新型Al-Mg-Si-Cu-Zn合金板材組織、織構(gòu)和性能的優(yōu)化調(diào)控

新型Al-Mg-Si-Cu-Zn合金板材組織、織構(gòu)和性能的優(yōu)化調(diào)控OPTIMIZATION AND CONTROLLING ON THE MICROSTRUCTURE, TEXTURE AND PROPERTIES OF AN ADVANCED Al-Mg-Si-Cu-Zn ALLOY SHEET

通過(guò)OM、SEM，TEM觀察以及EBSD和力學(xué)性能測(cè)試等手段研究了不同熱加工工藝對(duì)Al-Mg-Si-Cu-Zn合金板材組織、織構(gòu)和成形性能，以及固溶淬火后等溫時(shí)效對(duì)其析出行為的影響規(guī)律。結(jié)果表明，兩種熱加工工藝對(duì)T4P預(yù)時(shí)效態(tài)合金的強(qiáng)度和應(yīng)變硬化指數(shù)n基本無(wú)影響，但是對(duì)?r、Δr以及不同方向延伸率影響顯著；不同熱加工過(guò)程對(duì)合金組織和織構(gòu)演化均有影響，成形性能較好的固溶淬火態(tài)合金板材平均晶粒尺寸略大且呈雙模型晶粒尺寸分布特征，其織構(gòu)組分較多，但是強(qiáng)度較低。對(duì)該淬火態(tài)合金進(jìn)行185 ℃人工時(shí)效20min，其硬度即可升高65HV，進(jìn)一步時(shí)效到5h達(dá)到峰值硬度132HV，對(duì)應(yīng)的拉伸性能可達(dá)σ0.2=318 MPa，σb=364 MPa，δ=13%，拉伸斷口為典型的塑性斷裂。該合金在185 ℃時(shí)效時(shí)仍以Mg-Si相析出為主，如?"、?’和Q’相等，峰時(shí)效后?"主要沿b軸方向生長(zhǎng)最后轉(zhuǎn)化為?’和Q’相，合金表現(xiàn)出較好的時(shí)效穩(wěn)定性。

To reduce the weight of car body, Al-Mg-Si-Cu series alloys have been widely used to produce outer body panels of automobiles due to their favorable high-strength-to-weight ratio, corrosion resistance and good formability. Moreover, the strength of Al-Mg-Si-Cu series alloys can be enhanced by artificial aging treatments. However, their formability and final strengths still need to be further improved compared to steels, which are the major obstacles to wide-scale application of aluminum in the automotive fields. In this study, both the effect of different thermomechanical processes on formability, microstructure and texture of Al-Mg-Si-Cu-Zn alloy, and the influence of aging treatment on its precipitation behavior were studied through mechanical property tests, OM, SEM, TEM and EBSD measurements. The results reveal that both the strengths and strain-hardening component n value of the T4P treated alloys are not affected by the two thermomechanical processes, but the ?r, Δr and elongations in the different directions are significantly affected. The microstructure and texture evolution of the alloy in the two thermomechanical processes are different from each other. Both the microstructure of a little coarser and bi-modal grain size distribution, and the texture characteristics of much more components but with quite lower intensities can be seen in the solution treated alloy sheet which possessing a better formability after the T4P treatment. The hardness increment of 65HV can be achieved in the quenched alloy after artificial aging treatment of 185 ℃/20min. And then the peak-aging state can be obtained after aging 5hs, the hardness and tensile properties, i.e. yield strength, ultimate tensile strength and elongation, are as follows, 132HV, 318MPa, 364MPa and 13%, respectively, and ductile fracture is the main fracture feature as observed by SEM examination of fracture surface. Mg-Si precipitates, such as ?"、?’ and Q’ phases, are still the main precipitates formed after artificial aging at 185℃, and ?" phases mainly grow along its b axis and finally transform into ?’ and Q’ phases, which is the main reason for the observed better aging stability during long time artificial aging treatment.

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