Particle Reinforced Al Matrix Composites Research Articles

High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites: Synthesis, mechanical, microstructural and thermal characterization

This study aims to introduce a novel type of particulate reinforced Al matrix composite. High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites were produced via a combined process of different powder metallurgy methods. Firstly, boride compounds (HfB2, TiB2, ZrB2, VB2, NbB2) were synthesized in the laboratory scale using the related metal oxide, boron oxide, and magnesium by mechanochemical synthesis (MCS) and leaching processes under optimum conditions. Secondly, the synthesized and purified boride powders were mixed in equimolar ratios using a planetary ball mill for 72 h, and they were sintered at 2000 °C under 30 MPa via spark plasma sintering (SPS). Thirdly, equimolar high entropy (HfTiZrVNb)B2 bulks were crushed, converted into powder forms, and added into Al powders at different amounts as 1, 2, 5, 10, and 15 wt %. Lastly, these powder blends were mechanically alloyed in a vibratory ball mill for 6 h, cold pressed and pressureless sintered at 630 °C for 2 h. For characterization techniques, X-ray diffractometry (XRD), thermal analysis, scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), density measurements using pycnometer and Archimedes' methods, microhardness and dry sliding wear tests were conducted on the sintered composites. The highest hardness (∼1.5 GPa) and the lowest wear rate (∼0.0012 mm3/Nm) were obtained in the Al-15 wt % (HfTiZrVNb)B2 sample.

Quasi-static and dynamic deformation of aluminum matrix composites reinforced by core-shell Al35Ti15Cu10Mn20Cr20 high-entropy alloy particulates

Core-shell structured particles are potential reinforcement agents for metal matrix composites. In this work, aluminum matrix composites reinforced with core-shell structured Al35Ti15Cu10Mn20Cr20 high-entropy alloy (HEA) particles were fabricated by spark plasma sintering (SPS) and high-temperature diffusion post-treatment. Dynamic compression behavior and adiabatic shear failure mechanism in the composites were investigated by split Hopkinson pressure bar (SHPB), scanning electron microscopy and transmission electron microscopy. Results showed that the shell thickness of the core-shell particles ranged from 0.4 to 1.6 μm, which were formed by thermal diffusion between HEA core and aluminum alloy. The 30 vol% (Al35Ti15Cu10Mn20Cr20)p/2024Al composite showed a high compressive strength (594 MPa) and strain-to-failure (26.7 %) under quasi-static compression, as well as a high flow stress (602 MPa) and strain-to-failure (45.3 %) under dynamic compression, which are superior to common ceramic particles reinforced Al matrix composites. The (Al35Ti15Cu10Mn20Cr20)p/Al composites with ∼20–40 vol% core-shell HEA particles failed as bulging, 45° shearing or splitting when compressed at ∼1000-3000 s−1. Micro-damages in these composites were due to microcracks originated from the HEA core, while propagation of cracks was effectively restrained by the shell. Deformation bands and phase transformation (melting of aluminum) were both observed in the composites under dynamic loads. Chain-shaped deformation bands were formed by the fragmentation and rearrangement of the core-shell particles, instead of the recrystallized structure of metal matrix in particle-reinforced Al matrix composites reported previously. The formation of molten Al phase transformation bands was owing to shear localization and significant adiabatic temperature rise under dynamic compression.

Ductile-brittle transition mechanism of SiC particle-reinforced Al-MMCs under ultrasonic assisted grinding with single grain

High volume fraction (45 %) silicon carbide particle-reinforced Al matrix composites (SiCp/Al-MMCs) play an important role in various engineering fields due to their excellent properties, but the high hardness and brittleness of the SiC reinforcements result in poor surface integrity during conventional grinding (CG). Ultrasonic assisted grinding (UAG) is an efficient machining process to improve the quality of finished surface for hard-brittle materials. In this study, comparison tests between UAG and CG with single grain were designed and the grinding force, specific grinding energy, material removal rate, surface and subsurface morphology, and the ductile-brittle transition mechanism of SiC particle were investigated. The results showed that ultrasonic vibration can increase the critical depth of ductile-brittle transition for SiC particles, making it easier to realize the micro brittle fracture and effectively reduce the surface and subsurface damage of SiCp/Al composites.

