金屬材料成型加工於摩擦界面處產生變化層區域之探討

The Layer Of Intensive Plastic Deformation In The Vicinity Of The Friction Surface In Metal Forming Processes

何漢城(He,Hancheng)

指導教授 ： 鄭友仁

國立中正大學/工學院/機械工程學系/碩士(2011年)

摘要

塑性加工又稱為金屬成型，是一種具經濟效益的生產方式，因過程簡易，省時，便宜等優點使其大量運用於機件的生產。在金屬加工成型過程中，胚料邊界與成型模具間會產生高摩擦力與高溫，在高摩擦力產生高應力之下，迫使胚料產生高度的應變加工成型，而在此高應力與應變之下，邊界摩擦面所承受的剪應力極高，剪應力流線（Shear flow）的分佈也變為密集，在邊界此密集的剪應力線形成一薄且硬的剪流層(Thin shear boundary layer)，此變化層影響成品的均勻性。為進一步探討其性質影響與變化，必須先能夠預測其變化的趨勢，再發展出運用不同加工製程參數來控制其變化的區域範圍。
本研究主要探討於擠製加工過程中，設計一微傾斜角度(5°、10°、15°)圓錐形模具，探討金屬材料承受不同應力與應變時所產生的變化之間的關連。將擠製後的成品進行金相實驗與奈米壓痕試驗，從金相實驗中去觀察晶粒分佈的情形與變化，於邊界處晶粒細小且分佈密集，再進行奈米壓痕硬度試驗，得到硬且薄的一層變化層。當量測此變化層的厚度時，發現不同的擠製傾斜角度模具所產生的成品其變化層厚度也不同，代入一應變與變化層寬度所延伸推導的相關式中，可得到一相同的材料係數，即為鎂合金於此加工過程中的材料參數，藉由這材料係數可經由計算在此加工過程中預測不同傾斜角度擠製模具下鎂合金的變化層厚度。

關鍵字

摩擦界面 ； 擠製加工 ； 應變率 ； 金屬成型

並列摘要

Plastic processing, is also known as metal forming, it’s the effective way of production, because its process is simple, time-saving. It is suitable to product a large number of parts. In metal processing, the boundary between the billet and the dies will have high friction and high temperature , and than the boundary friction surface are exposed to high shear stress, the shear stress flow lines (Shear flow) becomes dense. In the reason, it is formation of a thin hard layer of shear flow (Thin shear boundary layer) near the boundary, and than this layer affects the uniformity of the finished product. To further explore the property, must be able to predict trends, and then develop process using different way parameters to control the region -wide changes.
Study focused on the extrusion process, the design dies of the micro-inclined angle (5 °, 10 °, 15 °), to explore if the material under different the high stress and strain will changes or not. The extruded product will be experimented by metallographic and nano-indentation, to observe the experiment from the metallographic grain distributions and changes in circumstances, in the fine grain boundary and the distribution density, then the nano-indentation hardness experiments, get a thin layer of hard layer. Equivalent thickness measuring this change, we found a different angle extrusion dies product produced the thickness of the layer is different, and calculate with the width of the layers can derive in a same material coefficient, this is the magnesium alloy material coefficient, by which material coefficients can be calculated by this process in different dies angles, to predict the next extruded magnesium alloy dies produce the thickness of layer.

並列關鍵字

Friction Surface ； extrusion ； strain rate ； metal forming

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