。在這種情況下滑移在這幾個(gè)滑移面上同時(shí)發(fā)生。通常情況下，不可能預(yù)言具體那個(gè)晶面會(huì)發(fā)生滑移。在另一方面，這些金屬比六方晶系具有更多的滑移體系，所以它們比其它晶體結(jié)構(gòu)的金屬有更好的塑性。As compared with f.c.c.metals,the slip planes in b.c.c.metals differ less appreciably from the other planes of the b.c.c.lattice and have a lower density of atoms packing than the slip planes in the f.c.c.lattice.For that reason,a higher shear stress is required to initiate slip in b.c.c.crystals but they offer a lower resistance to the development of plastic deformation before fracture.和面心立方晶體相比，體心立方晶體滑移面上的原子排列密度和其它晶面并沒(méi)有太大的差距，也小于面心立方晶體的原子密排面的密度。因這個(gè)原因，體心立方晶體滑移開(kāi)動(dòng)需要一個(gè)更大的剪切應(yīng)力，但體心立方晶體開(kāi)始變形后在斷裂前對(duì)塑性變形的阻礙較小。Slip systems in metallic crystal structures金屬晶體結(jié)構(gòu)的滑移體系In general,the ductility of b.c.c.metals,such as a-iron,tungsten,molybdenum,or|-brass has intermediate values between those of f.c.c.and c.p.h.metals.總體來(lái)說(shuō)，體心立方晶體金屬，像鋼、鎢、鉬或|-brass 等的延展性介于面心立方晶體和六方晶體之間。nomenclature 術(shù)語(yǔ)Schmid-Boas law Resolved shear stress Critical resolved shear stress TwinningOctahedral Indeterminacy Incoherent boundaries分切應(yīng)力臨界分切應(yīng)力孿生八面體的不確定不連貫界面Partial coherent boundaries部分連貫界面Incoherent boundary不連貫界面Resolved shear stress 分剪切應(yīng)力Schmid-Boas law臨界切應(yīng)力定律，這方面有經(jīng)典著作“晶體范性學(xué)”O(jiān)rientation factor 角度因素(Schmid factor)EXAMPLE PROBLEM 1.Hexagonal close-packed zinc slips by basal plane slip.A zinc single crystal is oriented so that the normal to its slip plane makes an angle of 60 with the tensile axis.If the three slip directions have angles of 38,45,and 84 with respect to this axis,and the critical resolved shear stress for Zn is 2.3 MN/m2,determine the tensile stress at which plastic deformation commences.六方密排晶體鋅，以底面為滑移面。一鋅單晶的滑 移面的法線和拉力成60，如果三個(gè)滑移方向和拉 力分別成30、45、84，并且鋅的臨界切應(yīng)力 為2.3MN/m2，請(qǐng)確定鋅開(kāi)動(dòng)滑移的拉應(yīng)力。EXAMPLE PROBLEM 2.A single crystal having a simple cubic structure(slip planes 100,slip directions)is oriented such that the tensile axis is parallel to the 010 crystal axis.Make a list of the slip systems in this crystal and calculate the Schmid factor for this loading geometry.一個(gè)單晶體為簡(jiǎn)單立方晶體結(jié)構(gòu)（滑移面為100，滑移方向?yàn)椋?，它受到的拉力和晶向平行，?qǐng)寫(xiě)出此晶體的所有滑移體系，并且為它們分別計(jì)算Schmid幾何因子。T.A.010001Consider this problem for a situation where the tensile axis is parallel to the 011 crystal axis.當(dāng)其受到的拉應(yīng)力平行于晶向011 時(shí)，再考慮到這個(gè)問(wèn)題。Effect of orientation factor on slip stress角度因素對(duì)滑移應(yīng)力的影響Effect of temperature on in Mg鎂中溫度對(duì)的影響Effect of temperature on and in Mg鎂中溫度對(duì) 和 的影響Effect of temperature on in Cu and Cu alloys在Cu-Cu合金中溫度對(duì)的影響The relationship between and composition of f.c.c.single crystals 和面心單晶體結(jié)構(gòu)的關(guān)系Effect of concentration of alloying elements on in Mg alloysMg合金的成分濃度對(duì)的影響1-Mg2-Mg-In3-Mg-Cd4-Mg-Ti5-Mg-Al6-Mg-ZnEffect of alloying elements on depending on the difference in atomic diameters合金元素對(duì)的影響取決于原子直徑的不同。The relationship between and composition of f.c.c.single crystalsCrystallographic diagram of twinning孿晶的晶體學(xué)圖示Twinning takes place where the shear stress attains the critical value and,like slip,obeys certain crystallographic relationships.The mirror image plane is called the twinning plane and the direction of displace is called the twinning direction.