材料成型金屬學(xué)ch08 金屬組織性能控制

1、 Chap.8 金屬組織性能控制 (1) 8.1 金屬的強(qiáng)化機(jī)制 strengthening mechanism 1.晶界強(qiáng)化microstructure hardening原子排列的正常結(jié)構(gòu)遭到破壞/大量晶格缺陷 /第二相 夾雜物晶界能 晶界兩側(cè)晶粒取向不同,滑移難以連續(xù)進(jìn)行.易滑移/難滑移需滿足變形連續(xù)性.單晶體晶?？朔Ц褡枇﹄s質(zhì)原子對(duì)位錯(cuò)阻力多晶體晶?？朔Ы缱枇icrostructure hardening2.形變強(qiáng)化work hardening形變位錯(cuò)受到阻礙 interaction加工硬化古老又普遍的現(xiàn)象 理論仍不完善Some applications of physical

2、metallurgy Work (dislocation density) hardening加工硬化加工硬化 位錯(cuò)密度與應(yīng)力的關(guān)系2/ 10k : flow stress : measured dislocation density= 加工硬化與位錯(cuò)有直接關(guān)系 -cmStress02/10kk = b3.固溶強(qiáng)化solid solution hardening固溶體強(qiáng)度基體金屬 固溶體solution 溶質(zhì)solute 溶劑solvent固溶度 solubility有限互溶/完全互溶 流變應(yīng)力溶質(zhì)濃度 稀固溶體理論 位錯(cuò)釘扎pinning effect 摩擦機(jī)制不動(dòng)的溶質(zhì)原子應(yīng)力場，位錯(cuò)運(yùn)動(dòng)

3、阻力.固溶強(qiáng)化固溶強(qiáng)化 Solid-solution hardeningHardness of Steel vs. Interstitial Carbon Content金屬的拉拔高強(qiáng)度金屬絲high strength steel wire (p69) The strongest known metal (disregardingwhisker filament) is drawn pearlitic wire. Not only with extremely high strength , but also with an amazing ductility at this strength

4、 level. 珠光體鋼絲超高強(qiáng)度、高塑性珠光體鋼絲超高強(qiáng)度、高塑性Limitation: only being produced by drawing wire to a reduction in area of over 90%fine wires 細(xì)絲Description UTS Range (MPa)Piano wire 17902400 Mandolin wire 20002760Wire cables 2210Galvanized suspension cable wire 13801590Mechanical spring wires 2960Patenting 鉛浴鉛浴Pat

5、enting 奧氏體化奧氏體化淬火（熔融淬火（熔融鉛池）空鉛池）空冷拉拔冷拉拔The purpose of heat treatment: to achieve the finest possible pearlite spacing prior to drawing4.彌散強(qiáng)化Particle hardening第二相彌散質(zhì)點(diǎn) dispersed second phase particle 位錯(cuò)切過第二相質(zhì)點(diǎn).位錯(cuò)饒過第二相質(zhì)點(diǎn)Orowan機(jī)制質(zhì)點(diǎn)尺寸Step 1: Solution-treat at a temperature between 340 to 451C to form a s

6、ingle-phase a solid solutionStep 2: Quench to room temperature fast enough to prevent the precipitate phase from formingStep 3: Age at a temperature below 340C to from a fine dispersion of phase451C340CPrecipitation hardening is accomplished by two different heat treatments1.Solution heat treatmentD

7、uring solution heat treatment all solute atoms are dissolved to form a single-phase solid solutionQuenching or rapid cooling to room temperature to form a nonequilibrium supersaturated solid solution (to prevent diffusion and the accompanying formation of any second phase) Precipitation hardening is

8、 accomplished by two different heat treatments2.Precipitation heat treatment (aging) The supersaturated solid solution is heated to an intermediate temperature within the two-phase regionat this temperature diffusion rates become appreciable The precipitates of the second phase form as finely disper

9、sed particles. (aging) Typical Precipitation Hardened Alloys Al 2014Forged Aircraft Fittings, Al Structures 2024High strength forgings, Rivets 7075Aircraft Structures, Olympic Bikes CuBeryllium Bronze: Surgical Instruments, Non sparking tools, Gears MgAM 100ASand CastingsAZ80AExtruded products NiRen

10、e 41High TemperatureInconel 700up to 1800F FeA-286High Strength Stainless17-10PPrecipitation Hardening Precipitation Hardening is a thermodynamic reaction that involves creation of a new phase change Precipitation Heat Treatment: precipitates form on grain boundaries lower fracture toughness compare

