Deformation and Prefered Orientation of Precipitates in Cold Worked AI-Zn Alloys

Transcription

1 MEMOIRS OF THE SCHOOL OF ENGI!'<EERING, OKAYAMA UNIVERSITY Vl. 6, 1'\0.1, SEPTEMBER 1971 Defrmatin and Prefered Orientatin f Precipitates in Cld Wrked AI-Zn Allys Mutsu OHTA, * Fumi HASHIl\IOTO* * and Hirnbu MAEDA * * Department f Industrial Science ** Department f Electrnics (Received April 30, 1971) Fiber textures f drawn wires f AI-In allys cntaining precipitates were studied mainly by X-ray methds. In supersaturated slid slutin the wire texture was a duble fiber texture with [IOOJ and [III]. It was cnsidered that a phase precipitates were rtated with matrix, while they were defrmed. And then the matrix cntaining stable precipitates (Zn) had [IOOJ and [IIIJ textures. The intense spts, crrespnding t [IIIJ fiber texture f matrix, in the Debye rings f (002)1' and (101)1' planes f precipitates were clearly bserved. But, n the ther hand, spts, crrespnding t [looj fiber texture f matrix, shwn the prefered rientatin f precipitates in (002)/, Debye ring were very weak and brdening. " 1. Intrductin The varius precipitates are frmed n ageing AI-Zn allys. HirsawaD had investigated fiber textures f extruded aluminium ally rd by X-ray methds. Prefered rientatin f precipitates in drawn Al ally wire, hwever, was scarcely reprted. AI-Zn ally is knwn as ne f age-hardenable aluminium ally. The precipitatin prcess in AI-Zn ally is summaried as fllw; Supersaturated Slid Slutin a->- Spherical G. P. znes + a->- elliptic G. P. znes + a-> Rhmbhedral transitin phase + a-" cubic transitin phase+a->- Zinc-rich stable precipitates+a. In this wrk, fiber textures f supersaturated slid slutin, and allys cntaining a phase r Zn-rich stable precipitates were studied. 2. Experitnental Prcedure Specimens were made frm pure aluminium and pure zinc. Each ally was melted in the high alumina crucible in the air. The nminal atmic cmpsitins f allys used in this study were AI-6.Sat96Zn and AI-IOat%Zn. Ingts f 15mm in diameter were frged at abut 400 C t 5mm thick sheets, and then cld rlled t the thickness f 2. Omm with intermediate annealing at abut 450 C. Strips fr drawing were cut dwn frm these sheets. The specimens fr X-ray small angle scattering methd were rlled t the thickness f abut 0.05mm. Specimens were cled in electric furnace r quenched int iced water after hmgenized at 400 C fr 1~5 hurs. Specimen cntaining supersaturated slid slutin was immediately drawn after quenching, and specimen cntaining a' cubic transitin phase was annealed at 125 C fr 25 hurs after quenching, and then was drawn. T btain hexagnal zinc precipitates, the specimen was cled in electric furance. Defrmatin rate was 75 ~ 9696 in reductin f area by wire drawing. After these treatments, specimens were examined by metallurgical micrscpe and X-ray methd with mncrmated Cuk a radiatin. Since effective thickness fr diffractin in case f X-ray used is abut O.lmm frm surface, specimen was electrplished less than ne-third in diameter t btain the X-ray phtgraphy f central part f specimen. 3. Result and Discussin Pht. 1 shws the fiber texture f AI-6. Sat 90Zn ally that is quenched and subsequently drawn with reductins in crss-sectinal area f 91 per cent. The wire textures are [looj texture in additin t same [111J texture as 27