像滑移一樣，當(dāng)剪切力達(dá)到臨界值時(shí)即可發(fā)生孿晶現(xiàn)象。它遵行一定的晶體學(xué)規(guī)律。對(duì)稱(chēng)鏡面稱(chēng)為孿晶面，其滑移方向稱(chēng)為孿生方向。The twinning direction is polar;孿晶方向是相反的。Twinning shear can occur in only direction only;孿晶剪切只能發(fā)生在一個(gè)方向。Atomic planes are displaced in twinning through the same very small distance(smaller than the interatomic distance),so that no individual visible strain traces form on the surface of a twin band.孿晶中的原子面由相同的非常小的間隔（其小于原子間距）移動(dòng)，所以沒(méi)有可見(jiàn)的應(yīng)變痕跡留在孿晶帶的表面上。The role of the twinning process usually increases with decreasing temperature of deformation and/or increasing rate of deformation.孿晶通常降低了變形時(shí)的溫度，或增加了變形量。Since the stress needed for propagation（增值）of a twin is much higher than the slip stress,it is clear that twinning is possible under particular conditions when the resolved shear stress turns out to be high.孿晶形成時(shí)需要的臨界剪切應(yīng)力遠(yuǎn)大于滑移應(yīng)力，因此在分剪切應(yīng)力很高時(shí)才形成孿晶。Twinning in b.c.c.and f.c.c.crystals is usually observed at low temperatures and high deformation rates and in c.p.h.crystals,when the available orientations are unfavourable for basal slip.在面心立方和體心立方中，只有當(dāng)溫度很低，或變形量很大時(shí)才形成孿晶。在六方晶體中，只有在滑移方向不利于基面滑移時(shí)，才形成孿晶。Effect of the grain size d on the critical stresses of twinning t ans slip s 晶粒大小對(duì)孿晶臨界應(yīng)力t和滑移臨界應(yīng)力s的影響。The supressing effect of fine grain on twinning can be attributed three reasons:晶粒細(xì)化對(duì)孿晶形成的張力效果可以歸結(jié)為三個(gè)原因：A higher dislocation density;更高的位錯(cuò)密度。A lower stress concentration;(nucleation)更低的應(yīng)力集中（形核）。Grain boundaries are barriers for the growth of twins.(critical-size twins)晶界是形成孿晶的障礙。（孿晶的臨界大小）。Twinning deformation of Cr-20%Fe孿晶變形 nomenclature 術(shù)語(yǔ)SinusoidalConditioned MultiplicationProportional Luders-Chernov bands Configuration Avalanche Interstitial ConvexSchematic正弦曲線有條件的增殖、乘法比例的、均衡的呂德斯帶、拉伸應(yīng)變帶、滑移線痕構(gòu)造、結(jié)構(gòu)、配置、外形雪崩空隙的凸起的示意性的Luders-Chernov bandsShear in an ideal crystal(a);Variations of force and 理想晶體中的剪切energy in shear(b);剪切下力和能量的變化。Variations of energy in shear of two adjacent atomic planes with account of energy variations in the source of deformation(c).兩相鄰剪切面間的能量隨變形量的變化。Successive stages of unit shear剪切時(shí)原子連續(xù)變化步驟Movement of an edge dislocation in simple cubic lattice簡(jiǎn)單立方晶體中一個(gè)刃型為錯(cuò)的運(yùn)動(dòng)。Yield Stress Peak應(yīng)力屈服極限Crystals with impurities雜質(zhì)晶體In crystals with impurities,especially in b.c.c.crystals,the plastic flow starts at a certain drop of the deforming stress.雜質(zhì)晶體，特別是體心立方晶體中，塑性變形在變形應(yīng)力下降的時(shí)候發(fā)生。After that one can observe a continuous deformation with almost constant stress,which is accompanied with the propagation of the Luders-Chernov bands.可觀察到一個(gè)在恒定應(yīng)力作用下連續(xù)的變形，并且伴隨著拉伸應(yīng)變帶的增殖。This type of variation of flow stress is often attributed to locking of dislocations by impurity atoms.這種塑性變形應(yīng)歸因于雜質(zhì)原子對(duì)位錯(cuò)運(yùn)動(dòng)的阻礙作用。Especially strong interaction can be observed between dislocations and interstitial impurities in b.c.c.metals.通常能在體心立方晶體中觀察到位錯(cuò)和間隙雜質(zhì)原子之間的強(qiáng)相互作用。