Effect of equal channel angular pressing on AZ31 wrought magnesium alloys

AZ31 wrought magnesium alloys are light weight materials which play an important role in order to reduces the environmental burdens in modern society because of its high strength to weight ratio,corrosion resistance,and stiffness and machinability.Applications of this material are mainly in structural component i.e.,in constructions,automobile,aerospace,electronics and marine industries.In the present work,the microstructure characterization of the AZ31 alloys up to four ECAP passes at temperature of 573 K was observed for route Bc.Average grain size of the material was reduced from 31.8μm to 8μm after four ECAP passes.Mechanical properties of the alloy improved with increase in number of ECAP passes.Moreover,X-ray diffraction analysis was carried out for as received and ECAP processed material.

Review on non-conventional machining of shape memory alloys

Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Therefore, the SMAs are used in many applications such as aerospace, medical and automobile. However, the conventional machining of SMAs causes serious tool wear, time consuming and less dimensional deformity due to severe strain hardening and pseudoelasticity. These materials can be machined using non-conventional methods such as laser machining, water jet machining （WJM） and electrochemical machining （ECM）, but these processes are limited to complexity and mechanical properties of the component. Electrical discharge machining （EDM） and wire EDM （WEDM） show high capability to machine SMAs of complex shapes with precise dimensions. The aim of this work is to present the consolidated references on the machining of SMAs using EDM and WEDM and subsequently identify the research gaps. In support to these research gaps, this work has also evolved the future research directions.

Analysing the combined effect of crystallographic orientation and grain refinement on mechanical properties and corrosion behaviour of ECAPed ZE41 Mg alloy

Two step equal channel angular pressing carried out on as cast ZE41 Mg alloy resulted in a remarkable grain refinement.As compared to grain size of 46p.m in as cast sample,refinement upto 2.5^01 was achieved after 8th pass equal channel angular pressing(ECAP).The combined effect of crystallographic orientation and grain refinement was investigated by analysing the mechanical properties and corrosion behaviour of ZE41 Mg alloy using electron back scattered diffraction(EBSD).The first stage comprises of 1st,2nd,3rd and 4th passes at a processing temperature of 300℃while the 5th,6th,7th and 8th passes were ECAPed at 275℃in second stage.The mechanical properties of ZE41 Mg 158 yield tensile strength(YTS),230 ultimate tensile strength(UTS)and 7%elongation in as cast condition is enhanced to 236 YTS,295 UTS and 19.76%,respectively,after first stage ECAP.The yield tensile strength deteriorated due to the effect of texture predominating grain refinement during the second stage ECAP.The corrosion resistance of ZE41 Mg was significantly enhanced by ECAP and is inferred from electrochemical impedance spectroscopy(EIS)and potentiodynamic polarisation results.The role of microstructure was minimal on corrosion behaviour of ZE41 Mg due to extra resistance when tested in 0M NaCl.However,the influence of grain refinement greatly influenced the improvement in corrosion resistance of ZE4I Mg rather than crystallographic orientation observed from EBSD.In contrast,the crystallographic orientation predominated the effect of grain refinement during ZE41 Mg corrosion in chloride containing(0.1 M and 1 M NaCl)solutions.From the observation of results it is found that equal channel angular pressing has the dual advantage of improving mechanical properties and corrosion resista nee of ZE41 Mg alloy.

Influence of Route-R on wrought magnesium AZ61 alloy mechanical properties through equal channel angular pressing

A new fundamental route entitled‘Route-R’is introduced to refine the grains in the material through Equal Channel Angular Pressing(ECAP)process.In route R,specimen is inverted to the original position in each ECAP pass.In the present work,AZ61 alloy is processed using ECAP process for three different fundamental routes mainly route A,route Bc,and route R.ECAP experiment is carried out on AZ61 alloy at lower temperature of 483 K up to two passes.Microstructural characterization is evaluated on unECAPed and ECAPed specimens for three routes.Average grain size of the alloy is to be reduced from 66μm to 16μm,14.1μm and 10μm for route A routes Bc,and route R respectively.Vickers microhardness of the alloy is found to be 60 HV for as received material.This microhardness of the alloy is increased to 71 HV,72 HV,and 74 HV for route A,route Bc,and route R respectively.Mechanical properties of the AZ61 alloy are observed to be route R is providing maximum YS,UTS,and percentage elongation than other route A and route Bc.Tensile fracture topography of the specimen is analyzed using three different routes for two passes.

Use of Discrete Wavelet Features and Support Vector Machine for Fault Diagnosis of Face Milling Tool

This paper presents the fault diagnosis of face milling tool based on machine learning approach.While machining,spindle vibration signals in feed direction under healthy and faulty conditions of the milling tool are acquired.A set of discrete wavelet features is extracted from the vibration signals using discrete wavelet transform(DWT)technique.The decision tree technique is used to select significant features out of all extracted wavelet features.C-support vector classification(C-SVC)andν-support vector classification(ν-SVC)models with different kernel functions of support vector machine(SVM)are used to study and classify the tool condition based on selected features.From the results obtained,C-SVC is the best model thanν-SVC and it can be able to give 94.5%classification accuracy for face milling of special steel alloy 42CrMo4.

Wire electric discharge machining characteristics of titanium nickel shape memory alloy

Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.