chevron_left 文章

The Basics of Nonferrous Metallurgy

142 文章

Tungsten Heavy Alloys

The name "tungsten" is derived from the Swedish term meaning "heavy stone". Tungsten has been assigned the chemical symbol W after its German name Wolfram.
WHAs are produced by a powder metallurgy (P/M) technique known as liquid phase sintering (LPS), in which completely dense, fully alloyed parts are formed from pressed metal powders at a temperature less than half the melting point of pure tungsten.

Twin Roll Casting of Al Alloys: Part One

Aluminum twin roll casting is a relatively new processing technology which allows for liquid aluminum to be transformed into strip directly with the integration the casting and hot rolling production phases.
The advantages are outstanding particularly in relation to cost savings through the simplified process, and low energy costs but how does the technique compare to more established processes like direct chill methods when we are considering the microstructure and subsequent attained material properties?

Work Hardening Aluminum Alloys: Part One

This article examines the fundamental principles and applications of strain hardening in aluminum alloys. It explains how work hardening naturally occurs during forming operations and significantly enhances strength properties in both heat-treatable and non-heat-treatable aluminum alloys. The paper details the standardized temper designation system for strain-hardened alloys, covering the full spectrum from quarter-hard to extra-hard conditions.

Work Hardening Aluminum Alloys: Part Two

The internal structural changes produce substantial changes in the mechanical properties of aluminum and its alloys. Tensile properties are among those most affected.
Work-hardening curves for several non-heat-treatable alloys illustrate the increase in strength that accompanies cold work. This increase is obtained at the expense of ductility, as measured by the per cent elongation in the tensile test and by reduced formability in operations such as bending and drawing.

Zinc and Zinc Alloys

Chemical specifications for zinc casting alloys are given in ASTM B86 for No. 2, No. 3, No. 5 and No. 7 alloys and ASTM B791 for ZA-8, ZA-12 and ZA-27.
Alloys covered by B86 are hypo-eutectic (i.e. they contain less aluminum than the eutectic chemistry of 5% Al) with a composition close to 4% Al. Alloys included in B791 are hypereutectic with an aluminum content greater than the eutectic chemistry. All of the zinc casting alloys have dendritic/eutectic microstructures, however, the hypoeutectic alloys solidify with zinc-rich dendrites, whereas hypereutectic alloys solidify with aluminum-rich dendrites.

Zinc-Aluminum Alloys as Tribomaterials

The high-aluminum zinc-based alloys comprise a new family of die-casting alloys that have proven themselves in a wide variety of demanding applications. These alloys feature clean, low temperature and energy-saving melting, excellent castability, high as-cast strength and hardness, corrosion resistance and equivalent or even superior bearing and wear properties as compared to standard bronze bearing.
Zn-Al alloys are characterized by significantly lower price, and can be successfully machined by standard casting procedures, like sand casting, centrifugal, permanent and continual casting. Total savings of substitution bronzes with these alloys are estimated up to the level of 35-90%.