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Effects of annealing treatment on properties of CoCrFeNiTiAlxmulti-componentalloys

Effects of annealing treatment on properties of CoCrFeNiTiAlxmulti-componentalloys
Effects of annealing treatment on properties of CoCrFeNiTiAlxmulti-componentalloys

Effects of annealing treatment on properties of CoCrFeNiTiAl x multi-component alloys

Kuibao Zhang a ,*,Zhengyi Fu b

a State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials,Southwest University of Science and Technology,Mianyang 621010,China b

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology,Wuhan 430070,China

a r t i c l e i n f o

Article history:

Received 2December 2011Received in revised form 8March 2012

Accepted 26March 2012

Available online 28May 2012Keywords:

C.Heat treatment

B.Mechanical properties A.Intermetallics B.Fracture mode B.Work-hardening

a b s t r a c t

CoCrFeNiTiAl x (x :molar ratio)multi-component alloys were prepared by vacuum arc-melt casting and the as-cast alloys were subsequently heat treated at 1000 C for 2h.Effects of Al content and annealing treatment on the mechanical,electrical and magnetic properties were investigated.The addition of Al exhibits signi ?cant in ?uence on mechanical properties of the as-cast and the as-annealed alloys,which is actually induced by the evolution of phase composition.The prepared alloys demonstrate good resis-tance against anneal-softening,as most of the as-annealed alloys show even higher hardness than the as-cast ones.As-annealed Al 0possesses excellent mechanical property with high compressive strength of 2.46GPa and strain rate of 12.7%.Strengthening mechanism is revalued in this study as phase compo-sition is considered as a critical factor.The as-cast and the as-annealed CoCrFeNiTiAl x alloys exhibit high electrical resistivity and novel magnetic properties as well.

ó2012Elsevier Ltd.All rights reserved.

1.Introduction

High-entropy alloys (HEAs),a newly developed alloy system proposed by Yeh and Cantor [1e 3],have attracted considerable attentions in recent years.HEAs,which are de ?ned as alloys con-taining at least ?ve principal elements with atomic concentration between 5%and 35%,have broken the traditional alloy design concept based on one or two principal components [1e 5].It was reported that HEAs usually formed simple solid-solutions rather than many complex phases under proper composition design [6e 10].Meanwhile,high lattice distortion and nano-scale precipi-tates readily form in HEAs,which are attributed to the effect of high mixing entropy such as random solid-solution and sluggish diffu-sion [6,7,11].Relevant results demonstrate that HEAs are promising materials for engineering applications due to their multiple excel-lent properties,such as high hardness,high strength,good thermal stability,special thermophysical and magnetic properties,as well as outstanding resistances against wear,oxidation and corrosion etc.[9e 16].

Selection and composition of constituent elements are essential considerations in alloy design as the microstructure and phase composition will be de ?nitely affected by these factors and

eventually re ?ected in the physical properties [17].Addition of Al was identi ?ed to exert signi ?cant effects on the structural forma-tion and mechanical properties of HEAs due to its relatively larger atomic radius [18e 20].The excellent mechanical properties of HEAs are commonly deemed as the strengthening effects of solid-solution and nanoprecipitation [13].In our previous report,CoCr-FeNiTiAl x alloys were prepared by arc-melt casting and effects of Al addition on the structure and mechanical properties were studied [21].De ?nite phase composition of these alloys was characterized by deep-going analysis of the research results,which con ?rmed that the as-cast and as-annealed CoCrFeNiTiAl x alloys contained not only multi-component solid-solutions but also many intermetallic phases [22].Meanwhile,the ordered BCC phase in the widely researched CoCrFeNiCuAl alloy was determined as NiAl interme-tallic phase [23].Thus,the conclusions about the strengthening mechanism of HEAs need to be revalued as there are many complex phases formed in many HEAs systems.

In this study,CoCrFeNiTiAl x alloys with varied Al content were fabricated by vacuum arc-melt casting.As thermal stability is an important parameter for industrial applications [24,25],the as-cast CoCrFeNiTiAl x alloys were heat treated at 1000 C for 2h to study the evolution of physical properties after annealing.The annealing condition was con ?rmed according to the previous study that annealing at 1000 C for 2h exerted remarkable in ?uence on the structural and properties evolution of CoCrFeNiCuAl alloy [26].The effects of Al content and annealing treatment on properties of the

*Corresponding author.Tel./fax:t868162419201.

