《材料力學性能》中英文全套PPT課件

《材料力學性能》中英文全套PPT課件,材料力學性能,材料,力學性能,中英文,全套,PPT,課件 Plastic deformation and Strain hardening塑性變形和應變硬化NomenclaturePlastic deformation Strain hardeningSlip Resolved shear stressCritical resolved shear stress Austenitic ()IntersectLacquer塑性變形應變硬化滑移分切應力臨界分切應力奧氏體的相交、交叉、橫斷漆、涂漆于使表面光滑術語Nomenclature 術語Peculiarity Polycrystalline Periodically Isothermal CrystallographyHexagonal Syngony 特性多晶的周期性地等溫的結晶學、晶體學六角形的，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.金屬和合金的力學行為由它們對彈性和塑性的變形以及斷裂的抵抗性來描述。The isothermal(等溫的)mechanical behaviour of a metal is determined by four factors:Stress,time,shape,and structure.金屬的等溫力學行為由四個因素描述：壓力，時間，形狀和結構。Peculiarities of Mechanical(力學的)behaviour金屬力學特性的特征(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.在過去二三十年間，依靠位錯理論，原子級結構的觀察，連續(xù)體研究的發(fā)展。金屬和合金力學特性的分析也得到了發(fā)展。這些力學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.金屬宏觀力學機制在其它課程中已經討論了。我們這里只研究位錯級的金屬塑性變形機制。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.塑性變形是不隨時間而變化，應力去除后仍然保留的形變。Effect of deformation rate on stress-strain curve 變形效應對應力應變曲線的影響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力作用時滑移方向的變化。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到另一部分的位置，并且在移動過程兩部分晶體的結構保持不變。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構的滑移面（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%時的微觀結構Strain bands of low-carbon steel低碳鋼的應變帶 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：只有當晶體發(fā)生塑性變形時才可能達到最大的拉應力。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 四個滑移體系相互作用，所以它不可能使晶體轉到一個方向使其只受拉應力和壓應力，使這些面上的剪切應力為0；但其中至少有一個滑移體系會成為最優(yōu)滑移體系。對fcc金屬晶體（鋁銅鉛金銀）而言受拉應力、或壓應力，在斷裂之前通常已經發(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，對滑移有影響的是，其有一系列密排方向，體對角線。在滑移時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，方向對應于幾種不同的滑移面相互構成不同的滑移系。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滑移面上同時發(fā)生。通常情況下，不可能預言具體那個晶面會發(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構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。因這個原因，體心立方晶體滑移開動需要一個更大的剪切應力，但體心立方晶體開始變形后在斷裂前對塑性變形的阻礙較小。Slip systems in metallic crystal structures金屬晶體結構的滑移體系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.總體來說，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 術語Schmid-Boas law Resolved shear stress Critical resolved shear stress TwinningOctahedral Indeterminacy Incoherent boundaries分切應力臨界分切應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 分剪切應力Schmid-Boas law臨界切應力定律，這方面有經典著作“晶體范性學”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，如果三個滑移方向和拉 力分別成30、45、84，并且鋅的臨界切應力 為2.3MN/m2，請確定鋅開動滑移的拉應力。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.一個單晶體為簡單立方晶體結構（滑移面為100，滑移方向為），它受到的拉力和晶向平行，請寫出此晶體的所有滑移體系，并且為它們分別計算Schmid幾何因子。T.A.010001Consider this problem for a situation where the tensile axis is parallel to the 011 crystal axis.當其受到的拉應力平行于晶向011 時，再考慮到這個問題。Effect of orientation factor on slip stress角度因素對滑移應力的影響Effect of temperature on in Mg鎂中溫度對的影響Effect of temperature on and in Mg鎂中溫度對 和 的影響Effect of temperature on in Cu and Cu alloys在Cu-Cu合金中溫度對的影響The relationship between and composition of f.c.c.single crystals 和面心單晶體結構的關系Effect of concentration of alloying elements on in Mg alloysMg合金的成分濃度對的影響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，當剪切力達到臨界值時即可發(fā)生孿晶現象。它遵行一定的晶體學規(guī)律。對稱鏡面稱為孿晶面，其滑移方向稱為孿生方向。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，所以沒有可見的應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.孿晶形成時需要的臨界剪切應力遠大于滑移應力，因此在分剪切應力很高時才形成孿晶。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，只有當溫度很低，或變形量很大時才形成孿晶。在六方晶體中，只有在滑移方向不利于基面滑移時，才形成孿晶。Effect of the grain size d on the critical stresses of twinning t ans slip s 晶粒大小對孿晶臨界應力t和滑移臨界應力s的影響。The supressing effect of fine grain on twinning can be attributed three reasons:晶粒細化對孿晶形成的張力效果可以歸結為三個原因：A higher dislocation density;更高的位錯密度。A lower stress concentration;(nucleation)更低的應力集中（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?。?。