Dependence of bonding strength and variations in residual stress on interface wedge angles and bonding temperature condi
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.156
Dependence of bonding strength and variations in residual stress on interface wedge angles and bonding temperature conditions Shunsuke Muraoka1 and Masayoshi Tateno1 1
Kogakuin University Graduate School, 2665-1 Nakano-machi, Hachioji, Tokyo, Japan.
Abstract
Residual stress can considerably weaken systems with ceramics-to-metal joints. Herein, we investigate the dependence of bonding strength and residual stress variation of a ceramics-tometal joint system on the interface wedge angle and bonding temperature condition. First, disparity between large-scale displacement models with varying work-hardening parameters was confirmed using thermal elastoplastic Finite Element Method (FEM) analysis. Each interface wedge shape was set to a plane surface to compare FEM results to experimental results related to the effect of the interface wedge angle on the practical bonding strength. The experimental results were specifically for a system consisting of Si 3N4-WC/TiC/TaC bonded to Ni plate. The effects of the wedge angle of the metal side on residual stress near the interface edge were numerically predicted using FEM models. The interface wedge angles for this model,1 and 2, were defined using the configuration angle between the interface and free surfaces of both materials. The numerical results showed that the stress r on the free surface of the ceramic side was concentrated near the interface edge at which discontinuity in the stress state is generated. Dependence of the residual stress variation on both the wedge angle and temperature conditions can be predicted. It was confirmed that the bonding strength improves with decreasing residual stress in geometrical conditions. Therefore, residual stress appears to be a predominant factor affecting bonding strength. The observed fracture pattern showed that the fracture originated near the interface edges, after which small cracks propagated on the ceramic side. The residual stress is presumed to dominate bonding strength as the fracture occurred near the interface edge of the ceramic side. Results showed that the maximum bonding strength appears at the geometrical condition where the fracture pattern changes to 2 lower than 90º of joint bonded at 980 ºC. Therefore, the optimum interface wedge angle depends on a combination of materials and bonding temperature conditions, because the weak point of the bonded joint system will affect the stiffness balance of both materials and the adhesion power of the bonded interface.
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INTRODUCTION Bonded dissimilar materials are often significantly weakened by thermal residual stress generated near the interface edges. This is due to the difference between material constants and thermal expansion coefficients of the materials [1, 2]. Redu
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