E-mail address:xiaobao0320@https://www.sodocs.net/doc/52100190.html, (K.

Zhang).

Contents lists available at SciVerse ScienceDirect

Intermetallics

journal homepage:www.elsev https://www.sodocs.net/doc/52100190.html,/locat

e/intermet

0966-9795/$e see front matter ó2012Elsevier Ltd.All rights reserved.doi:10.1016/j.intermet.2012.03.059

Intermetallics 28(2012)34e 39

as-cast and the as-annealed CoCrFeNiTiAl x alloys were investigated from extensive measurement of their mechanical,electrical and magnetic properties.Strengthening mechanism of these alloys was explored as well based on intensive analysis of their de?nite phase compositions,microstructure and mechanical properties.

2.Experimental details

Alloy ingots with nominal composition of CoCrFeNiTiAl x(x: molar ratio,x?0,0.5,1.0,1.5,2.0,denoted as Al0,Al0.5,Al1.0,Al1.5, Al2.0respectively)were fabricated using vacuum arc-melt casting under a Ti-gettered high-purity Ar atmosphere with a water-cooled copper mould.Elemental metal sheets and granules with purity higher than99wt%were employed as the raw materials to facilitate the ignition of arc-melt casting.The ingots were remelted four times and?ipped after each melt to improve the chemical homogeneity.The prepared samples were subsequently heat treated at1000 C for2h in?owing argon atmosphere.Room temperature compressive properties of the as-cast and as-annealed CoCrFeNiTiAl x alloys were tested on a materials testing machine(Instron,MTS810)using F4?10mm cylindrical speci-mens with4mm in diameter and10mm in height under a loading speed of1mm/min.Three compression tests were performed to obtain the average value.The samples for compression testing were prepared by electric-discharged cutting from the cast buttons.Surfaces of the machined samples were polished on600 grit sand papers to eliminate the stress concentration.Fracture surfaces of the as-cast Al0and Al1.5alloys after compression tests were observed by scanning electron microscope(SEM,Hitachi-S3400N).High temperature compressive testing of the as-cast alloys was conducted at800 C in a thermal-simulated materials testing machine(Gleeble-3500)using F4?10mm cylindrical specimens under loading speed of1mm/min and heating rate of 10 C/min.Hardness measurements were conducted using a Visk-ers hardness tester(Wolpert-430SVD)under a load of49N and holding time of15s.Densities of the as-cast and as-annealed alloys were measured from Archimedes method using water as the immersion medium.Electrical resistivity of these samples was tested by an SZT-2four-probe instrument using rectangular specimens of15?15?2mm in dimension.At least seven tests were conducted to obtain the average values of Viskers hardness, density and electrical resistivity.Magnetic properties of the as-cast and as-annealed alloys were analyzed on the ADE Model4HF vibrating sample magnetometer(VSM)with sample dimension of F5?2mm.3.Results and discussion

3.1.Mechanical properties of as-cast CoCrFeNiTiAl x alloys

Fig.1presents the room temperature and800 C compressive true stress e strain curves of as-cast CoCrFeNiTiAl x alloys.The as-cast alloys demonstrate two kinds of fracture model as shown in Fig.1(a).The as-cast Al0and Al1.5alloys exhibit plastic-like defor-mation with high capacity of work-hardening.The Al1.5alloy is broken under compressive strength of2.11GPa,which is followed by a yielding platform arised at1.84GPa in the compressive true stress e strain curve.The true stress e strain curves of Al0.5,Al1.0and Al2.0alloys exhibit a simple linear relationship,which is a testimony of brittle deformation[27].These alloys also show medium or low compressive strength,which can be associated with their relatively low work-hardening capacity.The detailed mechanical properties of as-cast CoCrFeNiTiAl x alloys,such as elastic modulus(E), compressive strength(s b),ductility(3p)and Viskers hardness,are calculated and listed in Table1.The value of E,which represents loading requirement of unit deformation for the tested sample,is measured from the testing of compressive stress e strain.Al1.0alloy possesses the highest value of elastic modulus and compressive strength,147.6GPa and2.28GPa respectively,while the strain rate is as low as4.4%.Al0alloy demonstrates excellent integral prop-erties with high strength of2.02GPa and good ductibility of8.3%.

