耐熱相關(guān)金屬學(xué)問(wèn)題

1、耐熱的相關(guān)金屬學(xué)問(wèn)題材料結(jié)構(gòu)在高溫環(huán)境中的演化及其對(duì)力學(xué)性能的影響北京科技大學(xué) 楊善武內(nèi) 容 范性變形的一般機(jī)制與強(qiáng)化措施 改善材料高溫力學(xué)性能的主要措施 高溫力學(xué)行為及其對(duì)應(yīng)的結(jié)構(gòu)演化范性變形的一般機(jī)制與強(qiáng)化措施 范性變形的微觀機(jī)制 金屬與合金的宏觀范性變形在微觀上對(duì)應(yīng)位錯(cuò)的滑移（包括螺型位錯(cuò)在高溫的交叉滑移）、攀移（發(fā)生于高溫）、晶體的孿生（主要發(fā)生于低溫）和多晶體沿晶界的滑動(dòng)（發(fā)生于高溫），其中以位錯(cuò)滑移為最常見(jiàn)的方式。 刃型位錯(cuò)滑移孿生刃型位錯(cuò)攀移“趁熱打鐵”的道理 升高溫度導(dǎo)致鋼的變形抗力（位錯(cuò)運(yùn)動(dòng)阻力）減弱 溫度超過(guò)一定值后，鋼基體由體心立方結(jié)構(gòu)轉(zhuǎn)變?yōu)槊嫘牧⒎浇Y(jié)構(gòu)，更易于變形 升溫

2、導(dǎo)致的軟化效應(yīng)（回復(fù)、再結(jié)晶、析出相粗化、晶粒長(zhǎng)大等）可以抵消變形導(dǎo)致的硬化（加工硬化）T金屬單晶體的切變強(qiáng)度隨溫度的變化趨勢(shì)原因：熱激活可以幫助位錯(cuò)克服短程阻力，但對(duì)長(zhǎng)程阻力無(wú)作用。硬度時(shí)間回復(fù)過(guò)程中硬度隨時(shí)間的變化再結(jié)晶體積分?jǐn)?shù)時(shí)間再結(jié)晶體積分?jǐn)?shù)隨時(shí)間的變化范性變形的一般機(jī)制與強(qiáng)化措施 強(qiáng)化金屬的主要措施 以阻礙位錯(cuò)運(yùn)動(dòng)為基本出發(fā)點(diǎn)，強(qiáng)化措施主要包括：位錯(cuò)強(qiáng)化、細(xì)化晶粒的強(qiáng)化、固溶強(qiáng)化（高溫適用） 、析出強(qiáng)化（高溫適用） 和相變強(qiáng)化（為前幾類強(qiáng)化方式的綜合）。改善材料高溫力學(xué)性能的主要措施 強(qiáng)化晶界 降低界面能 增加位錯(cuò)運(yùn)動(dòng)的晶格阻力（P-N力） 在材料內(nèi)部引入穩(wěn)定的應(yīng)力場(chǎng)度度強(qiáng)強(qiáng)晶界與晶

3、內(nèi)強(qiáng)度隨溫度的變化晶界工程-降低界面能的有效途徑 利用面心立方結(jié)構(gòu)的金屬易于發(fā)生退火孿生這一現(xiàn)象，通過(guò)反復(fù)進(jìn)行的變形和退火處理，可以在材料中得到大量=3, 9, 27的重位點(diǎn)陣晶界，從而降低界面能，提高晶界的熱穩(wěn)定性。Grain boundary character distribution of the as-received (AR) and GBE-treated samples as a function of initial percentage reduction in thickness (5%, 9%, and 13%). The symbols in open, diagon

4、al cross, cross, and single horizontal bar denote the number of thermomechanical cycles from 1 to 4 applied to the samples. Fraction of low-R CSLBs of the as-received and GBE treated samples, GBE1 and GBE2. L. Tan et al.Effect of thermomechanical processing on grainboundary character distribution of

