The role of shear deformation component in pressure welding samples of dissimilar cast and wrought nickel-based alloys

Abstract

A material plastic flow finite-element modeling during pressure welding (PW) of two-element and three-element samples was carried out for dissimilar wrought (EP975) and cast intermetallic (VKNA-type) alloys at 1125°C and 10-4 s-1 initial strain rate. The finite-element modeling was performed in a two-dimensional setup (plane strain). In the two-element samples case, the top element was ultrafine grained EP975 and the bottom one was VKNA-25. The top and bottom elements of the threeelement samples were made from VKNA-25 while the intermediate element was ultrafine-grained EP975. The geometry in the X and Y directions were 40.5 and 5 mm for the EP975 samples and 40.5 and 3 mm for the VKNA-25 samples respectively. Experiments on PW intermetallic Ni 3 Al alloy and heat-resistant nickel alloy EP975 with ultrafine-grained (UFG) structure were carried out. Samples were parallelepipeds of size 10×40×3 mm 3 and 10×40×5 mm 3 respectively. PW was carried out at 1125°C. Several combinations of welded sample surfaces with flat and grooved relief were considered. The relief made on both welded surfaces was equivalent to increase of friction between them. This results in a shear deformation reduction near the contact surfaces and degrades the welding quality as compared to the flat surfaces conventional welding. Relief applied only to one of the elements being welded results in a more efficient welding process since active deformation zones are created in the central zone, where in the other samples stagnant zones are observed. There are no deformation peculiarities in PW of the three-element samples, compared to two-element sample.

Computer simulation of pressure welding of heat resistant heterophase nickel-based superalloys specimens through an interlayer

“…Основными стадиями СД является образование контакта, т. е. сближение соединяемых заготовок за счет пластической деформации микронеровностей на свариваемых поверхностях, и активация контактных поверхностей [4 -6]. Качество твердофазного соединения (ТФС) зависит от многих факторов: приложенного давления, температуры сварки, скорости нагружения, схемы деформирования [4 -8,17,19], рельефа свариваемых поверхностей [3,13 -14], геометрии соединяемых деталей [13,14], исходной микроструктуры заготовок [10,11,15] и напряженно-деформированного состояния (НДС) в зоне ТФС свариваемых материалов [3,15,17]. Подготовленная для образования физического контакта между заготовками структура должна быть однородной и мелкозернистой, чтобы обеспечить деформацию микронеровностей на контактных поверхностях заготовок в режиме СП [10,11,15].…”

Finite element modeling of superplastic forming of ideal and intentionally defected titanium alloy products for the purpose of non‐destructive control

“…Improvement of the three‐layered structure superplastic forming technology requires solution of a number of problems . Firstly, to achieve homogeneous deformation of the material during superplastic forming one has to ensure optimal temperature and strain rate conditions of superplasticity .…”