Mechanical properties of metallic materials are mainly deter-mined by their phase compositions and microstructure[28].It has been studied in our previous research that all as-cast CoCrFeNiTiAl x alloys exhibit cast-dendrite morphology with similar nano-precipitations and elemental segregation[22].Therefore,the effects of phase composition on the mechanical properties should be emphasized in this alloy system.Multi-component FCC solid-solution was con?rmed as the main phase in the as-cast Al0

alloy https://www.sodocs.net/doc/52100190.html,pressive true stress e strain curves of as-cast CoCrFeNiTiAl x alloys under different conditions:(a)room temperature and(b)800 C.

Table1

Mechanical properties of as-cast CoCrFeNiTiAl x multi-component alloys.

Alloy Elastic

modulus E(GPa)Room

temperature

800 C Viskers

hardness(HV) s b(GPa)3p(%)s b(GPa)3p(%)

Al0104.6 2.028.30.9124.8597.6

Al0.5106.8 1.60 3.50.8624.9673.3

Al1.0147.6 2.28 4.40.8039.8721.9

Al1.5133.4 2.11 6.80.7532.3654.4

Al2.093.5 1.03 2.8e e629.9

K.Zhang,Z.Fu/Intermetallics28(2012)34e3935

with BCC solid-solution and CoTi 2as the minor phases.The major phase transforms to stabilized BCC solid-solution as Al content increasing gradually.The as-cast Al 1.0alloy is mainly composed of (a -Fe,Cr)-based BCC solid-solution with a minority of CoTi 2-,FeTi-and NiAl-based intermetallic phases.According to the basic struc-tural factor,the crystal structure with more slip system results in lower lattice friction during dislocation motion and higher ductility [29].FCC structure possesses 48slip systems,which is more than that of the BCC structure with 12slip systems.Thus,the FCC-structured sample should be in higher ductibility and lower strength than the specimen with BCC crystal structure.As the main phase of as-cast Al 1.0alloy is BCC solid-solution,it exhibits higher strength and lower ductibility over the as-cast Al 0alloy with FCC solid-solution as the major phase.On the other hand,the strain rate of as-cast Al 1.0alloy is further restrained as there are more precipitation of intermetallic compounds besides the BCC solid-solution.High strength and good ductibility are obtained concur-rently in the as-cast Al 1.5alloy,which can be attributed to the simple phase composition of (a -Fe,Cr)-based BCC solid-solution and NiAl-based intermetallic phase.The low values of compres-sive strength and ductibility in as-cast Al 2.0alloy,1.03GPa and 2.8%,may be associated to the excessive addition of Al.As Al exhibits intrinsic lower strength than other component elements,its surplus addition would de ?nitely reduce the mechanical strength.On the other hand,the increment of Al addition leads to the formation of supersaturated solid-solutions,which would increase the rate of lattice distortion and inhibit the plastic deformation of this alloy.Viskers hardness of the as-cast CoCrFeNiTiAl x alloys can also be explained by the phase composition.Al 0alloy exhibits the lowest Viskers hardness of 597.6HV as the alloy is mainly consisted of FCC solid-solution.On the contrary,Al 1.0alloy shows the highest Viskers hardness of 721.9HV because the alloy is mainly composed of BCC solid-solution with precipitation of intermetallic compounds.

High temperature performance is an important consideration for industrial applications of metallic materials.Many metallic components are utilized under heat radiation and even some alloys are specially designed for high temperature applications.Thus,it is necessary to explore the high temperature properties of HEAs.In this study,compressive properties of as-cast CoCrFeNi-TiAl x alloys were measured at 800 C with the true stress e strain curves demonstrated in Fig.1(b)and the detailed data calculated in Table 1.Unfortunately,the data of as-cast Al 2.0alloy were failed to be obtained in this test.It is obvious that the compressive strength under 800 C is much lower than the value obtained at room temperature.Al content exhibits ignorable effect on the compressive strength as all the as-cast alloys demonstrate comparable compressive strength around 0.85GPa under 800 C.Al 0alloy shows the highest strength of 0.91GPa while Al 1.5alloy shows the lowest value of https://www.sodocs.net/doc/52100190.html,pared with the strain rates obtained under room temperature,the values obtained at 800 C decrease dramatically.The alloys demonstrate compressive strain between 24.8%and 39.8%at 800 C with no fracture performance in the stress e strain curves as shown in Fig.1(b).It is reported that temperature exerts a signi ?cant in ?uence on the yielding performance of engineering materials,especially under medium and low temperature range [29].The evolution of yielding performance under high temperature is actually obstruction re ?ection of dislocation slip.The crystal lattice is activated and the atomic bonding strength is lowered under elevated temperature,which makes the dislocation slip readily performs.Thus,the compressive strength decreases dramatically while the ductibility increases substantially.