It is assumed that the upper yield limit corresponds to stress required to“tear off”dislocations from the atmosphere of impurities and the low yield limit is the stress required to move free(unlocked)dislocations through the lattice.通常認(rèn)為較大的屈服極限時(shí)讓被雜質(zhì)原子鎖住的位錯(cuò)運(yùn)動(dòng)的應(yīng)力，而較小的屈服應(yīng)力極限則是在點(diǎn)陣中移動(dòng)自由位錯(cuò)所需的應(yīng)力。Variations of the critical resolved shear stress with deformation in(a)Ge and(b)LiF single crystals(a)Ge和(b)LiF單晶變形所需剪切應(yīng)力的變化In rather pure crystals在較純晶體中The concentration of impurities is very low or at least insufficient for dislocation locking;雜質(zhì)原子的濃度非常小，或者對(duì)位錯(cuò)運(yùn)動(dòng)的阻礙非常小。The drop of the yield stress in such crystals on passage into plastic region is conditioned,first,by a low density of dislocations and,second,by a strong stress sensitivity of the speed of dislocations movement.這種晶體在塑性范圍變化時(shí)屈服極限的下降是有條件的：1.較低的位錯(cuò)密度；2.位錯(cuò)的運(yùn)動(dòng)速率有強(qiáng)烈的應(yīng)力敏感性。A distinct（明顯的）yield stress exhibits in such b.c.c.crystals:體心立方晶體中的應(yīng)力屈服極限(i)in the original state,the density of unlocked(mobile)dislocations decreases down to 102-104 cm-2;初始時(shí)，自由為錯(cuò)的密度下降到102-104 cm-2(ii)in subsequent（后來(lái)的）deformation,the density of dislocations increases with strain roughly by a factor of 1010;在接下來(lái)的變形中，位錯(cuò)的密度以1010的比值增加(iii)the rate of movement of dislocations is strongly stress-sensitive.位錯(cuò)的運(yùn)動(dòng)速率有強(qiáng)烈的應(yīng)力敏感性。Many researchers suppose that the yield stress peak in b.c.c.metals is associated mainly with the strong stress sensitivity of the rate of dislocation movement and,to a less extent,with unpinning of dislocations from impurities.許多研究者認(rèn)為：在體心立方金屬中屈服應(yīng)力極限主要是位錯(cuò)運(yùn)動(dòng)速率對(duì)應(yīng)力的敏感性，其次才是雜質(zhì)原子阻礙位錯(cuò)的運(yùn)動(dòng)。General theory The general theory of interrupted plastic flow attributes the appearance of a sharp yield peak to rapid increase of the number of mobile dislocations at the beginning of plastic flow.塑性變形被打斷的一般理論把屈服極限的出現(xiàn)歸因于在塑性變形開(kāi)始階段大量增加的移動(dòng)位錯(cuò)。In other words,a sharp yield peak appears always when the initial density of mobile dislocations is low,but dislocations can multiply rapidly in the course of plastic deformation.另一方面，一個(gè)屈服極限開(kāi)始出現(xiàn)時(shí)通?？梢苿?dòng)位錯(cuò)的密度很低，但開(kāi)始塑性變形后，位錯(cuò)的密度快速增殖。The drop of the stress at the upper yield limit yu is determined by nucleation and multiplication of mobile dislocations.The latter usually starts at stress concentrators and continues in the Luders-Chernov bands.上屈服極限應(yīng)力的下降是由形核和位錯(cuò)的大量增殖所決定，位錯(cuò)增殖在應(yīng)力集中時(shí)即開(kāi)始，在Luders拉伸應(yīng)變帶中繼續(xù)。In real crystals,the intensity of pinning of mobile dislocations may be different.If the are pinned only weakly,plastic flow begins owing to their unpinning;with strong blocking of dislocations,plastic flow starts due to the creation of new dislocations at stress concentrators.在實(shí)際晶體中，被釘扎的可移動(dòng)位錯(cuò)的強(qiáng)度也許不同。如果它們被少量阻擋時(shí)，塑性變形的開(kāi)始是由于它們沒(méi)有被鎖住。如果位錯(cuò)被強(qiáng)力阻擋時(shí)，塑性變形的開(kāi)始時(shí)由于應(yīng)力集中時(shí)產(chǎn)生的新位錯(cuò)。In polycrystals,grain boundaries inhibit（抑制，禁止）the propagation of plastic flow from grain to grain until the stress concentration at the ends of a slip band(or twinning band)causes flow in an adjacent（鄰近的）grain either by dislocation unlocking(with weak locking)or by creation of new dislocations in volumes at the other side of of the grain boundary(with strong locking).