11、d to strain hardeningGrain BoundariesMicrostructure of A 7150-T651 Aluminum Alloy after Precipitation HardeningFig. 11.24 A transmission electron micrograph showing the microstructure of a 7150-T651 aluminum alloy (6.2Zn-2.3Cu-2.3Mg-0.12Zr-balanced Al) that has been precipitation hardened. The light

12、 matrix phase is an Al solid solution. Microstructure of Copper-Beryllium before and after Precipitation Hardening(a) Solution heat-treated(b) Precipitation hardened(x 750) 8.2 強(qiáng)韌性能的控制 強(qiáng)韌性強(qiáng)韌性strength and toughness 金屬的韌性與韌化. 強(qiáng)度指標(biāo)：屈服極限、抗拉強(qiáng)度 yield strengthtensile strength 韌性指標(biāo)：沖擊韌性、 脆性轉(zhuǎn)變溫度.材料承受載荷時(shí)在破壞前單

13、位橫截面吸收的變形功。沖擊試驗(yàn)：擺錘法沖擊試驗(yàn)：擺錘法脆性轉(zhuǎn)變溫度 以沖擊試樣斷口上開始出現(xiàn)脆性特征或斷口上出現(xiàn)50脆斷面積時(shí)的溫度； 沖擊值為完全韌性斷裂于完全脆性斷裂試樣沖擊值的平均值時(shí)的溫度。-140-120-100-80-60-40-20020406080010203040 1#帶 鋼3#帶 鋼Ak/JT/ 脆性轉(zhuǎn)變溫度曲線 1號(hào)和3號(hào)帶鋼的脆性轉(zhuǎn)變溫度（Tk）分別為：-37.2，-70.8。 工業(yè)生產(chǎn)工業(yè)生產(chǎn)Super-SS400Super-SS400鋼組織性能分析鋼組織性能分析實(shí)驗(yàn)鋼沖擊斷口形貌 (a) 1#20 (b) 1#-100 (c) 3#20 (e) 3#-100 (d)

14、 3#-70 工業(yè)生產(chǎn)工業(yè)生產(chǎn)Super-SS400鋼組織性能分析鋼組織性能分析影響強(qiáng)韌性能的因素 合金成分控制 氣體、夾雜物 晶粒尺寸晶粒尺寸晶粒尺寸dDBTTductilebrittle traction T晶界 位錯(cuò)塞積在晶界處引起的應(yīng)力集中程度小/分散 脆性晶粒細(xì)化 同時(shí)提高強(qiáng)韌性的唯一方式形變熱處理 提高鋁合金的韌性 脫溶沉淀 根據(jù)相變相變與形變形變發(fā)生的順序，調(diào)整熱處理工藝： 1 加工始態(tài)是固溶還是時(shí)效，決定了是相變前還是相變后進(jìn)行形變； 2 加工溫度形變過程是否伴隨相變； 3 加工后時(shí)效形變后相變。 8.3 沖壓性能的控制沖壓性能的控制冷軋深沖板汽車板：汽車板：超深沖冷軋板、超深

15、沖冷軋板、IF鋼電鍍鋅鋼板、鋼電鍍鋅鋼板、IF鋼深沖電鍍鋅鋼鋼深沖電鍍鋅鋼板、烘烤硬化鋼、汽車摩擦片用鋼。板、烘烤硬化鋼、汽車摩擦片用鋼。家電用鋼：家電用鋼：家電用電鍍鋅、耐指紋板、熱鍍鋅板、彩涂板、彩家電用電鍍鋅、耐指紋板、熱鍍鋅板、彩涂板、彩電框架用鋼、冰箱內(nèi)板、側(cè)板和面板。電框架用鋼、冰箱內(nèi)板、側(cè)板和面板。熱沖壓成形：熱沖壓成形：Exposed quality dual phase with GI, GA, EG coatings500 DP GA0.6 mm 600 DP GI, EGFerrite-martensite DP600 GI高強(qiáng)度汽車鋼板的進(jìn)展高強(qiáng)度汽車鋼板的進(jìn)展DP外板

16、外板成形效果的比較 TRIP(transformation induced plasticity) +B+ R retained austenite德國采用薄規(guī)格鍍錫板生產(chǎn)易拉罐22283200.511.522.533.544.51983199320030.30.260.2鍍錫板厚度，mm萬噸05101520253035g生產(chǎn)一億個(gè)易拉罐所耗鍍錫板數(shù)量每個(gè)罐重量深沖深沖 deep drawing板料板料 中心部位中心部位 受沖頭的作用產(chǎn)生拉延受沖頭的作用產(chǎn)生拉延 外緣部位外緣部位 受沖模的作用產(chǎn)生模壓受沖模的作用產(chǎn)生模壓沖壓性沖壓性沖壓變形過程中不產(chǎn)生裂紋等缺陷的變形極限。條件：板料沿厚度方向

