回復(fù)與再結(jié)晶ppt課件(2)(參考版)
2025-01-17 11:40本頁面
【正文】 載荷（ N ） 標(biāo)距長度（ 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 。如何區(qū)分冷、熱加工？動態(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，打開爐門，欲吊出工件時(shí)，鋼絲繩發(fā)生斷裂，試分析原因。 C， FCC結(jié)構(gòu)。 C以上為 BCC結(jié)構(gòu)； Al的熔點(diǎn)為 660176。 C，在883176。 C）軋制的難易順序。 60 金屬經(jīng)過塑性變形后 回復(fù) 加工硬化 殘余應(yīng)力 √ ? 退化處理 再結(jié)晶 晶粒長大 特點(diǎn) 特點(diǎn) 晶粒形核和長大 再結(jié)晶溫度 長大特點(diǎn) 本章小結(jié) 61 Laws of recrystallization There are several, largely empirical laws of recrystallization: Thermally activated. The rate of the microscopic mechanisms controlling the nucleation and growth of recrystallised grains depend on the annealing temperature. 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 196M
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