Al-Zn-Mg-Cu-Zr-0.12Ce合金鑄錠的均勻化退火及組織演變

Al-Zn-Mg-Cu-Zr-0.12Ce合金鑄錠的均勻化退火及組織演變Homogenization treatment of as-cast Al-Zn-Mg-Cu-Zr-0.12Ce aluminum alloy and microstructure evolution during homogenization

采用光學(xué)顯微鏡(OM)、掃描電鏡(SEM)、電子探針(EPMA)、波譜分析(WDS)、X射線衍射(XRD)以及差示掃描量熱儀(DSC)等技術(shù)對(duì)Al-Zn-Mg-Cu-Zr-0.12Ce合金鑄態(tài)組織及均勻化退火過程中的組織演變進(jìn)行研究。結(jié)果表明：該合金鑄態(tài)組織存在嚴(yán)重的枝晶偏析，主要由α(Al)基體、α(Al)+Mg(Zn, Al, Cu)2 非平衡共晶組織以及少量的θ(Al2Cu)相、Al8Cu4Ce相、Al7Cu2Fe相構(gòu)成；均勻化退火過程中，大量層片狀共晶組織溶入基體，同時(shí)轉(zhuǎn)變生成Al2CuMg相；合金的過燒溫度為474.87 ℃；合金的最佳單級(jí)均勻化退火工藝為465 ℃、40 h，這與均勻化動(dòng)力學(xué)方程測算結(jié)果接近；合金經(jīng)(435 ℃，8 h)+(470 ℃，32 h)雙級(jí)均勻化退火處理后，回溶效果更好，主要?dú)埩粝酁殡y溶的Al2CuMg相，少量含F(xiàn)e雜質(zhì)相以及Al8Cu4Ce相。

The microstructure of the as-cast Al-Zn-Mg-Cu-Zr-0.12Ce aluminum alloy and microstructure evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA), wavelength dispersive spectroscopy (WDS), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The results indicate that the severe dendritic segregation exists in Al-Zn-Mg-Cu-Zr-0.12Ce alloy ingot. The as-cast microstructure mainly involves α(Al), non-equilibrium eutectics (α(Al)+Mg(Zn, Al, Cu)2), and small amounts of θ(Al2Cu), Al8Cu4Ce and Al7Cu2Fe phases. During homogenization, the lamellar eutectic structures in the as-cast alloy is dissolved into the matrix, meanwhile, a transformation from Mg(Zn, Al, Cu)2to Al2CuMg phase also occurs. The overburnt temperature of the alloy is 474.87 ℃. The optimum parameters of single homogenization are (465 ℃, 40 h), which is consistent with the result of homogenization kinetic analysis. The eutectic phases are eliminated more sufficiently with two-step homogenization treatment at 435 ℃ for 12 h and then at 470 ℃ for 32 h. The residual second particles after homogenization are some small Al2CuMg, Fe-rich and Al8Cu4Ce phases.

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