回復(fù)與再結(jié)晶ppt課件(2)-資料下載頁(yè)
2025-01-14 11:40本頁(yè)面
【正文】 mperature. Arrheniustype equations indicate an exponential relationship. 62 Critical temperature. Following from the previous rule it is found that recrystallization requires a minimum temperature for the necessary atomic mechanisms to occur. This recrystallization temperature decreases with annealing time. Critical deformation. The prior deformation applied to the material must be adequate to provide nuclei and sufficient stored energy to drive their growth. 63 Laws of recrystallization(cont) There are several, largely empirical laws of recrystallization: Deformation affects the critical temperature. Increasing the magnitude of prior deformation, or reducing the deformation temperature, will increase the stored energy and the number of potential nuclei. As a result the recrystallization temperature will decrease with increasing deformation. 64 Initial grain size affects the critical temperature. Grain boundaries are good sites for nuclei to form. Since an increase in grain size results in fewer boundaries this results in a decrease in the nucleation rate and hence an increase in the recrystallization temperature Deformation affects the final grain size. Increasing the deformation, or reducing the deformation temperature, increases the rate of nucleation faster than it increases the rate of growth. As a result the final grain size is reduced by increased deformation. 65 思 考 題 概念 臨界分切應(yīng)力、孿生、固溶強(qiáng)化、 Orowan機(jī)制、應(yīng)變時(shí)效、二次再結(jié)晶、回復(fù) Why are FCC metals more ductile than either HCP or BCC metals? How do changes in the dislocation density affect the strength and ductility (. its ability to deform plastically)? Why? 66 已知平均晶粒直徑為 1mm和 aFe的屈服強(qiáng)度分別為 196MPa, 問(wèn)平均晶粒直徑為 aFe的屈服強(qiáng)度為多少？ 試指出 Cu和 aFe兩晶體易滑移的晶面和晶向，并求出他們的滑移面間距，滑移方向上的原子間距及點(diǎn)陣阻力。（已知GCu=， GaFe =， v=） 今有純 Ti、 Al、 Pb三種鑄錠，試判斷它們?cè)谑覝兀?20176。 C）軋制的難易順序。是否可以連續(xù)軋制？如果不能，應(yīng)采取什么措施才能使之軋制成薄板？（已知 Ti的熔點(diǎn) 1672176。 C，在883176。 C以下為 HCP結(jié)構(gòu)， 883176。 C以上為 BCC結(jié)構(gòu)； Al的熔點(diǎn)為 660176。 C， FCC結(jié)構(gòu)； Pb的熔點(diǎn)為 328176。 C， FCC結(jié)構(gòu)。） 67 簡(jiǎn)述一次再結(jié)晶與二次再結(jié)晶的驅(qū)動(dòng)力。如何區(qū)分冷、熱加工？動(dòng)態(tài)再結(jié)晶與靜態(tài)再結(jié)晶后組織結(jié)構(gòu)的主要區(qū)別是什么？ 某工廠用一冷拉鋼絲繩將一大型鋼件吊入熱處理爐內(nèi)，由于一時(shí)疏忽，未將鋼繩取出，而是隨同工件一起加熱至 860℃ ，保溫時(shí)間到了，打開(kāi)爐門(mén)，欲吊出工件時(shí)，鋼絲繩發(fā)生斷裂，試分析原因。 68 有一截面為 10mm*10mm的鎳基合金試樣，其長(zhǎng)度為 40mm，拉伸實(shí)驗(yàn)結(jié)果如下表，試計(jì)算其抗拉強(qiáng)度 ?b，屈服強(qiáng)度 ?，彈性模量 E以及延伸率 d。 載荷（ N ） 標(biāo)距長(zhǎng)度（ mm ） 0 4 0 . 0 43 ， 100 4 0 . 1 86 ， 200 4 0 . 2 1 02 ， 000 4 0 . 4 1 04 ， 800 4 0 . 8 1 09 ， 600 4 1 . 6 1 1 3 ， 8 00 42. 4 1 21 ， 300 4 4 . 0 1 26 ， 900 4 6 . 0 1 27 ， 600 4 8 . 0 1 1 3 ， 8 00 （破斷） 5 0 . 2
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