2 28 M.OHTA, F. HASHIMOTO and H. MAEDA pure AI. Besides, diffractin spts f this ally is t brding alng the Debye incmparisn with pure Al drawn same rate. Pht. I Diffractin pattern f wire f AI-6.8at96 Zn ally after quenching frm 400 C int ice water. Pht.2 is pwder phtgraph f AI-6. Sat 96Zn ally that is annealed at 125 C fr 25 hurs after quenching frm 400 C. The lines crrespnd t phase is detected utside each line f matrix because f lattice cnstant f phase smaller than that f matrix. Small angle scattening f X-ray frm AI-6.S at96zn ally aged at 125 C fr 25 hurs after quenching frm 400 C int ice water is shwn in Pht. 3. Pht. 3 (a) is undrawn specimen. That i nt shwn the usual hal due t spherical G. P. zne, but uneven hal. This may be cnsiderable that the shape t cluster in matrix is nt spherical, but rd shape. Cnsidering the heat treatment carried ut, the scattering bdy may be crystallite f a l phase. The X-ray small angle scattering phtgraphy f AI-6. Sat96Zn ally applied the same heat treatment and cld rlled with reductin in th ickness f 9096 is shwn in pht.3 (b). Arrw shws directin f rlling. The regin f scattering angle is cnsiderably narrwer than ne f nt rlled sample. This crrespnds t elgatin f crystallite alng rlling directin, that is t say, it may be deduced that intermediate a l phases are given the defrmatin when wrking a sample. t I Pht.2 Pwder diffractin pattern f AI-6.8atZn ally annealed at 125 C fr 25 hurs after quenching frm 400 C int iee water. I 'mall angle scattering f X-ray frm AI-6.8at06Zn ally aged fr 25 hur at 125 C after Pht. 3 quenching frm 4OO'C int ice water. (Arrw shws the rlling directin)

3 Defrmatin and Prefered Orientatin f Precipitates 29 Pht.4 shws Debye phtgraph fdrawn wire f ally cntaining a' phase. On the utside f maximum scattering intensities n Debye rings f (Ill).\{ and (200).I[ planes, the spt frm a' phase are detected, but nt bserved at smewhere else. Frm this fact, it is cnsidered that defrmatin f a' phases are undergne in the same way f that f matrix, while a' phases are defrmed themselves when defrming the specimen. Pht.4 Diffractin pattern f drwn wire f Al 6.8at96Zn ally aged fr 25hr. at 125 C after quenching frm 400 C int ice water. Pht. 5 shws the phtgraph t metallurgical micrscpe with drwn wire f ally cntaining precipitates (Zn). This is shwn that the precipitate particles are assembled in large quantities at exterir side than interir Pht.5 Phtgraph f metallugical micrscpe f drawn wire f AI-IOat96Zn Cntaining precipitates (Zn). X500 side f wire. And the state f distributin f precipitate particles is cell structure. Figure 1 illustrates the pattern that is btained with mnchrmatic X-ray frm a clddrawn wire f AI-Zn ally cntaining precipitates, assuming that the defrmatin f precipitate particles is undergne in the same way t that f matrix wrked. The black spts represent [III] fiber texture f matrix and a wh ite dt represents [100] fiber texture f matrix. The thick lines and thin lines represent Debye rings f matrix and precipitates, respectively. There are sme crystallgraphic relatins between slid slutin and precipitates, that is, plates n (Ill) M (l11)".j" (OOI)p, <110>.".j" <11O>p2l. Cnsequently, Fig. I describes where lcate ideal ples fr (Ill).", (200).", (loi)p and (002)p planes in a wire f AI Zn ally having tw [111], [100] fiber textures assuming the precipitates defrmed with attaching themselves matrix. The spst f fiber texture f precipitates lie at the same angle t matrix in the Debye rings, since (002)p planes are parallel t (III).". Namely, there are sme pairs f intense spts n the inside f tw Debye rings, (002)p and (III),,[ planes. On the ther hand, sme spts n the uter Debye rings represent the ple figure f drawing textures fr (200),,[ and (loi)p planes. In this case, there appeare the spts in nt pair but separately because f (lol)p being nt parallel t (002).1[' I~;~ r(ii '\:.1 \~ \ " ((, (ODD. ));1 \. ~<III>" J/ I \,\ ~ / cl 0.~ /0 ~~ Fig. I Pattern f drwing AI-Zn wire Radiatin f a single wavelength incident perpendiculart the wire axis, which is vertical.