Dispersion of reinforcing micro-particles in the laser welding of metal matrix composites: High-fidelity modeling with experimental characterization

Understanding the interaction mechanism between keyhole, solid phase (ceramic particles), and liquid phase (metal matrix) will offer key insights into laser welding/additive preparation of high-performance metal matrix composites. The laminar SiC particle–reinforced Al matrix composite, which is extensively used in aviation structural parts, is utilized as the experimental model. The effect of the keyhole mode on the migration behavior of SiC particles in the weld pool was revealed by simulating the multiphysical thermal fluid flow during the laser-welding process. The simulation results revealed that the flow of the molten pool and the keyhole mode have significant effects on the migration behavior of particles. The variation of keyhole mode leads to considerable changes in molten pool dynamics and corresponding SiC particle distributions in the molten pool. The observed selective distribution of SiC particles is due to the flow characteristics of the molten pool. In addition, results showed that the keyhole mode can maximize the uniform distribution of SiC particles in the melt pool, thereby addressing the nonuniformity problem of SiC particles. This work is a fundamental advancement in the modeling of laser-welded SiC particle–reinforced Al matrix composites and provides unprecedented details on the effects of keyhole patterns on weld pool dynamics. This work can further offer practical guidance for “temperature field–regulating reaction behavior” and “velocity field–regulating distribution behavior.”

Constitutive equation and microstructural evolution of one distinctive Al–based hybrid composite reinforced by nano–AlN and micro–TiC particles during hot compression

In this study, an (8.2AlN + 4TiC)/Al–0.3Fe–0.1Mn composite was successfully fabricated for elevated– temperature applications by the liquid–solid reaction method, and the high–temperature performance (hot workability) of the composite was evaluated by unidirectional hot deformation experimentation. The tested temperatures and strain rates were 350–500 °C and 0.001–1 s−1, respectively. The results indicated that the peak stress of the composite was as high as 226 MPa at 350 °C and 1.0 s−1, which was significantly higher than the reported strength values of commercial deformed aluminum alloys or other particle–reinforced Al matrix composites under the same experimental conditions. Although the flow stress of the composite decreased with the increase of deformation temperature and the decrease of strain rate, the peak stress remained at 82 MPa under the experimental conditions of 500 °C and 0.001 s−1. This reflected the excellent high–temperature synergistic strengthening effect of the in–situ nanosized AlN and submicron TiC particles. Based on the true stress–true strain curve, the hot deformation constitutive equation of the composite was established and fitted. The relative microstructural evolution of the composite during hot deformation was characterized by electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the Orowan strengthening and load–transfer strengthening effect of the nanosized AlN and submicron TiC particles were the main reasons for their high–temperature strengthening, and the softening effect of the composite could be attributed to dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX), accompanied by partial discontinuous dynamic recrystallization (DDRX). This study provided a new strategy for the design of heat–resistant Al alloys and their high–temperature strengthening and softening mechanism. This study may provide new insights for designing and achieving good workability in Al–based composites for elevated temperature applications.

Mechanical response and microstructure evolution of SiC particle-reinforced Al-MMCs under ultrasonic loading

High volume fraction(≥45 vol.%) SiC particle-reinforced Al matrix composites are difficult for forming and manufacture. A simple and efficient method is proposed in this research to realize rapid plastic deformation at room temperature. By applying ultrasonic load to the composites, 40% compressive strain is obtained within 1s, while the stress is only 59MPa, about 1/10 of its compressive strength. Ultrasonic loading can produce a high instantaneous strain rate (up to 103 s-1) and a high-frequency (20000Hz) cyclic load compared with conventional loading. The stress superposition and relief effects produced by ultrasonic loading lead to the diffusion and annihilation of dislocation in the Al matrix, the dispersion, and the plastic deformation of SiC particles. The microstructure evolution reduces the accumulation of dislocation, promotes the formation of sub-grain, weakens the deformation texture, and improves the synergetic deformation of Al and SiC.

