摩擦攪拌銲接純鈦與6061鋁合金之接合性質與銲後熱處理效應研究

Abstract

本研究將純鈦與6061鋁合金使用摩擦攪拌銲接技術選用偏位與置中兩種接合方法進行異質接合，攪拌棒選用高速鋼，偏位銲接攪拌棒凸銷設計為圓柱形，而置中銲接攪拌棒凸銷設計為半圓球形，傾斜角為2∘，探討不同主軸轉速、進給速度以及攪拌棒形狀對於銲道機械性質之影響，而後對其施以時效與固溶時效處理，比較熱處理前與熱處理後之金相顯微組織、機械性質分析以及元素分布分析。實驗結果顯示在偏位與置中接合，在主軸轉速1000 rpm、進給速度80 mm/min皆可得到最佳的銲道機械性質，兩種接合方法進行拉伸試驗皆斷在熱影響區，偏位接合最大抗拉強度為158 MPa，而置中接合最大抗拉強度為176 MPa，金相顯微組織可觀察到攪拌區因動態再結晶而有晶粒細化的效果，熱影響區有晶粒粗大化的現象，導致銲件在此區硬度下降。根據EPMA與微硬度分析可觀察到，純鈦與鋁合金在銲道中劇烈攪拌，在兩種材料介面形成金屬間化合物(IMC)，其硬度值最高到達600 HV，與偏位接合相比，置中接合攪拌區純鈦攪動範圍較大，被攪入的鈦碎屑也較多，IMC層厚度也較厚且較為複雜。經由FSW銲後熱處理使用時效處理及固溶時效處理，鋁合金攪拌區及熱影響區晶粒組織有均質化的效果，固溶時效處理可觀察到粗大的晶粒組織會與周圍的組織相結合，形成緊密的組織結構，在微硬度測試可觀察到，鋁合金經由時效處理攪拌區及熱影響區硬度由未進行熱處理的60 HV提升至80 HV；經由固溶時效則可提升100 HV，接近鋁合金母材的硬度，FSW純鈦與鋁合金對接使用固溶時效處理最大抗拉強度可提升至166 MPa。In this study, the technology of friction stir welding was used to join the dissimilar materials of aluminum alloy 6061 and commercially pure titanium by means of offset joint and center joint. The offset welding stirring rod pin was designed to be cylindrical, while the center welding stirring rod pin was designed to be hemispherical, with an inclination angle of 2˚. The influence of different rotating speeds, travel speeds and shape of stirring rod on the mechanical properties of the weld bead was discussed, and then it was subjected to aging and solution aging treatment, and the metallographic microstructure, mechanical properties, element distribution analysis before and after heat treatment were compared.The experimental results showed that the best mechanical properties of the weld joint could be obtained at the rotational speed of 1000 rpm and the travel speed of 80 mm/min in the offset joints and center joints. The maximum tensile strength of the offset joint was 158 MPa, and the maximum tensile strength of the center joint was 176 MPa. The metallographic microstructure could observe that the stirring zone has the effect of grain refinement due to dynamic recrystallization, and the heat-affected zone has grains, the phenomenon of coarsening causes the hardness of the weldment to decreased in this area. According to EPMA and microhardness analysis, it could be observed that pure titanium and aluminum alloy were vigorously stirred in the weld bead, and an intermetallic compound (IMC) was formed at the interface of the two materials, and its hardness value was up to 600 HV. The stirring range of pure titanium in the middle-joining stirring zone was larger, and more titanium scraps were stirred, and the thickness of the IMC layer is also thicker and more complicated. Through FSW post-weld heat treatment using aging treatment and solution aging treatment, the grain structure of the aluminum alloy stirring zone and heat affected zone has the effect of homogenization. It could be observed that the coarse grain structure will be combined with the surrounding structure in the solution aging treatment, forming a compact structure. In the microhardness test, it could be observed that the hardness of the aluminum alloy in the stirring zone and heat affected zone is increased from 60 HV without heat treatment to 80 HV after aging treatment, The hardness of the aluminum alloy base metal, the tensile strength of the FSW butt joint could be increase to 166 MPa by solution and aging treatment.