Fabricating Process of Stainless Steel Interpenetrating Phase Composites and Their Friction and Wear Properties and Cutting Performance

Author:Yao Bi Bo

Supervisor:zhou zhao yao

Database:Doctor

Degree Year:2019

Download:19

Pages:177

Size:9830K

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Interpenetrating phase composite(IPC)is a new type of composite structure with three-dimensional interconnectivity of both phases.The metal-polymer composite materials can be used to synthesize the properties of components,that is,the plasticity and strength of metal and the energy absorption of polymer.ZA alloys have good mechanical and tribological properties but those properties decrease significantly with increasing temperature to above 100 ℃.It is demonstrated that the adding of reinforcements can improve the properties of ZA alloy at high temperature.In order to produce polymer matrix IPCs with good mechanical and energy absorption properties and zinc matrix IPCs with good mechanical and tribological properties at elevated temperature,the novel stainless steel-unsaturated polyester resin IPCs and stainless steel-zinc alloy IPCs are fabricated.The anisotropic microstructures and mechanical properties of those novel IPCs are analyzed.The sliding wear and friction properties at room and elevated temperatures,and cutting performance of the stainless steel fiber/ZA8 IPCs are investigated.The 304 stainless steel fibers fabricated by cutting stainless steel ropes into segments with rotary multi-cutters are pressed and then solid-sintered to gain the stainless steel fiber preforms.Enwound stainless steel meshes are also used as preforms.The novel stainless steel/resin IPCs are fabricated by vacuum infiltration and the novel stainless steel/ZA8 zinc alloy IPCs are produced by squeeze casting.The structure of the stainless steel/ZA8 zinc alloy IPC is anisotropy and consists of numerous small and particulate first solidified primary β dendrites distributed in an eutectic matrix(α + η).η phases nucleate on the prior β dendrites,and form thick coating as "haloes" on them.The eutectic matrix(α + η)has various morphologies in different areas,i.e.,lamellar and granular structures.The effects of stainless steel fiber fractions and diameters,sampling directions on the mechanical properties of stainless steel fiber/resin IPCs are investigated.The mechanical properties are anisotropy and finer fiber can improve the mechanical properties of the novel IPCs.Sawtooth-like fluctuations can be noted during plastic deformation of tension tests.The tensile strength is higher and elongation at maximum stress of the IPC in the in-plane direction is larger than those in the through-thickness direction.Uniaxial tensile strength,elasticity modulus and elongation at maximum stress of the IPCs increase with increasing fiber fractions in both in-plane and through-thickness directions.The compression processes of the IPC specimens in the in-plane direction exhibit distinct elastic-plastic behavior(three deformation stages),i.e.,an elastic stage,a quasi-platform stage that occurs after yielding,and a final densification stage.While the compression process of the IPC in the through-thickness direction does not have a long quasi-platform stage.The pseudo-platform stress and elasticity modulus of the IPC increase with increasing fiber fractions.Compared with the in-plane direction,the IPCs have higher pseudo-platform stress and strain in the through-thickness direction.The peak energy absorption efficiency of the IPC is slightly lower than that of the preform.The peak energy absorption efficiency of the IPC decreases with increasing fiber fractions in a certain range.Compared with the in-plane direction,the IPCs have a higher three-point bending strength and flexural modulus but a lower displacement in the through-thickness direction.Flexural strength increases nearly linearly with increasing fiber fractions in both directions.The Charpy impact toughness of the metal-resin IPCs in both directions is higher than that of the preform and increases with increasing fiber fractions.The Charpy impact toughness of the IPC in the through-thickness direction is higher than that of the in-plane direction.The coefficients of thermal expansion of alloy and the stainless steel fiber/ZA8 zinc alloy IPCs increase with increasing temperatures.The coefficient of thermal expansion of the IPC is lower than that of ZA8 zinc alloy and decreases with increasing fiber fractions.The hardness of both sections of the IPC increases with the increase of fiber volume fractions.The hardness of the IPC is anisotropy.Finer fiber can improve the hardness and decrease the coefficient of thermal expansion of the IPC.The effects of stainless steel fiber fractions and diameters,sampling directions on the mechanical properties of the stainless steel fiber/ZA8 zinc alloy IPCs are investigated.During the uniaxial compression process at room temperature,the