\documentclass[a4paper]{article}

\usepackage{pgfplots}

\begin{document}

\begin{tikzpicture}
%\tracingcommands=2\tracingmacros=2
	\begin{axis}[
		scale mode=scale uniformly,
		scale uniformly strategy=change horizontal limits,
		scale uniformly strategy=auto,
%		scale uniformly strategy=units only,
%		unit rescale keep size=false,
		x=0.1cm,
		y=0.5cm]
	\addplot {x};	
	\end{axis}
\end{tikzpicture}
\end{document}