4 30 M.OHTA, F. HASHIMOTO and H. MAEDA (a) (b) Pht.6 Phtgraphs f crss sectin f drwn AI-IOat 0 6Zn ally cled frm 400 c C t rm tempe rature at rate f IrC/hr. The Debye phtgraph f drawn wire f AI 10at96Zn ally which is cled frm 400 C t rm temperature at a rate f 12 C/hr. after hlding at 400 C fr I hur and drawn with reductin in crss-sectinal area f 75 per cent, is sh\1"n in Pht. 6. Pht. 6 (a) rcpresentes the diffractin pattern frm the ncar surface f specimen because f wire being abut 0.7 mm in diameter, and (b) is X-ray phtgraph frm central part f same specimen electrplishedless than 0.3mm in diametcr. Pht. 6 (a) shws that the wire texture fr matrix is a duble fiber texture lacking in clearness, in particulary, the spts crrespnd ing t [100] fiber axis braden fairly and the spts crreapnding t fiber texture f precipitates are als faint. In the central part f same specimen (pht. 6 (b)), intense spts equivalent fr fiber axis a~e clearly bserved. [100] fiiber axis n the Debye ring f (002)" plane, hwever, is weak and brdening. And there recgnize n Iy fur spts n the ring f (10 I)" planes. Fr parent phase, the spts crrespnd ing t the bth fiber texture, [100] and [Ill] are appreciated bviusly. Fig.2 shws the intensity alng the Debye ring in pht. 6 (b). )lamely, blackness alng Debye rings are measured by phtmeter and reduced t intensity frm by standard intensity scale. The spt lcated at 52 34' is crrespndfa ~n,o~~ 040, 50' 60' 70' 80' 90' 10.0 ~ ""I 0 40, j 40' 50' 60' 70' 80' ~ ~ 50' 60' 70' 80' 90' Fi,.2 Intensity eurve alng the Debye ring in pht. 6 (b). ing t [100] drawing texture. This spt is seemed very \\'eak in intensity and brdening, n the ther hand, in tensity f spt f [Ill] fiber axis is cnsiderably strng.

5 Defrmatin and Preftred Orientatin f Precipitates 31 In the(lo1)p plane, fur peaks f intensity is all crrespnding t [ll1j fiber axis, and peaks crrespnding t [100J fiber axis is nt recgnized. But, if it appear, then there shuld be lcated at 48 40', 57 14' and 82 13'. At thse place, the intensity is nt zer as shwn in (002)p diffractin ring, s that the peak crrespnding t [IOOJ fiber texture may be masked. 4. SUlDlDary The experimental results and discussin btained by X-ray methd and bservatin f metallugical micrscpe may be summarized as fllws: (1) In supersaturated slid slutin fiber axes were [100J texture in additin t same [111] texture as in pure AI. (2) It was cnsidered that «' phase were rtated with matrix while defrming themselves. (3) Precipitates were mved in attaching t matrix, and then they shwed the apperent fiber texture. Namely, prefered rientatin was the same ne f matrix. (4) The part f sureface: the fiber textures f matrix were [111J and [IOOJ axes. Accrding t darkness f diffractin spts, [111] axis cmpnent seemed strnger than [IOOJ axis cmpnent. The intense spts n the Debye rings f (002)p and (101)p planes f precipitates were clearly bserved with equivalent fr [lllj fiber texture fmatrix, but, n the ther hand, the spts equivalent fr [100J fiiber axis f matrix were less than [111J fiber axis. (5) The central part: the fiber texture f rna trix was same with ne f surface part and each spt crrespnding t fiber texture was mre clear. On the diffractin rings f (002)p and (101)p planes f precipitates, the spts crrespnding t [IOOJ axis were b. served, in additin t the spts due t crystallgraphic relatin between matrix and precipitates. And diffractin pattern f precipitates resembled t ne f matrix, namely, there were fairly clear prefered rientatin in precipitates. (6) With respect t micrstructure f crs-sec. tin f drawn wire after furnace cling, the precipitate particles were assemabled in large quntities at exterir side than interir part f wire. Reference J) H. HIROSAWA: J. Japan Inst. Metals, 2 (962), 95. 2) A. H. GEISLER, C. S. BARRETT and R. F. MEHL : Trans. AIME Vl. 152, p