Twinning deformation of Cr-20%Fe孿晶變形 nomenclature 術語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、拉伸應變帶、滑移線痕構造、結構、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剪切時原子連續(xù)變化步驟Movement of an edge dislocation in simple cubic lattice簡單立方晶體中一個刃型為錯的運動。Yield Stress Peak應力屈服極限Crystals with impurities雜質晶體In crystals with impurities,especially in b.c.c.crystals,the plastic flow starts at a certain drop of the deforming stress.雜質晶體，特別是體心立方晶體中，塑性變形在變形應力下降的時候發(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.可觀察到一個在恒定應力作用下連續(xù)的變形，并且伴隨著拉伸應變帶的增殖。This type of variation of flow stress is often attributed to locking of dislocations by impurity atoms.這種塑性變形應歸因于雜質原子對位錯運動的阻礙作用。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和間隙雜質原子之間的強相互作用。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.通常認為較大的屈服極限時讓被雜質原子鎖住的位錯運動的應力，而較小的屈服應力極限則是在點陣中移動自由位錯所需的應力。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;雜質原子的濃度非常小，或者對位錯運動的阻礙非常小。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屈服極限的下降是有條件的：1.較低的位錯密度；2.位錯的運動速率有強烈的應力敏感性。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，自由為錯的密度下降到102-104 cm-2(ii)in subsequent（后來的）deformation,the density of dislocations increases with strain roughly by a factor of 1010;在接下來的變形中，位錯的密度以1010的比值增加(iii)the rate of movement of dislocations is strongly stress-sensitive.位錯的運動速率有強烈的應力敏感性。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.許多研究者認為：在體心立方金屬中屈服應力極限主要是位錯運動速率對應力的敏感性，其次才是雜質原子阻礙位錯的運動。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歸因于在塑性變形開始階段大量增加的移動位錯。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，一個屈服極限開始出現時通?？梢苿游诲e的密度很低，但開始塑性變形后，位錯的密度快速增殖。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.上屈服極限應力的下降是由形核和位錯的大量增殖所決定，位錯增殖在應力集中時即開始，在Luders拉伸應變帶中繼續(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.在實際晶體中，被釘扎的可移動位錯的強度也許不同。如果它們被少量阻擋時，塑性變形的開始是由于它們沒有被鎖住。如果位錯被強力阻擋時，塑性變形的開始時由于應力集中時產生的新位錯。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）。當滑移帶（孿晶帶）末端應力集中時，相鄰晶粒由于可活動位錯（當其未被鎖住時），或是由于體積中形成了新位錯（位錯被鎖嚴重時）而產生塑性變形。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.這個機制對面心立方晶體并不太適用。因為位錯只能和雜質原子極其微弱地作用。事實上，在這些晶體中，沒有觀察到由于位錯沒被阻擋而導致屈服極限下降的形象，除了合金濃度很高的單晶體外。另一個重要的事實是面心立方晶體中位錯的移動速度對應力的依賴度也很小。例如：這種關系大約對銅成200 的比例，對銀成300 的比例。Schematic stress-strain curves at two different temperatures(T2T1)兩個不同溫度下應力應變曲線簡圖Diagram of the Cottrell-Stokes experiment for determining the effect of test temperature on deforming stress Cottrell-Stokes實驗圖像中表現出來的溫度和變形應力間的關系Effect of the amount of deformation on the ration of the deforming stresses at variations of test temperature(of Al)Al在不同測試溫度下變形量對變形應力的影響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)當溫度由低到高時，有效屈服點和屈服加長區(qū)出現。Stress-strain curves of an aluminium crystal鋁晶體應力應變曲線ABCtensioning in liquid air;the specimen at point C was held at room temperature(recovery（回復）or age-harding（時效硬化）);DEfurther tensioning in liquid air.ABC在液態(tài)空氣中拉長，在C點試樣保持在室溫（回復或時效硬化），DE在空中繼續(xù)拉長。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.晶體的力學機制不能簡單的僅僅由一個結構參數決定。例如，用位錯的密度描述時，至少要加一個額外的參數，如位錯的分布，因為它間接地描述了所形成的位錯結構的穩(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粗一些。一般認為滑移帶附近的材料好像是被“退火”了：就像它在某個特定的溫度（在變形的最低溫度上面，且靠近最高溫度）。因這個原因，高溫變形時形成的新滑移帶靠近已經存在的滑移帶，所以看起來粗一些。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，前者是由于晶體內更大的不均勻性位錯分布的一致性較差。低溫變形在阻礙處會塞積更多的位錯和更大的內應力。這晶體缺陷使低溫造成的應變硬化變形時不穩(wěn)定的。在后來的高溫變形中，這些不穩(wěn)定的應變硬化由于同時發(fā)生溫度和應力效應而迅速消失。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致位錯雪崩大量增加，在晶體內移動使其在一個較小應力作用下就開始滑移，或者由于交滑移而使塞積位錯得到釋放。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單晶中的應力剪切力簡圖 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，這個易滑移對應于單滑移在滑移體系中的 具有最大值。由于位錯間的相互作用所導致的加工硬化并沒有出現。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變主要是由于多滑移間的相互作用，更強的加工硬化是由于非平行晶面上的位錯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：第一步的應變擴展增加率隨溫度而減小，這和在較高溫度時多系滑移容易開動是一致的。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.類似的，第二步中應變擴展增加率隨溫度而減小，這和在較高溫度時其