Achieving high strength and ductility in high-entropy alloy particle reinforced Al matrix composites with proper proportion of layered structures

Particle spatial distribution has a significant influence on mechanical behavior of particulate reinforced Al matrix composites fabricated by powder metallurgy, which has been systematically investigated in our work. The results showed that, by regulating the milling time for 1 h, 10 h and ≥ 20 h, assisted by hot pressing and hot extrusion processes, three typical distributions of high-entropy alloy (HEA) particles within the Al matrix composites were constructed, i.e., particle agglomerated composite, uniformly distributed composite, and layered structure composite, respectively. After a long-time high energy milling, alloying behavior did not occur between the Al and HEA particles. Moreover, the composite with a proper proportion (19 vol%) of layered structures achieved good combination of yield strength (445.2 MPa) and fracture strain (5.4%), which was ascribed to the strengthening and toughening effect induced by bimodal gain structure. The effect of layered structure on the composite was reflected in two points: first, due to the differences in dislocation density and consumption degree of Cu atoms, the size and density of precipitates in the large particle zones differ from those in the layered structured zones. Second, according to the finite element analysis, though high content of layered structures brought high strength in the composites, it also caused stress concentration, which could reduce the ductility of composites. The dominant strengthening contribution of the layered structure in the composites was derived from the grain boundary strengthening. This research provides a new insight into Al matrix composites with different reinforcing particle distribution.

Deformation mechanisms in the cutting process of SiCp/Al composites using the molecular dynamics (MD) approach

In order to clarify the reasons for the emergence of problems such as high machining difficulty and poor machining surface quality encountered in the machining process of SiCp/Al composites, this paper presents a simulation study of the deformation mechanism occurring during the cutting process of SiCp/Al (SiC particle-reinforced Al matrix composites) by using the molecular dynamics (MD) method. The mechanism of strengthening and hardening occurring during cutting of SiCp/Al composites is discussed in terms of the slip expansion of dislocations and the interaction between different types of dislocations. It is found that the presence of SiC balls hinders the slip and expansion of dislocations in the Al (aluminum) matrix, resulting in the strengthening of the Al matrix between the SiC (silicon carbide) balls, mainly because the dislocations in the workpiece interact with each other during the cutting process to form dislocation tangles, stacking layer dislocations and dislocation locks, which hinder the slip and expansion of dislocations and thus increase the strength of the Al matrix. By analyzing the stress distribution inside the workpiece during the cutting process, it is found that the stress inside the workpiece is mainly concentrated in the area where the tool flank face is in contact with the workpiece, which is the main reason for the occurrence of working hardening in SiCp/Al composites.

Microstructure evolution, interface and mechanical properties of SiCp/2A14 joint during laser keyhole welding

Welding problems have restricted the applications of lightweight SiCp/Al composites in aerospace. In this work, the controllability of the keyhole mode, nucleation mechanism, and mechanical properties of the laser-welding process are studied in detail. The extrusion effect formed by the open keyhole pushes SiC particles to the bottom of the molten pool. To observe the nucleation and growth mechanism of the Al4C3 of keyhole laser-welded SiC/2A14Al composites, the dissolution–precipitation behavior of the SiC particles and growth behavior of the Al4C3 tip were observed. Owing to its high chemical properties, Al4C3 mainly begins nucleating from the open edges of the SiC particles and its formation is mainly distributed along the direction of Al grains. Al4C3 was the main crack source and propagation path while the small-sized SiC particles hindered the crack propagation. This work innovatively regulates the keyhole mode to achieve ‘small damage breakdown’ laser welding, greatly reducing the volume fraction of Al4C3. It also provides new insight into fusion welding of SiC particle-reinforced Al matrix composites.

Improving the wear resistance of 50 wt% Si particle-reinforced Al matrix composites treated by over-modification with a Cu-P modifier

As lightweight wear-resistant structural materials, Sip/Al composites have the potential to be utilized in the automotive, aerospace, and electronics industries. However, coarsening of the Si particles occurs, thereby limiting the development of such materials. In this work, the effects of a Cu-P modifier on the microstructure and wear resistance of a 50 wt% Sip/Al composite are investigated using SEM, EBSD, TEM, nanoindentation, and reciprocating wear tests. The refining effect on Si particles in the composite is optimal when the modifier content is 3 wt%, but the wear resistance is not ideal. After over-modification, the wear performance reaches a peak with a wear rate of 3.32 × 10−7 mm2/N, realizing a reduction of 83.6 % and 21.7 % compared to the unmodified and optimal modified composites. Since the Al2Cu phase is formed in situ in the Cu-P modified composites and the strength of the Al2Cu phase is higher than that of the matrix, the performance of the over-modified composite is improved. The wear of the unmodified composite is dominated by delamination wear, accompanied by oxidation wear, adhesive wear, and abrasive wear. After modification, the composite is subject to the combined action of abrasive wear, oxidation wear, and adhesive wear. These results suggest that the over-modification of the Cu-P modifier is an effective approach to improving the wear resistance of Sip/Al composites.

