Showing papers by "Marc A. Meyers published in 1985"

Adiabatic shear localization in titanium and Ti-6 pct Al-4 pct V alloy

Abstract: Ballistic impact experiments were conducted on 12.5 mm thick commercial purity titanium and Ti-6 pct Al-4 pct V alloy plates using steel “stepped” projectiles with 10.5 mm diameter. The impact velocities varied between 578 m per second and 846 m per second, and a flash X-ray technique was used to determine projectile velocity and to assure the normality of impact. The microstructural damage mechanisms associated with impact (shear band formation, shock wave propagation, and dynamic fracture) were analyzed by optical, and scanning and transmission electron microscopy. Elliptical and spherical cavities were observed along the bands. Microindentation hardness differences between the bands and adjacent regions were slight for the targets; for the projectiles, the hardness in the band was significantly lower than that of surrounding regions. Observation of the fractured regions along the bands showed unique features indicating possible melting. Transmission-electron microscopy of a shear band in titanium revealed microcrystalline features (∼0.3 µm diameter) with poorly defined grain boundaries.

Mechanical and thermal response of shock-consolidated Mar-M 200 rapidly-solidified powder

Abstract: Consolidation of rapidly solidified Mar-M 200 powder was carried out successfully using the axi-symmetric and plane-wave (using contact explosives with normal incidence) geometries. However, cracking produced by reflected waves remains a major problem and considerable development work will be required until it can be eliminated. The ambient temperature ultimate compressive strength of the consolidated powder is approximately 2200 MPa. The change in micro-indentation hardness and microstructure as a function of isochronal anneals of one hour between 600 and 1200° C are presented. Ageing compact to optimum hardness (850° C/1 h) raises the ultimate compressive strength to 2250 MPa.

Inhomogeneities of shock‐wave deformation in Fe‐32 wt. % Ni‐0.035 wt. % C alloy

Abstract: Low‐pressure plane impact experiments performed on Fe‐32 wt. % Ni‐0.035 wt. % C alloy revealed, after recovery, markings which are attributed to shock‐induced inhomogeneities. Shear of the material does not occur homogeneously, but in preferential planar regions. These regions are made visible by a martensitic transformation [fcc (austenite)→bcc (martensite)] produced by the tensile pulses generated by the reflection of the compressive shock wave at a free surface. The bands with higher plastic deformation served as preferential nucleation sites for martensitic transformation. The formation of these bands is attributed to inhomogeneous yielding due to work softening of the material during tensile loading.