Effect of HEA/Al composite interlayer on microstructure and mechanical property of Ti/Mg bimetal composite by solid-liquid compound casting

In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can effectively inhibit the interfacial diffusion between Al and Mg,which is conducive to the formation of solid solution,especially when the thickness of HEA is 800 nm.With the increase of casting temperature from 720 ℃ to 730 ℃,740℃,and 750 ℃,α-Al(Mg),α-Al(Mg)+Al3Mg2,Al3Mg2+Al12Mg17,and Al12Mg17+δ-Mg are formed at the interface of Ti/Mg bimetal,respectively.When the thickness of the HEA layer is 800 nm and the pouring temperature is 720 ℃,the bonding strength of the Ti/Mg bimetal can reach the maximum of 93.6 MPa.

Deformation Characteristics and Mechanical Properties of Ti/Al Bimetallic Composite Materials Fabricated by Wire Plus Arc Additive Manufacturing

We focused on Ti/Al composite materials fabricated by wire and arc addictive manufacturing,and the microstructure and interface characteristics of them before and after hot compression deformation were compared.After compression deformation,allαstructures of titanium were compacted with the emergence of Widmanstatten structures.Coarsened coloniesαof titanium were elongated and waved along the original growth direction,resulting in anisotropy of grains.Pores and Ti/Al intermetallic compounds of aluminum are significantly decreased after hot compression.Meanwhile,a good bonding interface between titanium and aluminum is obtained after hot compression,and the element diffusion is more intense.In addition,the mechanical properties and fracture behaviors of Ti/Al composite material with different clad ratio that is defined as the ratio of the thickness of titanium to that of the Ti/Al composite material are investigated by uniaxial tensile test.The experimental results show that the ultimate tensile strength of Ti/Al composite material is between that of single deposited titanium and aluminum,while the elongation of Ti/Al composite material with low clad ratio is lower than that of single aluminum due to the metallurgical reaction.As the clad ratio increases,the two component layers are harder to separate during deformation,which is resulted from the decrease of the inward contraction stress of three-dimensional stress caused by necking of aluminum.This work may promote the engineering application of Ti/Al bimetallic structures.

Microstructural characteristics and mechanical properties of bronze/steel bimetallic laminated composite prepared by protective atmosphere casting process

The bonding quality of bronze/steel bimetallic laminated composite is the key factor to whether it can be used in poor working conditions.In this study,bimetallic billets were prepared by the protective atmosphere casting process.The microstructural characteristics,mechanical properties and interface bonding mechanism of the bronze/steel bimetallic composites were analyzed comprehensively through a series of microstructure analysis(inicluding OM,SEM,and EDS)and mechanical properties tests.The experimental results demonstrate that the vaporization of lead(Pb)element in the bronze is only 0.4%in weight,and alloy elements are diffused into both sides at the interface.Moreover,the hardness in the bronze region exceeds 100.0 HV which indicates excellent wear resistance.Tensile and shear tests indicate that the fractures mainly occur on the bronze side with the interaction of the brittle fracture of Pb particles and the ductile fracture of Cu-Sn solid solution.The maximum tensile strength and shear strength reach 204.0 MPa and 211.0 MPa,respectively.These results demonstrate that the protective atmosphere casting process is applicable for the preparation of bronze/steel bimetallic laminated composite with high quality.

High strength bimetallic composite material fabricated by electroslag casting and characteristics of its composite interface

Bimetallic composite material of bainitic steel and PD3 steel was produced with electroslag casting process, and element distribution of its composite interface was investigated by theoretical calculation and energy dispersive spectrometer(EDS). Results show that the tensile strength(1,450 MPa), hardness(HRC 41-47) and impact toughness(94.7J·cm^(-2)) of bainitic steel were comparatively high, while its elongation was slightly low(4.0%). Tensile strength(1,100 MPa), hardness(>HRC 31) and elongation(7.72%) of the interface were also relatively high, but its impact toughness was low at 20.4 J·cm^(-2). Results of theoretical calculation of the element distribution in the interface region were basically consistent with that of EDS. Therefore, electroslag casting is a practical process to produce bimetallic composite material of bainitic steel and PD3 steel, and theoretical calculation also is a feasible method to study element distribution of their interface.

Influence of mandrel-cores filling on size effect of cross-section distortion of bimetallic thin-walled composite bending tube

Two new size factors of cross-section hollow coefficient and bending degree are introduced to reveal the size effect of bending forming of bimetallic composite tube.Hollow coefficient and bending degree can limit the commonly used bent tube to the size description range of(0,2.00).The evolution laws of the cross-section distortion forms in the hollow coefficient-bending degree interval are revealed as well as the action of the mandrel-cores on the size effect.Results show the mandrel-cores filling can expand the forming limit of the bent tube,but also bring two other forming defects of wrinkle and rupture.The identification factor(hollow coefficient multiply bending degree)provides a method for querying the cross-section distortion forms of all composite bending tubes.In the identification factor interval(0,1.00),the distribution area of bending forming defects of the composite tube is continuous.The thin-walled composite bending tube collapses when identification factor in(0,0.39),wrinkles when identification factor in[0.39,0.50),and ruptures when identification factor in[0.50,1.00).The mathematical model of size effect is derived,by which the average cross-section distortion rate is found to distribute like a radial leaf in the hollow coefficient-bending degree qualified forming space.The best forming zone is hollow coefficient 0.46-0.68,and bending degree 0.25-0.47.

Effect of Extrusion Combination Types on Microstructure and Mechanical Properties of the AZ31/GW103K Bimetallic Composite Plates

The AZ31/GW103 K bimetallic composite plates were prepared by co-extrusion of different combination types(sandwich extrusion type and double semicircle extrusion type),and effects of different extrusion combination types on the microstructure and mechanical properties of bimetallic composite plates were systematically investigated.The results show that both the AZ31/GW103 K bimetallic composite plates prepared by different extrusion combination types have good metallurgical bonding,and changing the combination type does not affect the thickness of the interfacial transition layer of composite plates.Compared with the monolithic AZ31 and GW103 K extruded plates,co-extrusion can promote the dynamic recrystallization(DRX)of AZ31 and GW103 K components in composite plates,and double semicircular extrusion type has a better promotion effect on the DRX than sandwich extrusion type.In addition,the texture of AZ31 in both monolithic AZ31 and AZ31/GW103 K/AZ31(A/G/A)plates is a typical(0002)basal texture,while that in the AZ31/GW103 K(A/G)composite plate shifts to the tangent direction(TD)of extruded plate.Compared with the monolithic AZ31 extruded plate,both the yield strength and tensile strength of A/G and A/G/A bimetallic composite plates are significantly improved.The strength of A/G/A composite plate is higher than that of A/G composite plate,but its elongation is worse.Meanwhile,co-extrusion reduces the dislocation density of AZ31 and GW 103 K components in composite plates,and different extrusion combination types also affect the dislocation density.