UNCLASSIFIED AD NUMBER ADB069620 NEW LIMITATION CHANGE TO Approved for public release, distribution unlimited FROM Distribution authorized to U.S. Gov't. agencies only; Test and Evaluation; Jun 1982. Other requests shall be referred to Air Force Wright Aeronautical Labs., Wright-Patterson AFB, OH 45433. AUTHORITY AFWAL ltr, 6 Feb 1987 THIS PAGE IS UNCLASSIFIED AFWAL-TR-82-4086 R&D ON COMPOSITION AND PROCESSING4 OF TITANIUM ALUMINIDE ALLOYS FOR TURBINE ENGINES United Technologies Corporation Pratt & Whitney Aircraft Group Govomment Products Division West Palm Beach, Flodda 33402 July 1982 -1 Interim Report for Period October 1980 to January 1982 Distribution limited to government agencies only; contains Test and Evaluation June 1982: Other requests for this document must be referred to I, Air Force Weight Aeronautical Laboratyo riesg, Wright- Patterson Air Force Base, Ohio 45433 . L. SUBJECT TO EXPORT CONTROL LAWS This document contains information for manufacturing or using mu- nitions of war. Export of the information contained herein, or release to foreign nationals within the United States. without first obtaining an export license. is a violation of the International Traffic-in-Arms Regulations. Such violation is subject to a penalty of up to 2 years im- prisonment and a fine of $100.000 under 22 USC 2778. Include this notice with any reproduced portion of this document. MATERIALS LABORATORY AIR FORCE WRIGHT AERONAUTICAL LABORATORIES AIR FORCE SYSTEMS COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OHIO 46433 82 12 13 ()6.L NOTICE When Government drawings, specifications, or other data are used for any purpose other than in connection withi a definitely related Government procurement operation, the United States Government thereby incurs no responsibility nor any obligation whatsoever; and the fact that the Government may have formulated, furnished, or in any way supplied the said drawings, specifications, or other data, is not to be regarded by implication or other- wise as in any manner licensing the holder or any other person or corporation, or conveying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related thereto. This technical report has been reviewed and is approved for publication. 4.2 / /;ARRY LIPS NORMA M. GEYER Projec Engineer Technical Area Manager Processing & High Temperature Materials Branch Metals & Ceramics Division FOR T1 C(OEN HW4NER: 'I1ýNRY CV/GRAHAM, Chief Processing & High Temperature Materials Branch Metals & Ceramics Division "If your address has changed, if you wish to be removed from our mailing list, or if the addressee is no longer employed by your organization, please notify AFWAL/MULM , W-P AFB, Ohio 45433 to help maintain a current mailing list". Copies of this report should not be returned unless return is required by security considerations, contractual obligations, or notice on a specific document. INCLASSIF-ED SECURITY CLASSIFICATION OF THIS PAGE (When ate. Ent...d) REPORT DOCUMENTATION PAGE READ INSTRUCTIONS BEFORE COMPLETING FORM 1. REPORT NUMBER 2. OVT ACCESSION NO. 3-RECIPIENT'S CATALOG NUMBER A.FWAL-TR-82-4086- 4. TITLE (and Subitfle) S TYPE OF REPORT I PERIOO COVEREO R&D ON COMPOSITION AND PROCESSING OF Interim Technical Report TITANIUM ALUMINIDE ALLOYS FOR TURBINE October 1980-January 1982 ENGINES PP ERFORMING ORG. REPORT NUMBER FR- 16259 7. AUTHOR(s) 8 CONTRACT OR GRANT NUMBER(s) M. J. Blackburn NI.P . Slmth F33615-80-C-5163 9. PERFORMING ORGANIZATION NAME AND AODRESS 10. PROGRAM ELEMENT. PROJECT. TASK AREA 6 WORK UNIT NUMBERS UTC - Pratt & Whitney Aircraft Group Government Products Division 24200127 West Palm Beac&, FL 33402 III . CONTROLLING OFFICE NAME AND AOODESS 12. REPORT DATE Materials Laboratory (MLLI) June 1982 Air Force Wright Aeronautical Laboratories 13. NUMBEROF PAGES Wright-Patterson AFB- Ohio 45433 91 14. MONITORING AGENCY NAME & AOORESS(it dileretnt trom Controllinn4 O1fict) IS. SECURITY CLASS. (of this report) Unclassified IS4. OECL ASSI FI CATION/ OOWNGRAOING SCHEDULE 16. DISTRIBUTION STATEMENT (of this Rpoatt) Distribution limited to U.S. Government agencies only. Test and Evaluation; June 1982. Other requests for this doc~uent niust be referred to AFWAL/MLLM, 1%PAFB, Ohio 45433 I?. DISTRIBUTION STATEMENT (of the abstract entered in Block 20. It dil.leternt Itrai Report) IS. SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on #evote#o lde it neceessay and Identify by block numlber) Titanium Alumninides, Alloy Development, Isothermal Forging, Titanium Ingot Production, Mechanical Properties, Titanium Alloy Microstructures, Titanium Machining, Titanium Casting 20. ABSTRACT (Continu ,re an evde aie It n.cee.asv end Identify by block number) Materials based on the intermetallic phases Ti3Al (a2) and TiAl (y) exhibit several attractive features that make them candidates for gas turbine engine applications. Low density, good oxidation resistance and high temperature strength are such characteristics and could result in substitution for the nickel alloys currently used for turbine engine components that operate at internediate temperatures. Basic alloy development studies over the past eight years have identified the base Ti-Al-Nb-V and Ti-Al-V systems, DID FjA'r3 1473 EDITION OF I NOV 6S IS OBSOLETE UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Date EIe,eJd) UNCLASSIFIED SECURITY CLASSIFgC&TION Or THIS PAOGIr(3?i Data Itute.,d) Block 20 (Cont'd.) respeqtively, ad the most attractive ba'se compositions for the two alloy S--4ypes- In this current program, one alpha-two and several gamma compositions were selected, produced as large ingots and isothermally forged. Extensive mechanical property testing was conducted on these forgings. In addition, various material processing methods such as casting, rolling, extrusion and machining were evaluated. The alpha-two alloy Ti-2SAl-IONb-3V-IMo exhibited the best balance of tensile and stress-nrpture properties found to date and had a higher elastic modulus. Beta grain size was shown to have major effects on creep, low cycle fatigue and fracture toughness. Alloy stability, as measured by post-exposure tensile ductility, was poor and was tentatively traced to precipitation of an unidentified phase in the beta. Heat treatment modifications were suggested to alleviate this problem. Processing studies showed that many of the methods developed for forging, joining and rolling of conventional titanium alloys can be applied to the alpha-two alloys. Screening tests conducted on four gamma alloys did not identify an alloy with a betteýr property balance than Ti-48AI-lV-.lC which had been evaluated pre- viously. Properties were more consistent with previous small scale ingots, although ductility and impact strength were somewhat lower, and quite good toughness levels were measured. Alloy stability was excellent after exposure and processing studies establis'ed machining procedures and demonstrated that the alloy has fair castability.%z- l ii WICLASSIFIED SECURITY CLASSIFICATION Of THIS PAOEJfWbfa Data Krnet,,d) PREFACE This is an interim Technical Report (PWA Report FR-16259) covering work performed under Contract F33615-80-C-5163 during the period between October 1980 and January 1982. The investigation was conducted by the Commercial Products Division of Pratt & Whitney Aircraft, East Hartford, Connecticut, under the technical "direction of Dr. H. A. Lipsitt, AFWAL/MLLM, Wright-Patterson Air Force Base, Ohio. Dr. M. J. Blackburn was the Program Manager, Mr. M. P. Smith was the responsible engineer and Mr. D. R. Haase was the experimental assistant. Thanks are extended to Ms. Nancy Giampolo for typing and editorial assistance. • I, , ° "; '.. ": SI f,. iii ---------------------------------- TABLE OF CONTENTS SECTION PAGE I INTRODUCTION 1 II PROGRAM SCOPE AND APPROACH 2 1. Background 2 2. Program Plan 3 3. Alloy and Process Selection - 3 Alpha-Two Alloy | 4. Alloy and Process Selection - 4 Gamma Alloys III EXPERIMENTAL DETAILS 7 1. Material Procurement 7 and Processing a. Large Ingots and Forgings 7 IV RESULTS AND DISCUSSION 20 1. Introduction 20 2. Material Characterization - 20 Alpha-Two Alloy 3. Material Characterization - 44 Gamma Alloys 1-4 a. Screening Tests 44 b. Material Characterization - 48 Ti-48Al-lV-. lC 4. Processing Studies 64 a. Net Shape Gamma Alloy Casting 64 b. Gamma Alloy Machinability 69 c. Forged Alpha-Two Alloy Compressor 82 Blade d. Alpha-Two Alloy Sheet Analysis 82 V ANALYSIS AND CONCLUSIONS 87 REFERENCES 91 S..V LIST OF ILLUSTRATIONS FICURE PACE 1 As-received titanium aluminide ingots supplied 9 by RMI. (a) S/N 20007; (b) left to right, S/N 20008, S/N 20009, S/N 20010, S/N 20011. 