AD-A268 323

Atlas of Formability

Waspaloy

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ATLAS OF FORMABILITY

WASPALOY

by

Prabir K. Chaudhury and Dan Zhao

National Center for Excellence in Metalworking Technology1450 Scalp Avenue

Johnstown, PA 15904

for

Naval Industrial Resource Support ActivityBuilding 75-2, Naval Base

Philadelphia, PA 19112-5078

July 31, 1992

The views, opinions, and/or findings contained in this report are those of the authors andshould not be construed as an official Department of the Navy position, policy, ordecision, unless so designated by other documentation

Form Approved'REPORT DOCUMENTATION PAGE OMB No 0704-0188PuIc renortmng burden for this coitecon of information s estimated !c a3eraqe i nour per esonrse, including the time for reviewing instructions. searching exstnrq data sources.'aphinrnl and mainta•n•ng the data needed. and comrnieting and revei nq the collection of information Send comments regarding this burden estimate or any other aspect of t•fscoliettion )t ,nt•irmatton. nouodng suggestions for reducing in Iurcen to Washington HeadQuarters Services. Directorate for onformation OperatiOns and Reports. 1215 JeffersonOav,s H,.hav. Ste '204. A0,1 gton. VA 22202-4302. and to the Off e )f Management and Budget. Paperwork Reduction Project (0704-0188). Wasr•ington. DC 20503

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

I July 31, 1992 Final, April 30, 1992-July 31, 19924. TITLE AND SUBTITLE S. FUNDING NUMBERS

Atlas of FormabilityWaspaloy C-NO0140-88-C-RC21

6. AUTHOR(S)

Prabir K. ChaudhuryDan Zhao

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) B. PERFORMING ORGANIZATIONREPORT NUMBER

National Center for Excellence in MetalworkingTechnology (NCEMT)1450 Scalp AvenueJohnstown, PA 15904

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/ MONITORINGAGENCY REPORT NUMBER

Naval Industrial Resources Support ActivityBuilding 75-2, Naval BasePhiladelphia, PA 19112-5078

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION /AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

In this investigation, flow behavior of Waspaloy alloy was studied by conductingcompression tests overr awide range of temperautres and strain rates. Constitutiverelations were determined from the flow behavior, and a dynamic material modelingwas conducted on this alloy. Thus, the optimum processing condition in terms oftemperature and strain rate was identified. Microstructural changes during hightemperature deformation were also characterized.

14. SUBJECT TERMS 15. NUMBER OF PAGES

Waspaloy, Deformation Processing, High Temperature 1 C

Deformation, Processing Map, Metalworking 16.PRICECODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACTOF REPORT OF THIS PAGE OF ABSTRACT

Unclassified Unclassifed Unclassified

NSN 7540-01-280-5500 Stanard Form 298 ýRev 2 89)r-3 %To :I IQ .

TABLE OF CONTENTS

Introduction ................................... I

Experimental Procedure ............................ 1

R esults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Sum mary .................................... 26

Implementation of Data Provided by the Atlas of Formability ........ 26

Acoession For

NIIS GRA&I W2

DTIC TAB 0ST#,Uhnanoune ed 0]ST #A, AUTR USNAVIRSA (MR PLONSKY 8/443-6684) JustificationPER TELFCON, 17 AUG 93 CB

Availability Codesl

Avnil audsi or

Vac Q-J f1

LIST OF TABLE

Table 1. List of figures, testing conditions and microstructural observationsfor Waspaloy ......... .................................. 2

ii

Waspaloy

Introduction

High performance requirements in the application of superalloys, such as aircraftgas turbines, has increased the need to understand both the mechanical andmicrostructural behavior of superalloys in metalworking processes. Flow behavior ofWaspaloy through compression testing at various temperatures and strain rates wasperformed to determine the constitutive relations. From the constitutive relations adynamic material modeling on Waspaloy was carried out to optimize processingconditions such as temperature and strain rate. In addition, microstructural changes werecharacterized to show the effect of temperature and strain rate on the resulting deformedmicrostructure. In some forming practices of superalloys, high strain rates are oftenencountered during the processing, such as hammer forging. Thus the present studyextends the testing strain rate up to 25 s- 1.

Experimental Procedure

Commercially available Waspaloy wrought bars in the heat treated and agedcondition was tested. Typical microstructure of the as-received materials showingequiaxed grains is shown in Figure 1. The initial grain size was 25 pgm (7.5ASTM).

Cylindrical compression test specimens with a diameter of 12.7 mm and a heightof 15.9 mm were machined, and compression tests were conducted isothermally on anMTS testing machine. Boron nitride lubricant was applied to reduce friction. Thetemperatures selected include those which are both above and under y' (1040 C) solvus.The test matrix was as follows:

Temperature, C (F): 982 (1800), 1010 (1850), 1038 (1900), 1079 (1975) and 1149(2100);

Strain rate, s-1 : 0.01, 0.14, 1.84 and 25.

Load and stroke data from the tests were acquired by a microcomputer and laterconverted to true stress-true strain curves. Immediately after the compression test, thespecimens were quenched in order to retain the deformed microstructure. Longitudinaland transverse sections of the quenched specimens were examined using opticalmicroscope. The photomicrographs presented were taken from the center of thelongitudinal section of the specimens.

