Effect of applied pressure on microstructure and mechanical properties of linear friction welded AA1050-H24 and AA5052-H34 joints

Abstract

Linear friction welding (LFW) of AA1050 and AA5052 was performed at various applied pressures. The strengthening contributions of the joints were examined to investigate the relationship between the microstructure and mechanical properties. The dominant strengthening mechanisms at the weld centre of the AA1050 joint were both the grain-boundary strengthening and dislocation strengthening. While the weld centre in the AA5052 joint was dominated by the grain-boundary strengthening since the dynamic recrystallisation (DRX) during LFW was promoted due to the relatively low stacking fault energy (SFE). On the other hand, the strengthening mechanism in the regions away from the weld centre in the AA1050 and AA5052 joints was mainly dominated by the dislocation strengthening due to increased dislocation introduced during LFW.

Thermal Cycling, Microstructure, and Mechanical Properties of Al-Mg-Si-Cu Alloy Bobbin Tool Friction Stir Welded Joints Based on Thermal Index

“…This is due to the parameters of the advancing side and the retreating side of the thermo-mechanically affected zone of the low-angle grain boundary content increasing; thus, dislocation plugging leads to increased grain deformation resistance, so the yield strength is the highest. This finding is in agreement with Jeong-Won Choi et al [28]. The main strengthening mechanisms in this study are also grain boundary strengthening and dislocation strengthening.…”

Quasi-equal strength and toughness matching rail steel joint obtained via friction welding below Ac1 temperature

“…The refined grain size and the high proportion of high-angle grain boundaries indicating the high density of GNDs microstructure in WCZ of Trial I resulted in a combined effect of grain-boundary and dislocation strengthening. 15 This effect enhanced the comprehensive performance of the as-welded joint and accounted for quasi-equal strength and toughness matched that of U75V BM.…”

“…Under the combing effect of pressure and relatively low peak temperature, the grain-boundary and dislocation strengthening effects were generated, achieving sound as-welded joints. 15 Thus, CDFW is an attractive option for joining difficult-to-be-welded materials such as high-strength steels and has potential application prospects in the railway industry, including seamless rail line welding. Harnessing CDFW enables the creation of high-caliber, dependable rail welded joints capable of enduring the rigours of heavy-duty railway operations over extended periods.…”

Effect of Applied Pressure on Microstructure and Hardness of Linear Friction Welded Martensitic Steel

“…LFW の発明は 1929 年に遡り 7) ，その後 1969 年に線形往 復運動を行うことのできる装置が製造された 8) 。装置が 高額なこともあり，鉄鋼材料を用いた LFW の研究は少な く 5,[9][10][11][12][13][14][15] ，主に高付加価値の航空機材料に用いられる Ti，Ni 合金を中心に LFW の研究が進められてきた [1][2][3]6,[16][17][18][19][20][21][22][23] 。現 在，航空機用エンジン部品である動翼(Blade)とディスク (Disk)を一体化したブリスク(Blisk)の製造方法として実 採用されるに留まっている 24) 。一方，装置の低コスト化の 動きもあり 25) ，今後，本接合法は，多くの素材への適用や 幅広い産業分野での使用が期待される。 LFW の主なプロセスパラメーターとして，振動周波数， 振幅，印加圧力が挙げられ，これらは接合部や熱影響部 (HAZ)の温度履歴に大きく影響を及ぼす。その結果，接合 部の組織や特性が変化することが予想される。近年，著者 らのグループにより，印加圧力を変化させることにより接 合温度を容易に制御できることが明らかとなった 5,15) 。例 えば，フェライトとパーライトから成る中炭素鋼 S45C を 用いて低印加圧力(100 MPa)で継手を作製すると，接合部 温度は A 3 点以上の温度となり，その領域では冷却速度が大 きいためマルテンサイト組織となり，著しく硬化した 5,15) 。 一方，高印加圧力(250 MPa 以上)で継手を作製すると，A 1 点以下の温度に接合温度を制御することが可能となり，接 合部では硬化領域が見られず，母材とほぼ同等の均一な硬 さが得られた 5,15) 。Al 合金においても同様に， 接合部で母材 とほぼ同等の硬さとなり，引張試験において母材破断とな る継手が得られている [26][27][28] 。さらに，摩擦圧接 29) やジュー ル熱を用いた圧力制御接合プロセス 30…”