Evaluation of a Ni-20Cr Alloy Processed by Multi-Axis Forging

Abstract

This paper discusses the development of a novel processing route to produce ultra finegrain bulk alloy forgings; the microstructural response of these forgings to thermal exposure; and the comparison of mechanical properties to those from conventionally processed material. A Ni- 20Cr [wt%] alloy was processed by near-isothermal multi-axis forging to a grain size of approximately 1 μm. A heat-treatment study over the range 900 to 1200°C was conducted to determine the resultant grain size as a function of time and temperature. Tensile properties were measured at room temperature, 500°C, and 930°C. High-cycle fatigue properties were measured at room temperature. The room-temperature tensile strength was approximately 2.5 times greater than that of conventionally processed Ni-20Cr. Fatigue data showed that the room-temperature highcycle fatigue run-out stress was greater than 100% of the yield stress.

Characterization of Fatigue Fracture in Ni-20 Pct Cr Alloys Using White Light Interference Microscopy and Scanning Probe Microscopy

“…[21] Figure 1(b) shows the structure of the multiaxis-forged sample as having equiaxed grains varying in size from 160 nm to 5.5 lm with an average grain size of 1.3 lm. [22] The microstructure of the cryomilled sample also shows an equiaxed grain structure with fine-grain sizes as shown in Figure 1(c).…”

Effect of Cooling and Annealing Conditions on the Microstructure, Mechanical and Superelastic Behavior of a Rotary Forged Ti–18Zr–15Nb (at. %) Bar Stock for Spinal Implants

“…For additional control of the structural and phase state, the deformed material can also be submitted to post-deformation annealing [ 45 ]. Considering that, in some cases, the RF–PDA combination cannot entirely eliminate the heterogeneity resulting from the RSR operation, the latter can also be replaced by multi-axial forging [ 48 ].…”

Application of 3D EBSD to a Two-Phase, Ultra-Fine Grain Titanium Alloy

“…To better understand the influence of key factors in 3-D EBSD acquisition and processing on fine grain materials, we examined a two-phase titanium alloy with a sub-micron average grain size in both the alpha and beta phases, processed by Multi-Axis Forging (MAF) [3]. A backscattered electron image is presented in FIG 1.…”