Fig.2displays SEM images of the fracture surface for as-cast Al 0and Al 1.5alloys after compressive testing.The fracture model and crack origination can be found from intensive observation of the fracture surface as it faithfully records the whole fracturing process of crack initiation,extension and eventually separation [27].There are large amount of small cavities and dimples existed in the fracture surface of as-cast Al 0alloy as labeled and displayed in Fig.2(a).This kind of fracture surface can be regarded as typical shearing fracture of microvoid aggregation,which is usually clas-si ?ed as ductile fracture.The ductile fracture of as-cast Al 0alloy is attributed to its phase composition with FCC solid-solution as the major phase while BCC solid-solution and CoTi 2as the minor phases.Origination and extension of dimples are related with second phase and nano-scaled precipitates in the tested sample.Morphology of the fracture surface changes greatly when Al is added as the as-cast Al 1.5alloy is representatively explored in Fig.2(b).The fracture surface is mainly composed of planar facets,which are actually cleavage steps originated from dislocation movements.Cleavage is usually classi ?ed as brittle fracture [27].There are also tearing edges existed in the fracture surface of as-cast Al 1.5alloy.The combination of cleavage steps and tearing edges is the testimony of quasi-cleavage,which is a mixing result of cleavage and microvoids aggregation.Quasi-cleavage is the inter-mediate fracture model across ductile fracture and brittle fracture.From the above analysis,we can deduce that as-cast Al 0alloy is in ductile fracture and Al 1.5in quasi-cleavage fracture while Al 0.5,Al 1.0and Al 2.0are in brittle

fracture.

Fig.2.SEM images for the fracture surfaces of as-cast alloys:(a)Al 0and (b)Al 1.5.

K.Zhang,Z.Fu /Intermetallics 28(2012)34e 39

36

3.2.Mechanical properties of as-annealed CoCrFeNiTiAl x alloys Fig.3presents the compressive true stress e strain curves of as-annealed CoCrFeNiTiAl x alloys measured at room temperature with the obtained values listed in Table 2.The as-annealed Al 0alloy shows excellent mechanical properties with high compressive strength of 2.46GPa and strain rate of 12.7%,which are higher than the values of as-cast Al 0alloy (2.02GPa and 8.3%).The high elon-gation of 12.7%for as-annealed Al 0is due to the role of its FCC matrix.The good ductibility may also be related with desolution of the solid-soluted atoms after annealing treatment,which induces the release of distortion energy and reduces the obstruction of dislocation movement.The high strain rate promotes the work-hardening capacity and enhances the compressive strength.On the

other hand,intermetallic phases,such as CoTi 2,FeTi and unknown phases [22],precipitate in the as-annealed Al 0alloy and the strength is enhanced further.As-annealed Al 0.5alloy exhibits the highest compressive strength of 2.59GPa for the as-annealed CoCrFeNiTiAl x alloys,as well as a medium strain rate of 7.2%.The compressive strength decreases abruptly to 1.54GPa as Al content increases to x ?1.0.The same phenomenon can also be observed for the as-annealed Al 1.5and Al 2.0alloys.The as-annealed Al 1.5alloy shows the lowest strength of 1.19GPa while the Al 1.0alloy demonstrates the lowest ductibility of 4.1%.The reduction of compressive strength for the as-annealed alloys with high Al content may be related with the intrinsic weakness of Al and the decreased amount of intermetallic phases.However,the decrement of strain rate for these alloys can hardly be explained by traditional metallurgy theories.In the compressive testing,the obtained results are greatly in ?uenced by the friction resistance between the end surfaces of the cylindrical samples and the punch surfaces of the testing machine.This in ?uence may cause the testing results greatly deviated from the real values.The mechanical property evolution of as-annealed alloys needs to be investigated intensively in the future study.