Interface structure and tensile behavior of high entropy alloy particles reinforced Al matrix composites by spark plasma sintering

Aluminum matrix composites (AMCs) reinforced with AlCoCrFeNi high entropy alloy (HEA) particles were fabricated by spark plasma sintering (SPS). The interface formation between the HEA particles and Al matrix, tensile properties and fracture behavior were investigated. The interface has a two-layer structure, the interface reaction layer close to the HEA particles was Al13(CoCrFeNi)4, and the interface reaction layer near the Al matrix was composed of Al9(CoFeNi)2 and Al18Cr2Mg3. The addition of HEA particles increased the yield strength, and reduced tensile strength and elongation of the composites. The fracture occurred at the interface reaction layer near the HEA particles, exhibiting obvious brittle fracture feature. The tensile fracture mechanism of the SPSed HEA/Al AMCs can be attributed to the poor plastic deformation ability of continuously distributed Al13(CoCrFeNi)4 and aggravated degree of stress concentration at interface reaction layer close to the HEA particles.

Effect of volume fraction ratio of Ti to Al3Ti on mechanical and tribological performances of the in situ Ti–Al3Ti core–shell structured particle reinforced Al matrix composite

Effect of volume fraction ratio of Ti to Al3Ti on mechanical and tribological performances of the in situ Ti–Al3Ti core–shell structured particle reinforced Al matrix composite

Influence of high-melting particle implantation on microstructure of Al alloy thin-wall components fabricated by droplet + arc additive manufacturing

In this paper, a novel droplet + arc additive manufacturing has been proposed for fabricating particle-reinforced Al matrix composites parts with high efficiency and low cost. The tilted arc was used as heat source, Al-2219 was used as matrix, and the microscale spherical WC and Ti particles were used as reinforced phases respectively. Thin-wall parts of 8.0 vol% WCP/Al and 7.5 vol% TiP/Al were successfully fabricated. The results showed that the interface pore defects were significantly affected by the wettability between particle and liquid Al matrix. Obvious pore defects were found at WC-Al interface, but no pore defects were observed at Ti-Al interface. It is also found that the complete transition from coarse columnar grains to fine equiaxed grains can be realized by particle implantation. Compared with the Al-2219 part, the average grain size of the 7.5 vol% TiP/Al part is reduced from about 100 μm to 20.7 μm.

In-situ formation of particle reinforced Aluminium matrix composites by laser powder bed fusion of Fe2O3/AlSi12 powder mixture using laser melting/remelting strategy

In-situ preparation of particle reinforced Al matrix composites (PRAMCs) by laser powder bed fusion (LPBF) is a promising strategy to strengthen Al-based alloys. The laser-driven thermite reaction can be a practical mechanism to in-situ synthesise PRAMCs. However, the introduction of elements oxygen by adding Fe2O3 makes the powder mixture highly sensitive to form porosity and Al2O3 film during LPBF, bringing challenges to prepare dense materials. This work develops an LPBF processing strategy combined with consecutive high-energy laser melting scanning and low-energy laser remelting scanning to prepare dense PRAMCs from Fe2O3/AlSi12 powder mixture. A high relative density (98.2 ± 0.55 %) was successfully obtained by optimising laser melting (Emelting) and remelting energy density (Eremelting) to Emelting = 35 J/mm2 and Eremelting = 5 J/mm2. Results reveal the necessity to increase Emelting to improve metal liquid’s spreading/wetting by breaking up Al2O3 films surrounding molten pools; however, the high-energy laser melting produced much porosity. Low-energy laser remelting could close the resulting internal pores, backfill open gaps and smoothen solidified surfaces. Although with two-times laser scanning, the microstructure still shows fine cellular Si networks with Al grains inside (grain size 370 nm) and in-situ nano-precipitates (Al2O3, Si and Al-Fe(-Si) intermetallics). Finally, the fine microstructure, nano-structured dispersion strengthening and high-level densification strengthen the prepared in-situ PRAMCs, reaching yield strength of 426 ± 4 MPa and tensile strength of 473 ± 6 MPa. Furthermore, the results can provide valuable information to process other powder mixtures with severe porosity/oxide-film formation potential considering the evidenced contribution of laser melting/remelting strategy to densify material and obtain good mechanical properties during LPBF.