在多晶體中，晶界阻礙了晶粒間的塑性變形（主要指滑移）。當(dāng)滑移帶（孿晶帶）末端應(yīng)力集中時(shí)，相鄰晶粒由于可活動(dòng)位錯(cuò)（當(dāng)其未被鎖住時(shí)），或是由于體積中形成了新位錯(cuò)（位錯(cuò)被鎖嚴(yán)重時(shí)）而產(chǎn)生塑性變形。In f.c.c.metalsThe mechanism described is in principle poorly applicable to f.c.c.metals crystals since dislocations in them can only weakly interact with impurity atoms.Indeed,no yield drop due to dislocation unpinning is practically observed in these crystals,except for singles crystals of heavily alloyed metals.An important circumstance is also that the speed of dislocation movement in f.c.c.crystals is only weakly depend on stress;for instance,this relationship is estimated to be proportional to roughly 200 for copper and to 300 for silver.這個(gè)機(jī)制對(duì)面心立方晶體并不太適用。因?yàn)槲诲e(cuò)只能和雜質(zhì)原子極其微弱地作用。事實(shí)上，在這些晶體中，沒(méi)有觀察到由于位錯(cuò)沒(méi)被阻擋而導(dǎo)致屈服極限下降的形象，除了合金濃度很高的單晶體外。另一個(gè)重要的事實(shí)是面心立方晶體中位錯(cuò)的移動(dòng)速度對(duì)應(yīng)力的依賴度也很小。例如：這種關(guān)系大約對(duì)銅成200 的比例，對(duì)銀成300 的比例。Schematic stress-strain curves at two different temperatures(T2T1)兩個(gè)不同溫度下應(yīng)力應(yīng)變曲線簡(jiǎn)圖Diagram of the Cottrell-Stokes experiment for determining the effect of test temperature on deforming stress Cottrell-Stokes實(shí)驗(yàn)圖像中表現(xiàn)出來(lái)的溫度和變形應(yīng)力間的關(guān)系Effect of the amount of deformation on the ration of the deforming stresses at variations of test temperature(of Al)Al在不同測(cè)試溫度下變形量對(duì)變形應(yīng)力的影響Appearance of the valid yield point and yield elongation zone on the stress-strain curve on a change from a low temperature(1)to a higher temperature(2)當(dāng)溫度由低到高時(shí)，有效屈服點(diǎn)和屈服加長(zhǎng)區(qū)出現(xiàn)。Stress-strain curves of an aluminium crystal鋁晶體應(yīng)力應(yīng)變曲線ABCtensioning in liquid air;the specimen at point C was held at room temperature(recovery（回復(fù)）or age-harding（時(shí)效硬化）);DEfurther tensioning in liquid air.ABC在液態(tài)空氣中拉長(zhǎng)，在C點(diǎn)試樣保持在室溫（回復(fù)或時(shí)效硬化），DE在空中繼續(xù)拉長(zhǎng)。The mechanical state of a crystal cannot be described by a single fine-structure parameter,for instance,by dislocation density,and that at least one additional parameter is needed,such as the distribution of dislocations which describes indirectly the stability of the dislocation structure formed.晶體的力學(xué)機(jī)制不能簡(jiǎn)單的僅僅由一個(gè)結(jié)構(gòu)參數(shù)決定。例如，用位錯(cuò)的密度描述時(shí)，至少要加一個(gè)額外的參數(shù)，如位錯(cuò)的分布，因?yàn)樗g接地描述了所形成的位錯(cuò)結(jié)構(gòu)的穩(wěn)定性。With the same amount of low-temperature and high-temperature deformation,slip lines in the later case are positioned thicker.It has been supposed that the material near an operative slip band is“annealed”,as it were at a certain temperature:above the lower temperature of deformation and near the higher temperature.For this reason,new slip lines in the high-temperature deformation are formed preferably close to the existing ones,thus forming a thicker set.低溫和高溫下同樣的變形，高溫下的滑移線看起來(lái)粗一些。一般認(rèn)為滑移帶附近的材料好像是被“退火”了：就像它在某個(gè)特定的溫度（在變形的最低溫度上面，且靠近最高溫度）。因這個(gè)原因，高溫變形時(shí)形成的新滑移帶靠近已經(jīng)存在的滑移帶，所以看起來(lái)粗一些。