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1 Contents ists avai!eb!e at SciVer;;e ScienceDirect Resuts in Physics jo. rna homepage: urn a s.esevie r.com/resu ts-i n physics xtrusion die geometry effects on the energy absorbing properties and deformation response of 663-type A-Mg-Si au1ninum aoy* O.P. Gbenebora, O.S.. Fayomi a,b,*, A.P.. Popooa, A.O. negbenejora. F. Oyawa}f a <> CrossMark Coege of Science and Technoogy, Mechanica ngineering Department, Covenant Univer,;ity, P.M.B 23, Ota, Ogun State, Nigeria b Facuty of ngineering and the Buit nvironment, Chemica and Metaurgica ngineering Department, Tshwane University of Technoogy, P.M.B X68, Pretoria, South Africa ARTCL NFO Artice history: Received 3 September 212 Accepted 12 january 213 Avaiabe onine 9 February Keywords: xtrudate Strain rate Compressive srrcngth Deformation ength zone Die ange nergy absor bing property ABSTRACT The response of 663-type A-Mg-Si aoy to deformation via extrusion was studied using too stee dies with 15,3,45,6 and 75o entry anges. Compressive oads were subjected to each sampe using the AVRY DNSON machine, adapted to suppy a compressive oad on the punch. The abiity of the extrudate to absorb energy before fracture was cacuated by integrating numericay the poynomia reationship between the compressive stress and sarnpe strains. Strain rate was cacuated for each specimen and the deformation zone ength ws mathematicay derived from the die geometry to decipher its infuence on both atera and axia deformations. Resuts shcv-1d that cxtntr:ing with a 15 die was the fastest as a resut of the ow fow ;.iress encountered. Outstanding compressive strer:gth. pastic deformation, strain rate and e:1e1gy absorinz ca1acity were observed for the aoy extruded with a 75" di> ange. ncrease in die ;mges ed to a decrej;e in ceformjtion zone ength and sampes deformed more in the axia direction than in the atera e>.cep for the 45 die which showed the opposite; the sampe aso showed the east ductiity. 213 The Authors. Pubished by sevier B.V. A rights reserved. 1. ntroduction The outstanding properties of auminum have ed to their wide usage in the fied of engineering ( 1.2]. As a resut of this, different meta working processes such as roing, forging, and extrusion, have been empoyed to obtain different desired shapes and properties. n meta forming processes, the fow stress of the meta is an important factor to consider for a successfu operation (3,14-18]. This fow stress is a function of forming pressure and the deformation oad. The stress is usuay reduced with temperature; hence a high working temperature is beneficia to carry out the operation with a ow oad or pressure. Since extrusion invoves the appication of an externa oad on a materia which forces it through wear resistant openings (die), the stresses induced in this meta (due to the appication of externa forces) are greater th;;n its yied strength but ess than its fracture strength (4.6]. Cod extrusion is major\y empoyed for the manufacture of specia sections as the This is an open-access artice distributed urrder the terms of.he Creative Commons Attribution-NonCommercid1-ShareAii:e License, which permits non- commercia use, distribution, and reproduction in any medium, provided the origina author and source are credited. * Corresponding author at: Facuty of ngineering and the Buit nvironment, Chemica and Metaurgica ngineering Department, Tshwane University of Technoogy, P.M.B X68, Pretoria, South Africa. Te.: mai addresses: ouwashina.gbenebor@covenantuniversity.edu.ng (O.P. C.benebor), ojosundayfayomi3@gmai.com {O.S.. Fayomi). meta is made to fow under cod conditions (room temperature) and a high pressure; this imparts good mechanica properties and surface finish on the work piece (5]. xtruding a biet above the recrystaization temperature (hot extrusion) engenders pressure decrease aong the container as the ram/punch advances and when the ram speed incrtases, a structure with no coarse grains occurs (6,7]. nvestigations on die geometry effects and extrusion speed on auminum and ead aoys have shown that average hardness and radii of curvature of these extruded materias aong circumferentia soid positions increase with oading rates and increase with