5、 a Ni-based superalloy. Journal of Nuclear Materials 371 (2007) 171175Deviation angle from exact R3 of the as-received and GBE-treated samples, GBE1 and GBE2.Thermal stability of the grain boundary character distribution of GBE-treated samples, GBE1 and GBE2, after exposure at 850 for 672 h.位錯(cuò)運(yùn)動(dòng)的晶格阻

6、力（P-N力）)1 (2exp12)4exp(12babp其中)1 (2a為位錯(cuò)半寬度由上式可以看出，位錯(cuò)運(yùn)動(dòng)的晶格阻力與溫度無(wú)關(guān)，在高溫仍能得到維持。高溫力學(xué)行為及其對(duì)應(yīng)的結(jié)構(gòu)演化在材料內(nèi)部引入應(yīng)力場(chǎng)的途徑 固溶強(qiáng)化 主要是利用低固溶度元素的過(guò)飽和固溶 析出強(qiáng)化 主要依賴于彌散、細(xì)小的共格或半共格析出相產(chǎn)生的共格應(yīng)力場(chǎng)( d ) 不同類型的相界面(a)完全共格；(b)部分共格；(c)切變共格；(d)非共格An illustration for the concept to lengthen thermal fatigue lives. N. Fujita et al. Changes of

7、microstructures and high temperature properties during high temperature service of Niobium added ferritic stainless steels. Materials Science and Engineering A351 (2003) 272/281Effects of Nb and Mo on the 0.2% proof strength at 900 for 13Cr steels.Relationship between addition contents and amounts i

8、n solid solution of Nb and Mo for 13Cr steels.Relationship between 0.2% proof strength at 900 and Nb addition contents of 13Cr steels as annealed and aged at 900 for 500 h.Relationship between Nb amounts in solid solution and Nb addition contents of 13Cr steels as annealed and aged at 900 for 500h.T

9、ransmission electron micrographs and their analysis results by electron diffraction of 0.01C/13Cr/0.5 Nb steels as annealed (a) and aged at 900 for 500 h (b).Corresponding EDS results of (a) and (b)Transmission electron micrographs and their analysis results by electron diffraction and EDS of 0.01C/

10、14Cr/0.1Ti/0.3Nb/0.5Mo steels asannealed (a) and aged at 900 for 500 h (b).Changes of Nb and Mo amounts in solid solution with agingtime at 900 for 0.5Nb and 0.3Nb/0.1Ti/0.5Mo steels.Changes of 0.2% proof strength at 900 with aging time at900 for conventional 19Cr/0.4Nb and 14Cr/0.3Nb/0.1Ti/0.5Mo st

11、eels.Comparison of thermal fatigue lives between conventional19Cr/0.4Nb and 14Cr/0.3Nb/0.1Ti/0.5Mo steels. The thermalfatigue tests were performed with sheet specimens with 2 mm thick which were heated and cooled repeatedly between 200 and 900 in a constraint ratio of 100% of thermal expansion.Chang

12、e in yield strength at 700 with aging time. G.M. Sim et al. Effect of Nb precipitate coarsening on the high temperature strength in Nb containing ferritic stainless steels. Materials Science and Engineering A 396 (2005) 159 165Change of Nb amount in precipitates measured by ICP with aging time.Relat

13、ionship between high temperature strength and Nb content in solid solution in Nb containing steels.Average diameter of precipitates with aging time in Nb containing steels.(a) NbC particle after aging for 60,000 min in 0.01C0.38Nb steel, (b) HR-TEM micrograph showing interface between NbC and the Fe

14、 matrix, (c) SAD pattern of interface (arrows indicate overlapped spot) and (d) schematic illustration of SAD pattern.(a) Fe2Nb particle after aging for 60,000 min in 0.01C0.38Nb steel, (b) HR-TEM micrograph showing interface between Fe2Nb and the Fe matrix, (c) SAD pattern of interface (arrows indi

