à Ìåðñèíñêèé óíèâåðñèòåò, ôàêóëüòåò ìàøèíîñòðîåíèÿ, ×èôòëèê, Ìåðñèí, Òóðöèÿ á Êàôåäðà ìåòàëëóðãèè è ìàòåðèàëîâåäåíèÿ, ôàêóëüòåò ìàøèíîñòðîåíèÿ, Óíèâåðñèòåò Êûðûêêàëå, Êûðûêêàëå, Òóðöèÿ â Êàôåäðà ìåòàëëóðãèè è ìàòåðèàëîâåäåíèÿ, ôàêóëüòåò ìàøèíîñòðîåíèÿ, Óíèâåðñèòåò Êàðàáóêà, Êàðàáóê, Òóðöèÿ ã Ôàêóëüòåò ïðîôåññèîíàëüíî-òåõíè÷åñêîãî îáðàçîâàíèÿ, Óíèâåðñèòåò Êàðàáóêà, Êàðàáóê, Òóðöèÿ Èññëåäîâàíî âëèÿíèå ïðîöåññà ñòàðåíèÿ íà øåðîõîâàòîñòü ïîâåðõíîñòè è ìåõàíè÷åñêèå ñâîéñòâà àëþìèíèåâûõ ñïëàâîâ AA6061 è AA7075. Ìåõàíè÷åñêèå ñâîéñòâà èññëåäîâàëè ïðè èñïûòàíèÿõ íà ìèêðîòâåðäîñòü è ðàñòÿaeåíèå. Ïîâåðõíîñòü îáðàçöîâ èññëåäîâàëè ñ ïîìîùüþ ðåíòãåíîñòðóêòóðíîãî àíàëèçà. Ïîñëå èñïûòàíèÿ íà ðàñòÿaeåíèå ïîâåðõíîñòü ðàçðóøåíèÿ èññëåäîâàëè ìåòîäîì ðàñòðîâîé ýëåêòðîííîé ìèêðîñêîïèè. Âëèÿíèå ïðîöåññà ñòàðåíèÿ íà øåðîõîâàòîñòü ïîâåðõíîñòè èçó÷àëè ñ ïîìîùüþ àòîìíî-ñèëîâîãî ìèêðîñêîïà. Ïîêàçàíî, ÷òî ñ ðîñòîì øåðîõîâàòîñòè ïîâåðõíîñòè óâåëè÷èâàåòñÿ êîëè÷åñòâî âûäåëèâøèõñÿ ôàç.Êëþ÷åâûå ñëîâà: àëþìèíèåâûå ñïëàâû, àòîìíî-ñèëîâîé ìèêðîñêîï, ìåõàíè÷åñêèå ñâîéñòâà, ðàñòðîâàÿ ýëåêòðîííàÿ ìèêðîñêîïèÿ.
Introduction.Aluminum alloys offering high strength-to-weight ratio, good formidability and high corrosion resistance are extensively used in various fields such as the aerospace and automobile industries [1][2][3][4][5][6][7][8]. Magnesium alloys, the lightest of the structural metals with a two-thirds density of aluminum alloys, have been extensively explored for practical industrial applications during the past decade [9][10][11]. The high strength-to-weight ratio makes utilization of 6xxx series Al alloys favorable for a wide variety of applications [10][11][12][13][14]. Various structural applications in automobile and aerospace
Fracture toughness is one of the parameters, which are used to estimate the fatigue life of resistance spot-welded (RSW) joints. A spot-welded pair is affected by the shear stress of the weld zone when it is exposed to tensile load. Repetitive loads reduce the fatigue life of the spot weld, and the material splits at the spot-welded region. This study investigates the effect of welding current, weld time and nucleus size ratios on the fracture toughness of RSW of galvanized DP450 steels having 1.0 mm thickness. The specimens were joined by spot welding at different welding currents and times. Welding processes were carried out using 3, 5, 7 and 9 kA welding current and 10, 20, 30 and 40 cycles (1 cycle = 0.02 s) weld time and the electrode pressure was fixed at 600 MPa. All series of specimens were exposed to tensile shear test in order to determine the fracture toughness. The fracture toughnesses for all series of RSW joints were calculated by using the formula given in the literature. The nugget diameters, core sizes and their heights were measured via an optical microscope. The Vickers microhardness measurement was carried out on the weld nugget, heat affected zone (HAZ) and base metal. Nucleus size ratios were calculated. The results of the study demonstrated that the fracture toughness of RSW depended not only on the nugget diameter D, but also sheet thickness t, tensile rupture force F, hardness H and nucleus size ratios hn/dn.
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