Some 99.90 pure tin tubes (0.15 mm thick) used for packaging a chemical compound cracked on bending and underwent brittle fracture prior to filling, while others remained ductile and showed no sign of failure. Examination showed that specimens prepared by mechanical methods such as electrolytic and hand polishing and the vibration method resulted in poor edge and crack edge definition due to material thickness. Etching experiments involved a grain surface attack and hence produced a rather strong surface relief from which the grain boundary cracks could again not clearly be differentiated. The sections were therefore examined unetched in polarized light. The microstructure of the cracked tubes was shown to have much smaller grains than the ductile and showed cracks from the surface down along the grain boundaries. Material hardness also differed between the unusable tubes and the ductile, and chemical analysis showed a higher level of aluminum in the brittle specimens. Failure obviously occurred due to the high material aluminum content that increased hardness which then caused embrittlement at the surface which led to cracks or fracture on bending. Since no explanation of how the aluminum entered the tin was available, no recommendations could be made.

A crane long-travel worm drive shaft was found to be chipped during unpacking after delivery. Chemical analysis showed that the steel (EN36A with a case depth of 1 mm, or 0.04 inch did not meet specifications. Magnetic particle inspection revealed a crack on the side of the shaft opposite the chip. Metallographic examination indicated that the case depth was approximately 2 mm (0.08 in.) and that a repair weld of an earlier chip had been made in the cracked area. The chipping was attributed to excessive case depth and rough handling. It was recommended that the shaft be returned to the manufacturer and a replacement requested.

A commercial hybrid-iron golf club fractured during normal use. The club fractured through its cast aluminum alloy hosel. Optical analysis revealed casting pores through 20% of the hosel thickness. Mechanical properties were determined from characterization results, then used to construct a finite element model to analyze material performance under failure conditions. In addition, a full scale structural test was conducted to determine failure strength. It was concluded that the club failed not from ground impact but from a force reversal at the bottom of the downswing. Large moments generated during the downswing aggravated by manufacturing defects and stress concentration combined to create an overload condition.

A brackish water pump impeller was replaced after four years of service, while its predecessor lasted over 40 years. The subsequent failure investigation determined that the nickel-aluminum bronze impeller was not properly heat treated, which made the impeller susceptible to aluminum dealloying. The dealloying corrosion was exacerbated by erosion because the pump was slightly oversized. The investigation recommended better heat treating procedures and closer evaluation to ensure that new pumps are properly sized.

A segment from a premium-quality H13 tool steel die for die casting of aluminum failed after only 700 shots. The segment was subjected to visual, macroscopic, hardness, and metallographic testing. The investigation revealed that failure occurred as a result of fatigue at an electrical-discharge-machined surface where the resulting rehardened layer had not been removed. This rehardened layer had cracked, providing a source for fatigue initiation.

Two complete aircraft undercarriage-leg 2014 aluminum alloy forgings and a number of sectional ends that exhibited cracks during nondestructive testing were examined to determine the extent of damage and the type of cracking. Cracks were primarily confined to the diaphragm and adjoining wall between the steel sleeve and the steel diaphragm washer. Metallographic analysis and accelerated corrosion tests showed that the cracks had originated as stress-corrosion failures.

Several wires in aluminum conductor cables fractured within 5 to 8 years of, service in Alaskan tundra. The cables were comprised of 19-wire strands; the wires were aluminum alloy 6201-T81. Visual and metallographic examinations of the cold-upset pressure weld joints in the wires established that the fractures were caused by fatigue loading attributable to wind/thermal factors at the joints. The grain flow at the joints was transverse to the wire axis, rendering the notches of the joints sensitive to fatigue loading. An additional contributory factor was intergranular corrosion, which assisted fatigue crack initiation/propagation. The failure was attributed to the departure of conductor quality from the requirements of ASTM B 398 and B 399, which specify that “no joints shall be made during final drawing or in the finished wire” and that the joints should not be closer than 15 m (50 ft). The failed cable did not meet either criterion. It was recommended that the replacement cable be inspected for strict compliance to ASTM requirements.