2 Pancake forging preforms machined from PRI 10 titanium aluminide ingots a) S/N 20007; b) S/N 20008; c) S/N 20009; d) S/N 20010; e) S/N 20011. Note fairly extensive porosity on gamma alloy ingots (b-e) compared to the alpha-two alloy a). Top and bottom riews of as-forged Ti-47A1-2V- 12 2Nb-lMo alloy pancake. 4 ToT, and bottom views of as-forged Ti-47AI-2V 13 al',y pancake. 5 Top and bottom views of as-forged Ti-47A1-2V-.IC 14 alloy pancake. 6 Top and bottom views of as-forged Ti-48A1-lV-.lC is alloy pancake. Note better die fill and less cracking. 7 Top and bottom views of as-forged Ti-25AI-10Nb- 16 3V-lMo alloy pancake. 8 Specimen used to measure tensile, creep and low 17 cycle fatigue capability of titanium aluminide alloy. 9 Specimens used for impact and fracture toughness 18 evaluation of titanium aluminide alloys. 10 Physical property specimens used for titanium 19 aluminide study. a) thermal expansion; b) modulus of elasticity; c) specific heat; d) conductivity 11 Macro- and microstructure of the forged and heat 21 treated Ti-25A1-l0Nb-3V-lMo pancake forging (a). The rim, mid-radius and center microstructures are in b, c and, respectively. 12 Microstructures of various titanium aluminide creep 24 specimens tested at 650C/372 MPa (1200F/S5 ksi). vi LIST OF ILLUSTRATIONS (ONT'D.) FIGUR11 PAGE 13 Macrostructure of as- forged Ti- 25A1-10Nb- 3V- iMo 24 alloy pancake forging. This was forged on iso- thermal dies at 1120C (20SOF) in one step from a cast ingot. 14 Macrostructure of Ti-25A.-10Nb-4V pancake forging 25 from a previous program(4). Top, as-conventionally upset and forged at 1120C (2050F); bottom, heat treated llS0C (2100F)/l/ + salt quench to 81SC (ISOOF)/. S/AC. Is Effect of thermal exposure on hardness of Ti-25A1- 28 l0Nb-3V-Ilo tensile specimens. 16 Surface of exposed Ti-25A1-l0Nb-3V-1Mo alloy tensile 28 specimen showing alpha case contamination, which has a hardness of DPH 700-800. 17 SEN fractographs of tested Ti-2SA1-1ONb-3V-lMo 29 tensile specimens. 18 General microstructure of Ti-2SA1-l0Nb-3V-lilo 30 alloy thin foils cut from tensile specimens. 19 Enlarged view of Figure 18 showing the relatively 32 "clean" beta phase in the unexposed specimen 2588 and the darkened beta phase with heavy precipi- tation in the exposed specimen 2933. 20 General microstructure of the unexposed Ti-2SA1- 33 1ONb-3V-lMo tensile specinten 2588 showing spectrum and composition of alpha-two and beta phase. 21 S/N curve for smooth Ti-2SAl-l0Nb-3V-lMo alloy 36 specimens tested at 650C (1200F). 22 S/N curves for notched Ti-25Al-Nb-3V-lBlo specimens 37 tested at 650C (1200F) based on grain size. 23 Selected notched Ti-25A1-lONb-3V-lMo LCF specimens 38 showing extremes in grain size but similar micro- structures. 24 Young's modulus of Ti-2SAI-1ONb-3V-lIo alloy specimen 40 vs. temperature. 25 Thermal conductivity of the Ti-25AI-l0Nb-3V-D~o alloy. 42 vii .. .-...-.- ,---.- LIST OF ILLUSTRATIONS (CONT'D.) FIGURE PAGE 26 Enthalpy of the Ti-25A1-lONb-3V-lMo alloy. 42 27 Heat capacity of the Ti-25A1-lONb-3V-lMo alloy. 43 28 Thermal expansion of the Ti-25AI-lONb-3V-lMo alloy. 43 29 Cross sections of tested gamma alloy titanium 46 alum-inide tensile specimens showing internal porosity (arrow, brackets). 30 Grinding cracks and porosity on thread surface of 47 Ti-48A1-lV-.IC tensile specimen. Right, a cross section of a thread root on the same specimen revealing a root crack. 31 Microstructures of Ti-48A1-lV-.IC creep specimens so showing relative amounts of acicular phase present. 32 Continuous oxide layer formed on Ti-48A1-lV-. lC 53 alloy specimens after a thermal exposure of 500 hours at 675C (1250F) plus 100 hours at 730C (1350F) (brackets). 33 Fracture mode in precracked slow bend toughness 56 specimens. Left column, Ti-48Al-lV-.1C; right column, Ti-25Al-l0Nb-3V-1Mo. Note difference in grain size. 34 S/N curves for smooth Ti-48AI-IV-. lC LCF specimens 57 drawn to show effect of grain size on 650C (1200F) life. 35 Fracture appearance and microstructures of smooth 58 Ti-48Al-lV-.lC LCF specimens tested at 650C (1200F) and 344 MPa (50 ksi). 36 Ti-48A!-lV-.lC smooth LCF specimens tested at 650C 59 (1200F) and 344 MPa (50 ksi). Note origins in coarse grain areas in specimen 3744 (a) and 3749 (b). Fracture path (c) is basically intergranular. 37 S/N curve for 815C (1500F) notched low cycle fatigue 61 specimens. 38 Young's modulus of the Ti-48A1-lV-.lC alloy. 62 39 Thermal conductivity of the Ti-48Al-lV-.lC alloy. 63 viii