A study on the formation of multiple intermetallic compounds of friction stir processed high entropy alloy particles reinforced Al matrix composites

In this paper, AlCoCrFeNi high-entropy alloy (HEA) particles was used as the reinforcement for aluminum matrix composites fabricated by friction stir processing. HEA particles were uniformly dispersed in the aluminum matrix. The formation of multiple intermetallic compounds and interface behavior were closely evaluated. The HEA-Al interface consisted of Al13(CoCrFeNiMg)4, Al9(CoFeNi)2 and Al18Cr2Mg3, and the interface formation and growth behavior were investigated by coupling the thermodynamics and kinetics factors. The low effective Gibbs free energy of Al13(CoCrFeNiMg)4 and Al9(CoFeNi)2 phases is the thermodynamic nature of their generation at the interface. Compared with as-received Al, the fabricated composites exhibited 16.8% higher yield strength and 28.1% higher tensile strength, and the elongation was retained to 15.3%. Both of brittle and ductile fracture characteristics were observed on the surface of the HEA particles.

Ablated surface morphology evolution of SiCp/Al composites irradiated by a nanosecond laser

Metal matrix composites are widely used in aircraft and aerospace components due to their low weight and high strength. Since their processing by conventional methods is quite problematic, laser processing techniques have to be used and optimized. In this study, two SiC particle-reinforced Al matrix composites with different volume refractions and average particle sizes, namely SiC p /AA2024 (45%, 30 μm) and SiC p /AA6061 (60%, 3 μm) were irradiated by a nanosecond laser with a pulse fluence range of 0.68–6.83 J/cm 2 . The ablated surface morphology evolution was studied by SEM, and the elements' distribution was analyzed by EDS. At increased pulse fluence, the molten matrix firstly spilled from spaces between silicon carbide particles and then spread on their surfaces, forming a smooth surface in the first composite with small particle size but failing to cover SiC particles in the second one with large particle size. The SiC particles on the laser-treated surface were seriously oxidized, while distributions of Al and Si elements on the laser-ablated surfaces were independent. The dispersion of Si element increased with the fluence. The ablation threshold and surface roughness of SiC p /AA6061 was lower than those of SiC p /AA2024, in contrast to the ablation depth. The performed thermal simulation confirmed the heat conduction existence between the matrix and reinforcement, as well as the particle's volume refraction and average size effects on the heating behavior of SiC p /Al composites. The results obtained are considered instrumental in substantiating the applicability of various laser processing techniques to SiC particle-reinforced Al matrix composites. • The ablated surface evolved from aluminum pre-melting, spilling out, spreading on surface, and wrapping particles up when fluence increased. • For small-sized particle-reinforced SiC p /AA6061, the molten aluminum is easier fused overspreading small SiC particles and formed an physically integral layer. • The Si and Al chemical distributions on the ablated surface were independent, but the Si element’s dispersion increased with the pulse fluence. • The ablation threshold and surface roughness of SiC p /AA6061 was lower than those of SiC p /AA2024, in contrast to the ablation depth.

SiC particle reinforced Al matrix composites brazed on aluminum body for lightweight wear resistant brakes

Aluminum alloys are well known light-weight alloys and very interesting materials to optimize the strength/weight ratio in order to reduce automotive vehicle weight, fuel consumption and CO2 emissions; unfortunately, they are also relatively soft and therefore cannot be used for high wear applications.The aim of this work was to develop an aluminum alloy brake disc with wear-resistant SiC particle reinforced aluminum matrix composites (SiC/Al) joined on to its surface.Different approaches based on brazing or shrink fitting joining technologies were used to join SiC/Al to the aluminum alloy surface.A functional graded structure was built by brazing thin layers of aluminum matrix composites reinforced with progressively higher amount of SiC particles by using a Zn–Al based alloy as joining material. Several samples were prepared by shrink fitting and brazing: 40 mm x 40 mm x 10 mm samples and a 100 mm diameter brake disc with 68% SiC particle reinforced Al matrix surface and aluminum alloy A365 body. Tribological tests demonstrated that an aluminum alloy brake disc with wear-resistant SiC particle reinforced aluminum matrix composites (SiC/Al) brazed on its surface is a promising technical opportunity.