decrease in die reduction in the area (8]. Using a die with a guiding ange eiminates shrinkage cavities of sampes owing to the axia stress which changes from tensie to compressive in the centra zone. Dead zon generation is reduced as the meta fow remarkaby becomes homogenous (9]. Die anges are observed to eiminate surface cracks of the exit die as a resut of the reduction of axia stresses at this zone. The initia stagr:s of the deformation, where the biets are primariy affected by the fow stress of the materia and the r<1tes, at whic; the work i.s carried out, have proven to.re of some significance in dictating the m;;\:eria fow distribution during the extrusion process (1]. The response of metas to deformation is key in the extrusion process because it affects the too ife; it determines product deivery rate and most importanty, the performance of products when used in engineering appications. Hence, in this study, the need to /$- see front matter 213 The Authors. Pubished by sevier B.V. A rights reserved. 16/j.rinp

2 2 D.P. Gbenebor eta/.. Resurs in P1ysics 3 (213) 1-6 (Pun Container aoy (Ji-Mg-Si type) were sand cast into cyindrica shapes and machined to a 25.1 mm diameter and 19 mm height for extrusion. The shaped auminum components are extruded at room temperatures to obtain good surface finishes, better dimensiona consisteiky and improved strengths. ach die was fitted into the form too base and extrusion was carried out at room temperature with the AVRY DNSON machine, which was adapted to suppy a compressive oad on the punch. The extrusion oad (in KN) appied on the ram was read on this machine rhie a gauge, attached to the machine, was used in determining the time deformation took pace at each point in the die. As each oad was appied, the pointer on the meter rotated and a compete rotation was taken for 1 mm punch dispacement. 3. Resuts and discussion 3.1. xtrusion oad against punch dispacement curve Fig. 1. The punch and the form too set up. decipher the dependence of aoys pastic fowabiity (per time) and energy absorption properties on die geometry and deformation oad was ascertained. 2.xperinnentaprocedure Mid stee, owing to its appreciabe abundance and cheapness with a chemica composition of 99.2% Fe as the major constituent, was used in designing the punch and the form too, comprising the cyindrica container and the base as shown in Fig. 1. These components were heated to a temperature of 85 oc and quenched in water for 1 min after hoding for three hours in the furnace so as to increase their strength and hardness to suite the deformation process and prevent wear and deformation during extrusion. The extrusion dies used were made of too stee and were designed such that five entry anges (15, 3,45, 6, and 75 ) were fabricated to produce cyindrica extrudates. Biets made of auminum Fig. 2 shows the extrusion oad - punch dispacement reationship for different die anges. The curves for extrusions with 6 and 75 dies show that auminum sampes deformed in a simiar mode though different oads were needed to deform these sampes whie the punch traveed at varying dispacements. According to [ 11], the curves for these two dies have shown that a maximum degree of pastic deformation was achieved when 65 and 75 dies were used as compared with the rest (15, 3 and 45, respectivey). Maximum extrusion pressure for each sampe, which was obtained by dividing maximum oad by sampes origina area (shown in Fig. 3 ), reveas that the maximum pressure needed to deform the auminum aoy increases with increasing die anges. Reating these reationships shows that how far a punch traves during extrusion is not whoy dependent on the magnitude of the maximum pressure- geometry of the die (especiay the entry ange) but however, biets inherent properties coud induce such deformation conditions based on the hardenabiity of the materia which is a function of energy tenaency Sampe dispacement with time The dispacement versus time reationships at constant temperature sj1own in Fig. 4 does not ony show the dispacement of each aoy, it aso shows the time (at each point) it takes in achieving z "" " : 2 - c:.q ) ::> w e so Punch Dispacement (mm) 1 15 Fig. 2. Variation of extrusion oad with punch dispacement.