An 1100 aluminum alloy connector of a high-tension aluminum conductor steel-reinforced (ACSR) transmission cable failed after more than 20 years in service, in a region of consider able industrial pollution. The steel core was spliced with a galvanized 1020 carbon steel sheath. Visual examination showed that the connector had undergone considerable plastic deformation and necking before fracture. The steel sheath was severely corroded, and the steel splice was pressed off-center in the axial direction inside the connector. Examination of the fracture surface and micro-structural analysis indicated that the failure was caused by mechanical overload, which occurred because of weakening of the steel support cable by corrosion inside the fitting. The corrosion was ascribed to defective assembly of the connector which allowed moisture penetration.

Two investment-cast A356 aluminum alloy actuators used for handles on passenger doors of commercial aircraft fractured during torquing at less than the design load. Visual examination showed that cracking had occurred through a machined side hole. Fractography revealed that the cracks originated in hot tear locations in the castings. Microprobe analysis of fracture surfaces in the hot tear region indicated a much higher silicon-to-aluminum ratio compared with the overload fracture area. No microstructural anomalies related to the failure were found during metallographic examination. It was concluded that the strength of the castings had been compromised by the presence of the casting defects. Modification of the gating system for casting was recommended to eliminate the hot tear zone. It was also suggested that the balance of the castings from the same manufacturing lot be radiographically inspected.

Various aluminum bronze valves and fittings on the essential cooling water system at a nuclear plant were found to be leaking. The leakage was limited to small-bore socket-welded components. Four specimens were examined: three castings (an ASME SB-148 CA 952 elbow from a small-bore fitting and two ASME SB-148 CA 954 valve bodies) and an entire valve assembly. The leaks were found to be in the socket-weld crevice area and had resulted from dealloying. It was recommended that the weld joint geometry be modified.

Three instances involving the failure of aluminum wiring at the service entrance to single-family homes are discussed. Arcing led to a fire which severely damaged a home in one case. In a second, the failure sequence was initiated by water intrusion into the service entrance electrical box during construction of the home. In the third, failure was caused by a marginal installation. Strict adherence to all applicable electrical codes and standards is critical in the case of aluminum wiring. Electrical components not specifically designed for aluminum must never be used with this type of wiring. All doors, panels and similar portions of electrical boxes should be secured to prevent damage to surroundings in the event of an electrical fault. If symptoms of arcing are observed, professional service should be sought. The latest designs of connectors for use with aluminum wiring are less susceptible to deviations in installation practice.

During the preproduction stages of forging, an initial batch of 50 mm (2 in.) diam Al-4Cu alloy (L77) extruded bar stock material was found to be cracking randomly. Failure analysis was conducted to determine the metallurgical factors underlying the phenomenon. Microexamination of sections across the defects revealed intergranular cracks tracing a path of round, segregated particles and oxide film discontinuities. The segregated particles were rich in copper It was concluded that the cracking was the result of segregations occurring in poor-quality raw material. The source of segregation was suspected to be the use of improperly made master alloys. Use of improved melting techniques and proper master alloys was recommended.

Leaks developed at random locations in aluminum brass condenser tubes within the first year of operation of a steam condenser in a nuclear power plant. One failed tube underwent scanning electron microscopy surface examination and optical microscope metallography. It was determined that the tube failed from crevice corrosion under seawater deposits that had formed on the inner surface. Mechanical cleaning of the condenser tubes every 6 months and installation of intake screens of smaller mesh size were recommended.

An investigation of the impeller and deposit samples from a centrifugal compressor revealed that an aluminum IR-12 refrigerant reaction had occurred, causing extensive damage to the second-stage impeller and contaminating the internal compressor components. The spherical surface morphology of the impeller fragments suggested that the aluminum had melted and resolidified. The deposits were similar in composition and were identified by XRD as consisting primarily of aluminum trifluoride. In addition, EDS analysis detected major amounts of chlorine and iron. Results of a combustion test indicated that the compressor deposit was comprised of a 9. 8 wt% carbon and that the condenser deposit contained 8.7 wt% carbon. It was concluded that the primary cause of failure was the rubbing of the impeller against the casting and that a self-sustaining Freon fire had occurred in the failed compressor

The failure mode of through-wall cracking of a butt weld in a 5083-O aluminum alloy piping system in an ethylene plant was identified as mercury liquid metal embrittlement. As a result of this finding, 226 of the more than 400 butt welds in the system were ultrasonically inspected for cracking. One additional weld was found that had been degraded by mercury. A welding team experienced in repairing mercury contaminated piping was recruited to make the repairs. Corrective action included the installation of a sulfur-impregnated charcoal mercury-removal bed and replacement of the aluminum equipment that was in operation prior to the installation of the mercury-removal bed.