17、的強(qiáng)度沿板面方向的強(qiáng)度 板料沿厚度方向不易變形，沿板面方向容易變形。 改善沖壓性能改善沖壓性能沖壓性能的測定 1）模擬法 杯突法 壓入的深度值杯突值杯突值杯突值杯突值 沖壓性能？沖壓性能？ 2）拉伸試驗(yàn)法）拉伸試驗(yàn)法 屈強(qiáng)比 加工硬化系數(shù) Q：1.屈強(qiáng)比與加工硬化指數(shù)？ 2.n沖壓性能？加工硬化系數(shù) 材料不容易出現(xiàn)細(xì)頸 杯突性能 沖壓性能塑性變形比Rb寬度方向的應(yīng)變；h厚度方向的應(yīng)變.R值越高，深沖性能越好。00111010lnlnlnlnLBLBBBhHBBRhb塑性應(yīng)變比的平均值4/ )2(90450RRRR1）反映沖壓性能的優(yōu)劣；2）衡量各向異性。影響沖壓性能的主要因素影響沖壓性能的主要

18、因素 （1）晶粒度 晶粒尺寸 屈強(qiáng)比 沖壓性能晶粒尺寸過大 桔皮缺陷桔皮缺陷(2) 形變時(shí)效 屈服點(diǎn)延伸 屈服平臺(tái)屈服平臺(tái)沖壓 “呂德絲帶” luders bands措施：平整 temper rolling(1%)8.4 熱強(qiáng)性能的控制熱強(qiáng)性能high temperature properties 使用過程中承受一種或多種形式的應(yīng)力作用拉伸、彎曲、扭轉(zhuǎn)、沖擊、振動(dòng)及熱應(yīng)力等； 高溫下抵抗塑性變形和斷裂 使用性能承受載荷的時(shí)間時(shí)間Key words: high temperature, service property, plastic deformation , fracture 室溫性能及短

19、時(shí)間高溫性能不能代表長時(shí)間的性能熱強(qiáng)性能：熱強(qiáng)性能：高溫蠕變極限、高溫持久極限、高溫疲勞極限以及在高溫下的屈服強(qiáng)度、抗拉強(qiáng)度等。（1）蠕變極限 金屬在高溫高溫條件下受力作用時(shí)，雖然應(yīng)力遠(yuǎn)小于該溫度的屈服極限，但隨著時(shí)間時(shí)間的不斷增長，金屬也會(huì)逐漸變形，甚至產(chǎn)生斷裂。 蠕變creep 蠕變極限：蠕變極限：在一定溫度下和所規(guī)定的時(shí)間內(nèi)引起一定變形量的應(yīng)力應(yīng)力值。temperature,time, strain and stress三階段（1）減速蠕變；（2）恒速蠕變；（3）蠕變加速階段。蠕變機(jī)制 空位運(yùn)動(dòng) movements of vacancies； 位錯(cuò)運(yùn)動(dòng) movement of dislo

20、cations； 界面滑動(dòng) grain boundary sliding.（2）高溫持久極限 在一定溫度下和所規(guī)定的時(shí)間內(nèi)， 使材料 斷裂的應(yīng)力應(yīng)力值。受力狀態(tài)的時(shí)間越久，材料斷裂時(shí)所需的應(yīng)力值越大/越??？ 強(qiáng)度隨時(shí)間變化的現(xiàn)象， 隨溫度的升高更明顯/不明顯？（3）疲勞極限 疲勞：材料在周期應(yīng)力下或溫度交變作用下，產(chǎn)生破壞。高溫疲勞極限：在規(guī)定的應(yīng)力循環(huán)次數(shù)下引起破壞的應(yīng)力值。 （4） 短時(shí)拉伸性能高溫高溫/應(yīng)力應(yīng)力 晶界的行為晶界的行為 （1）原子或空位的擴(kuò)散 （2）晶界滑動(dòng)晶界強(qiáng)度下降晶界強(qiáng)度下降 等強(qiáng)溫度等強(qiáng)溫度Equicohesive temperature (ECT)應(yīng)變速率的影響應(yīng)

21、變速率的影響Decreasing the strain rate lowers the ECT and therefore increases the tendency for intergranular fractureEffect of strain rateEffect of purity For metals and alloys of commercial purity the ECT will occur within a fairly sharp temperature interval.However, for high-purity material there is a wide range