鑄鍛與陽極處理對Al-1.2Mg-1.0Si-1.0Cu合金的機械性質與疲勞性質研究

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题名:	鑄鍛與陽極處理對Al-1.2Mg-1.0Si-1.0Cu合金的機械性質與疲勞性質研究
作者:	林家瑋;Lin, Jia-Wei
贡献者:	機械工程學系
关键词:	鑄/鍛;疲勞;應力強度因子△K
日期:	2017-08-22
上传时间:	2017-10-27 16:21:02 (UTC+8)
出版者:	國立中央大學
摘要:	本研究利用鑄/鍛生產Al-1.2Mg.1.0Si-1.0Cu合金。合金透過熔煉和澆注到Y型模具形成鑄件。經過均質化處理後，試塊會將冒口端切除，並在193K的溫度下放置600秒。將冷凍下來的鑄件，經過變形量50%的鍛造變形。鍛造完的試塊，經過T6熱處理後，將試塊熱加工成拉伸試棒，經過疲勞測試後得到抗拉強度420MPa，延伸率12%的拉伸性質。本研究會探討微結構與機械性質的關係。將有/無陽極的後的疲勞試棒，使用旋轉彎曲疲勞試驗機進行疲勞測試，測量在1 × 107圈數下的疲勞強度，並且建立疲勞曲線與比較有/無陽極處理的疲勞性質。在1 × 107壽命下，疲勞強度為117MPa，陽極過後的疲勞強度為110MPa。本實驗利用SEM觀察疲勞破斷面，紀錄破裂型態與計算裂紋起始的面積。結果，本實驗觀察反覆應力在120MPa下的疲勞破斷試棒，獲得裂紋起始的應力強度因子(△Kini)為1.97MPa√m。;Cast/forging process was used to produce Al-1.2Mg-1.0Si- 1.0Cu alloy samples in this study. The alloy was melt and poured to get Y-block castings. After homogenization treatment, the block samples were cut to remove top risers and at 193 K (dry ice) for 600 s. The frozen casting blocks were forged by a set of open die to produce 50 % reduction in thickness. After T6 heat treatment the forged blocks were machined to get tensile specimens and then tested to obtain tensile properties of UTS of 420 MPa and an elongation of 12%. Relations of microstructure and mechanical properties were discussed in this study. Parts of specimen with/ without anodization were prepared for running high-cycle fatigue test up to 1 × 107 cycles. The stress (S)-cycle life (N) curves of samples with/without anodization were constructed and compared. The former sample displayed fatigue strength of 117 MPa and the latter samples yielded fatigue strength of 110MPa at 1 × 107 life cycles. SEM was used to observe fracture surface of samples. The fractured morphologies were recorded and used for computing crack initiation area. As a result, stress intensity factor for crack initiation (ΔKinit) was obtained as 1.97 MPa√m (1 × 106) at 120 MPa stress amplitude.
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