ECAP 성형가공한 Al 2024 초미세결정립 재료의 소성변형량에 따른 강도 변화

Abstract

Strength change ofan over-aged Al2024material was studied afterbeingsubjected to several stages of severe plastic deformation by ECAP (Equal Channel Angular Pressing).Various kinds of strength value were measured using the conventional tensile test, Rockwell and Vickers hardness and the SP (small punch) test. Due tolimitation of the specimen size,tension test in transverse direction could not be conducted. Hence, SP test was employed for assessing the strength in transverse direction. Based on TEM observation themeasured strength characteristics were explainedbased on the relation between microstructure,dislocation and strength.As the number of ECAP pass increases, the strength of Al2024 was alsoincreased. However, considerable change ofstrength, which is generally predicted, was not observed in this study. Forthe strength in transverse direction even decrease of the strength was observed after 6 passes of ECAP.Itwas argued that this decrease was due to dynamic recovery of dislocation density during or after ECAP processes at 150 C.Thestrength assessment equation proposed by the authors in the previouspaperwas shown to be very accurate. This argumentwas supported by comparing theresults of conventional tensile test with those of SP test. It was also pointed that the Rockwell hardnessvalue seemed to be able to represent the strength in the transverse direction.