不同鍛造製程對AA7005 鋁合金 微結構、織構與機械性質的影響

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题名:	不同鍛造製程對AA7005 鋁合金微結構、織構與機械性質的影響
作者:	陳又維;Chen, Yu-Wei
贡献者:	機械工程學系
关键词:	鋁合金;擠型;鍛造;微結構;織構;晶界;機械性質;Aluminum alloy;Extrusion;Forging;Microstructure;Texture;Grain Boundary;Mechanical Properties
日期:	2022-08-08
上传时间:	2022-10-04 12:13:21 (UTC+8)
出版者:	國立中央大學
摘要:	本研究使用F 狀態之AA7005 鋁合金熱擠型圓棒作為原料，並先後將其進行去應力退火、鍛造以及T6 處理，其中鍛造的參數會以變形溫度與壓縮率區分成四種鍛造模式，並以垂直於擠型的方向進行壓縮；測試機械性質所使用的拉伸試棒是依照ASTM-E8 之規範進行製作，而測試的方向則是平行於初始擠型件的擠型方向，最後透過織構、晶界等微結構性質來探究機械性質差異的原因。本研究將擠型方向定義為Y 軸，鍛壓方向定義為Z 軸，而主要的分析平面為 Y-Z 平面，此外，本研究採用階段性的分析，整個鍛後熱處理流程分成鍛造前、鍛造後以及熱處理後三個階段，以了解微結構差異之成因；本研究使用光學顯微鏡(OM)、背向電子繞射儀(EBSD)進行分析，並取得晶粒形狀、晶界角度比例、晶界總長度以及織構狀態的結果。分析結果表示擠型過程會依照不同的力學狀態將材料由表層至中心區分成三個部分，即粗晶層、過渡層以及纖維狀晶層，熱鍛之鍛件會導致過渡層轉變為粗晶，而纖維狀晶層則是發生部分再結晶，並保留了擠型過程中所形成的帶狀結構，冷鍛之鍛件則會發生完全再結晶的現象。拉伸試棒所測試的區域對應纖維狀晶層的結構狀態，而在不同鍛造製程之條件下，四組鍛件的機械性質皆符合規範之要求(YS≧290 MPa、UTS≧350 MPa、 TEL≧13%)，其中各鍛件所存在的機械性質差異分別與不同微結構指標有關，YS 值與Y 軸方向的織構有關，<111>織構佔比與YS 值呈正相關，UTS 與Y-Z 平面上的晶界總長度呈正相關，TEL 與X-Z 平面上晶粒的縱橫比呈負相關。;In this study, the AA7005 aluminum alloy hot-extruded round bar in F state was used as the raw material, and it was subjected to stress relief annealing, forging and T6 treatment successively. Compression is carried out in the direction perpendicular to the extrusion; the tensile test bar used for testing mechanical properties is made in accordance with the specifications of ASTM-E8, and the direction of the test is parallel to the extrusion direction of the initial extrusion, and finally through the weaving. microstructural properties such as structure and grain boundaries to explore the reasons for the differences in mechanical properties. In this study, the extrusion direction is defined as the Y axis, the forging direction is defined as the Z axis, and the main analysis plane is the Y-Z plane. In addition, this study adopts a staged analysis, and the whole post-forging heat treatment process is divided into pre-forging, post-forging and heat treatment. The latter three stages are used to understand the causes of microstructural differences; this study uses optical microscopy (OM), electron back scatter diffraction (EBSD) for analysis, and obtains grain shape, grain boundary angle ratio, grain boundary total length and The result of the texture state. The analysis results show that the extrusion process will divide the material into three parts from the surface layer to the center according to different mechanical states, namely the coarse grain layer, the transition layer and the fibrous grain layer. The fibrous crystal layer is partially recrystallized and retains the band-like structure formed during the extrusion process, while the cold-forged forgings will be completely recrystallized. V The area tested by the tensile test bar corresponds to the structural state of the fibrous crystal layer, and under different forging process conditions, the mechanical properties of the four groups of forgings all meet the requirements of the specification (YS≧290 MPa, UTS≧350 MPa, TEL≧ 13%), in which the difference in mechanical properties of each forging is related to different microstructure indicators, the YS value is related to the texture in the Y-axis direction, the <111> texture proportion is positively related to the YS value, and the UTS and Y-Z planes are related to The total grain boundary length is positively correlated with the TEL, and the TEL is negatively correlated with the aspect ratio of the grains in the X-Z plane.
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