3 D.P. Gbenebor et o.f.esuts n Physics 3 (213) , r , " " a. c: c;; " x " } "" --r r r L J6----ro Die Ange Fig. 3. ffect of maximum extrusion pressure against die ange t T , r r T ,,...,...-: : ?Z" t,f 12 " <D 1 " a. C/) 8 i5 <D a. (j) " 2 : :,/: : : j " -- -: ;,.-J : : ;r-, ; ;.f"" #" -----_;_ A : ; : y<i R :, T : :-:-::: ; -----!:== ----! )! --. : 411> j. L L : : : _:-+- Time(s) Fig. 4. Variation of sampe dispacement with time. this. This gives an understanding of the ease with which each sampe is deformed. As discussed in Figs. 2 and 3, more time (;:,;585 and 625 s) was needed for aoys to eongate to their fina sizes (axiay) with 6 and 75 dies, respectivey. Using a 15 die, the best deformation ease was attained as 157 s was needed for a compete deformation. The ongest process was discovered to take pace using a 75 die though its deformation was the best. Deforming the aoy with a 45 die shows that it is possibe for sampes to cover a itte dispacement within a arge space of time nergy absorbing property of extmdates sure of the tendency of the extrudates to absorb energy before faiure during service, was cacuated by integrating numericay using the expression [ 12,13 ). Resuts on extrusion pressures and corresponding sampe strains for each entry ange were cacuated and with the use of MATLAB, poynomia reationships between these tvvo variabes were computed. The energy (per unit voume) U, which is a meat U = o Pde where P and e are the extrusion pressure and sampe strain respectivey. The capacity of sampes to absorb energy before pastic deformation ceasure is moderatey arge (in increasing order) for extrusions with 15,3,6 and 75 die anges (Fig. 5).1t is obvious that 75 die gives the aoy a superative absorbing capacity whie the owest energy absorbing capacity is observed for a 45 die ange. ts response to itte dispacement coud have been responsibe for this. More so, it can be observed that the heat-treated entry anges die formed mid stee enabes sips and disocation movement of the sampe to take pace with ease having a better eongation and

4 4 O.P. Gbenebor et a.fresuits in Physics.3 (213) , , ,.----, r--- """1"-:-..., , _,_ : J : , T r " :::; "" -:;: <> c: w , , r r r , o _j C Die ange Fig. 5. ffect of energy absorbing capacity against die ange :;;; i.5 :: " c:: (/) r L L L--! L , r r , r , , r r , , r r r : " : / : L Die Ange Fig. 6. ffect of s<rain rate against die ange. deformation due to the precipitation and grain crysta orientation formed as a resut of the cooing system and the high energy absorbed during quenching. Hence, the hardness of each extruded sampe increases as the entry ange increases ffect on strain rates The strain rate curve shown in Fig. 6 was cacuated by using the equation [14] where Vis the average ram speed, De is the container bore, D is the diameter of the extruded sampe, and a is the die ange. According to [15] who affirmed that materia having high strain rates possesses high compressive strengths and eongation with high pressure required achieving this, the strain rate curve in Fig. 6 justifies this statement. Product from each die whose strain rates foiowed an increasing order, correates with its increasing maximum pressure except for the aoy extruded with a 45 die. ts ow strain rate as compared with the rest coud be a reason for its ow energy absorbing tendency. The ow di::pacement achieved shoud aso be responsibe for this despite having maximum pressure of :::::85 MPa. This resuit has shown that the sampe extruded with a 45 die exhibits the east ductiity.

