摩擦攪拌銲接鎂基/鋁基異質合金之銲道微觀組織及拉伸機械性質研究

Welding Microstructural Feature and Tensile Mechanical Properties of Friction Stir Welding Dissimilar Mg and Al Alloys

陳群明(Chung-Ming Chen)

指導教授 ： 郭央諶

共同指導教授 ： 楊崇煒(Chung-Wei Yang)

國立虎尾科技大學/工程學院/材料科學與綠色能源工程研究所/碩士(2014年)

https://doi.org/10.6827/NFU.2014.00261

摘要

鎂、鋁合金為常用的輕金屬材料，鎂合金具有高比強度、制震性佳及電磁屏蔽效應等優點，鋁合金具導電性、塑性、耐蝕性及抗氧化能力佳等特色。本研究以鎂基合金Mg-9Li-1Zn (LZ91)、Mg-9Al-1Zn (AZ91)、鋁基合金1050、6061等材料進行異質摩擦攪拌銲接，並調查銲後微觀組織變化形態、相組成織構改變、機械性質變化和拉伸破壞行為。研究結果從攪拌銲接區金相組織發現層狀塑性流紋，並發現經過動態再結晶產生之等軸晶粒，AZ91/LZ91之銲接區散布塊狀的Mg17Al12，鋁/鎂銲接區邊界析出IMC層。XRD分析結果發現AZ91/LZ91銲道比起後退端之LZ91具有織構與優選方位的改變。微硬度分析結果顯示FSW異質接合之銲道區硬度值皆有上升現象，顯示攪拌過程之動態再結晶與晶粒細化效應所致。FSW銲接拉伸測試顯示AZ91/LZ91接合強度可達到母材抗拉強度的89%，鋁/鎂接合強度可達母材抗拉強度70%以上，SEM與EPMA分析發現銲接區邊界LZ91端發現Al元素的分佈，6061-O/LZ91、6061-T6/LZ91攪拌區的鋁/鎂流紋邊界亦證實存在IMC層。AZ91/LZ91銲接試片斷裂位於LZ91端，鋁/鎂銲接斷裂面之BEI影像與EPMA分析發現裂紋起源於IMC與銲接區邊界。

關鍵字

摩擦攪拌銲接 ； 異質金屬接合 ； 鎂合金 ； 鋁合金 ； 金屬間化合物 ； 界面分析

並列摘要

Magnesium (Mg) and aluminum (Al) alloys are widely used light metals. Mg alloys have advantages such as high specific strength, good vibration resistance and good electro-magnetic shielding effect. Al alloys show good conductivity, plasticity, good corrosion and oxidation resistance. The aim of present study is to join the Mg-9Li-1Zn (LZ91), Mg-9Al-1Zn (AZ91), Al-1050 and Al-6061 dissimilar alloys through the friction stir welding (FSW) technique. The relationship of microstructure evolution, phase composition, texture, tensile strength and failure behaviors are also discussed and concluded in this study. Experimental results show that lamellar plastic flow curves and equal axial grains, which resulted from the dynamic recrystallization (DRX), are observed within the welding zone (WZ). In addition, Mg17Al12 particles are dispersed in the WZ of AZ91/LZ91, and some intermetallic compounds (IMC) are precipitated at the WZ boundary of Al/Mg joints. X-ray analysis results show that apparent variations of texture and preferred orientations are observed at the WZ compared with the retreating side (RS) for the AZ91/LZ91 joint. The microhardness of the WZ for these dissimilar joints is increased after welding. It can be recognized that the increased of microhardness is resulted from the DRX and grain refining effect during welding. Tensile testing results show that the joining strength of AZ91/LZ91 joint is about 89% of the based metal, and the joining strength of Al/Mg joints is generally higher than 70% of the based metal. SEM and EPMA analysis detect the distribution of Al element on the fracture surface of WZ close to the LZ91 side. The IMC layer is demonstrated at the boundaries of Al/Mg flow curves at the WZ of 6061-O/LZ91、6061-T6/LZ91 joints. The fracture of AZ91/LZ91 joint is occurred near the LZ91 side, and the fracture of Al/Mg joints is resulted from the interface of IMC and WZ from the observation of BEI and EPMA analysis.

並列關鍵字

Friction stir welding (FSW) ； Dissimilar alloy joints ； Magnesium alloys ； Aluminum alloys ； Intermetallic compound (IMC) ； Interface analysis

參考文獻

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