Viskers hardness of the as-annealed CoCrFeNiTiAl x alloys is lis-ted in Table 2and the hardness comparison of the as-cast and as-annealed alloys is plotted in Fig.4(a).All the as-annealed alloys exhibit high Viskers hardness over 600HV.The as-annealed Al

1.0

https://www.sodocs.net/doc/52100190.html,pressive true stress e strain curves of as-annealed CoCrFeNiTiAl x alloys.

Table 2

Mechanical properties of as-annealed CoCrFeNiTiAl x multi-component alloys.Alloy

s b (GPa)

3p

(%)

Viskers

hardness (HV)Density (g/cm 3)As-cast As-annealed Al 0 2.4612.7607.97.527.55Al 0.5 2.597.2713 6.67 6.67Al 1.0 1.54 4.1735.7 6.69 6.71Al 1.5 1.19 6.1606.3 6.37 6.41Al 2.0 1.36

6.3

653.7

6.12

6.18

https://www.sodocs.net/doc/52100190.html,parison of the as-cast and as-annealed CoCrFeNiTiAl x alloys:(a)Viskers hardness and (b)

density.

Fig.5.Electrical resistivity of as-cast and as-annealed CoCrFeNiTiAl x alloys.

K.Zhang,Z.Fu /Intermetallics 28(2012)34e 3937

alloy shows the highest hardness of 735.7HV.Viskers hardness re ?ects stiffness of the tested materials and shows direct propor-tion with the elastic modulus.This relationship is testi ?ed in the as-cast alloys as the as-cast Al 1.0alloy exhibits the highest elastic modulus.It can be concluded from the hardness comparison that CoCrFeNiTiAl x alloys reveal excellent anneal-softening resistance as most of the as-annealed alloys (except for Al 1.5)show higher Viskers hardness over the as-cast ones.From previous reports,the high strength of HEAs is mainly due to the strengthening results of solid-solution and nanoprecipitation [8e 10,13].This conclusion should be revalued according to the present study.The strength-ening effects of solid-solution and nanoprecipitation should be lowered after annealing because of the resolution of solid-soluted elements and grain growth of nanoprecipitation.However,some of the as-annealed CoCrFeNiTiAl x alloys exhibit even higher strength and hardness than the as-cast ones.The strengthening effect of the as-annealed alloys should be attributed to the evolu-tion of phase composition as more intermetallic compounds precipitate after annealing.The enhanced strength of as-cast CoCrFeNiTiAl x alloys is partially related with the formation of intermetallic phases as well.According to our previous study [22],HEAs can be classi ?ed as two kinds based on their phase compo-sitions:(1)alloys ful ?lling the proposed formation rules of simple solid-solution phases;and (2)alloys dissatisfy the phase formation criterion of simple solid-solution.Strengthening effect of the ?rst kind is mainly caused by the formation of solid-solutions and nanoprecipitations.However,intermetallic phases should be considered as an important factor for HEAs systems falling into the second kind as complex phases inevitably precipitate in these alloys.Thus,the strengthening mechanism of HEAs should be adjusted to cater for de ?nite alloy systems with different resultant phase compositions.

Densities of the as-cast and as-annealed CoCrFeNiTiAl x alloys were measured by Archimedes method using water as the immersing medium.The calculated densities are listed in Table 2and density comparison of the as-cast and as-annealed alloys is plotted in Fig.4(b).The density decreases gradually as Al content increases,which can be easily understood as Al exhibits the lowest intrinsic density in CoCrFeNiTiAl alloy system.The as-annealed alloys exhibit slightly higher densities than the as-cast ones.The increment of density is associated with the low melting point of Al,which leads Al component partially evaporated under 1000 C annealing for 2h and the integral density increases correspond-ingly.The increment of density after annealing is more obvious for alloys with high Al content,such as the density of as-cast Al 2.0alloy is 6.12g/cm 3while this value increases to 6.18g/cm 3for as-annealed Al 2.0alloy.

