Weldability of a rapid solidification/powder metallurgy Al-8Fe-2Mo alloy

Thesis/Dissertation · Sat Dec 31 23:00:00 EST 1988

OSTI ID:7025845

Krishnaswamy, S

The investigation utilized EB and Nd:YAG pulsed laser welding processes to produce autogenous, full-penetration welds with a high depth-to-width ratio FZ and minimal HAZ; characterized weld microstructure using light microscopy, SEM and TEM; evaluated weld mechanical properties; established interrelationships between weld microstructure, mechanical properties and fracture characteristics, and determined FZ solidification behavior. The results revealed significant microstructure variations across EB and pulsed Nd:YAG laser weld FZ. High FZ cooling rates ({approx equal}10{sup 3} C/s) generated an extremely fine FZ structure which exhibited a hardness comparable with base metal. However, occurrence of a coarse-grained FBR in these welds formed a weak-link with base metal, promoted preferential failure with low ductility and minimum weld joint efficiency (73%). Utilization of lower EB weld energy inputs and higher FZ cooling rates ({approx equal}10{sup 5} C/s) eliminated the coarse FBR and promoted failure in HAZ with acceptable ductility and high joint efficiency (88%). Nd:YAG pulsed laser welding provided a higher energy density and rapid FZ cooling rate ({approx equal}10{sup 6} C/s), produced submircon-sized spherical intermetallic particles in a fine-grained columnar-dendritic alpha aluminum matrix, and promoted preferential failure in the unaffected base metal indicating 100% joint efficiency. Solidification analysis related the occurrence of specific FZ microstructures to the presence of unmelted/undissolved base metal dispersoid particles and local thermal conditions. At relatively shallow temperature gradients and low FZ cooling rates, these particles produced coarse-grained FZ microstructures. In contrast, rapid FZ cooling rate limited the growth of the particles.

• Research Organization: Ohio State Univ., Columbus, OH (USA)
• OSTI ID: 7025845
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
COOLING TIME
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
FABRICATION
FRACTURE PROPERTIES
GRAIN SIZE
HARDNESS
HEAT AFFECTED ZONE
INTERMETALLIC COMPOUNDS
IRON ALLOYS
JOINING
JOINTS
LASERS
MECHANICAL PROPERTIES
METALLURGY
MICROSCOPY
MICROSTRUCTURE
MOLYBDENUM ALLOYS
OPTICAL MICROSCOPY
PHASE TRANSFORMATIONS
POWDER METALLURGY
SCANNING ELECTRON MICROSCOPY
SIZE
SOLIDIFICATION
TEMPERATURE GRADIENTS
TRANSMISSION ELECTRON MICROSCOPY
WELDABILITY
WELDED JOINTS
WELDING
ZONES