CAJ | 학술논문

在温度为300-450℃和应变速率为0.01-10 s-1的变形条件下,对Al-Zn-Mg-Cu-Zr合金(7056和7150铝合金)进行热压缩实验.结果表明:在一定的应变峰值出现后,流动应力随应变增加单调下降,呈现出流动软化.峰值应力取决于温度补偿应变速率Z的大小,可用包含Zener-Hollomon参数的双曲正弦关系来描述合金热流变行为.7056合金的变形激活能为244.64 kJ/mol,而7150合金的为229.75 kJ/mol;在同样的变形条件下,前者的峰值应力却低于后者.在高Z值条件下,在延长晶粒的亚晶粒中存在大量析出物;而在低Z值条件下,再结晶化的晶粒内出现完整的亚晶.7150合金中存在细小亚晶和大量析出物,由于亚结构强化和析出硬化造成其峰值应力比7056合金高.
재온도위300-450℃화응변속솔위0.01-10 s-1적변형조건하,대Al-Zn-Mg-Cu-Zr합금(7056화7150려합금)진행열압축실험.결과표명:재일정적응변봉치출현후,류동응력수응변증가단조하강,정현출류동연화.봉치응력취결우온도보상응변속솔Z적대소,가용포함Zener-Hollomon삼수적쌍곡정현관계래묘술합금열류변행위.7056합금적변형격활능위244.64 kJ/mol,이7150합금적위229.75 kJ/mol;재동양적변형조건하,전자적봉치응력각저우후자.재고Z치조건하,재연장정립적아정립중존재대량석출물;이재저Z치조건하,재결정화적정립내출현완정적아정.7150합금중존재세소아정화대량석출물,유우아결구강화화석출경화조성기봉치응력비7056합금고.
The hot compression tests of Al-Zn-Mg-Cu-Zr aluminum alloys (7056 alloy and 7150 alloy) were performed in a temperature range from 300 to 450 ℃ and at strain rate range from 0.01 to 10 s-1. The results show that the true stress-true strain curves exhibit a peak stress at a critical strain,then the flow stresses decrease monotonically until high strains,showing a dynamic flow softening. The peak stresses depend on the temperature compensated strain rate,which can be represented by the Zener-Hollomon parameter Z in the hyperbolic-sine equation with hot deformation activation energy of 244.64 k J/mol for 7056 alloy and 229.75 kJ/mol for 7150 alloy,respectively,while the peak stresses for the former are lower than those for the latter under the similar compression condition. The deformed microstructures consist of a great amount of precipitates within subgrains in the elongated grains at high Z value and exhibit well formed subgrains in the recrystallized grains at low Z value. The smaller subgrains and greater density of fine precipitates in 7150 alloy are responsible for the high peak stresses because of the substructural strengthening and precipitating hardening compared with 7056 alloy.