5 O.P. Gbenebor et ofj,qesuts in p,ysb 3 (213) Container bore et eongated more in the directions parae to fow stresses than in directions perpendicuar to them with the exception of a 45 die, which was the r everse case at the same constant temperature of deformation. De WOkzone Concusions n this work, too stee extrusion die geometry has been used to study the response of 663 auminum aoys to deformation and aso, the effects of these responses on their toughness during engineering appications. From a indications, it is noted that: Fig. 7. Reationship among the deformation zone ength, extrudate and initia biet diameters Deformation within the work zone Within the work zone of the die whose geometry is shown in Fig. 7, the ength of deformation zone L can be cacuated mathematicay [16) as L =(De- D) 2tana where the initia diameter of the biet is same as the container bore diameter (25.1 mm ). With the extrudate diameter and the die ange known, the ength of the deformation zone was cacuated. Fig. 8 shows that the ength of the deformation zone reduces with increasing die ange and the reduction in ength for each ange increase is approximatey 5%. Resut shows that with deformation ength zone of 2 mm, axia eongation and atera reduction of 15 mm and 1 mm respectivey, can be achieved. The ordery reduction of die anges has cuminated in the ordery reductions in the deformation zone ength and ordery increase in axia biet eongations with an anomay experienced with the 45 die. ach bi- The highest magnitude of the maximum oad is needed to give the aoy a maximum dispactment on extruding with a 75o die. This makes it possess the best pastic deformation. A 6 die wi be a second option as the biet deformed in a simiar pattern but with a esser dispacement. Maximum oads needed to be appied on the aoy to respond to deformation increases with increasing die ange and this justifies why the maximum extrusion pressure for each ange foows the ordery trend. How far a punch wi trave during deformation by extrusion does not depend on the magnitude of the maximum pressure aone but aso, the geometry of the die couped with the biets inherent properties. The ow fow stress (as compared with the rest) in a 15 die engendered the fastest and the best deformation case. The appication of a product wi be imited to certain oads since it has a ow tendency to absorb energy unike that of a 75 die whose energy absorbing property had the highest magnitude. The owest vaue discovered with a 45 die coud be attributed to its ow dispacement. For each die ange increase, axia eongation increased whie the ength of deformation zone decreased (with the exception of a 45 die whose eongation was the owest). More so, each sampe deformed more in the axia direction, except for the 45 die where reverse was the case. 2 -e- Deformation ength zone Axia eongation Latera reduction r , lj 14.s 12 c Q) 1 " en Q) " 8 ::;; r t "o T T :+-; , , ! , Die ange 7 8 Fig. 8. Variations of deformation zone ength, atera reduction and axia eongation of sampes with die ange.

6 6 O.P. Gbenebor et ai./resuits in Physics 3 (213) 1-6 From the overa view, using a 75 die wi be the most preferabe owing to the outstanding properties the aoy has over the re>t of the dies. References [1 1 Khomamizadeh F. Ghasemi A. Sci ran 24;11 :386. [21 Mr6wka-Nowotnik G, Sieniawski j. Wierzbiiiska M. Arch Mat Sci ng 27;28:69. [31 Osakada Kj. Phys V France 1997:7:37. [41 Sharma PC. A Text Book of Production Technoogy. Chand and Compny Limited; 27. p [51 Tiernan P. Hiery MT. Draganescu B. Gheorghe M. j Mat Pro Techno! 25;168:36. [61 Arifa AFM. Sheikha AK. Qamaraand SZ, A-Fuhaid KM. Mat Manuf Pro 21 ;16(5):71. [71 Bingo! S, Keskin MS.J Achiev Mat Manuf ng 27;23(2):39. [81 Onuh SO, koja M, Adeyemi MB. J Mat Pro Techno! 23;132:274. [91 Yuan S, Li F. He Z. j Mat Sci Techno! 28;24(2):256. [11 Fitta, Sheppard T. nstitute of Materias Mineras and Mining 23;19:838. [ 11 1 Shaffer JP, Saxena A, Antoovich SO, Sanders jr TH, Warner SB, Richard D. The science and design of engineering materias,!rein nc; p [121 Zhang C, Feng Y, Zhang X. Trans Non-ferrous Met Soc China 21;2:138. [131 Caste AF, Sheppard T. Met Techno1976;3(1). [14] Pres MM, Fogagnoo JB, Coimbrao DD, Kiminami CS, Botta Wj, Bofarini FC, orge J_r AM. Congresso Brasieiro de ngenharia e Ciencia dos Mat 26;b:6631. [15] Fundamentas of extrusion, < [161 Li N, LuX, jian-zhong C. Trans Nonferrous Met Soc China 28;18:541. [17] Gbenebor O.P. Abduwahab M. Fayomi O.S.L, Popooa AP.L Chaco Letters. 212; 9:21. [13] Abduwahab M, Madugu A, Yaro SA, Hassan SB, Popooa AP. Mat Des 211 ;32:1159.