A review on developing high-performance ZE41 magnesium alloy by using bulk deformation and surface modification methods

Magnesium(Mg)alloys are generally used in light-weight structural applications due to their higher specific strength.However,the usage of these Mg alloys is limited due to their poor formability at room temperature,which is attributed to lower count of slip systems associated with the hcp crystal structure.To address these limitations,several new magnesium alloys and also many processing strategies have been developed and reported in the literature.ZE41 Mg is an alloy with significant quantities of zinc(Zn)and rare earth(RE)elements and has emerged as a promising material for aerospace,automotive,electronics,biomedical and many other industries.To make this alloy more competitive and viable,it should possess better mechanical and corrosion properties.Hence,the current paper reviews the effect of bulk mechanical processing on grain refinement,microstructural modification,and corresponding changes in the mechanical behaviour of ZE41Mg alloy.Further,the effect of various surface modification techniques on altering the surface microstructure and surface properties such as wear and corrosion are also briefly summarized and presented.This review also discusses the challenges and the future perspectives in developing high-performing ZE41 Mg alloys.

Influence of heat treatment on the machinability and corrosion behavior of AZ91 Mg alloy

In the present study,AZ91 Mg alloy was heat treated at 410℃ for 6,12 and 24 h to investigate the influence of heat treatment on machinability and corrosion behavior.The effect of soaking time on the amount and distribution of Mg 17 Al 12(β-phase)was analyzed under the optical microscope.Microhardness measurements demonstrated the increased hardness with increased heat treatment soaking time,which can be attributed to the solid solution strengthening.The influence of super saturatedα-grains on reducing the cutting force(F z)with respect to increased cutting speed was observed as prominent.The corrosion behavior of the heat treated specimens was studied by conducting electrochemical tests.Surprisingly,corrosion rate of heat treated samples was observed as increased compared with the base material.From the results,it is evident that the machinability of AZ91 Mg alloy can be improved by producing super saturatedα-grains through heat treatment but at the cost of losing corrosion resistance.

Magnesium based surface metal matrix composites by friction stir processing

Surface metal matrix composites(MMCs)are a group of modern engineered materials where the surface of the material is modified by dispersing secondary phase in the form of particles or fibers and the core of the material experience no change in chemical composition and structure.The potential applications of the surface MMCs can be found in automotive,aerospace,biomedical and power industries.Recently,friction stir processing(FSP)technique has been gaining wide popularity in producing surface composites in solid state itself.Magnesium and its alloys being difficult to process metals also have been successfully processed by FSP to fabricate surface MMCs.The aim of the present paper is to provide a comprehensive summary of state-of-the-art in fabricating magnesium based composites by FSP.Influence of the secondary phase particles and grain refinement resulted from FSP on the properties of these composites is also discussed.

Joining of AZ91 Mg alloy and Al6063 alloy sheets by friction stir welding

In the present work,the effect of process parameters on joining of AZ91 Mg alloy and Al6063 aluminum alloy sheets during friction stir welding(FSP)was studied.A successful joint was achieved at 1100 r.p.m.tool rotational speed and 25 mm/min tool travel speed.Combination of tool rotational speed and tool travel speed has observed a profound effect on the material flow mechanisms at the nugget zone.From the microstructural studies,the joint formation was observed as mainly due to mechanical mixing of the materials.The level of metallurgical continuity at the nugget zone was observed as poor and a sharp interface at the joint was noticed.The microhardness measurements across the weld joint also revealed the lack of establishment of a perfect metallurgical bonding.X-ray diffraction analysis of weld zone showed presence of both magnesium and aluminum.Hence from the preliminary observations,it can be understood that the joining of AZ91 Mg alloy and Al6063 alloy can be achieved by FSP;however,complex issues in material mixing still need further investigations.

An investigation on the hardness and corrosion behavior of MWCNT/Mg composites and grain refined Mg

In the present work,multi walled carbon nanotubes(MWCNT)reinforced magnesium(Mg)matrix composite was fabricated by friction stir processing(FSP)with an aim to explore its mechanical and electrochemical behavior.Microstructural observations showed that the thickness of the produced composite layer was in the range of 2500μm.FSP resulted uniform distribution of CNT near the surface while agglomerated layers in the subsurface.Grain refinement of Mg achieved by FSP improved the hardness but significant enhancement in the hardness value was observed for FSPed MWCNT/Mg composites.Potentiodynamic polarization studies revealed that the increase in corrosion current density was observed for MWCNT/Mg composite compared with grain refined Mg and pure Mg,implying the significance of secondary phase(MWCNT)in decreasing the corrosion resistance of the composite.

Machining characteristics of fine grained AZ91 Mg alloy processed by friction stir processing

AZ91Mg alloy was considered and friction stir processing(FSP)was adopted to achieve grain refinement to investigatethe effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds.Super saturatedAZ91Mg alloy was obtained after FSP and the grain refinement was achieved from(166.5±8.7)μm to(21.7±13.5)μm.Surprisingly,hardness reduced for FSP AZ91Mg alloy(88.95±6.1)compared with AZ91alloy(108.2±15.6),which was attributed to the reducedsecondary phase.However,the mean cutting force for FSP-treated(FSPed)AZ91Mg alloy was marginally increased.The edgedamage of the drilled holes was lower for FSPed AZ91Mg alloy compared with unprocessed AZ91Mg alloy.Hence,it can beunderstood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achievedin machining of AZ91Mg alloy.

Developing Mg–Zn surface alloy by friction surface allosying: In vitro degradation studies in simulated body fluids

A new variant of friction-assisted process named friction surface alloying(FSA)for developing surface alloys was demonstrated in the present work.In FSA,the dispersed phase is melted and allowed to react with the matrix material to form an alloy at the surface of a metallic substrate.In the present work,magnesium(Mg)sheets and zinc(Zn)powder were selected,and fine grained(~3.5μm)Mg–Zn surface alloy with improved hardness was produced by FSA.X-ray diffraction studies confirmed the formation of intermetallic phases of Mg and Zn at the surface.From the in vitro degradation studies carried out by immersing in simulated body fluids,a lower corrosion rate was observed for the Mg–Zn surface alloy compared with pure Mg.The surface morphologies after immersion studies indicated large degraded areas on the base Mg compared with Mg–Zn.The results demonstrate the potential of FSA in developing Mg-based surface alloys without melting the substrate to impart better surface properties.

Review of the crushing response of collapsible tubular structures

Studies on determining and analyzing the crushing response of tubular structures are of significant interest,primarily due to their relation to safety.Several aspects of tubular structures,such as geometry,material,configuration,and hybrid structure,have been used as criteria for evaluation.In this review,a comprehensive analysis of the important findings of extensive research on understanding the crushing response of thin-walled tubular structures is presented.Advancements in thin-walled structures,including multi-cell tube,honeycomb and foam-filled,multi wall,and functionally graded thickness tubes,are also discussed,focusing on their energy absorption ability.An extensive review of experimentation and numerical analysis used to extract the deformation behavior of materials,such as aluminum and steel,against static and dynamic loadings are also provided.Several tube shapes,such as tubes of uniform and nonuniform(tapered)cross sections of circular,square,and rectangular shapes,have been used in different studies to identify their efficacy.Apart from geometric and loading parameters,the effects of fabrication process,heat treatment,and triggering mechanism on initiating plastic deformation,such as cutouts and grooves,on the surface of tubular structures are discussed.