3.3.Electrical and magnetic properties of as-cast and as-annealed CoCrFeNiTiAl x alloys

Fig.5presents the comparison of electrical resistivity for as-cast and as-annealed CoCrFeNiTiAl x alloys with detailed data listed in Table 3.All as-cast and as-annealed alloys exhibit high electrical resistivity,which are about two orders of magnitude higher than relevant pure metals.The high electrical resistivity is also found in other HEAs systems [16,30].The electrical conduction of metals is caused by ordered movement of free electrons under electric ?eld,which is affected by phase composition and defect concentration of the tested specimen.As the as-cast CoCrFeNiTiAl x alloys are mainly composed of solid-solution and intermetallic phases,the random solid-solution of the component elements increases the concen-tration of lattice defects while the intermetallic phases possess higher intrinsic electrical resistivity than relevant pure metals.These effects are re ?ected in the electrical resistivity of the as-cast alloys.It is interesting that all as-annealed alloys show higher electrical resistivity than the as-cast ones.The as-annealed Al 0alloy exhibits the highest electrical resistivity of 396mU cm.The incre-ment of electrical resistivity after annealing can be explained by the evolution of phase composition and lattice distortion.The lattice distortion energy and defect concentration are greatly reduced as resolution of the component elements occurs after annealing,which would lower electrical resistivity of the as-annealed samples.On the contrary,the amount of intermetallic phases increases after annealing,which elevates electrical resistivity of the as-annealed samples.The increasing effect of intermetallic phases

Table 3

Electrical and magnetic properties of as-cast and as-annealed CoCrFeNiTiAl x multi-component alloys.Alloy

Electrical resistivity (mU cm)M s (emu/g)H c (Oe)As-cast

As-annealed As-cast As-annealed As-cast As-annealed Al 0107396 4.830.621420Al 0.573132 2.48 2.1341285Al 1.011424314.78 3.1022226Al 1.58515110.327.635621Al 2.0

60

175

0.76

15.74

14

22

Fig.6.Magnetic properties of CoCrFeNiTiAl x alloys:(a)as-cast and (b)as-annealed.

K.Zhang,Z.Fu /Intermetallics 28(2012)34e 39

38

exceeds the decreasing effect of resolution and causes the electrical resistivity increased eventually.

Fig.6presents the magnetic hysteresis loops of as-cast and as-annealed CoCrFeNiTiAl x alloys with the detailed parameters of magnetic properties calculated in Table3.Saturated magnetization (M s)of the as-cast alloys increases?rstly and then decreases as Al content increasing(Fig.6(a)).As-cast Al1.0alloy exhibits the highest M s value of14.78emu/g.The as-cast alloys display paramagnetic characteristic with relatively low coercivity(H c)among14e56Oe. The value of M s is usually affected by many factors,which makes the analysis complicated in HEAs.However,the in?uence of M s can be eventually attributed to the magnetic phases,especially due to the contribution of BCC phases.The magnetic properties of HEAs will be explored profoundly in our future work.Values of M s for the as-annealed alloys increase gradually as Al content increases (Fig.6(b)).The as-annealed Al2.0alloy shows the highest M s value of 15.74emu/g.Small hysteresis loops exist in the as-annealed Al0.5 and Al1.0alloys,which means these alloys are in weak ferromag-netic feature.As-annealed Al0.5and Al1.0alloys also exhibit high H c of285Oe and226Oe while other alloys show low values around 20Oe.The results of magnetic properties reveal that the as-cast and as-annealed CoCrFeNiTiAl x alloys are semi-hard magnetic mate-rials.These kind of magnetic materials can?nd some applications in magnetic relayers,magnetic hysteresis motors and signal memory devices.

4.Conclusions

In this study,CoCrFeNiTiAl x multi-component alloys were prepared by vacuum arc-melt casting and the as-cast alloys were subsequently heat treated at1000 C for2h.Effects of Al content and annealing treatment on the physical properties were studied by intensive characterization of their mechanical,electrical and magnetic properties.Al content exhibits signi?cant in?uence on physical properties of the as-cast and as-annealed alloys.The CoCrFeNiTiAl x alloys show good resistance of anneal-softening as most of the as-annealed alloys show higher hardness than the as-cast ones.As-annealed Al0possesses excellent mechanical prop-erties with high strength of2.46GPa and strain rate of12.7%. Formation of intermetallic phases is considered as a critical factor for the strengthening effect of HEAs.The CoCrFeNiTiAl x alloys exhibit high electrical resistivity because of high content of lattice defects and precipitation of intermetallic phases.Both as-cast and as-annealed alloys are in novel magnetic properties,which can be classi?ed as semi-hard magnetic materials.Acknowledgment

The authors would like to acknowledge the?nancial support by the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials(Southwest University of Science and Technology,No.11zxfk26),and the project supported by State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology,No.2012-KF-15).

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