stress of the IPC decreases sharply and happens to fracture after reaching compressive strength,while the stress of ZA8 alloy continue to increase after plastic deformation and no cracks appear in the sample.The compressive yield strength and elasticity modulus of the IPC are higher than those of ZA8 zinc alloy,and they increase with a increase of fiber fractions.The compressive strength and elongation at maximum stress of the IPCs in the through-thickness direction are higher than those in the in-plane direction.The IPC in the radial direction has higher steady stress than that of longitudinal direction during high temperature compression.The steady stress of the IPC increases with increasing fiber fractions and is higher than that of squeeze-cast ZA8 alloy.The Charpy impact toughness of the IPCs exhibits slightly anisotropy and the values of the impact of the IPCs in the longitudinal directions are slightly higher than those in the radial directions.The impact toughness of the IPCs of the ZA8 alloy is improved after adding fibers and the impact toughness of the IPC increases with increasing fiber fractions.The effects of stainless steel wire fractions and diameters,sampling directions and whether the preform is sintered on the tensile and compressive properties of enwound stainless steel wire mesh/ZA8 zinc alloy composites are investigated.The tensile strength and elongation at maximum stress of the composites increase with increasing wire fractions but are lower than those of ZA8 zinc alloy.The tensile properties of the composites in the longitudinal directions are better than those of radial directions.The tensile strength decreases after sintering the enwound wire mesh preform.It is interesting to find that the tensile property of the composites at high temperature is higher than those of ZA8 zinc alloy when fiber fraction reaches a certain value.The compressive strength and elongation at maximum stress of the composites in longitudinal directions at room temperature are higher than those of the composites in radial directions.After sintering the enwound wire mesh preform,compressive strength and elongation at maximum stress of the composites are improved but the yield strength decreases.The compressive strength and elongation at maximum stress of the composites increase with a increase of wire fractions.Cross-cubic model and circular cross-section spiral wire framework model are put forward to simulate the uniaxial compressive behaviors of the stainless steel-resin and stainless steel-zinc alloy IPCs.The two models are suitable for simulating the elastic stage and initial plastic deformation,while the finite numerical results do not match well with the experimental results when the strain is larger.The sliding wear and friction behaviors of the stainless steel fiber zinc alloy IPCs at different temperatures(room temperature and 120 ℃)are investigated.Compared with unreinforced alloy,the composites exhibit lower friction coefficients at both room and elevated temperatures.The IPCs in the longitudinal direction have better wear resistant properties.At room temperature,the friction coefficients and wear rates of the IPCs decrease with increasing fiber fraction,but the changes are opposite when the fiber fractions are too high.There is the best fiber fraction(35.98 vol% in this paper)that the wear rate is lowest and is lower than that of ZA8 alloy.A higher applied load leads to a higher wear rate of the IPC.At 120 ℃,the wear rate of the composite is significantly lower than that of ZA8 zinc alloy,and decreases firstly and then increases with increasing fiber fractions.Examination of worn surfaces reveals that predominating wear mechanisms for the ZA8 alloy are from severe delamination wear with slight abrasive wear at room temperature to severe abrasive wear and plastic deformation at 120 ℃,while the IPCs present predominated abrasive(groove)wear with slight adhesive wear at both temperatures.The dry cutting performance of zinc alloy and its composites is studied.The cutting force-time curves of the IPCs fluctuate severer than those of the zinc alloy,and the fluctuation degree increases with the increase of the fiber fractions,while the cutting force of the IPC is lower than that of the zinc alloy.The cutting force of the IPC varies with cutting speed,feed rate,cutting depth and is different from those of zinc alloy.The fiber fraction has a complicated effect on the cutting force.At low speed,the cutting force of the IPC with higher fiber fraction has a lower cutting force,but the cutting force is higher when the speed is too high.The chips of zinc alloy and the IPC consist of free surfaces and smooth back surfaces.The chips of zinc alloy are sawtoothed strips,while the chip of the IPC is a sawtoothed C chip.The surface morphologies and tool wear mechanisms after machining ZA8 alloy and the IPCs are different.The surface of the machined IPC is rougher than that of machined ZA8 alloy.