(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083；
2. 中南大學(xué) 輕合金研究院，長(zhǎng)沙 410083；
3. 中南大學(xué) 高性能復(fù)雜制造國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083)
摘 要: 采用硬度測(cè)試、拉伸性能測(cè)試、透射電鏡分析(TEM)、掃描電鏡(SEM)斷口形貌觀察以及疲勞性能測(cè)試等研究3種時(shí)效工藝對(duì)軌道交通用Al-Zn-Mg-Cu合金組織和性能的影響。結(jié)果表明：三級(jí)時(shí)效(120 ℃, 0.5 h, WC)+(65 ℃, 240 h)+(120 ℃, 24 h)態(tài)合金的抗拉強(qiáng)度達(dá)到640.2 MPa，高于二級(jí)時(shí)效(120 ℃, 4 h)+(175 ℃, 6 h)態(tài)合金的477.7 MPa和四級(jí)時(shí)效(105 ℃, 7 h)+(120 ℃, 7 h)+(155 ℃, 4 h)+(175 ℃, 4 h)態(tài)合金的483.5 MPa；二級(jí)時(shí)效和四級(jí)時(shí)效態(tài)合金中微米量級(jí)第二相粒子數(shù)量多，且尺寸較大；而三級(jí)時(shí)效態(tài)合金中，無(wú)論是微米量級(jí)第二相還是晶內(nèi)η′析出相，其尺寸都小于二級(jí)和四級(jí)時(shí)效態(tài)合金的；3種時(shí)效工藝疲勞試驗(yàn)試樣的裂紋源均起于試樣表層，在頻率50 Hz、應(yīng)力比為-1的加載條件下，二級(jí)時(shí)效、三級(jí)時(shí)效和四級(jí)時(shí)效態(tài)合金的疲勞極限分別約為 145、239和180 MPa。
關(guān)鍵字: 7050鋁合金；時(shí)效工藝；拉伸性能；疲勞極限
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Light Alloy Research Institute, Central South University, Changsha 410083, China;
3. State Key Laboratory of High Performance and Complex Manufacturing, Central South University, Changsha 410083, China）
Abstract:The effects of aging system on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy for rail transportation were investigated by hardness measurement, tensile test, transmission electron microscopy, scanning electron microscopy observation and fatigue performance tests. The results show that after the three-stage aging (120 ℃, 0.5 h, WC)+(65 ℃, 240 h)+(120 ℃, 24 h) treatment, the tensile strength of alloy is 640.2 MPa, which is higher than 477.7 MPa of the two-stage aging (120 ℃, 4 h)+(175 ℃, 6 h) and 483.5 MPa of the four-stage aging (105 ℃, 7 h)+(120 ℃, 7 h)+(155 ℃, 4 h)+(175 ℃, 4 h). The two-stage aging and four-stage aging samples have the larger number of second phase particles and larger size. However, for the three-stage aging samples, whether it is the micron scale second phase, or intragranular η′ precipitates, their sizes are less than those of the two-stage and four-stage aging samples. The crack sources of three kinds of samples in the aging process fatigue test all start on the sample surfaces. The fatigue limits of the two-stage aging, three-stage aging and four-stage aging alloys are about 145 MPa, 239 MPa and 180 MPa, respectively.
Key words: Al-Zn-Mg-Cu alloy; aging system; tensile property; fatigue life