An AMS 4126 (7075-T6) aluminum alloy impeller from a radial inflow turbine fractured during commissioning. Initial examination showed that two adjacent vanes had fractured through airfoils in the vicinity of the vane leading edges, and one vane fractured through an airfoil near the hub in the vicinity of the vane trailing edge. Some remaining vanes exhibited radial and transverse cracks in similar locations. Binocular and scanning electron microscope examinations showed that the cracks had been caused by high-cycle fatigue and had progressed from multiple origins on the vane surface. Structural analysis indicated that the fatigue loading probably had been caused by forced excitation, resulting in the impeller vibrating at its resonant frequency. It was recommended that the impeller design, control systems, and material of construction be changed.

Large quantities of aluminum-clad spent nuclear materials have been in interim storage in the fuel storage basins at The Savannah River Site while awaiting processing since 1989. This extended storage as a result of a moratorium on processing resulted in corrosion of the aluminum clad. Examinations of this fuel and other data from a corrosion surveillance program in the water basins have provided basic insight into the corrosion process and have resulted in improvements in the storage facilities and basin operations. Since these improvements were implemented, there has been no new initiation of pitting observed since 1993. This paper describes the corrosion of spent fuel and the metallographic examination of Mark 31A target slugs removed from the K-basin storage pool after 5 years of storage. It discusses the SRS Corrosion Surveillance Program and the improvements made to the storage facilities which have mitigated new corrosion in the basins.

The T-section cross member of the lifting sling failed in service while lifting a 966 kg (2130 lb) load. The L-section sling body and the cross member were made of aluminum alloy 5083 or 5086 and were joined by welding using aluminum alloy 4043 filler metal. The fracture was found by visual examination to have occurred at the weld joining the sling body and the cross member. Inadequate joint penetration and porosity was revealed by macrographic examination of the weld. Lower silicon content and a higher magnesium and manganese content than the normal for alloy 4043 filler metal were found during chemical analysis. It was revealed by examination of the ends of the failed cross member that a rotational force that had been applied on the cross member caused it to fracture near the sling body. It was concluded that brittle fracture at the weld was caused by overloading which was attributed to the misalignment of the sling during loading. Aluminum alloy 5183 or 5356 filler metal was recommended to be used to avoid brittle welds.

A failure analysis investigation was conducted on a fractured aluminum tailwheel fork which failed moments after the landing of a privately owned, 1955 twin-engine airplane. Nondestructive evaluation via dye-penetrant inspection revealed no discernible surface cracks. The chemical composition of the sand-cast component was identified via optical emission spectroscopy and is comparable to an aluminum sand-cast alloy, AA 712.0. Metallographic evaluation via optical microscopy and scanning electron microscopy revealed a high degree of porosity in the microstructure as well as the presence of deleterious intermetallic compounds within interdendritic regions. Macrohardness testing produced hardness values which are noticeably higher than standard hardness values for 712.0. The primary fracture surfaces indicate evidence of mixed-mode fracture, via intergranular cracking, cleaved intermetallic particles, and dimpled cellular regions in the matrix. The secondary fracture surface demonstrates similar features of intergranular fracture.

Extensive cracking was found in a batch of die-cast ZAMAK 3 solenoid valve seats during commissioning of the system in which they were installed. Scanning electron microscopic and chemical analyses conducted on one of the failed valve seats showed that the composition of the alloy was different from that specified. The presence of excess aluminum and lead impurities that had segregated to the grain boundaries, coupled with an inadequate amount of magnesium, resulted in intergranular corrosion and subsequent intergranular failure. Corrosion was accelerated by storage in a humid environment in a coastal area. It was recommended that proper chemical analysis of the zinc-aluminum alloy be carried out as a quality control procedure.