损伤对LY12CZ铝合金和H62黄铜板料超塑可成形性的影响

On Effect of Damage on Superplastic Formability of LY12CZ Aluminium Alloy and H62 Brass Sheet

损伤对ＬＹ１２ＣＺ铝合金和Ｈ６２黄铜板料超塑可成形性的影响杜志孝，李淼泉，吴诗惇经作者的深入研究后发现：至今为止，还未见有关损伤对合金板料超塑可成形性影响研究的文献报导．而这种影响常常体现在板料的成形极限图（ＦＬＤ）中．本文实验研究了ＬＹ１２ＣＺ铝合...

After very careful search, the authors have not found in the open literature any nit'ornlation on effect of damage on supcrplastic formability of alloy sheet. Such information is usually given in FLD(Forming Limit Diagram).The authors present results of their cxperirncntal research on supcrplastic forming limit under different strain states of two alloys: (1) LY12CZ aluminium alloy (corresponding to ASTM 2024; sheet thickness is 2mm; hardness HB is 131; grain size is 18.3μm); (2) half--hardened H62 brass(corrcsponding to ASTM 280; sheet thickness is 1.5mm; hardness HB is 60; grain size is 14.2μm). The experimental findings arc:(1) The supcrplastic formability as revealed in Fig.1. In Fig.l, ε1 and ε2 are principal strains in the middle plane of the sheet. The third principal strain ε3 is in the direction perpendicular to the plane.Only when the absolute value of ε2 is small (ε2=0 corresponding to pure plane strain), is the supcrplastic formability of LY12CZ sheet better than that of H62 brass sheet. When absolute value of ε2 is bigger than 0.3 approximately, the inverse is true.(2) The effect of damage on supcrplastic formability as implied in Fig.2. In Fig.2,the ordinate fc represents cavity area fraction, the abscissa ε represents equivalent strain (a quantity taking all three principal strains into consideration). As ε increases fa for LY12CZ increases at a faster rat than fa for H62 brass. Considering the above two cxpcrimcntal findings, the authors make the following deduction with confidence: during the proeess of supcrplastic deformation, cavity damage makes continuity of transfer of strain worse and worse, thus accelerating the drift of externally applied strain state toward plane strain state with lowcring of supcrplastic forming limit of sheet as the natural result.