Abstract A columnar grain structure and improved high temperature, high mechanical strength properties are provided in a metal article by solid state method. First the article is formed in a manner which places the metal microstructure in a condition of dislocation density which results in the metal microstructure undergoing relatively rapid transformation to relatively large grains when heated in the range of about 50 to less than 100 percent of the metal incipient melting temperature in degrees Rankine. Then the article so preconditioned is progressively and selectively heated in that temperature range but below the incipient melting temperature of the metal. This is accomplished by heating the article in a narrow zone. Such zone traverses the article, as a result of relative movement between the article and the source of heat energy, from the cooler portion and in the direction desired for growth of the principle axis of the columnar grains, with the zone having a thermal gradient of at least about 500*F/in. A preferred form of a processed wrought article is characterized by grains of at least about 2000 microns in diameter and a length to diameter ratio of at least about 10.
The method of claim 1 in which: the article is wrought; the alloy of the article is based on an element selected from the group consisting of Fe, Ni, Co, Ti and the refractory metals, the alloy being capable of maintaining high temperature, high mechanical strength properties when operating at temperatures of at least about 50 percent to less than 100 percent of the metal incipient melting temperature in degrees Rankine; the thermal gradient is in the range of 500* - 5,000*F/in.; and the rate of traverse of the thermal gradient is 0.5 - 144 inch/hr.
Claim 2
Dependent Claim
41 words
The method of claim 2 in which: the alloy is based on en element selected from the group consisting of Fe, Ni and Co; and, the temperature of the high temperature zone is in the range of about 1,650* - 2,450*F.
Claim 3
Dependent Claim
58 words
The method of claim 3 in which: the alloy is one strengthened by elements which produce strengthening selected from the group consisting of gamma prime, oxide dispersion, rare earth addition and their combinations; the thermal gradient is at least about 1,500*F/in.; and the temperature of the high temperature zone is in the range of about 2,000* - 2,450*F.
Claim 4
Dependent Claim
29 words
The method of claim 4 in which: the alloy is a nickel base oxide dispersion strengthened alloy; and, the temperature of the high temperature zone is about 2,400* -2,450*F.
Claim 5
Dependent Claim
68 words
A wrought alloy article made by the method of claim 1: having a columnar grain structure; being capable of maintaining high temperature, high mechanical strength properties when operating at temperatures of at least about 50 percent of the alloy incipient melting temperature in degrees Rankine; and, further characterized by having grains of at least about 2,000 microns in diameter and a length-to-diameter ratio of at least about 10.