15、cate overlapped spot) and (d) schematic illustration of SAD pattern.小結(jié) 對(duì)于鐵素體不銹鋼而言，Nb的固溶強(qiáng)化是提高其高溫強(qiáng)度的有效機(jī)制。但是，Nb的析出與析出相的粗化會(huì)導(dǎo)致鋼的高溫強(qiáng)度迅速下降。而適當(dāng)降低Nb含量并復(fù)合添加Mo、Ti有利于得到持久穩(wěn)定的強(qiáng)化。析出類型及析出基體界面的共格程度對(duì)析出相的長(zhǎng)大、粗化速度有重要影響。0246810121416182022130140150160170180190200210220230240250260270280HvTempering Time/h No relaxation Re

16、laxed for 30s Relaxed for 60s Relaxed for 200s Relaxed for 1000s（a）0246810121416182022100120140160180200220240260280HvTempering time/h Relaxed for 60s Relaxed for 1000s（b）含Nb鋼在850變形25%后弛豫不同時(shí)間的樣品在650（a）和700（b）重加熱過(guò)程中的硬度變化 0246810121416182022150160170180190200210220230240250260270280HvTime/h No Relaxat

17、ion Relaxed for 60s Relaxed for 1000s真應(yīng)變真應(yīng)變0.4弛豫不同時(shí)間的樣品在弛豫不同時(shí)間的樣品在650重加熱過(guò)程中的硬度變化重加熱過(guò)程中的硬度變化b0.1 me0.5 maa)a)0.5 mc0.5 md0.1 mf0.1 m不同弛豫時(shí)間的樣不同弛豫時(shí)間的樣品重加熱等溫前的品重加熱等溫前的透射電鏡形透射電鏡形(a),(b) 弛豫弛豫0s；(c),(d) 弛豫弛豫60s；(e),(f) 弛豫弛豫1000s(a)(b)0.1 m(c)弛豫不同時(shí)間的樣品弛豫不同時(shí)間的樣品650重加熱等溫重加熱等溫0.5h后的位錯(cuò)組態(tài)后的位錯(cuò)組態(tài) (a)弛豫弛豫0s；(b) 弛豫弛

18、豫60s；(c) 弛豫弛豫1000s0.2m0.3m變形奧氏體中的位錯(cuò)網(wǎng)絡(luò)在貝氏體相變后的形態(tài) (b)0.1 m(a)0.1 m 弛豫60s的樣品650重加熱等溫3h后的位錯(cuò)和析出形態(tài) (a)明場(chǎng)像 (b)暗場(chǎng)像； (a)0.15 m(b)0.15 m弛豫弛豫60s的樣品的樣品650重加熱等溫重加熱等溫10h后的位錯(cuò)和析出形態(tài)后的位錯(cuò)和析出形態(tài) (a) 明場(chǎng)像明場(chǎng)像 (b) 暗場(chǎng)像暗場(chǎng)像(b)0.5 m(a)0.5 m弛豫弛豫60s的樣品的樣品700重加熱等溫不同時(shí)間的位錯(cuò)形態(tài)重加熱等溫不同時(shí)間的位錯(cuò)形態(tài) (a)重加熱等溫重加熱等溫 5h；(b) 重加熱等溫重加熱等溫7h(a)0.75 m(d)0.1 m(c)0.25 m(b)0.25 m弛豫弛豫60s的樣品的樣品700重加熱等溫重加熱等溫10小時(shí)后板條邊界形態(tài)小時(shí)后板條邊界形態(tài)(a)1m0.3m(b)(c)0.1m弛豫弛豫60s的樣品的樣品700重加熱等溫重加熱等溫20小時(shí)后板條邊界的再結(jié)晶形態(tài)小時(shí)后板條邊界的再結(jié)晶形態(tài) (a), (b), (c)為同一位置不同放大倍數(shù)的形貌為同一位置不同放大倍數(shù)的形貌10m(d