With the same elongation in the low-and high-temperature deformation,dislocations in the former case will be arranged less uniformly（一致地）on the account of the greater inhomogeneity(gradient梯度)of deformation in the bulk of a crystal.A low-temperature deformation produces more local pile-ups of dislocations at barriers and local fields of internal stress.This highly distorted state of a crystal results in that the strain hardening obtained by low-temperature deformation is unstable.In subsequent high-temperature deformation,the unstable component of strain hardening disappears quickly owing to the simultaneous effect of temperature and stress.在低溫和高溫下發(fā)生的同等變形，前者是由于晶體內(nèi)更大的不均勻性位錯(cuò)分布的一致性較差。低溫變形在阻礙處會(huì)塞積更多的位錯(cuò)和更大的內(nèi)應(yīng)力。這晶體缺陷使低溫造成的應(yīng)變硬化變形時(shí)不穩(wěn)定的。在后來(lái)的高溫變形中，這些不穩(wěn)定的應(yīng)變硬化由于同時(shí)發(fā)生溫度和應(yīng)力效應(yīng)而迅速消失。This occurs either by destruction of barriers(at tips of pile-up),after which the freed（釋放的）avalanche（雪崩）of unpinned dislocations moves in a crystal and produces slip at a lower stress or by liberation of dislocations in pile-ups due to activation of cross-slip.這種消失一方面是由于阻礙物的減小導(dǎo)致位錯(cuò)雪崩大量增加，在晶體內(nèi)移動(dòng)使其在一個(gè)較小應(yīng)力作用下就開(kāi)始滑移，或者由于交滑移而使塞積位錯(cuò)得到釋放。Variations of the conditional yield limit with temperature in(I)single-phase and(II)two-phase alloys單相和兩相合金的條件屈服極限隨溫度的變化1-carbonyl nickel;鎳碳合金2-Ni+13%Al,alloy with precipitates微小析出相;3-Ni+13%Al,supersaturated solid solution;過(guò)飽和固溶體4-Ni+10%Al,single phase alloy 單相合金Work Hardening加工硬化Schematic of the shear stress-shear strain curve of a single crystal單晶中的應(yīng)力剪切力簡(jiǎn)圖 Stage I:The crystal work-hardening rate after yielding is initially low(has a low value of d/d).This easy glide is associated with single slip on the slip system having the maximum value of ;The strong work hardening resulting from interactions of dislocations does not occur.第一步：晶體在屈服后的加工硬化很低，這個(gè)易滑移對(duì)應(yīng)于單滑移在滑移體系中的 具有最大值。由于位錯(cuò)間的相互作用所導(dǎo)致的加工硬化并沒(méi)有出現(xiàn)。The work hardening observed during easy glide results from the overlap（重疊）of dislocation stress fields among dislocations gliding on parallel planes;易滑移區(qū)所觀察到得加工硬化是由于平行于晶面滑移的位錯(cuò)相互重疊而造成的。Stage II:the linear hardening region,the slope of the curve is large,on the order of G/300.The transition from Stage I to Stage II behavior is almost invariably associated with the onset（開(kāi)始）of multiple slip,and the strong work hardening resulting from interactions among dislocations on nonparallel planes.第二步：“線性硬化”區(qū)，曲線的斜率很大，大約在G/300左右。由第一步到第二步的轉(zhuǎn)變主要是由于多滑移間的相互作用，更強(qiáng)的加工硬化是由于非平行晶面上的位錯(cuò)間的相互作用而造成的。Stage III,“exhaustion”or“saturation”hardening,is characterized by a reduction in the work-hardening rate in comparison to Stage II.第三步：“耗盡”或“飽和”硬化區(qū)，其特征是和第二步相比其硬化率下降。The above description is in accord with many experiments.For example,the strain extent of Stage I decreases with temperature,and this is consistent with the easier onset of multiple slip at higher temperatures.例如：第一步的應(yīng)變擴(kuò)展增加率隨溫度而減小，這和在較高溫度時(shí)多系滑移容易開(kāi)動(dòng)是一致的。Likewise,the extent of Stage II is reduced as temperature is raised and this is consistent with recovery processes operating more effectively at higher temperatures.類(lèi)似的，第二步中應(yīng)變擴(kuò)展增加率隨溫度而減小，這和在較高溫度時(shí)其