Browsing by Subject "Hot forming"
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Item Combination of Cladding Processes with Subsequent Hot Forming as a New Approach for the Production of Hybrid Components(2022) Budde, L.; Merkel, P.; Prasanthan, V.; Bährisch, S.; Faqiri, M.Y.; Lammers, M.; Stonis, M.; Hermsdorf, J.; Hassel, T.; Uhe, J.; Behrens, B.-A.; Breidenstein, B.; Overmeyer, L.A new process chain for the manufacturing of load-adapted hybrid components is presented. The "Tailored Forming” process chain consists of a deposition welding process, hot forming, machining and an optional heat treatment. This paper focuses on the combination of laser hot-wire cladding with subsequent hot forming to produce hybrid components. The applicability is investigated for different material combinations and component geometries, e.g. a shaft with a bearing seat or a bevel gear. Austenitic stainless steel AISI 316L and martensitic valve steel AISI HNV3 are used as cladding materials, mild steel AISI 1022M and case hardening steel AISI 5120 are used as base materials. The resulting component properties after laser hot-wire cladding and hot forming such as hardness, microstructure and residual stress state are presented. In the cladding and the heat-affected zone, the hot forming process causes a transformation from a welding microstructure to a fine-grained forming microstructure. Hot forming significantly affects the residual stress state in the cladding the resulting residual stress state depends on the material combination.Item Retrogression-reaging and hot forming of AA7075(2014-05) Ivanoff, Thomas Alexander; Taleff, Eric M.The retrogression-reaging (RRA) and hot forming behavior of AA7075 were studied. AA7075 is a high-strength alloy used in applications where weight is of particular importance, such as in automobiles. Like many of the high-strength aluminum alloys, AA7075 requires elevated temperature forming to achieve ductility comparable to steels at room temperature. Since AA7075 is a precipitation hardening alloy, heat treatments during forming and production need to be closely controlled to limit any loss of strength due to changes in the microstructure. Two new forming concepts are introduced to explore the feasibility of forming AA7075 in manners compatible with current automotive manufacturing processes. They are RRA forming and solution forming. These concepts seek to improve upon the room-temperature formability of AA7075-T6 and incorporate the paint-bake cycle (PBC) into the heat treatment process. The PBC is a mandatory heat treatment used to cure the paint applied to automobiles during production. Currently, the PBC is conducted at 180 °C for 30 minutes. RRA behavior was studied with molten salt bath treatments between 200 and 350 °C. The PBC was used in lieu of the standard 24 hour reaging treatment conducted at 121 °C. It was determined that retrogression treating below 250 °C was acceptable for RRA forming, with retrogressing at 200 °C producing the hardest material after reaging by the PBC. The formability of AA7075-T6 during RRA forming was evaluated by tensile testing at 200 and 225 °C. Ductility of AA7075-T6 at RRA forming temperatures was double compared to those produced at room temperature. RRA forming was demonstrated to achieve this improved ductility and a final material hardness after the PBC of only slightly less than the peak-aged condition. In addition, solution forming behavior was studied at 480 °C. Solution forming can increase ductility compared to RRA forming, but it requires aging at 121 °C prior to the PBC to produce peak-aged hardness.Item Simulation and experimental investigation of hot forming of aluminum alloy AA5182 with application towards warm forming(2012-05) Lee, John Thomas; Taleff, Eric M.; Bourell, David L.This study focuses on hot and warm forming properties of aluminum alloy AA5182 sheet, with attention toward warm forming, by using gas pressure to form sheet material. A temperature range of 300°C to 450°C and a pressure range of 690 kPa (100 psi) to 2410 kPa (350 psi) were used in a test matrix of twenty one different test conditions for gas-pressure forming of a sheet into hemispherical dome in a gas-pressure bulge test. Multiple sets of tensile data were used to develop a material model that predicts the dome height and shape of an axisymmetric bulge specimen at any given time during forming. In simulations of the forming process, 17 simulations of the total 21 experimental conditions showed good agreement with the experimentally measured dome heights throughout forming tests. The four cases that did not show good agreement between simulation and experiment are a result of strain-hardening in the material during forming. Strain hardening was not significant in tension testing of specimens and was not accounted for in the material model, which considered only strain rates slower than for these experimental bulge testing. This demonstrates an effect which must be considered in future simulations to predict forming approaching warm conditions. Two experimental bulge specimens were cross-sectioned post forming and grain sizes were measured to determine if grain growth occurred during the forming process. Experimental bulge specimens show no grain growth during the forming process. The tensile specimens from which the material model data were taken were measured to determine if plastic anisotropy was a possible issue. All specimens measured were proved to have deformed nearly isotropically. The results of this study show that predicting warm and hot forming of aluminum alloy AA5182 using gas pressure is possible, but that a more complex material model will be required for accurate predictions of warm forming. This is a very important step toward making hot and warm forming commercially viable mass production techniques.