Results

Table 1 is a list of the figures, test conditions and the deformed microstructuresobserved. All the true stress-true strain flow curves with the correspondingmicrostructure are shown in Figure 2 to Figure 21. True stress versus strain rate wasplotted in log-log scale in Figure 22 at a true strain of 0.5. The slope of the plot gave thestrain rate sensitivity m, which is not constant over the range of strain rate tested. Logstress vs. l/T at the same true strain is shown in Figure 23. A processing map at thisstrain was developed for Waspaloy and it is shown in Figure 24. The optimumprocessing conditions from the map can be obtained by selecting the temperature andstrain rate combination which provides the maximum efficiency in the stable region.This condition is approximately 1080 C (1975 F) at the lowest strain rate tested, 0.01 s-1.

• • i i I /| | |1

Table 1. List of figures, testing conditions and microstructural observations.

Figure Temperature Strain Rate NMicrostructure PageNo C (F) S-1 j2 tical Microsco No1 As-received: Equiaxed grains with an average 3

size of 25 ILm. A small proportion of larger

grains (40-50M) present.2 982(1800) 0.01 Deformed grains with extensive grain boundary 4

precipitation. Presence of some very largeisolated deformed grains.

3 982(1800) 0.14 Same as above, but with a less proportion of fine 5precipitates at the grain boundaries.

4 982(1800) 1.84 Same as above, but the proportion of fine 6precipitates kept decreasing.

5 982(1800) 25.00 Same as above (testing performed in an inert gas 7atmosphere).

6 1010(1850) 0.01 Deformed grains with some grain boundary 8precipitation. "Serrated" grain boundaries(initiation for dynamic recrystallization). Some_necklacing present.

7 1010(1850) 0.14 Same as above. 98 1010(1850) 1.84 Same as above, but necklacing is more evident. 109 10100850) 25.00 Same as above and necklacing is well defined. 1110 1038(1900) 0.01 Small and equiaxed dynamically recrystallized 12

grains, presence of twins. There is still thepresence of large grains (35-45 pim).

11 1038(1900) 0.14 Same as above. 1312 1038(1900) 1.84 Same as above, but the proportion of twins 14

increased.13 1038(1900) 25.00 Equiaxed duplex grain size; small grains 15

(-20jim) and relatively large grains (-4Ogm).Note that 1038 C is just bellow the y'solvus.

14 1079(1975) 0.01 Large equiaxed grains (-30pun). 1615 1079(1975) 0.14 Equiaxed and heavily twinned grains with a 17

size smaller than above.16 1079(1975) 1.84 Same as above, but smaller grain size (-25jim). 1817 1079(1975) 25.00 Equiaxed grains, but smaller than above. 1918 1149(2100) 0.01 Very large equiaxed grains (60-65pn), presence 20

of twins.19 1149(2100) 0.14 Same as above, but smaller grain size.(-55pn). 2120 1149(2100) 1.84 Same as above. 2221 1149(2100) 25 Smaller grains than above. 23

2

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Figure 1. As-received microstructure of Waspaloy.

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24

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Figure 24. Processing map of Waspaloy at a true strain of 0.5.

25

Summary

Compression tests have been performed on Waspaloy over a range oftemperatures and strain rates. The experimental conditions used in this work arerepresentative of those used in metalforming practices. From the stress-strain curves, theflow behavior was characterized and a map which indicates the optimum processingcondition was generated. This condition is approximately 1080 C and 0.01 s-1.

The deformed microstructures were characterized from the as-quenchedspecimens by optical microscopy and are presented for each testing condition togetherwith the stress-strain curves. Dynamic recovery, dynamic recrystallization and graingrowth occurred over the temperature and strain rate range tested.

Implementation of Data Provided by the Atlas of Formability

The Atlas of Formability program provides ample data on flow behavior ofvarious important engineering materials in the temperature and strain rate regimecommonly used in metalworking processes. The data are valuable in design and problemsolving of metalworking processes with advanced materials. Microstructural changeswith temperature and strain rates are also provided in the Bulletin, which helps the designengineer to select processing parameters leading to the desired microstructure.

The data can also be used to construct processing map using dynamic materialmodeling approach to determine stable and unstable regions in terms of temperature andstrain rate. The temperature and strain rate combination at the highest efficiency in thestable region provides the optimum processing condition. This has been demonstrated inthis Bulletin. However, in some metalworking processes such as forging, strain ratevaries within the workpiece. An analysis of the process with finite element method(FEM) can ensure that the strain rates at the processing temperature in the wholeworkpiece fall into the stable regions in the processing map. Furthermore, FEM analysiswith the data from the Atlas of Formability can be coupled with fracture criteria to predictdefect formation in metalworking processes.

Using the data provided by the Atlas of Formability, design of metalworkingprocesses, dynamic material modeling, FEM analysis of metalworking processes, anddefect prediction are common practice in Concurrent Technologies Corporation. Needsin solving problems related to metalworking processes can be directed to Dr. Prabir K.Chaudhury, Manager of the Atlas of Formability project, by calling (814) 269-2594.

26