Tribological behavior and mechanism of high proportion of ceramic particles reinforced Al composite

Al matrix composites reinforced with ceramic particles show excellent wear resistance and have great potential to replace convectional materials in many fields. In this paper, a high proportion (∼ 60%) of large ZrO2 particles reinforced Al matrix composites were manufactured by a high pressure infiltration method. The tribological behavior of the Al/ZrO2 composite and non-reinforced Al were investigated and compared using a GCr15 ball-on-disc apparatus under dry sliding wear condition. The microstructure, elements distribution and wear track morphology were analyzed to understand their tribological behavior and wear mechanisms. The wear rate of Al is 2.0 × 10−3 mm3 N−1 m−1, while the wear rate of Al/ZrO2 composite is only 0.15 × 10−3 mm3 N−1 m−1. The experimental results showed that Al is a combined wear mechanism of adhesive wear and abrasive wear. It also proved that the high proportion of large ceramic particle reinforced composite is stable under low load wear condition. The ceramic particles were firmly embedded in the Al matrix, and no ejection or removal of the particles was observed. The results showed that the wear mechanism of this composite is mainly three body abrasion in the stable wear stage.

Effect of sintering path on the microstructural and mechanical behavior of aluminum matrix composite reinforced with pre-synthesized Al/Cu core-shell particles

The effect of different sintering techniques (vacuum sintering, hot-pressing, spark plasma sintering) on microstructure and mechanical properties were investigated for pre-synthesized core-shell (Al/Cu) particles reinforced Al matrix composites (AMC). In the first step, copper was deposited on aluminum powder particles by galvanic replacement method to synthesize Al/Cu particulates. In the next step, green compacts of Al/Cu core-shell particles reinforced AMCs were prepared by using vacuum sintering (VS), hot-pressing (HP) and spark plasma sintering (SPS). The microstructure and phase analysis of the prepared composites were performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) while their mechanical properties were evaluated by performing compression test and microhardness test. The results revealed that the sintering path has a pronounced impact on the properties of prepared composites. Depending on the consolidation technique, the deposited Cu in the core-shell structure is transformed in-situ into various types of intermetallic. This results in specially tailored microstructures with improved strength along with varying toughness depending upon the sintering technique. Mechanical characterization showed that the spark plasma sintered composite has the highest microhardness and compressive strength. To meet the current industrial requirements for structural and functional applications, this study provides a methodology to obtain tailor-made microstructure of AMCs with much improved mechanical characteristics.

In situ mechanical testing of an Al matrix composite to investigate compressive plasticity and failure on multiple length scales

SiC particle-reinforced Al matrix composites exhibit high strength, high wear resistance, and excellent high-temperature performance, but can also have low plasticity and fracture toughness, which limits their use in structural applications. This study investigates the plasticity and failure of such a composite on multiple length scales, from strain localization through a complex microstructure to the debonding of individual microparticles from the matrix. Three microscale pillars containing microstructures with different complexities and sizes/volume fraction of SiC particles were used to study the effect of these features on deformation. For the matrix, nanoscale intermetallic precipitates within the Al grains contribute most to the strengthening effect, and the Al grain boundaries are shown to be effective obstacles for preventing strain localization by dominant shear bands and, therefore, catastrophic failure. When shear localization occurs, SiC particles can then debond from the matrix if the shear band and interface are aligned. To investigate whether the interface is a weak point during catastrophic failure, a number of SiC particles were separated from the matrix with direct debonding tests, which yield an interface strength that is much higher than the critical resolved shear stress for a pillar exhibiting both shear localization and interface debonding. Therefore, the matrix-particle interface is ruled out as a possible weak point, and instead shear localization is identified as the mechanism that can drive subsequent interface debonding.